Dnv Rules for Ships

RULES FORCLASSIFICATION OF

DET NORSKE VERITAS

Veritasveien 1, N-1322 Høvik, Norway Tel.: +47 67 57 99 00 Fax: +47 67 57 99 11

SHIPS

NEWBUILDINGS

HULL AND EQUIPMENTMAIN CLASS

PART 3 CHAPTER 1

HULL STRUCTURAL DESIGN SHIPS WITH LENGTH 100 METRES AND ABOVEJANUARY 2001

CONTENTS PAGE

Sec. 1 General Requirements ................................................................................................................ 7Sec. 2 Materials and Material Protection ............................................................................................ 13Sec. 3 Design Principles...................................................................................................................... 17Sec. 4 Design Loads ............................................................................................................................ 29Sec. 5 Longitudinal Strength............................................................................................................... 37Sec. 6 Bottom Structures..................................................................................................................... 49Sec. 7 Side Structures.......................................................................................................................... 58Sec. 8 Deck Structures ........................................................................................................................ 67Sec. 9 Bulkhead Structures ................................................................................................................. 73Sec. 10 Superstructure Ends, Deckhouse Sides and Ends, Bulwarks ................................................... 79Sec. 11 Openings and Closing Appliances ........................................................................................... 84Sec. 12 Welding and Weld Connections............................................................................................. 103Sec. 13 Direct Strength Calculations ................................................................................................. 108Sec. 14 Buckling Control .................................................................................................................... 113Sec. 15 Structures for High Temperature Cargo ................................................................................. 119Sec. 16 Special Requirements - Additional Class ............................................................................... 122Sec. 17 Fatigue Control ...................................................................................................................... 127Sec. 18 Corrosion Prevention.............................................................................................................. 128App. A Elastic Buckling and Ultimate Strength ................................................................................. 131

CHANGES IN THE RULES

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General

The present edition of the rules includes additions and amendmentsdecided by the board in December 2000, and supersedes the January2000 edition of the same chapter.

The rule changes come into force on 1 July 2001.

This chapter is valid until superseded by a revised chapter. Supple-ments will not be issued except for an updated list of minor amend-ments and corrections presented in Pt.0 Ch.1 Sec.3. Pt.0 Ch.1 isnormally revised in January and July each year.

Revised chapters will be forwarded to all subscribers to the rules.Buyers of reprints are advised to check the updated list of rule chap-ters printed in Pt.0 Ch.1 Sec.1 to ensure that the chapter is current.

Main changes

• Sec. 1 General Requirements

— Subsection D has been completely rewritten and a new Table D1has been added, collecting all requirements for structural andtightness testing in one place. (Cover IACS UR S14).

• Sec. 9 Bulkhead Structures

— Previous item A500 on testing has been deleted.

• Sec. 11 Opening and Closing Appliances

— Previous items A401 and A402 on testing have been deleted andprevious A403 to A405 have been renumbered A401 to A403.

— Previous items E108 and E109 on testing have been deleted.— Previous item G400 on testing have been deleted.

Corrections and ClarificationsIn addition to the above stated rule amendments, some detected errorshave been corrected, and some clarifications have been made in theexisting rule wording.

Rules for Ships, January 2001Pt.3 Ch.1 Contents –

DET NORSKE VERITAS

CONTENTS

SEC. 1 GENERAL REQUIREMENTS .......................... 7

A. Classification..........................................................................7A 100 Application........................................................................7A 200 Class notations ..................................................................7

B. Definitions ..............................................................................7B 100 Symbols.............................................................................7B 200 Terms ................................................................................7B 300 Ship types..........................................................................9

C. Documentation ......................................................................9C 100 Plans and particulars .........................................................9C 200 Specifications and calculations .......................................10C 300 Specific purpose documentation .....................................10

D. Structural and Tightness Testing .....................................10D 100 Definitions.......................................................................10D 200 General requirements ......................................................10D 300 Specific requirements for extent and type of testing.......10

E. Ships Built for In-Water Survey........................................12E 100 General ............................................................................12E 200 Rudder.............................................................................12E 300 Tailshaft ..........................................................................12

SEC. 2 MATERIALS AND MATERIAL PROTECTION.................................................... 13

A. General.................................................................................13A 100 Introduction.....................................................................13A 200 Material certificates.........................................................13

B. Hull Structural Steel ...........................................................13B 100 General ............................................................................13B 200 Material designations and classes ...................................13B 300 Basic requirements..........................................................13B 400 Requirements for low air temperatures (special features

notation DAT(-x°C)) ......................................................14B 500 Material at cross-joints....................................................14

C. Alternative Structural Materials .......................................14C 100 Aluminium ......................................................................14C 200 Stainless steel ..................................................................14

D. Corrosion Additions for Steel Ships..................................15D 100 General ............................................................................15D 200 Corrosion additions.........................................................15D 300 Class notation ICM (Increased Corrosion Margin).........15

SEC. 3 DESIGN PRINCIPLES ..................................... 17

A. Subdivision and Arrangement ...........................................17A 100 General ............................................................................17A 200 Definitions.......................................................................17A 300 Number of transverse watertight bulkheads....................17A 400 Position of collision bulkhead.........................................17A 500 Height of watertight bulkheads.......................................18A 600 Opening and closing appliances......................................18A 700 Cofferdams and tank contents.........................................18A 800 Forward compartment contents.......................................18A 900 Minimum bow height......................................................18A 1000 Access to and within narrow ballast tanks......................18A 1100 Steering gear compartment .............................................18

B. Structural Design Principles ..............................................19B 100 Design procedure ............................................................19B 200 Loading conditions..........................................................19B 300 Hull girder strength .........................................................19B 400 Local bending and shear strength....................................20B 500 Buckling strength ............................................................20B 600 Impact strength................................................................20B 700 Fatigue.............................................................................21B 800 Local vibrations ..............................................................21B 900 Miscellaneous strength requirements..............................21B 1000 Reliability-based analysis of hull structures ...................21

C. Local Design........................................................................ 21C 100 Definition of span for stiffeners and girders ...................21C 200 End connections of stiffeners..........................................22C 300 End connections of girders..............................................22C 400 Effective flange of girders ..............................................24C 500 Effective web of girders..................................................25C 600 Stiffening of girders. .......................................................26C 700 Reinforcement at knuckles..............................................27C 800 Continuity of local strength members.............................27C 900 Welding of outfitting details to hull................................27C 1000 Properties and selection of sections. ...............................28C 1100 Cold formed plating ........................................................28

SEC. 4 DESIGN LOADS ............................................... 29

A. General ................................................................................ 29A 100 Introduction.....................................................................29A 200 Definitions.......................................................................29

B. Ship Motions and Accelerations ....................................... 29B 100 General ............................................................................29B 200 Basic parameters .............................................................29B 300 Surge, sway /yaw and heave accelerations .....................30B 400 Roll motion and acceleration ..........................................30B 500 Pitch motion and acceleration.........................................30B 600 Combined vertical acceleration.......................................31B 700 Combined transverse acceleration ..................................31B 800 Combined longitudinal accelerations..............................31

C. Pressures and Forces.......................................................... 31C 100 General ............................................................................31C 200 Sea pressures...................................................................31C 300 Liquids in tanks...............................................................32C 400 Dry cargoes, stores, equipment and accommodation......35C 500 Deck cargo units. Deck equipment .................................36

SEC. 5 LONGITUDINAL STRENGTH....................... 37

A. General ................................................................................ 37A 100 Introduction.....................................................................37A 200 Definitions.......................................................................37

B. Still Water and Wave Induced Hull Girder Bending Moments and Shear Forces ............................................... 37

B 100 Stillwater conditions .......................................................37B 200 Wave load conditions......................................................39

C. Bending Strength and Stiffness......................................... 40C 100 Midship section particulars .............................................40C 200 Extent of high strength steel (HS-steel) ..........................40C 300 Section modulus .............................................................41C 400 Moment of inertia ...........................................................42

D. Shear Strength .................................................................... 42D 100 General ............................................................................42D 200 Ships with single or double skin and without other

effective longitudinal bulkheads .....................................43D 300 Ships with two effective longitudinal bulkheads ............43D 400 Ships with number of effective longitudinal bulkheads

different from two ...........................................................44D 500 Strengthening in way of transverse stringers ..................45

E. Openings in Longitudinal Strength Members................. 45E 100 Positions..........................................................................45E 200 Deduction-free openings.................................................45E 300 Compensations................................................................46E 400 Reinforcement and shape of smaller openings ...............46E 500 Hatchway corners............................................................46E 600 Miscellaneous .................................................................47

F. Loading Guidance Information ........................................ 47F 100 General ............................................................................47F 200 Conditions of approval of loading manuals ....................47F 300 Condition of approval of loading computer systems ......48


DET NORSKE VERITAS

SEC. 6 BOTTOM STRUCTURES ................................ 49

A. General ................................................................................ 49A 100 Introduction .....................................................................49A 200 Definitions.......................................................................49A 300 Documentation ................................................................49A 400 Structural arrangement and details..................................49A 500 Bottom arrangement........................................................50

B. Design Loads ....................................................................... 50B 100 Local loads on bottom structures ....................................50B 200 Total loads on double bottom..........................................50

C. Plating and Stiffeners .........................................................51C 100 General ............................................................................51C 200 Keel plate ........................................................................51C 300 Bottom and bilge plating.................................................51C 400 Inner bottom plating........................................................52C 500 Plating in double bottom floors and longitudinal

girders..............................................................................52C 600 Transverse frames ...........................................................53C 700 Bottom longitudinals .......................................................53C 800 Inner bottom longitudinals ..............................................53C 900 Stiffening of double bottom floors and girders ...............54

D. Arrangement of Double Bottom........................................54D 100 General ............................................................................54D 200 Double bottom with transverse framing..........................54D 300 Double bottom with longitudinals...................................54

E. Double Bottom Girder System below Cargo Holds and Tanks....................................................................................55

E 100 Main scantlings ...............................................................55

F. Single Bottom Girders........................................................55F 100 Main scantlings ...............................................................55F 200 Local scantlings...............................................................55

G. Girders in Peaks..................................................................55G 100 Arrangement....................................................................55G 200 Scantlings ........................................................................55G 300 Details .............................................................................55

H. Special Requirements .........................................................55H 100 Vertical struts ..................................................................55H 200 Strengthening against slamming .....................................55H 300 Strengthening for grab loading and discharging (special

features notation IB(+) ....................................................57H 400 Docking ...........................................................................57

SEC. 7 SIDE STRUCTURES......................................... 58

A. General ................................................................................ 58A 100 Introduction .....................................................................58A 200 Definitions.......................................................................58A 300 Documentation ................................................................58A 400 Structural arrangement and details..................................58

B. Design Loads ....................................................................... 59B 100 Local loads on side structures .........................................59

C. Plating and Stiffeners .........................................................60C 100 Side plating, general........................................................60C 200 Sheer strake at strength deck...........................................60C 300 Longitudinals ..................................................................61C 400 Main frames ...................................................................61C 500 'Tween deck frames and vertical peak frames ...............61

D. Girders................................................................................. 62D 100 General ............................................................................62D 200 Simple girders .................................................................62D 300 Complex girder systems..................................................62D 400 Cross ties .........................................................................62

E. Special Requirements .........................................................63E 100 Bar stem ..........................................................................63E 200 Tripping brackets ............................................................63E 300 Strengthening against bow impact ..................................63E 400 Strengthening against liquid impact pressure in larger

tanks ................................................................................65E 500 Fatigue control of longitudinals, main frames and 'tween

deck frames .....................................................................65

SEC. 8 DECK STRUCTURES ...................................... 67

A. General.................................................................................67A 100 Introduction .....................................................................67A 200 Definitions.......................................................................67A 300 Documentation ................................................................67A 400 Structural arrangement and details..................................67A 500 Construction and initial testing of watertight decks, trunks

etc. ...................................................................................68

B. Design Loads .......................................................................68B 100 Local loads on deck structures ........................................68

C. Plating and Stiffeners ......................................................... 70C 100 Strength deck plating ......................................................70C 200 Plating of decks below or above strength deck...............70C 300 Longitudinals ..................................................................70C 400 Transverse beams. ...........................................................70

D. Girders.................................................................................71D 100 General ............................................................................71D 200 Simple girders .................................................................71D 300 Complex girder systems..................................................71

E. Special Requirements ......................................................... 71E 100 Transverse strength of deck between hatches .................71E 200 Strength of deck outside large hatches............................71E 300 Pillars in tanks.................................................................72E 400 Strengthening against liquid impact pressure in larger

tanks ................................................................................72E 500 Foundations for deck machinery, cranes and masts........72E 600 Emergency towing arrangements for tankers..................72

SEC. 9 BULKHEAD STRUCTURES........................... 73

A. General.................................................................................73A 100 Introduction .....................................................................73A 200 Definitions.......................................................................73A 300 Documentation ................................................................73A 400 Structural arrangement and details..................................73

B. Design Loads .......................................................................74B 100 Local loads on bulkhead structures .................................74

C. Plating and Stiffeners ......................................................... 75C 100 Bulkhead plating .............................................................75C 200 Longitudinals ..................................................................75C 300 Vertical and transverse stiffeners on tank, wash, dry bulk

cargo, collision and watertight bulkheads.......................75

D. Girders.................................................................................76D 100 General ............................................................................76D 200 Simple girders .................................................................76D 300 Complex girder systems..................................................77

E. Special Requirements ......................................................... 77E 100 Shaft tunnels....................................................................77E 200 Corrugated bulkheads .....................................................77E 300 Supporting bulkheads......................................................77E 400 Strengthening against liquid impact pressure in larger

tanks ................................................................................77

SEC. 10 SUPERSTRUCTURE ENDS, DECKHOUSE SIDES AND ENDS, BULWARKS .................... 79

A. General.................................................................................79A 100 Introduction .....................................................................79A 200 Definitions.......................................................................79

B. Structural Arrangement and Details ................................ 79B 100 Structural continuity........................................................79B 200 Connections between steel and aluminium.....................79B 300 Miscellaneous..................................................................80

C. Design Loads .......................................................................80C 100 External pressure.............................................................80

D. Scantlings.............................................................................80D 100 End bulkheads of superstructures and deckhouses, and


DET NORSKE VERITAS

exposed sides in deckhouses ...........................................80D 200 Protected casings.............................................................80D 300 Bulwarks .........................................................................80D 400 Aluminium deckhouses...................................................81

E. Protection of the Crew........................................................81E 100 Regulation 25 ..................................................................81E 200 Interpretations .................................................................81

SEC. 11 OPENINGS AND CLOSING APPLIANCES ..................................................... 84

A. General.................................................................................84A 100 Introduction.....................................................................84A 200 Definitions.......................................................................84A 300 Documentation................................................................84A 400 Testing.............................................................................85

B. Access Openings in Superstructures and Freeboard Deck. ..................................................................85

B 100 Doors...............................................................................85B 200 Sill heights ......................................................................85B 300 Access openings in freeboard and

superstructure decks........................................................85

C. Side and Stern Doors ..........................................................86C 100 General. ...........................................................................86C 200 Structural arrangement....................................................86C 300 Design loads....................................................................86C 400 Plating .............................................................................87C 500 Stiffeners .........................................................................87C 600 Girders.............................................................................87C 700 Closing arrangement, general .........................................87C 800 Closing arrangement, strength ........................................88C 900 Closing arrangement, system for operation and

indication/monitoring......................................................88

D. Hatchway Coamings ...........................................................88D 100 General ............................................................................88D 200 Coaming heights .............................................................89D 300 Scantlings........................................................................89

E. Hatch Covers .......................................................................89E 100 General ............................................................................89E 200 Design loads....................................................................90E 300 Plating .............................................................................91E 400 Stiffeners .........................................................................91E 500 Girders.............................................................................92E 600 Stiffness of cover edges ..................................................92E 700 Structural analysis ...........................................................92

F. Hatchway Tightness Arrangement and Closing Devices....................................................................93

F 100 General ............................................................................93F 200 Design and tightness requirements .................................93F 300 Securing devices in general.............................................93F 400 Securing arrangement for weathertight hatch covers......94F 500 Securing arrangement for deep tank or cargo oil tank

hatch covers.....................................................................94F 600 Securing arrangement for hatch covers carrying

deck cargo .......................................................................94F 700 Drainage arrangement .....................................................95

G. Internal Doors and Hatches for Watertight Integrity .....95G 100 General ............................................................................95G 200 Operation.........................................................................95G 300 Strength ...........................................................................95

H. Ventilators............................................................................95H 100 Regulation 19 ..................................................................95H 200 Thickness of coamings....................................................96H 300 Arrangement and support................................................96

I. Tank Access, Ullage and Ventilation Openings................96I 100 General ............................................................................96I 200 Hatchways.......................................................................96I 300 Air Pipes..........................................................................96

J. Machinery Space Openings................................................97J 100 Regulation 17 ..................................................................97

J 200 Interpretations .................................................................97

K. Scuppers, Inlets and Discharges ....................................... 97K 100 Regulation 22 ..................................................................97K 200 Interpretations .................................................................98K 300 Discharges.......................................................................99K 400 Scuppers..........................................................................99K 500 Periodically unmanned machinery space........................99

L. Side Scuttles ........................................................................ 99L 100 Regulation 23 ..................................................................99L 200 Interpretations ...............................................................100L 300 Arrangement .................................................................100L 400 Glass dimensions, side scuttles and windows...............100

M. Freeing Ports..................................................................... 100M 100 Regulation 24 ................................................................100M 200 Interpretations ...............................................................101M 300 References.....................................................................101

N. Special Requirements for Type A Ships ........................ 101N 100 Regulation 26 ................................................................101N 200 Interpretation.................................................................102

SEC. 12 WELDING AND WELD CONNECTIONS .............................................. 103

A. General .............................................................................. 103A 100 Introduction...................................................................103A 200 Definitions.....................................................................103A 300 Welding particulars.......................................................103A 400 Radiographic examination. ...........................................103

B. Types of Welded Joints .................................................... 103B 100 Butt joints......................................................................103B 200 Lap joints and slot welds...............................................103B 300 Tee or cross joints .........................................................103

C. Size of Weld Connections ................................................ 104C 100 Continuous fillet welds, general ...................................104C 200 Fillet welds and penetration welds subject to high tensile

stresses ..........................................................................105C 300 End connections of girders, pillars and cross ties .........105C 400 End connections of stiffeners........................................106C 500 Intermittent welds .........................................................107C 600 Slot welds......................................................................107

SEC. 13 DIRECT STRENGTH CALCULATIONS ........................................... 108

A. General .............................................................................. 108A 100 Introduction...................................................................108A 200 Application....................................................................108A 300 Documentation..............................................................108

B. Calculation Methods ........................................................ 108B 100 General ..........................................................................108B 200 Computer program........................................................109B 300 Loading conditions and load application ......................109B 400 Acceptance criteria........................................................109

C. Global Analysis................................................................. 111C 100 General ..........................................................................111C 200 Loading conditions........................................................111C 300 Acceptance criteria........................................................111

D. Cargo Hold or Tank Analysis ......................................... 111D 100 General ..........................................................................111D 200 Loading conditions and load application ......................112D 300 Acceptance criteria........................................................112

E. Frame and Girder Analysis............................................. 112E 100 General ..........................................................................112E 200 Loading conditions and load application ......................112E 300 Acceptance criteria........................................................112

F. Local Structure Analysis ................................................. 112F 100 General ..........................................................................112F 200 Loading conditions and load application ......................112F 300 Acceptance criteria........................................................112


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SEC. 14 BUCKLING CONTROL ................................. 113

A. General .............................................................................. 113A 100 Introduction ...................................................................113A 200 Definitions.....................................................................113

B. Plating ................................................................................113B 100 General ..........................................................................113B 200 Plate panel in uni-axial compression ............................113B 300 Plate panel in shear .......................................................115B 400 Plate panel in bi-axial compression ..............................116B 500 Plate panel in bi-axial compression and shear ..............116

C. Stiffeners and Pillars ........................................................116C 100 General ..........................................................................116C 200 Lateral buckling mode ..................................................116C 300 Torsional buckling mode ..............................................117C 400 Web and flange buckling ..............................................118C 500 Transverse beams and girders .......................................118

SEC. 15 STRUCTURES FOR HIGH TEMPERATURE CARGO.............................................................. 119

A. General .............................................................................. 119A 100 Introduction ...................................................................119A 200 Special features notations..............................................119A 300 Documentation ..............................................................119A 400 Survey and testing .........................................................119A 500 Signboards.....................................................................119

B. Materials and Material Protection.................................. 119B 100 Hull and tank material ...................................................119B 200 Insulation material.........................................................119B 300 Corrosion protection .....................................................119

C. Ship Arrangement ............................................................ 119C 100 Location and separation of spaces ................................119C 200 Equipment within the cargo area ..................................119C 300 Surface metal temperature ............................................119C 400 Cargo heating media .....................................................119

D. Load Conditions................................................................119D 100 Full and partial cargo conditions...................................119D 200 Water ballast conditions................................................120

E. Scantlings of the Cargo area............................................ 120E 100 Construction considerations ..........................................120E 200 Thermal stress analysis .................................................120E 300 Acceptable stress level ..................................................120E 400 Girders...........................................................................121

F. Type of Cargoes ................................................................121F 100 List of cargoes ...............................................................121

SEC. 16 SPECIAL REQUIREMENTS - ADDITIONAL CLASS................................................................ 122

A. General .............................................................................. 122A 100 Objectives......................................................................122A 200 Application....................................................................122

B. Class Notation NAUTICUS(Newbuilding)......................122B 100 General ..........................................................................122

B 200 Finite element analysis ..................................................122B 300 Fatigue strength assessment ..........................................122

C. Class Notation PLUS-1 and PLUS-2 ...............................122C 100 General ..........................................................................122C 200 Application....................................................................122C 300 Documentation ..............................................................122C 400 Requirements for fatigue life ........................................123

D. Class Notation COAT-1 and COAT-2..............................123D 100 General ..........................................................................123D 200 Application....................................................................123D 300 Documentation ..............................................................123D 400 Requirements for corrosion prevention.........................123D 500 Survey and testing........................................................124

E. Class Notation CSA-2.......................................................124E 100 General ..........................................................................124E 200 Selection of loading conditions.....................................124E 300 Wave load analysis........................................................124E 400 Finite element analysis ..................................................125E 500 Acceptance criteria........................................................125E 600 Hull girder capacity.......................................................126E 700 Fatigue strength assessment ..........................................126

SEC. 17 FATIGUE CONTROL ................................... 127

A. General...............................................................................127A 100 Introduction ...................................................................127A 200 Application....................................................................127A 300 Loads .............................................................................127A 400 Design criteria ...............................................................127A 500 Calculation methods......................................................127

B. Basic Requirements ..........................................................127B 100 Longitudinals ................................................................127

SEC. 18 CORROSION PREVENTION ....................... 128

A. General...............................................................................128A 100 Definitions.....................................................................128A 200 Documentation ..............................................................128

B. Corrosion prevention systems .........................................129B 100 General ..........................................................................129B 200 Coatings ........................................................................129B 300 Cathodic protection .......................................................130

APP. A ELASTIC BUCKLING AND ULTIMATE

STRENGTH ..................................................... 131

A. Introduction.......................................................................131A 100 Scope and description ...................................................131

B. Calculation Procedure......................................................131B 100 Estimation of ultimate stress .........................................131B 200 Calculation of effective width.......................................131B 300 Ultimate load of stiffened panels ..................................131B 400 Ultimate strength of simple girders with stiffened panel

flange.............................................................................131B 500 Ultimate strength of complex girders............................132

Rules for Ships, January 2001Pt.3 Ch.1 Sec.1 –

DET NORSKE VERITAS

SECTION 1GENERAL REQUIREMENTS

A. Classification

A 100 Application

101 The rules in this chapter apply to steel hull structures forassignment of the main class for ships with length 100 metresand above.

102 The rules also apply to aluminium structures and wood-en decks to the extent that these materials are acceptable as al-ternative materials.

A 200 Class notations

201 The class notations applicable for the assignment of themain class are described in Pt.1 Ch.1.

202 The following special features notations are specified inthis chapter:

B. Definitions

B 100 Symbols

101 The following symbols are used:

L = length of the ship in m defined as the distance on thesummer load waterline from the fore side of the stemto the axis of the rudder stock.

L is not to be taken less than 96%, and need not to betaken greater than 97%, of the extreme length on thesummer load waterline. For ships with unusual sternand bow arrangement, the length L will be especiallyconsidered.

F.P. = the forward perpendicular is the perpendicular at theintersection of the summer load waterline with the foreside of the stem. For ships with unusual bow arrange-ments the position of the F.P. will be especially consid-ered.

A.P. = the after perpendicular is the perpendicular at the afterend of the length L.

LF = length of the ship as defined in the International Con-vention of Load Lines:

The length shall be taken as 96 per cent of the totallength on a waterline at 85 per cent of the least mould-ed depth measured from the top of the keel, or as thelength from the fore side of the stem to the axis of therudder stock on that waterline, if that be greater. Inships designed with a rake of keel the waterline onwhich this length is measured shall be parallel to thedesigned waterline.

B = greatest moulded breadth in m, measured at the sum-mer waterline.

D = moulded depth defined as the vertical distance in mfrom baseline to moulded deckline at the uppermostcontinuous deck measured amidships.

DF = least moulded depth taken as the vertical distance in mfrom the top of the keel to the top of the freeboard deckbeam at side.

In ships having rounded gunwales, the moulded depthshall be measured to the point of intersection of themoulded lines of the deck and side shell plating, thelines extending as though the gunwale was of angulardesign.

Where the freeboard deck is stepped and the raised partof the deck extends over the point at which the mould-ed depth is to be determined, the moulded depth shallbe measured to a line of reference extending from thelower part of the deck along a line parallel with theraised part.

T = mean moulded summer draught in m.∆ = moulded displacement in t in salt water (density 1,025

t/m3) on draught T. CB = block coefficient,

=

For barge rigidly connected to a push-tug CB is to becalculated for the combination barge/ push-tug.

C BF = block coefficient as defined in the International Con-vention of Load Lines:

=

∇ = volume of the moulded displacement, excluding boss-ings, taken at the moulded draught TF.

TF = 85% of the least moulded depth.V = maximum service speed in knots, defined as the great-

est speed which the ship is designed to maintain inservice at her deepest seagoing draught.

g0 = standard acceleration of gravity. = 9,81 m/s2

f1 = material factor depending on material strength group.See Sec.2.

tk = corrosion addition as given in Sec.2 D200 and D300,as relevant

x = axis in the ship's longitudinal direction.y = axis in the ship's athwartships direction.z = axis in the ship's vertical direction.E = modulus of elasticity of the material, = 2,06 · 105 N/mm2 for steel = 0,69 · 105 N/mm2 for aluminium alloy.CW = wave load coefficient given in Sec.4 B200.

Amidships = the middle of the length L.

B 200 Terms

201 Linear and angular motions of the ship are defined asfollows:

— surge is the linear motion along the x-axis— sway is the linear motion along the y-axis— heave is the linear motion along the z-axis— roll is the angular motion about the x-axis— pitch is the angular motion about the y-axis— yaw is the angular motion about the z-axis.

202 Moulded deck line, Rounded sheer strake, Sheer strake,and Stringer plate are as defined in Fig. 1.

DAT(-x°C) lowest design ambient temperature (Sec.2 B401)ICM increased corrosion margin (Sec.2 D300)HL(ρ) tanks for heavy liquid (Sec.4 C301)DK(+) decks for heavy cargo (Sec.4 C401)HA(+) hatches for heavy cargo (Sec.4 C401)IB(+) inner bottom strengthened for grab loading and

discharging (Sec.6 H300)

∆1 025 L B T,-----------------------------

∇LF B TF--------------------


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Fig. 1Deck corners

203 The freeboard assigned is the distance measured verti-cally downwards amidships from the upper edge of the deckline to the upper edge of the related load line.

204 The freeboard deck is normally the uppermost completedeck exposed to weather and sea, which has permanent meansof closing all openings in the weather part thereof, and belowwhich all openings in the sides of the ship are fitted with per-manent means of watertight closing. In a ship having a discon-tinuous freeboard deck, the lowest line of the exposed deck andthe continuation of that line parallel to the upper part of thedeck is taken as the freeboard deck. At the option of the ownerand subject to the approval of the Administration, a lower deckmay be designated as the freeboard deck provided it is a com-plete and permanent deck continuous in a fore and aft directionat least between the machinery space and peak bulkheads andcontinuous athwartships. When this lower deck is stepped thelowest line of the deck and the continuation of that line parallelto the upper part of the deck is taken as the freeboard deck.When a lower deck is designated as the freeboard deck, thatpart of the hull which extends above the freeboard deck istreated as a superstructure so far as concerns the application ofthe conditions of assignment and the calculation of freeboard.It is from this deck that the freeboard is calculated.

205 Strength deck is in general defined as the uppermostcontinuous deck. A superstructure deck which within 0,4 Lamidships has a continuous length equal to or greater than

is to be regarded as the strength deck instead of the coveredpart of the uppermost continuous deck.

H = height in m between the uppermost continuous deckand the superstructure deck in question.

Another deck may be defined as the strength deck after specialconsideration of its effectiveness.

206 Double bottom structure is defined as shell plating withstiffeners below the top of the inner bottom and other elementsbelow and including the inner bottom plating. Note that slop-ing hopper tank top side is to be regarded as longitudinal bulk-head.

207 Single bottom structure is defined as shell plating withstiffeners and girders below the upper turn of bilge.

208 Side structure is defined as shell plating with stiffenersand girders between the bottom structure and the uppermostdeck at side.

209 Deck structure is defined as deck plating with stiffeners,girders and supporting pillars.

210 Bulkhead structure is defined as transverse or longitu-dinal bulkhead plating with stiffeners and girders.

Watertight bulkhead is a collective term for transverse bulk-heads required according to Sec.3 A.

Cargo hold bulkhead is a boundary bulkhead for cargo hold.

Tank bulkhead is a boundary bulkhead in tank for liquid cargo,ballast or bunker.

Wash bulkhead is a perforated or partial bulkhead in tank.

211 Forepeak and afterpeak are defined as the areas forwardof collision bulkhead and aft of after peak bulkhead, respec-tively, up to the heights defined in Sec.3 A500.

212 Superstructure

a) A superstructure is a decked structure on the freeboarddeck, extending from side to side of the ship or with theside plating not being inboard of the shell plating morethan 4 per cent of the breadth (B). A raised quarter deck isregarded as a superstructure.

b) An enclosed superstructure is a superstructure with:

i) enclosing bulkheads of efficient construction,

ii) access openings, if any, in these bulkheads fitted withdoors complying with the requirements of Sec.11B101,

iii) all other openings in sides or ends of the superstruc-ture fitted with efficient weathertight means of clos-ing.

A bridge or poop shall not be regarded as enclosed unlessaccess is provided for the crew to reach machinery andother working spaces inside these superstructures by alter-native means which are available at all times when bulk-head openings are closed.

c) The height of a superstructure is the least vertical heightmeasured at side from the top of the superstructure deckbeams to the top of the freeboard deck beams.

d) The length of a superstructure (S) is the mean length of thepart of the superstructure which lies within the length (L).

e) A long forward superstructure is defined as an enclosedforward superstructure with length S equal to or greaterthan 0,25 L.

213 A flush deck ship is one which has no superstructure onthe freeboard deck.

214 Girder is a collective term for primary supporting mem-bers. Tank girders with special names are shown in Fig. 2.

Other terms used are:

— floor (a bottom transverse girder)— stringer (a horizontal girder).

215 Stiffener is a collective term for a secondary supportingmember. Other terms used are:

— frame— bottom longitudinal— inner bottom longitudinal— reversed frame (inner bottom transverse stiffener)— side longitudinal— beam— deck longitudinal— bulkhead longitudinal.

3B2---- H+

� �� m( )


DET NORSKE VERITAS

Fig. 2Tank girders

216 Probability density function f(x). The probability that arealisation of a continuous random variable x falls in the inter-val (x, x+dx) is f(x)dx. f(x) is the derivative of the cumulativeprobability function F(x).

217 Cumulative probability F(x) is defined as:

218 Exceedance probability Q(x) is defined as:

Q(x) = 1 – F(x)

219 Probability of exceedance, or exceedance probabilitymay be illustrated by the following example: x is to be taken ata probability of exceedance of q, means that the variable, x, isto be taken as the value, xq, defined as the upper q quantile inthe long term distribution of x.

220 Quantile. The p quantile may be defined as the value, xp,of a random variable x, which correspond to a fraction p of theoutcomes of the variable.

I.e. xp is the p quantile of the variable x. One may denote xp asthe lower p quantile of x, or alternatively as the upper 1– pquantile of x.

B 300 Ship types

301 A passenger ship is a ship which carries more than 12passengers.

302 A cargo ship is any ship which is not a passenger ship.

303 A tanker is a cargo ship constructed or adapted for thecarriage in bulk of liquid cargoes.

(p quantile of X = Upper p quantile of X

= Lower (1– p) quantile of X)

Fig. 3Probability density function

C. Documentation

C 100 Plans and particulars101 The following plans are normally to be submitted for ap-proval:

— midship section including main particulars (L, B, D, T,CB), maximum service speed V

— deck and double bottom plans including openings— longitudinal section— shell expansion and framing including openings and ex-

tent of flat part of bottom forward— watertight bulkheads including openings— cargo tank structures— deep tank structures— engine room structures including tanks and foundations

for heavy machinery components— afterpeak structures— forepeak structures— superstructures and deckhouses including openings,— hatchways, hatch covers, doors in the ship's sides and ends— supporting structures for containers and container secur-

ing equipment— arrangement of cathodic protection.

Identical or similar structures in various positions should pref-erably be covered by the same plan.

102 Plans and particulars for closing appliances (doors,hatches, windows etc.) to be submitted for approval are speci-fied in Sec.11 A300.

103 Loading guidance information (loading manual andloading computer system) is to be approved and certified in ac-cordance with Sec.5 F.

104 The following plans are to be submitted for information:

— general arrangement— engine room arrangement— tank arrangement— capacity plan— body plan, hydrostatic curves or tables.

105 For instrumentation and automation, including compu-ter based control and monitoring, see Pt.4 Ch.9 Sec.1.

F x( ) f x( ) xd∞–

x

�=

F xp( ) f x( ) xd∞–

xp� p= =


DET NORSKE VERITAS

C 200 Specifications and calculations201 All longitudinal strength calculations are to be submittedwith relevant information:

— maximum stillwater bending moments and shear forces asdefined in Sec.5 B102

— still water bending moment limits— mass of light ship and its longitudinal distribution— buoyancy data— cargo capacity in t— cargo, ballast and bunker distribution, including maxi-

mum mass of cargo (t) in each compartment.

202 Information which may be necessary for local strengthcalculations:

— minimum and maximum ballast draught and correspond-ing trim

— load on deck, hatch covers and inner bottom— stowage rate and angle of repose of dry bulk cargo— maximum density of intended tank contents— height of air pipes— mass of heavy machinery components— design forces for securing devices on hatch covers and ex-

ternal doors— design forces for cargo securing and container supports— any other local loads or forces which will affect the hull

structure.

203 Specifications for corrosion prevention systems for wa-ter ballast tanks, comprising selection, application and mainte-nance, are to be submitted for as defined in Sec.18.

C 300 Specific purpose documentation301 For hull equipment and appendages, see Ch.3.

302 For additional class notations, see Pt.5 and Pt.6.

303 For installations for which no notation is available or re-quested, all relevant information or documentation affectinghull structures or ship safety is to be submitted.

D. Structural and Tightness Testing

D 100 Definitions101 The following terms are used in D:

Structural testing is a hydrostatic test, carried out in order todemonstrate the tightness of the tanks and the structural ade-quacy of the design. Where practical limitations prevail andhydrostatic testing is not feasible, hydropneumatic testing maybe carried out instead.

Leak testing is an air or other medium test, carried out in orderto demonstrate the tightness of the structure.

Hydropneumatic testing is a combination of hydrostatic and airtesting, carried out in order to demonstrate the tightness of thetanks and the structural adequacy of the design.

Hose testing is a water test carried out to demonstrate tightnessof structural items.

Shop primer is a thin coating applied after surface preparationand prior to fabrication as a protection against corrosion duringfabrication.

Protective coating is a final coating protecting the structurefrom corrosion.

Watertight means capable of preventing the passage of waterthrough the structure under a head of water for which the sur-rounding structure is designed.

Weathertight means that in any sea conditions water will notpenetrate into the ship.

D 200 General requirements

201 Structural testing may be carried out after a protectivecoating has been applied, provided a leak test is carried out be-fore application of the protective coating. All pipe connectionsto tanks are to be fitted before structural testing.

When structural testing at the building berth is undesirable orimpossible, structural testing afloat may be accepted. Thestructural testing is to be carried out by filling each tank sepa-rately to the test head. Examination of bottom and lower sidestructures is to be made in empty tanks at the maximum prac-tical attainable draught.

202 Leak testing is to be carried out prior to the protectivecoating being applied to the welds. Shop primer may be ap-plied to welds.

An efficient indicating liquid is to be applied, when air is usedas the test medium. The air pressure is to be at a maximum of20 kN/m² and is to be reduced to a smaller value before inspec-tion. In addition to an effective means of reading the air pres-sure, a safety valve, or a reliable equivalent alternative, is to beconnected to the compartment being tested.

Guidance note:Silicate based shop primer may be applied to welds before leaktesting. The layer of the primer is to be maximum 50 microns.Other primers of uncertain chemical composition are to be max-imum 30 microns.

---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---

203 For hose testing, the hose pressure is to be at least 200kN/m2 and applied at a maximum distance of 1.5 m. The noz-zle inside diameter is to be at least 12.0 mm.

D 300 Specific requirements for extent and type of test-ing

301 The requirements in 302 and 303 give conditions fortesting for:

— gravity tanks included independent tanks of 5 m3 or morein capacity

— watertight or weathertight structures.

302 Leak testing is to be carried out on all weld connectionson tank boundaries, pipe penetrations and erection welds ontank boundaries except welds made by automatic processes.Selected locations of automatic erection welds and pre-erec-tion manual or automatic welds may be required to be similarlytested at the discretion of the surveyor taking account of thequality control procedures operating in the shipyard.

303 Extent of testing is given in Table D1.

For Tanker for Liquefied Gas, additional requirements aregiven in Pt.5 Ch.5.


DET NORSKE VERITAS

Table D1 Extent of testing

Item to be tested Type of testing Structural test pressure Extent of structural testingAll ship typesTanks containing liquid and the structures forming boundaries of tanks containing liquid

Structural testing The greater of the following:

— head of water up to top of overflow

— 2.4 m head of water above highest point of tank

— pressure valve opening pres-sure

Tank boundary tested from at least one side 1), 2)

Test of aft peak tank to be carried out after the stern tube has been fitted.

Fore peak not used as tank See SOLAS Reg. II-1/14After peak not used as tank Leak testingChain locker (if aft of collision bulkhead)

Structural testing Head of water up to top

Double plate rudders Leak testingWatertight doors below freeboard or bulkhead deck and watertight hatch covers

See SOLAS Reg. II-1/18 Each door and hatch cover 7)

Weathertight doors, hatch covers, and closing appliances

Hose testing

Watertight bulkheads and decks See SOLAS Reg. II-1/14.3 and II-1/19.5

3), 5), 6)

Ballast ducts Structural testing Ballast pump maximum pressureTrunks, tunnels and ventilators Hose test. See SOLAS Reg. II-1/

19.56)

Cofferdams Structural testing The greater of the following:



4)

Independent tanks Structural testing The greater of the following:




Dry bulk cargo carrierBallast holds Structural testing The greater of the following:



1), 2)

In the structural testing, a minor amount of water leakage from hatch cover sealing may be al-lowed.


DET NORSKE VERITAS

E. Ships Built for In-Water Survey

E 100 General101 For vessels built in accordance with the following re-quirements it will be accepted that every alternate bottom sur-vey is carried out with the ship afloat.

E 200 Rudder201 Bearing materials are to be stainless steel, bronze or anapproved type of synthetic material and are to satisfy the re-quirements in Ch.3 Sec.2.

202 Arrangements are to be made for measuring of ruddershaft and pintle clearances.

E 300 Tailshaft301 The tailshaft is to be fitted with an approved oil box.

Combination carriers (OBOs)Watertight hatch covers of cargo tanks

Structural testing The greater of the following:


— 2.4 m head of water above hatch coaming


At least every second hatch cov-er, provided that leak testing is carried out for all hatch covers.

Chemical carriersIntegral and independent cargo tanks

Structural testing 1) Integral and independent tanks with a design pressure of less than 0.7 bar, the great-er of the following:

— 2.4 m head of water above the highest point of the tank

— pressure valve opening pressure.

2) Independent tanks with a de-sign pressure exceeding 0.7 bar are to be tested to 1.5 times the pressure valve opening pressure.

Tank boundary tested from at least one side 1), 2)

1) Except for cargo space boundaries of Tanker for Chemical ESP, leak or hydropneumatic testing may replace structural testing, provided that at least one tank of each type is structurally tested.

2) Structural testing need not be repeated for subsequent vessels in a series of identical newbuildings, unless surveyors deem the repetition necessary. This relaxation does not apply to cargo space boundaries for vessels with any of the following notations Tanker for Oil ESP, Tanker for Oil ProductsESP, Bulk Carrier or Tanker for Oil ESP, Ore Carrier or Tanker for Oil ESP and Tanker for Chemicals ESP.

3) When a hose test cannot be performed without possible damage to outfitting (machinery, cables, switchboards, insulation, etc.) already installed, it may be replaced, at the Society's discretion, by a careful visual inspection of all the crossings and welded joints; where necessary, dye penetrant test, leak test or an ultrasonic leak test may be required.

4) Leak or hydropneumatic testing may be accepted under the conditions specified under 301 when, at the Society's discretion, the latter is considered significant in relation to the construction techniques and the welding procedures adopted.

5) Testing main compartments (not tanks for liquids) by filling them with water is not compulsory. When such testing is not carried out, a hosetest is compulsory. This test is to be carried out in the most advanced stage of the fitting out of the ship. In any case, a thorough inspectionof the watertight bulkheads is to be carried out.(SOLAS, Reg. II-1/14.3)

6) After completion, a hose or flooding test is to be applied to watertight decks and a hose test to watertight trunks, tunnels and ventilators.(SOLAS Reg. II-1/19.5)

7) Before installation (i.e. normally at the manufacturers) the watertight access doors/hatches are to be hydraulically tested from that side which is most prone to leakage. Test pressure = design pressure. Acceptance criteria:

— doors or hatches with gaskets: No leakage— doors or hatches with metallic sealing: Maximum water leakage 1 litre per minute.

Table D1 Extent of testing (Continued)


DET NORSKE VERITAS

SECTION 2MATERIALS AND MATERIAL PROTECTION

A. General

A 100 Introduction

101 In this section requirements regarding the application ofvarious structural materials as well as protection methods andmaterials are given.

A 200 Material certificates

201 Rolled steel and aluminium for hull structures are nor-mally to be supplied with DNV's material certificates in com-pliance with the requirements given in Pt.2.

202 Requirements for material certificates for forgings, cast-ings and other materials for special parts and equipment arestated in connection with the rule requirements for each indi-vidual part.

B. Hull Structural Steel

B 100 General

101 Where the subsequent rules for material grade are de-pendent on plate thickness, the requirements are based on thethickness as built.

Guidance note:

Attention should be drawn to the fact when the hull plating is be-ing gauged at periodical surveys and the wastage considered inrelation to reductions allowed by the Society, such allowed re-ductions are based on the nominal thicknesses required by therules.

The under thickness tolerances acceptable for classification areto be seen as the lower limit of a total «minus-plus» standardrange of tolerances which could be met in normal productionwith a conventional rolling mill settled to produce in average thenominal thickness.

However, with modern rolling mills it might be possible to pro-duce plates to a narrow band of thickness tolerances which couldpermit to consistently produce material thinner than the nominalthickness, satisfying at the same time the under thickness toler-ance given in Pt.2 Ch.2 Sec.1.

Therefore in such a case the material will reach earlier the mini-mum thickness allowable at the hull gaugings.

It is upon the shipyard and owner, bearing in mind the above sit-uation, to decide whether, for commercial reasons, stricter underthickness tolerances are to be specified in the individual cases.


B 200 Material designations and classes

201 Hull materials of various strength groups will be re-ferred to as follows:

— NV-NS denotes normal strength structural steel with yieldpoint not less than 235 N/mm2

— NV-27 denotes high strength structural steel with yieldpoint not less than 265 N/mm2



— NV-40 denotes high strength structural steel with yieldpoint not less than 390 N/mm2.

Normal and high strength steel may also be referred to as NS-steel and HS-steel respectively.

202 Hull materials of various grades will be referred to asfollows:

— A, B, D and E denotes NS-steel grades— AH, DH and EH denotes HS-steel grades. HS-steel may

also be referred to by a combination of grade and strengthgroup. In that case the letter H is substituted by one of thenumbers indicated in 201, e.g. A 36-steel.

203 The material factor f1 included in the various formulaefor scantlings and in expressions giving allowable stresses, isdependent on strength group as follows:

— for NV-NS: f1=1,00— for NV-27: f1=1,08— for NV-32: f1=1,28— for NV-36: f1=1,39— for NV-40: f1=1,43.

For a 34-steel (with yield point not less than 335 N/mm2) thematerial factor may be taken as f1 = 1,35.

204 In order to distinguish between the material grade re-quirements for different hull parts, various material classes areapplied as defined in Table B1.

B 300 Basic requirements

301 Materials in the various longitudinal strength membersare not to be of lower grades than those corresponding to thematerial classes given in Table B2.

For strength members not mentioned in Table B2, Class I maybe applied.

Single strakes required to be of class IV and V or of grade E/EH are within 0,4 L amidships to have breadths not less than(800 + 5 L) mm, maximum 1800 mm.

302 Materials in local strength members are not to be of low-er grades than those corresponding to the material class I.However, for heavy foundation plates in engine room, grade Amay also be accepted for NS-steel with thickness above 40mm.

Materials in heavily stressed (nominal tensile or shear stressesabove 80 f1 N/mm2) local foundations and supporting struc-

Table B1 Material classesThickness in mm

ClassI II III IV V

t ≤ 15 A/AH A/AH A/AH A/AH D/DH15 < t ≤ 20 A/AH A/AH A/AH B/AH E/DH20 < t ≤ 25 A/AH A/AH B/AH D/DH E/EH25 < t ≤ 30 A/AH A/AH D/DH E/DH E/EH30 < t ≤ 35 A/AH B/AH D/DH E/EH E/EH35 < t ≤ 40 A/AH B/AH D/DH E/EH E/EH40 < t ≤ 50 B/AH D/DH E/EH E/EH E/EH


DET NORSKE VERITAS

tures (e.g. crane foundations) at weather deck are to be of ClassIII.

(IACS UR S6)

303 For materials in:

— hull equipment and appendages (sternframes and rudders,anchoring and mooring equipment, masts and rigging,crane pedestals etc.), see Ch.3

— structure and equipment related to additional class nota-tions, see Pt.5 and Pt.6

— hull structures related to installations for which no nota-tion is available or requested, these will be considered andnotation requirements usually maintained.

B 400 Requirements for low air temperatures (special features notation DAT(-x°C))401 In ships intended to operate for longer periods in areaswith low air temperatures (i.e. regular service during winter toArctic or Antarctic waters), the materials in exposed structureswill be specially considered.

In that case the notation DAT(–x°C) will be assigned, indicat-ing the lowest design ambient air temperature applied as basisfor approval.

Design ambient temperature is considered to be comparablewith the lowest monthly isotherm in the area of operation.

402 For materials subjected to low temperature cargoes, seePt.5 Ch.5 Sec.2 and Pt.5 Ch.10 Sec.2 .

B 500 Material at cross-joints501 In important structural cross-joints where high tensilestresses are acting perpendicular to the plane of the plate, spe-cial consideration will be given to the ability of the plate mate-

rial to resist lamellar tearing. For a special test, see Pt.2 Ch.2Sec.1.

C. Alternative Structural Materials

C 100 Aluminium

101 Aluminium alloy for marine use may be applied in su-perstructures, deckhouses, hatch covers, hatch beams and sun-dry items, provided the strength of the aluminium structure isequivalent to that required for a steel structure.

102 For rolled products taking part in the longitudinalstrength, alloys marked A are to be used. The alloy is to be cho-sen considering the stress level concerned.

103 In weld zones of rolled or extruded products (heat affect-ed zones) the mechanical properties given for extruded prod-ucts may in general be used as basis for the scantlingrequirements.

Note that for the alloy NV-A1MgSil the most unfavourableproperties corresponding to -T4 condition are to be used.

104 Welding consumables giving a deposit weld metal withmechanical properties not less than those specified for the weldzones of the parent material are to be chosen.

105 The various formulae and expressions involving the fac-tor f1 may normally also be applied for aluminium alloyswhere:

s f = yield stress in N/mm2 at 0,2% offset, σf is not to be tak-en greater than 70% of the ultimate tensile strength.

For minimum thickness requirements not involving the factorf1 the equivalent minimum value for aluminium alloys maynormally be obtained when the requirement is divided by .

106 For aluminium structures earthing to steel hull is to be inaccordance with Pt.4 Ch.8.

C 200 Stainless steel

201 For clad steel and solid stainless steel due attention is tobe given to the reduction of strength of stainless steel with in-creasing temperature.

For austenitic stainless steel and steel with clad layer of auste-nitic stainless steel the material factor f1 included in the vari-ous formulae for scantlings and in expressions givingallowable stresses is given in 202 and 203.

202 For austenitic stainless steel the material factor f1 can betaken as:

σf = yield stress in N/mm2 at 0,2% offset and temperature+20°C (σ0,2).

t = cargo temperature in °C.

For end connections of corrugations, girders and stiffeners thefactor is due to fatigue not to be taken greater than:

f1 = 1,21 – 3,2 (t – 20) 10–3

203 For clad steel the material factor f1 can be taken as:

Table B2 Application of the material classesStructural member Within 0,4 L

amidshipsOutside 0,4 L

amidshipsLower strake in longitudinal bulkhead. Deck plating exposed to weather, in general. Side plating.

II I

Bottom plating including keel plate. Strength deck plating. 1) Continuous longitudinal members above strength deck excluding longitudinal hatch coamings. Upper strake in longitudinal bulkhead. Upper strake in top wing tank.

III I

Sheer strake at strength deck. 2) Stringer plate in strength deck. 2) Deck strake at longitudinal bulkhead. 3) Bilge strake. 4) Continuous longitudinal hatch coamings 5)

IVIII

(II outside 0,6 L)

1) Plating at corners of large hatch openings to be specially considered. Class IV or V to be applied in positions where high local stresses may occur. Normally class IV will be required for ordinary dry cargo and bulk carriers, class V for open type bulk carriers and container vessels.

2) Not to be less than grade E/EH within 0,4 L amidships in ships with length exceeding 250 m. Within the cargo hold length of container ships, class III to be applied also outside 0,6 L.

3) In ships with breadth exceeding 70 m, at least 3 deck strakes to be class IV.

4) May be of class III in ships with a double bottom over the full breadth and with length less than 150 m. Not to be less than D/DH in ships with length exceeding 250 m.

5) Not to be less than grade D/DH.

f1

σf

235---------=

f1

f1 3 9, t 20–650

-------------+� �� σf 4 15 t 20–( ), 220+– 10

3–=

f1

1 67σf, 1 37t,–

1000------------------------------------- 41 5 σf b

0 7,–,– 1 6,+=


DET NORSKE VERITAS

σ f = yield stress in N/mm2 at 0,2% offset of material inclad layer and temperature +20°C (σ0,2).

σ fb = yield strength in N/mm2 of base material.t = cargo temperature in °C.

f1 is in no case to be taken greater than that given for the basematerial in B203.

The calculated factor may be used for the total plate thickness.

204 For ferritic-austenitic stainless steel the material factorwill be specially considered in each case.

Guidance note:For ferritic-austenitic stainless steels with yield stress 450 N/mm2, the following material factor will normally be accepted:

For end connection of corrugations, girders and stiffeners thefactor should due to fatigue not be taken greater than:

For intermediate temperatures linear interpolation may be ap-plied for the f1 factor.


D. Corrosion Additions for Steel Ships

D 100 General

101 In tanks for cargo oil and/or water ballast the scantlingsof the steel structures are to be increased by corrosion additionsas specified in 200. In the following cargo oil will be used asa collective term for liquid cargoes which may be carried by oilcarriers (see list of cargoes in appendix to Pt.5 Ch.3).

D 200 Corrosion additions

201 Plates, stiffeners and girders in tanks for water ballastand/or cargo oil and of holds in dry bulk cargo carriers are tobe given a corrosion addition tk as stated in Table D1.

202 For members within or being part of the boundary oftanks for ballast water only, for which a corrosion protectionsystem according to 203 is not fitted, the magnitude of the cor-rosion addition tk is subject to special consideration.

203 It is assumed that tanks for ballast water only are protect-ed by an effective coating or an equivalent protection system.

D 300 Class notation ICM (Increased Corrosion Mar-gin)

301 For the main class a corrosion addition tk in mm as givenin Table D1 is added to the reduced scantlings in ballast tanks,cargo oil tanks and cargo holds in bulk cargo carriers as spec-ified in 200.

For an additional class notation ICM a further corrosion addi-tion tc in mm will be added in ballast tanks, cargo oil tanks andcargo holds in bulk cargo carriers. The following class nota-tions may be chosen:

or combinations of these notations as e.g. ICM(BT/CTu)meaning all ballast tanks and upper part (above D/2) of all car-go oil tanks where:

BT All ballast tanks.CT All cargo oil tanks.CH All cargo holds in the bulk carrier.u Upper part of the ship (above D/2).s Strength deck of the ship and 1,5 m below.

The practical procedure in applying tc in the rule scantling for-mula is outlined in the following items.

The corrosion addition tc in mm is defined in Table D2.

302 The hull girder actual section modulus is to be based onthe thickness t of plating, and web and flanges of stiffeners andgirders taken as:

t = tactual – tc (mm).

303 The local scantlings of plates, stiffener webs/flanges andgirder web/flanges where formulae are given in the rules withthe corrosion addition (tk), the total addition is to be taken as:

t´k = tk + tc (mm).

304 For stiffeners where formulae are given in the rules withthe wk increase in section modulus for compensation of thecorrosion addition (tk), the wk need not be additionally adjust-ed for the corrosion addition (tc).

305 For web frames and girder systems where scantlings arebased on a direct strength analysis, the allowable stresses in therules are given with reference to reduced scantlings. The re-duced thickness used in such analysis is to be:

treduced = tactual – (tk + tc) (mm).

306 The throat thickness of continuous and intermittent filletwelding is given in Sec.12 with an addition of 0,5 tk mm. Thetotal corrosion addition is to be taken as:

f1 = 1,6 at + 20°C= 1,36 at + 85°C

f1 = 1,39 at + 20°C= 1,18 at + 85°C

ICM(BT), ICM(BTu), ICM(BTs) for ballast tanksICM(CT), ICM(CTu), ICM(CTs) for cargo oil tanks

ICM(CH), ICM(CHu), ICM(CHs) for cargo holds in bulk carriers

Table D1 Corrosion addition tk in mm

Internal members and plate boun-dary between spaces of the given category

Tank/hold regionWithin 1,5 m below weather

deck tank or hold top

Elsewhere

Ballast tank 1) 3,0 1,5Cargo oil tank only 2,0 1,0 (0) 2)

Hold of dry bulk cargo carriers 4) 1,0 1,0 (3) 5)

Plate boundary between given space categories

Tank/hold regionWithin 1,5 m below weather

deck tank or hold top

Elsewhere

Ballast tank 1)/Cargo oil tank only 2,5 1,5 (1,0) 2)

Ballast tank 1)/Hold of dry bulk cargo carrier 4) 2,0 1,5

Ballast tank 1)/Other category space 3) 2,0 1,0

Cargo oil tank only/ Other cate-gory space 3) 1,0 0,5 (0) 2)

Hold of dry bulk cargo carrier 4)

/Other category space 3) 0,5 0,5

1) The term ballast tank also includes combined ballast and cargo oil tanks, but not cargo oil tanks which may carry water ballast according to Regulation 13(3), of MARPOL 73/78, see Pt.7 Ch.4 App.B B100.

2) The figure in brackets refers to non-horizontal surfaces.

3) Other category space denotes the hull exterior and all spaces other than water ballast and cargo oil tanks and holds of dry bulk cargo carriers.

4) Hold of dry bulk cargo carriers refers to the cargo holds, including bal-last holds, of vessels with class notations Bulk Carrier and Ore Car-rier, see Pt.5 Ch.2 Sec.5.

5) The figure in brackets refers to webs and bracket plates in lower part of main frames in bulk carrier holds.


DET NORSKE VERITAS

(0,5 t´k) = 0,5 (tk + tc) (mm). 307 The additional corrosion thickness tc is to be given in thedesign drawings in the form of a general note.

Guidance note:Example: Marking on the design drawing:ICM( ) Plating , mm Stiffeners web/flange , mm Girders web/flange , mm


Table D2 Corrosion addition tc in mm

Internal members and plate boundary between spaces of the given cat-egory

Tank/hold regionWithin 1,5 m

below weather deck tank or hold

top

Elsewhere

Ballast tank 1) 3,0 1,5Cargo oil tank only 2,0 1,0Hold of dry bulk cargo carriers 3) 1,0 1,0

Plate boundary between given space categories 4)

Tank/hold regionWithin 1,5 m

below weather deck tank or hold

top

Elsewhere

Ballast tank 1)/Cargo oil tank only 2,5 1,5Ballast tank 1)/Hold of dry bulk cargo carrier 3) 2,0 1,5

Ballast tank 1)/Other category space 2) 2,0 1,0

Cargo oil tank only/ Other category space 2) 1,0 0,5

Hold of dry bulk cargo carrier 3)

/Other category space 2) 0,5 0,5

1) The term ballast tank also includes combined ballast and cargo oil tanks, but not cargo oil tanks which may carry water ballast according to Regulation 13(3), of MARPOL 73/78, see Pt.7 Ch.4 App.B B100.

2) Other category space denotes the hull exterior and all spaces other than water ballast and cargo oil tanks and holds of dry bulk cargo carriers.

3) Hold of dry bulk cargo carriers refers to the cargo holds, including bal-last holds, of vessels with class notations Bulk Carrier and Ore Car-rier, see Pt.5 Ch.2 Sec.5.

4) For vessels with the notation ICM(BT), ICM(BTu) or ICM(BTs), car-go oil tanks and holds of dry bulk cargo carriers may be treated as "other category space".


DET NORSKE VERITAS

SECTION 3DESIGN PRINCIPLES

A. Subdivision and Arrangement

A 100 General

101 The hull is to be subdivided into watertight compart-ments.

Guidance note:The following requirements are considered to meet the relevantregulations of the International Convention on Load Lines, 1966and SOLAS 1974 as amended. Attention should, however, begiven to possible additional requirements of the Maritime Au-thorities in the country in which the ship is to be registered.

For passenger ships see Pt.5 Ch.2 Sec.2.

For dry cargo ships see also Pt.5 Ch.2 Sec.8.


A 200 Definitions.

201 Symbols:

LF = length in m as defined in Sec.1 BPF = perpendicular coinciding with the foreside of the stem

on the waterline on which LF is measured.

For ships with unconventional stem curvatures, e.g. abulbous bow protuding the waterline, the position ofPF will be specially considered

H = height of superstructure in mDF = least moulded depth to the freeboard deck in m as de-

fined in Sec.1 B.

A 300 Number of transverse watertight bulkheads.

301 The following transverse, watertight bulkheads are to befitted in all ships:

— a collision bulkhead — an after peak bulkhead— a bulkhead at each end of the machinery space(s).

302 For ships without longitudinal bulkheads in the cargo re-gion, the total number of watertight transverse bulkheads isnormally not to be less than given in Table A1.

303 After special consideration of arrangement and strength,the number of watertight bulkheads may be reduced. The actu-al number of watertight bulkheads will be entered in the «Reg-ister of Vessels classed with DNV».

304 Barges are to have a collision bulkhead and an after endbulkhead.

305 If the barge has discharging arrangements in the bottom,the regions having such bottom openings are to be bounded bywatertight transverse bulkheads from side to side.

A 400 Position of collision bulkhead

401 For passenger ships, see Pt.5 Ch.2 Sec.2 B200.

402 For cargo ships the distance xc from the perpendicularPF to the collision bulkhead is to be taken between the follow-ing limits:

xc (maximum) = 0,08 LF – xr (m)

For ships with ordinary bow shape:

xr = 0

For ships having any part of the underwater body extendingforward of PF, such as a bulbous bow, xr is to be taken as thesmallest of:

xr = 0,5 xb (m)

xr = 0,015 LF (m)

xr = 3,0 (m)

xb = distance from PF to the forward end of the bulbousbow, see Fig. 1.

Fig. 1Bulbous bow shape

403 An increase of the maximum distance given by 401 maybe acceptable upon consideration in each case, provided afloatability and stability calculation shows that, with the shipfully loaded to summer draught on even keel, flooding of thespace forward of the collision bulkhead will not result in anyother compartments being flooded, nor in an unacceptable lossof stability.

404 Minor steps or recesses in the collision bulkhead may beaccepted, provided the requirements to minimum and maxi-mum distances from PF are complied with.

405 In ships having a visor or doors in the bow and a slopingloading ramp forming part of the collision bulkhead above thefreeboard deck, that part of the closed ramp which is more than2,30 m above the freeboard deck may extend forward of thelimits specified in 401, see Fig. 2.

Table A1 Number of transverse bulkheads

Ship length in mEngine room

Aft Elsewhere85 < L ≤ 105 4 5

105 < L ≤ 125 5 6125 < L ≤ 145 6 7145 < L ≤ 165 7 8165 < L ≤ 190 8 9190 < L ≤ 225 9 10

L > 225 specially considered

xc (minimum) = 0,05 LF – xr (m) for LF < 200 m= 10 – xr (m) for LF ≥ 200 m


DET NORSKE VERITAS

Fig. 2Bow visor or door

The ramp is to be arranged for weathertight closing over itscomplete length.

The distance xk in Fig. 2 is not to be less than the minimum val-ue of xc as given in 401.

406 For barges the position of the collision bulkhead is tosatisfy the minimum requirement to xc as given in 401.

A 500 Height of watertight bulkheads

501 The watertight bulkheads are in general to extend to thefreeboard deck. Afterpeak bulkheads may, however, terminateat the first watertight deck above the waterline at draught T.

For an afterpeak bulkhead also being a machinery bulkhead,see 503.

502 For ships having complete or long forward superstruc-tures, the collision bulkhead is to extend weathertight to thenext deck above the freeboard deck. The extension need not befitted directly over the bulkhead below, provided the require-ments for distances from PF are complied with, and the part ofthe freeboard deck forming the step is made weathertight.

503 Bulkheads are to be fitted separating the machineryspace from cargo and passenger spaces forward and aft andmade watertight up to the freeboard deck. Afterpeak/machin-ery space bulkheads may terminate as given in 501 when theaft space is not utilised for cargo or passengers.

For ships without a long forward superstructure and for whichthe collision bulkhead has not been extended to the next deckabove the freeboard deck, any openings within the forward su-perstructure giving access to spaces below the freeboard deck,are to be made weathertight.

504 For ships with a continuous deck below the freeboarddeck and where the draught is less than the depth to this seconddeck, all bulkheads except the collision bulkhead may termi-nate at the second deck. In such cases the engine casing be-tween second and upper deck is to be arranged as a watertightstructure, and the second deck is to be watertight outside thecasing above the engine room.

505 In ships with a raised quarter deck, the watertight bulk-heads within the quarter deck region are to extend to this deck.

A 600 Opening and closing appliances.

601 Openings may be accepted in watertight bulkheads, ex-cept in that part of the collision bulkhead which is situated be-low the freeboard deck. However, See also 605.

602 Openings situated below the freeboard deck and whichare intended for use when the ship is at sea, are to have water-tight doors, which are to be closeable from the freeboard deckor place above the deck. The operating device is to be well pro-tected and accessible.

603 Watertight doors are accepted in the engine room 'tweendeck bulkheads, provided a signboard is fitted at each doorstipulating that the door be kept closed while the ship is at sea.

This assumption will be stated in the appendix to classificationcertificate.

604 Openings in the collision bulkhead above the freeboarddeck are to have weathertight doors or an equivalent arrange-ment. The number of openings in the bulkhead are to be re-duced to the minimum compatible with the design and normaloperation of the ship.

605 No door, manhole or ventilation duct or any other open-ing will be accepted in the collision bulkhead below the free-board deck.

The collision bulkhead may, however, be pierced by necessarypipes to deal with fluids in the forepeak tank, provided thepipes are fitted with valves capable of being operated fromabove the freeboard deck. The valves are generally to be fittedon the collision bulkhead inside the forepeak. The valves maybe fitted on the after side of the bulkhead provided that thevalves are readily accessible under all service conditions andthe space in which they are located is not a cargo space. Seealso Pt.4 Ch.6 Sec.3 A300.

A 700 Cofferdams and tank contents

701 The following dedicated tank types are to be separatedfrom each other by cofferdams:

— tanks for mineral oil— tanks for vegetable oil— tanks for fresh water.

A 800 Forward compartment contents

801 In ships of 400 gross tonnage and above, compartmentsforward of the collision bulkhead are not to be arranged forcarriage of oil or other liquid substances which are flammable.

A 900 Minimum bow height

For requirements to minimum bow height, see Ch.5 Sec.3M100.

A 1000 Access to and within narrow ballast tanks

1001 Vessels, except those exclusively intended for the car-riage of containers, are to comply with 1002.

1002 Narrow ballast tanks (such as double-skin construc-tion) are to be provided with permanent means of access, suchas fixed platforms, climbing/foothold rails, ladders etc., sup-plemented by limited portable equipment to give safe and prac-tical access to the internal structure for adequate inspection,including close-up survey as defined in Pt.7 Ch.2 Sec.3 F.

Guidance note:

In order to obtain a practical arrangement it is recommended toprovide for a fixed platform spacing of 3 to 5 metres.


A 1100 Steering gear compartment

1101 The steering gear compartment shall be readily acces-sible and separated from machinery spaces.

(SOLAS Reg. II-1/29.13.1)


DET NORSKE VERITAS

B. Structural Design Principles

B 100 Design procedure

101 Hull scantlings are in general based on the two designaspects, load (demand) and strength (capability). The probabil-ity distribution for the load and the strength of a given structuremay be as illustrated in Fig. 3.

Fig. 3Probability distribution

The rules have established design loads corresponding to theloads imposed by the sea and the containment of cargo, ballastand bunkers. The design loads are applicable in strength for-mulae and calculation methods where a satisfactory strengthlevel is represented by allowable stresses and/or usage factors.

102 The elements of the rule design procedure are shown inFig. 4 and further described in the following.

B 200 Loading conditions

201 Static loads are derived from loading conditions submit-ted by the builder or standard conditions prescribed in therules. The standard conditions are expected to give suitableflexibility with respect to the loading of ordinary ship types.

202 Unless specifically stated, dry cargoes are assumed to begeneral cargo or bulk cargo (coal, grain) stowing at 0,7 t/m3.Liquid cargoes are assumed to have density equal to or lessthan that of seawater.

203 Unless especially stated to be otherwise, or by virtue ofthe ship's class notation (e.g. Container Carrier) or the ar-rangement of cargo compartments, the ship's cargo and ballastconditions are assumed to be symmetric about the centreline.For ships for which unsymmetrical cargo or ballast condi-tion(s) are intended, the effect of this is to be considered in thedesign.

204 The determination of dynamic loads is based on longterm distribution of motions that the ship will experience dur-ing her operating life. The operating life is normally taken as20 years, considered to correspond to a maximum wave re-sponse of 10-8 probability of exceedance in the North Atlantic.Any pertinent effects of surge, sway, heave, roll, pitch and yawin irregular seas are considered. A uniform probability is nor-mally assumed for the occurrence of different ship-to-waveheading angles.

The effects of speed reduction in heavy weather are allowedfor.

Wave-induced loads determined according to accepted theo-ries, model tests or full scale measurements may be acceptedas equivalent basis for classification.

Fig. 4Rule design procedure for ships

B 300 Hull girder strength

301 A minimum strength standard determined by the sectionmodulus at bottom and deck is required for the hull girdercross-section amidships.


DET NORSKE VERITAS

B 400 Local bending and shear strength

401 For plating exposed to lateral pressure the thickness re-quirement is given as function of nominal allowable bendingstress as follows:

C = factor depending on boundary conditions of plate field,normally taken as 15,8 for panels with equally spacedstiffeners.

ka = correction factor for aspect ratio of plate field = (1,1 – 0,25 s/ l)2

= maximum 1,0 for s/ l = 0,4 = minimum 0,72 for s/ l = 1,0s = stiffener spacing in m. l = stiffener span in m.p = design lateral pressure in kN/m2.

The nominal allowable bending stressσ (in N/mm2) is to bechosen so that the equivalent stress at the middle of the platefield will not exceed specified limits corresponding to the de-sign pressure.

The equivalent stress is defined as:

σ1 and σ2 are normal stresses perpendicular to each other.

τ is the shear stress in the plane of σ1 and σ2.

402 For stiffeners exposed to lateral pressure, the sectionmodulus requirement is given as function of boundary condi-tions and nominal allowable bending stress.

The boundary conditions are included in a bending momentfactor. The bending moment factor corresponds to m in the fol-lowing expression:

M is the expected bending moment.

q = pbp = as specified in 401b = effective load breadth of stiffener in m, for uniform

pressure equal to stiffener spacing s l = the length of the member in m.

m-values normally to be applied are given separately for eachof the local structures.

For elastic deflections the m-value is derived directly fromgeneral elastic bending theory. In Table B1 m-values are givenfor some defined load and boundary conditions.

For plastic-elastic deflections the m-value is derived accordingto the following procedure:

— the pressure is increased until first yield occurs at one orboth ends

— the pressure is further increased, considering yielding endsas simple supports.

This procedure involves a built-in safety in that the bendingmoment at a yielding support is not increased beyond the valuecorresponding to first yield.

The nominal allowable bending stress is combined with possi-ble axial stresses so that the maximum normal stress will notexceed specified limits corresponding to the design pressure.

The sectional area requirement is given as a function of bound-ary conditions and nominal allowable shear stress.

The boundary conditions are included in a shear force factor,defined as ks in the following expression:

Q = ks P

Q is the expected shear force.

P is the total load force on the member.

ks-values normally to be applied are given separately for eachof the local structures.

In Table B1 ks-values are given for some defined load andboundary conditions.

403 Direct strength formulae for girders are limited to simplegirders. The boundary conditions and the nominal allowablestresses are given in a similar way as for stiffeners.

For girder systems the stress pattern is assumed to be derivedby direct computerised calculations. Allowable stresses corre-sponding to specified pressure combinations and indicatedmodel fineness are given for the most common structural ar-rangements.

B 500 Buckling strength

501 Requirements for structural stability are given to preventbuckling or tripping of structural elements when subjected tocompressive stresses and shear stresses.

The critical buckling stress is to be checked for the variousstrength members based on general elastic buckling formulae,corrected in the plastic range. For plate elements subject to ex-treme loading conditions, compressive stresses above the elas-tic buckling strength may be allowed. For calculation of elasticand ultimate compressive strength, see Sec.14.

B 600 Impact strength

601 Ships designed for a small draught at F.P. may have tobe strengthened to resist slamming. Requirements are given forbottom structures forward in a general form taking various

tC ka s p

σ---------------------- tk mm( )+=

σe σ12 σ2

2 σ1σ2 3τ2+–+=

Mq l

2

m---------- (kNm)=

Table B1 Values of m and ks

Load and boundary conditions

Bending moment and shear force factors

Positions 1 m1 ks1

2 m2 -

3 m3 ks3

1 Support

2 Field

3 Support

12,0 0,50 24,0 12,0

0,50

0,38 14,2 8,0 0,63

0,50 8,0 0,50

15,0 0,30 23,3 10,0

0,70

0,20 16,8 7,5 0,80

0,33 7,8 0,67


DET NORSKE VERITAS

structural arrangements into account, see Sec.6 H200. Thedraught upon which the slamming strength is based, will bestated in the the appendix to the classification certificate. If thebottom scantlings are based on full ballast tanks in the fore-body, this will also be stated.

In some cases impact loads from the sea on flat areas in after-bodies of special design may also have to be considered.

602 In ships with large bow flare and/or large bow radius,strengthening may be required in the bow region above thesummer load waterline. Requirements for structural arrange-ment and scantlings are given, see Sec.7 E300.

603 In large tanks for liquid cargo and/or ballast special re-quirements for strengthening against sloshing impact loadswill have to be considered, see Sec.4 C300.

B 700 Fatigue701 In general the susceptibility of hull structures to fatiguecracking has been taken care of by special requirements to de-tail design. However in some cases e.g. where high tensile steelis applied in stiffening members subjected to high frequencyfluctuating loads, a special calculation evaluating dynamicstresses, stress concentration factors and environment mayhave to be performed. For calculation of fatigue strength, seeSec.17.

B 800 Local vibrations

801 Vibrations in the hull structural elements are not consid-ered in relation to the requirements for scantlings given in therules. It is, however, assumed that special investigations aremade to avoid harmful vibrations, causing structural failures(especially in afterbody and machinery space tank structures),malfunction of machinery and instruments or annoyance tocrew and passengers. The structural response will depend onthe quantity of the impulse sources and the impulse propaga-tion. For a complete vibrational analysis it is therefore impor-tant also to consider the lines of the afterbody and thepossibilities for propeller cavitation as well as pulsating massforces from propeller, propulsion- and auxiliary machinery.

Reference is made to the separate publication, «Guidelines forPrevention of Harmful Vibration in Ships», issued by the So-ciety. Advice on performance of vibration analysis may also begiven by the Society.

B 900 Miscellaneous strength requirements901 Requirements for scantlings of foundations, minimumplate thicknesses and other requirements not relating relevantload and strength parameters may reflect criteria other thanthose indicated by these parameters. Such requirements mayhave been developed from experience or represent simplifica-tions considered appropriate by the Society.

B 1000 Reliability-based analysis of hull structures1001 This item gives requirements for structural reliabilityanalysis undertaken in order to document rule compliance, seePt.1 Ch.1 Sec.1 B200.

1002 The method and procedures for evaluation of reliabilityare subject to the acceptance by the Society in each individualcase. Acceptable procedures for reliability analyses are docu-mented in the Classification Note No. 30.6 «Structural Relia-bility Analysis of Marine Structures».

1003 Reliability analyses are to be based on level III reliabil-ity methods. These are methods that utilise probability of fail-ure as a measure, and which therefore require a knowledge ofthe distribution of all uncertain parameters.

1004 For the purpose of these rules, level III reliability meth-ods are mainly considered applicable to:

— unique design solutions— novel designs where limited (or no) experience exists

— special case design problems— calibration of level I methods to account for improved

knowledge. (Level I methods are deterministic analysismethods that use only one characteristic value to describeeach uncertain variable, i.e. the allowable stress methodnormally applied in the rules).

1005 Reliability analyses may be updated by utilisation ofnew information. Where such updating indicates that the as-sumptions upon which the original analysis was based are notvalid, and the result of such non-validation is deemed to be es-sential to safety, the subject approval may be revoked.

1006 Target reliabilities are to be commensurate with theconsequence of failure. The method of establishing such targetreliabilities, and the values of the target reliabilities them-selves, are to be approved by the Society in each separate case.To the extent possible, the minimum target reliabilities are tobe established based upon calibration against well establishedcases that are known to have adequate safety.

Where well established cases do not exist, for example in thecase of novel and unique design solutions, the minimum targetreliability values are to be based upon one (or a combination)of the following considerations:

— transferable target reliabilities from "similar", existing de-sign solutions

— decision analysis— internationally recognised codes and standards.

For further details, see Classification Note No. 30.6.

C. Local Design

C 100 Definition of span for stiffeners and girders

101 The effective span of a stiffener ( l) or girder (S) de-pends on the design of the end connections in relation to adja-cent structures. Unless otherwise stated the span points at eachend of the member, between which the span is measured, is tobe determined as shown on Fig.5 and 6. It is assumed thatbrackets are effectively supported by the adjacent structure.

Fig. 5Span points


DET NORSKE VERITAS

C 200 End connections of stiffeners

201 Normally all types of stiffeners (longitudinals, beams,frames, bulkhead stiffeners) are to be connected at their ends.In special cases, however, sniped ends may be allowed, see203. General requirements for the various types of connections(with brackets, bracketless, sniped ends) are given below.

Special requirements may be given for the specific structuresin other sections.

Requirements as to weld connections are given in Sec.12.

202 The scantlings of brackets for stiffeners not taking partin longitudinal strength may normally be taken as follows:

Thickness:

Z = rule section modulus in cm3 for the stiffener (smallestof connected stiffeners), without corrosion addition

k = 0,2 for flanged brackets = 0,3 for unflanged brackets.

tb need not be taken less than 6 mm, and not greater than 13,5mm.

tk need not be taken greater than 1,5 mm.

f1 = material factor for bracket.

f11 = material factor for stiffener.

Arm length:

The general requirement for arm length is given by:

Z as given above.

tb = thickness of bracket, with tk deductedc = 70 for flanged brackets = 75 for unflanged brackets.

The arm length a is in no case to be taken less than 2 times thedepth of the stiffener web. In case of different arm lengths a1and a2 (see Fig. 6), the sum is not to be less than 2a and eacharm not less than 0,75 a. Flange or edge stiffener is to be fittedwhen the edge length exceeds 50 tb. The flange width is nor-mally not to be taken less than:

The connection between stiffener and bracket is to be so de-signed that the section modulus in way of the connection is notreduced to a value less than required for the stiffener.

203 Bracketless end connections may be applied for longitu-dinals and other stiffeners running continuously through gird-ers (web frames, transverses, stringers, bulkheads etc.),provided sufficient connection area is arranged for.

For longitudinals, see special requirements in Sec.6 and 8.

Fig. 6Stiffener brackets

204 Stiffeners with sniped ends may be allowed where dy-namic loads are small and where vibrations are considered tobe of small importance, provided the thickness of plating sup-ported by the stiffener is not less than:

l = stiffener span in ms = stiffener spacing in mp = pressure on stiffener in kN/m2.

C 300 End connections of girders301 Normally ends of single girders or connections betweengirders forming ring systems are to be provided with brackets.Brackets are generally to be radiused or well rounded at theirtoes. The free edge of the brackets is to be stiffened. Scantlingsand details are given below.

Bracketless connections may be applied provided adequatesupport of the adjoining face plates is arranged for.

302 The thickness of brackets on girders is not to be less thanthat of the girder web plate.

Flanges on girder brackets are normally to have a cross- sec-tional area not less than:

A = l t (cm2)

l = length of free edge of brackets in m. If l exceeds 1,5 m,40% of the flange area is to be in a stiffener fitted par-allel to the free edge and maximum 0,15 m from theedge

t = thickness of brackets in mm.

Where flanges are continuous, there is to be a smooth taper be-tween bracket flange and girder face plate. If the flange is dis-continuous, the face plate of the girder is to extend well beyondthe toe of the bracket.

303 The arm length including depth of girder web may nor-mally be taken as:

tb3 k Z+

f1

f11

-----

-------------------- tk (mm)+=

a c Ztb---- (mm)=

W 45 1Z

2000------------+

� �� (mm), minimum 50 mm.=

t 1 25 l 0 5s,–( ) s pf1

--------------------------------, tk (mm)+=


DET NORSKE VERITAS

Z = rule section modulus in cm3 of the strength member towhich the bracket is connected.

t = thickness of bracket in mmC = 63 for bracket on bottom and deck girders = 88 for brackets on girders other than bottom and deck

girders. This requirement may be modified after spe-cial consideration.

304 An acceptable design of girder bracket normally givingthe nominal allowable stress levels in accordance with Sec.13is shown in Fig. 8 alt. I based on the following assumptions:

and

AK = 3,3 t (cm2)

AT = toe area in cm2

AK = cross sectional area of edge stiffener in cm2

h = edge stiffener height in mmt = thickness of bracket in mm.

The toe area is defined as the area of bracket measured at theend of and perpendicular to the sniped flange within a distanceof h to either side of the edge stiffener assuming snipe-angleequal to 30°, see Fig. 7 alt. I and alt. II.

Fig. 7Bracket toe area

Fig. 8Bracket design

The basic design may be improved by increasing theAT / AKratio. The brackets shown in Fig. 8 alt. II and alt. III are nor-mally considered better than the basic design. Other bracketsmay be accepted after special consideration.

The calculated normal stress at the middle of the free edge maybe accepted at a level equal to the stress given in Sec.13 D mul-tiplied by the design factor given in Table C1. For effectivewidth of curved flanges (alt. III) to be used in calculation, see407.

305 At cross joints of bracketless connections the requiredflange area of free flanges may be gradually tapered beyondthe crossing flange. For flanges in tension reduced allowabletensile stress is to be observed when lamellar tearing of flangesmay occur.

The thickness of the web plate at the cross joint of bracketlessconnection (between girder 1 and 2) is normally given by thegreater of (see Fig. 9):

a c Ztb---- (mm)=

AT

AK-------- 3h

1000------------=

Table C1 Design factorDesign FactorFig. 8 alt. Ifully compensated flange area(AT / AK = 1)

1,25

Fig. 8 alt. II and III 1,25


DET NORSKE VERITAS

Fig. 9Bracketless joint

or

A1, A2 = minimum required flange area in cm2 of girder 1and 2

h1, h2 = height in mm of girder 1 and 2t1, t2 = minimum required thickness (outside the cross-

joint) in mm of girder 1 and 2τ 1, τ 2 = shear stress in N/mm2 in girder 1 and 2σ1,σ2 = bending stress in N/mm2 in girder 1 and 2f1t = material factor for corner web plate.

C 400 Effective flange of girders

401 The section modulus of the girder is to be taken in ac-cordance with particulars as given in the following. Structuralmodelling in connection with direct stress analysis is to bebased on the same particulars when applicable. Note that suchstructural modelling will not reflect the stress distribution at lo-cal flange cut-outs or at supports with variable stiffness overthe flange width. The local effective flange which may be ap-plied in stress analysis is indicated for construction details invarious Classification Notes on «Strength Analysis of HullStructures».

402 The effective plate flange area is defined as the cross-sectional area of plating within the effective flange width.Continuous stiffeners within the effective flange may be in-cluded. The effective flange width be is determined by the fol-lowing formula:

be = C b (m)

C = as given in Table C2 for various numbers of evenlyspaced point loads (r) on the span

b = sum of plate flange width on each side of girder, nor-mally taken to half the distance from nearest girder orbulkhead

a = distance between points of zero bending moments = S for simply supported girders = 0,6 S for girders fixed at both endsr = number of point loads.

403 For plate flanges having corrugations parallel to thegirder, the effective width is as given in 402. If the corruga-tions are perpendicular to the direction of the girder, the effec-tive width is not to be taken greater than 10% of the valuederived from 402.

404 For effective width of plate flanges subject to elasticbuckling, see Sec.14 and Appendix A.

405 The effective plate area is not to be less than the effec-tive area of the face plate within the following regions:

— ordinary girders: total span— continuous hatch side coamings and hatch end beams:

length and breadth of the hatch, respectively, and an addi-tional length of 1 m at each end of the hatch corners.

406 The effective area of curved face plates is given by:

Ae = k tf bf (mm2)

bf = total face plate breadth in mmk = flange efficiency coefficient, see also Fig. 10

=

= 1,0 maximum

k1 =

for symmetrical and unsymmetrical free flanges

=

for box girder flange with two webs

=

for box girder flange with multiple webs

β =

b = 0,5 (bf – tw) for symmetrical free flanges = bf for unsymmetrical free flanges = s – tw for box girder flangess = spacing of supporting webs for box girder (mm)tf = face plate thickness in general (mm) = tw (maximum) for unsymmetrical free flangestw = web plate thickness (mm)r = radius of curved face plate (mm).

t3

σ1A1

h2------------- t2

τ2

100---------–

1f1t------ (mm)=

t3

σ2A2

h1------------- t1

τ1

100---------–

1f1t------ (mm)=

Table C2 Values of Ca/b 0 1 2 3 4 5 6 ≥ 7

C (r ≥ 6) 0,00 0,38 0,67 0,84 0,93 0,97 0,99 1,00C (r = 5) 0,00 0,33 0,58 0,73 0,84 0,89 0,92 0,93C (r = 4) 0,00 0,27 0,49 0,63 0,74 0,81 0,85 0,87C (r ≤ 3) 0,00 0,22 0,40 0,52 0,65 0,73 0,78 0,80

k1

r tf

b-------------

0 643 βsinh βcosh βsin βcos+( ),βsinh2 βsin2+

-------------------------------------------------------------------------------------

0 78 βsinh βsin+( ) βcosh βcos–( ),βsinh2 βsin2+

-----------------------------------------------------------------------------------------

1 56 βcosh βcos–( ),βsinh βsin+

----------------------------------------------------

1 285 b,r tf

-------------------- (rad)


DET NORSKE VERITAS

Fig. 10Effective width of curved face plates for alternative boundaryconditions

407 The effective flange area of curved face plates supportedby radial brackets or of cylindrical longitudinally stiffenedshells is given by:

k, bf, r, tf is as given in 407, see also fig. 11.

sr = spacing of radial ribs or stiffeners (mm).

Fig. 11Curved shell panel

C 500 Effective web of girders

501 The web area of a girder is to be taken in accordancewith particulars as given below. Structural modelling in con-nection with direct stress analysis is to be based on the sameparticulars when applicable.

502 Holes in girders will generally be accepted provided theshear stress level is acceptable and the buckling strength is suf-ficient. Holes are to be kept well clear of end of brackets andlocations where shear stresses are high. For buckling control,see Sec.14 B300.

503 For ordinary girder cross-sections the effective web areais to be taken as:

AW = 0,01 hn tw (cm2)

hn = net girder height in mm after deduction of cut-outs inthe cross-section considered

= hn1 + hn2.

If an opening is located at a distance less than hw/3 from thecross-section considered, hn is to be taken as the smaller of thenet height and the net distance through the opening. See Fig.12.

Fig. 12Effective web area in way of openings

504 Where the girder flange is not perpendicular to the con-sidered cross section in the girder, the effective web area is tobe taken as:

AW = 0,01 hn tw + 1,3 AFl sin 2θ sin θ (cm2)

hn = as given in 503AF l = flange area in cm2

θ = angle of slope of continuous flangetw = web thickness in mm.

See also Fig. 13.

Fig. 13Effective web area in way of brackets

Ae

3 r tf ksr2

+

3 r tf sr2

+------------------------- tf bf (mm

2)=


DET NORSKE VERITAS

C 600 Stiffening of girders.

601 In general girders are to be provided with tripping brack-ets and web stiffeners to obtain adequate lateral and web panelstability. The requirements given below are providing for anacceptable standard. The stiffening system may, however, bemodified based on direct stress analysis and stability calcula-tions according to accepted methods.

602 The spacing of stiffeners on the web plate is normallynot to exceed:

or

sv = spacing of stiffeners in m perpendicular to the girderflange

sh = spacing of stiffeners in m parallel to the girder flangetw = web thickness in mmτ = 90 f1 N/mm2 in general within 20% of the span from

each end of the girder = 60 f1 N/mm2 elsewhere.

τ may be adjusted after special consideration based on directstress calculations.

603 Deep longitudinal bottom and deck girders are normallyto be longitudinally stiffened. Unless special buckling analysishas been carried out, the following requirements are to be com-plied with:

— the spacing between the plate flange and the nearest stiff-ener is not to exceed:

sh = 0,055 (tw – tk) (m)

For each successive stiffener spacing away from the plateflange sh may be increased by 10%.

— below the transverse bulkhead verticals with adjoiningbrackets, the bottom girders are to have more closelyspaced horizontal stiffeners or additional vertical stiffen-ers. The spacing of the stiffeners is not to exceed:

sh = 0,045 (tw – tk) (m)

or

sv = 0,060 (tw – tk) (m)

— stiffening arrangement will be specially considered withrespect to docking.

604 The web plate of transverses is to be effectively stiff-ened. If the web plate is connected to the bottom longitudinalson one side only, vertical stiffeners are to be applied, or the freeedge of the scallop is to be stiffened.

605 If the web stiffeners are in line with the intersecting lon-gitudinals, frames or stiffeners, they are to be connected to theintersecting member.

Stiffeners on the web plate perpendicular to the flange may besniped towards side, deck or bulkhead plating.

606 The web plate is to be specially stiffened at openingswhen the mean shear stress exceeds 60 N/mm2. Stiffeners areto be fitted along the free edges of the openings parallel to thevertical and horizontal axis of the opening. Stiffeners may beomitted in one direction if the shortest axis is less than 400mm, and in both directions if length of both axes is less than300 mm. Edge reinforcement may be used as an alternative tostiffeners, see Fig. 14. Scallops for longitudinals, frames orstiffeners deeper than 500 mm are to be stiffened along theirfree edge.

Fig. 14Web plates with large openings

607 The spacing st of tripping brackets is normally not to ex-ceed the values given in Table C3 valid for girders with sym-metrical face plates. For girders with unsymmetrical faceplates the spacing will be specially considered.

608 Tripping brackets on girders are to be stiffened by aflange or stiffener along the free edge if the length of the edgeexceeds:

0,06 tt (m)

tt = thickness in mm of tripping bracket.

The area of the stiffening is not to be less than:

sv5 4,τ

--------- tw tk–( ) (m)=

sh6 0,τ

--------- tw tk–( ) (m)=

Table C3 Spacing between tripping brackets

Girder type 1) st (m)

Bottom transverse 0,02 bf, maximum 6

Side and longitudinal bulkhead vertical 2) 0,012 bfLongitudinal girder, bottom 3) 0,014 bfLongitudinal girder, deck 0,014 bf,

maximum SDeck transverse 0,02 bf,

maximum 6Transverse wash bulkhead vertical 0,009 bfTransverse tight bulkhead vertical 0,012 bfStringer 0,02 bf,

maximum 6bf = flange breadth in mm

S = distance between transverse girders in m.

1) For girders in tanks in the afterbody and machinery spaces st is not to exceed 0,012 bf.

2) If the web of a strength member forms an angle with the perpendicular to the ship's side of more than 10°, st is not to exceed 0,007 bf.

3) In general, tripping brackets are to be fitted at all transverses. For cen-tre girder, tripping brackets are also to be fitted at halfway between transverses.


DET NORSKE VERITAS

10 lt (cm2)

lt = length in m of free edge.

The tripping brackets are to have a smooth transition to adjoin-ing longitudinals or stiffeners exposed to large longitudinalstresses:

Tripping brackets are to be fitted as required in 607, and arefurther to be fitted near the toe of bracket, near rounded cornerof girder frames and in line with any cross ties. The trippingbrackets are to be fitted in line with longitudinals or stiffeners,and are to extend the whole height of the web plate. The armlength of the brackets along the longitudinals or stiffeners, isnot to be less than 40% of the depth of the web plate, the depthof the longitudinal or stiffener deducted. The requirement maybe modified for deep transverses.

609 Tripping brackets on the centre girder between the bot-tom transverses are at the bottom to extend to the second bot-tom longitudinal from the centre line.

On one side the bracket is to have the same depth as the centregirder, on the other side half this depth.

610 Hatch end beams supporting hatch side coamings are atleast to have tripping brackets located in the centre line.

611 The moment of inertia of stiffeners perpendicular to thegirder flange (including 400 mm plate flange) is not to be lessthan:

IV = 0,1 a sv tw3 (cm4)

a = as given in Table C4sv = as given in 602tw = as given in 602.

Corrosion addition (tk) is to be applied in tanks.

This requirement is not applicable to longitudinal girders inbottom and deck or transverse bulkhead vertical girders.

612 The moment of inertia of stiffeners parallel to the girderflange (including 400 mm plate flange) is not to be less than:

IH = k AS ls2 (cm4)

k = 2,5 in general = 3,3 for bottom and deck longitudinal girdersAS = cross-sectional area in cm2 of stiffener including 400

mm plate flangels = length in m of stiffener.

For flat bar stiffeners the height/thickness-ratio is not to exceed14.

613 The minimum thickness of tripping brackets and stiffen-ers is given in Sec.6 to Sec.9 covering the various local struc-tures.

C 700 Reinforcement at knuckles

701 Whenever a knuckle in a main member (shell, longitudi-nal bulkhead etc.) is arranged, it is important to have someform of stiffening fitted at the knuckle to transmit the trans-verse force. This stiffening, in the form of webs, brackets orprofiles, must be connected to the transverse members towhich they shall transfer the force (in shear), see Fig. 15. Al-ternatively closely spaced carlings may be fitted across the

knuckle between longitudinal members above and below theknuckle.

Fig. 15Reinforcement at knuckle

C 800 Continuity of local strength members

801 Attention is drawn to the importance of structural conti-nuity in general.

802 Structural continuity is to be maintained at the junctionof primary supporting members of unequal stiffness by fittingwell rounded brackets.

Brackets are not to be attached to unsupported plating.

Brackets are to extend to the nearest stiffener, or local platingreinforcement is to be provided at the toe of the bracket.

803 Where practicable, deck pillars are to be located in linewith pillars above or below.

804 Below decks and platforms, strong transverses are to befitted between verticals and pillars, so that rigid continuousframe structures are formed.

C 900 Welding of outfitting details to hull

901 Generally connections of outfitting details to the hull areto be such that stress-concentrations are minimised and weld-ing to highly stressed parts is avoided as far as possible.

Connections are to be designed with smooth transitions andproper alignment with the hull structure elements. Termina-tions are to be supported.

902 Equipment details as clips for piping, support of ladders,valves, anodes etc. are to be kept clear of the toe of brackets,edge of openings and other areas with high stresses.

Connections to topflange of girders and stiffeners are to beavoided if not well smoothened. Preferably supporting of out-fittings are to be welded to the stiffener web.

903 All materials welded to the hull shell structure are to beof ship quality steel, or equivalent, preferably with the samestrength group as the hull structure the item is welded to.

904 Gutterway bars on strength deck are to be arranged withexpansion joints unless the height/thickness ratio complieswith the formula

Table C4 Values of a

≥ 0,8 0,7 0,6 0,5 0,4 0,3

a 0,8 1,4 2,75 5,5 11,0 20,0

svls----


DET NORSKE VERITAS

where

σF = minimum upper yield stress of material in N/mm2.May be taken as 235 N/mm2 for normal strength steel

E = as given in Sec.1 B101.

905 For welding of deck fittings to a rounded sheer strake,see also Sec.7 C206.

C 1000 Properties and selection of sections.1001 The geometric properties (moment of inertia I and sec-tion modulus Z) of stiffeners and girders may be calculated di-rectly from the given dimensions in connection with theeffective plate flange (for girders, see 400), or obtained frompublished tables and curves. For stiffeners, the plate effectiveflange width may normally be taken equal to the stiffener spac-ing.

1002 The requirement for standard section modulus andshear area are valid about an axis parallel to the plate flange. Ifthe angle α between the stiffener web and the plate flange isless than 75 degrees, the requirement for standard section mod-ulus and shear area may be determined by multiplying the rulerequirement by 1/sin α.

1003 Where several members in a group with some variationin requirement are selected as equal, the section modulus maybe taken as the average of each individual requirement in thegroup. However, the requirement for the group is not to be tak-en less than 90% of the largest individual requirement.

1004 For stiffeners and girders in tanks and in cargo holds ofdry bulk cargo carriers, corrosion additions corresponding tothe requirements given in Sec.2 D are to be applied. For builtup sections the appropriate tk-value may be added to the weband flange thickness after fulfilment of the modulus require-ment.

For rolled sections the section modulus requirement may bemultiplied by a corrosion factor wk, given by the following ap-proximation:

t kw = corrosion addition tk as given in Sec.2 D200 with re-spect to the profile web

t kf = corrosion addition tk as given in Sec.2 D200 with re-spect to the profile flange.

For flat bars the corrosion addition tk may be added directly tothe thickness.

1005 The shear area, As, of panel stiffeners may (except inway of web scallops) be expressed as:

As = 0,01 (h + tp) (tw– tk) (cm2)h = stiffener height in mmtp = thickness of attached plate (mm)tw = stiffener web thickness (mm).

1006 The plastic section modulus of panel stiffeners, ZP,may be expressed as follows:

bf = flange breadth in mmh, tp and tw = as given in 1005hw = stiffener web height = h – tftf = stiffener flange thickness (mm)tk = as given in Sec.2 D200.

For bulb profiles, bf and tf may be taken as the mean breadthand thickness of the bulb.

C 1100 Cold formed plating1101 For important structural members, e.g. corrugatedbulkheads and hopper knuckles, the inside bending radius incold formed plating is not to be less than 4.5 times the platethickness for carbon-manganese steels and 2 times the platethickness for austenitic- and ferritic-austenitic (duplex) stain-less steels, corresponding to 10% and 20% theoretical defor-mation, respectively.

1102 For carbon-manganese steels the allowable insidebending radius may be reduced below 4.5 times the plate thick-ness providing the following additional requirements are com-plied with:

a) The steel is killed and fine grain treated, i.e. grade NV D/DH or higher.

b) The material is impact tested in the strain-aged conditionand satisfies the requirements stated herein. The deforma-tion is to be equal to the maximum deformation to be ap-plied during production, calculated by the formula t/(2 R +t), where t is the thickness of the plate material and R is thebending radius. Ageing is to be carried out at 250°C for 30minutes. The average impact energy after strain ageing isto be at least 27 J at 20°C.

c) 100% visual inspection of the deformed area is to be car-ried out. In addition, random check by magnetic particletesting is to be carried out.

d) The bending radius is in no case to be less than 2 times theplate thickness.

wk = 1 + 0,05 (t kw + tkf) for flanged sections= 1 + 0,06 t kw for bulbs

ht--- 2

3--- 1 28

EσF------,<

ZP

hw tw tk–( ) hw tp+( )2000

--------------------------------------------------bf tf tk–( ) hw

tf

2---

tp

2----+ +

� ��

1000--------------------------------------------------------- cm

3( )+=


DET NORSKE VERITAS

SECTION 4DESIGN LOADS

A. General

A 100 Introduction101 In this section formulae for wave induced ship motionsand accelerations as well as lateral pressures are given.

The given design wave coefficient is also a basic parameter forthe longitudinal strength calculations.

102 The ship motions and accelerations in B are given as ex-treme values (i.e. probability level = 10-8).

103 Design pressures caused by sea, liquid cargoes, dry car-goes, ballast and bunkers as given in C are based on extremeconditions, but are modified to equivalent values correspond-ing to the stress levels stipulated in the rules. Normally this in-volves a reduction of the extreme values given in B to a 10-4

probability level.

104 Impact pressures caused by the sea (slamming, bow im-pact) are not covered by this section. Design values are givenin the sections dealing with specific structures.

A 200 Definitions201 Symbols:

p = design pressure in kN/m2

r = density of liquid or stowage rate of dry cargo in t/m3.

202 The load point for which the design pressure is to be cal-culated is defined for various strength members as follows:

a) For plates:

midpoint of horizontally stiffened plate field.

Half of the stiffener spacing above the lower support ofvertically stiffened plate field, or at lower edge of platewhen the thickness is changed within the plate field.

b) For stiffeners:

midpoint of span.

When the pressure is not varied linearly over the span thedesign pressure is to be taken as the greater of:

pm, pa and pb are calculated pressure at the midpoint andat each end respectively.

c) For girders:

midpoint of load area.

B. Ship Motions and Accelerations

B 100 General101 Accelerations in the ship's vertical, transverse and longi-tudinal axes are in general obtained by assuming the corre-sponding linear acceleration and relevant components ofangular accelerations as independent variables. The combinedacceleration in each direction may be taken as:

n = number of independent variables.

Transverse or longitudinal component of angular accelerationconsidered in the above expression is to include the componentof gravity acting simultaneously in the same direction.

102 The combined effects given in the following may devi-ate from the above general expression due to practical simpli-fications applicable to hull structural design or based onexperience regarding phasing between certain basic compo-nents.

B 200 Basic parameters

201 The acceleration, sea pressures and hull girder loadshave been related to a wave coefficient as given in Table B1.

The above formulae are illustrated in Fig. 1.

Fig. 1Wave coefficient

pm and pa pb+

2-----------------

ac am2

m 1=

n

�=

Table B1 Wave coefficient CW

L CWL ≤ 100 0,0792 L100 < L < 300 10,75 – [ (300–L)/100 ]3/2

300 ≤ L ≤ 350 10,75L > 350 10,75 – [ (L–350)/150 ]3/2


DET NORSKE VERITAS

Fig. 2Acceleration parameter

202 For ships with restricted service, CW may in general bereduced as follows:

— service area notation R0: No reduction— service area notation R1: 10%— service area notation R2: 20%— service area notation R3: 30%— service area notation R4: 40%— service area notation RE: 50%.

203 A common acceleration parameter is given by:

CV =

C V1 =

Values of a0 according to the above formula may also be foundfrom Fig. 2.

B 300 Surge, sway /yaw and heave accelerations

301 The surge acceleration is given by:

302 The combined sway/yaw acceleration is given by:

ay = 0,3 g0 a0 (m/s2)

303 The heave acceleration is given by:

B 400 Roll motion and acceleration

401 The roll angle (single amplitude) is given by:

c = (1,25 – 0,025 TR) kk = 1,2 for ships without bilge keel = 1,0 for ships with bilge keel = 0,8 for ships with active roll damping facilitiesTR = as defined in 402, not to be taken greater than 30.

402 The period of roll is generally given by:

kr = roll radius of gyration in mGM = metacentric height in m.

The values of kr and GM to be used are to give the minimumrealistic value of TR for the load considered.

In case kr and GM have not been calculated for such condition,the following approximate design values may be used:

kr = 0,39 B for ships with even transverse distribution ofmass

= 0,35 B for tankers in ballast = 0,25 B for ships loaded with ore between longitudinal

bulkheadsGM = 0,07 B in general = 0,12 B for tankers and bulk carriers.

403 The tangential roll acceleration (gravity component notincluded) is generally given by:

RR = distance in m from the centre of mass to the axis of ro-tation.

The roll axis of rotation may be taken at a height z m above thebaseline.

z = the smaller of

404 The radial roll acceleration may normally be neglected.

B 500 Pitch motion and acceleration

501 The pitch angle is given by:

502 The period of pitch may normally be taken as:

a0

3CW

L------------ CVCV1+=

L50------- , maximum 0,2

V

L---------, minimum 0,8

ax 0 2 g0 a0 CB (m/s2),=

az 0 7 g0

a0

CB

------------- (m/s2),=

φ 50cB 75+---------------- (rad)=

TR

2kr

GM--------------- (s)=

ar φ 2πTR-------

� �� 2

RR (m/s2 )=

D4---- T

2---+ and

D2----

θ 0 25a0

CB------- (rad),=

TP 1 8 Lg0----- (s),=


DET NORSKE VERITAS

503 The tangential pitch acceleration (gravity componentnot included) is generally given by:

TP = period of pitchRP = distance in m from the centre of mass to the axis of ro-

tation.

The pitch axis of rotation may be taken at the cross- section0,45 L from A.P. z meters above the baseline.

z = as given in 403.

With TP as indicated in 502 the pitch acceleration is given by:

504 The radial pitch acceleration may normally be neglect-ed.

B 600 Combined vertical acceleration601 Normally the combined vertical acceleration (accelera-tion of gravity not included) may be approximated by:

kv = 1,3 aft of A.P. = 0,7 between 0,3 L and 0,6 L from A.P. = 1,5 forward of F.P.

Between mentioned regions kv is to be varied linearly, see Fig.3.

Fig. 3Acceleration distribution factor

If for design purposes a constant value of av within the cargoarea is desirable, a value equal to 85% of the maximum avwithin the same area may be used.

602 As an alternative the acceleration along the ship's verti-cal axis (acceleration of gravity not included) is given as thecombined effect of heave, pitch and roll calculated as indicatedin 100, i.e.:

az = as given in 303arz = vertical component of the roll acceleration given in

403apz = vertical component of the pitch acceleration given in

503.

Note that arz and apz are equal toar and ap using the horizontalprojection of RR and RP respectively.

B 700 Combined transverse acceleration

701 Acceleration along the ship's transverse axis is given asthe combined effect of sway/yaw and roll calculated as indicat-ed in 100, i.e.:

ary = transverse component of the roll acceleration given in403.

Note that ary is equal to ar using the vertical projection of RR.

B 800 Combined longitudinal accelerations

801 Acceleration along the ship's longitudinal axis is givenas the combined effect of surge and pitch calculated as indicat-ed in 100, i.e.:

apx = longitudinal component of pitch acceleration given in503.

Note that apx is equal to ap using the vertical projection of RP.

C. Pressures and Forces

C 100 General

101 The external and internal pressures considered to influ-ence the scantling of panels are:— static and dynamic sea pressures— static and dynamic pressures from liquids in a tank— static and dynamic pressures from dry cargoes, stores and

equipment.

102 The design sea pressures are assumed to be acting on theship's outer panels at full draught.

103 The internal pressures are given for the panel in questionirrespectively of possible simultaneous pressure from the op-posite side. For outer panels sea pressure at ballast draughtmay be deducted.

104 The gravity and acceleration forces from heavy units ofcargo and equipment may influence the scantlings of primarystrength members.

C 200 Sea pressures

201 The pressure acting on the ship's side, bottom andweather deck is to be taken as the sum of the static and the dy-namic pressure as:

— for load point below summer load waterline :

p1 = 10 h0 + pdp1) (kN/m2)

ap θ 2πTP------

2RP (m/s

2)=

ap 120 θRP

L------ (m/s

2 )=

av

kv g0 a0

CB------------------- (m/s

2)=

av max arz

2az

2+

apz2

az2

+��

= (m/s2)

at ay2

g0 φsin ary+( )2+ (m/s

2)=

al ax2

g0 θsin apx+( )2+ (m/s

2)=


DET NORSKE VERITAS

— for load point above summer load waterline :

p2 = a ( pdp – (4 + 0,2 ks) h0 ) 1) (kN/m2) = minimum 6,25 + 0,025 L1 for sides = minimum 5 for weather decks.

The pressure pdp is taken as:

pl = ks CW + kf

=

ks =

= 2 between 0,2 L and 0,7 L from AP

=

Between specified areas ks is to be varied linearly.

a = 1,0 for ship's sides and for weather decks forward of0,15L from FP, or forward of deckhouse front, which-ever is the foremost position

= 0,8 for weather decks elsewhereh0 = vertical distance from the waterline at draught T to the

load point (m)z = vertical distance from the baseline to the load point,

maximum T (m)y = horizontal distance from the centre line to the load

point, minimum B/4 (m)CW = as given in B200kf = the smallest of T and ff = vertical distance from the waterline to the top of the

ship's side at transverse section considered, maximum0,8 CW (m)

L1 = ship length, need not be taken greater than 300 (m).

1) For ships with service restrictions, p2 and the last term in p1 may be re-duced by the percentages given in B202. CW should not be reduced.

202 The sea pressure at minimum design draught which maybe deducted from internal design pressures is to be taken as:

TM = minimum design draught in m normally taken as 0,35T for dry cargo vessels and 2 + 0,02 L for tankers

z = vertical distance in m from the baseline to the loadpoint.

203 The design pressure on watertight bulkheads (compart-ment flooded) is to be taken as:

p = 10 hb (kN/m2)

hb = vertical distance in metres from the load point to thedeepest equilibrium waterline in damaged conditionobtained from applicable damage stability calcula-tions.

204 The design pressure on inner bottom (double bottomflooded) is not to be less than:

p = 10 T (kN/m2).

C 300 Liquids in tanks301 Tanks for crude oil or bunkers are normally to be de-signed for liquids of density equal to that of sea water, taken asρ = 1,025 t/m3 (i.e. ρ g0 ≈ 10). Tanks for heavier liquids maybe approved after special consideration. Vessels designed for

100% filling of specified tanks with a heavier liquid will begiven the notation HL(ρ), indicating the highest cargo densityapplied as basis for approval. The density upon which thescantling of individual tanks are based, will be given in the ap-pendix to the classification certificate.

302 The pressure in full tanks is to be taken as the greater of:

p = ρ (g0 + 0,5 av) hs (kN/m2) [ 1 ]

p = 0,67 (ρ g0 hp + ∆ pdyn) (kN/m2) [ 4 ]

p = ρ g0 hs + p0 (kN/m2) [ 5 ]

av = as given in B600φ = as given in B400θ = as given in B500H = height in m of the tankρ = density of ballast, bunkers or liquid cargo in t/m3,

normally not to be taken less than 1,025 t/m3 (i.e. ρ g0 ≈ 10)

b = the largest athwartship distance in m from the loadpoint to the tank corner at top of the tank which issituated most distant from the load point. For tanktops with stepped contour, the uppermost tank cor-ner will normally be decisive

bt = breadth in m of top of tankl = the largest longitudinal distance in m from the load

point to the tank corner at top of tank which is situ-ated most distant from the load point. For tank topswith stepped contour, the uppermost tank cornerwill normally be decisive

lt = length in m of top of tankhs = vertical distance in m from the load point to the top

of tank, excluding smaller hatchways.hp = vertical distance in m from the load point to the top

of air pipep0 = 25 kN/m2 in general = 15 kN/m2 in ballast holds in dry cargo vessels = tank pressure valve opening pressure when exceed-

ing the general value.∆ pdyn = calculated pressure drop according to Pt.4 Ch.6

Sec.4 K201.

For calculation of girder structures the pressure [4] is to be in-creased by a factor 1,15.

The formulae normally giving the greatest pressure are indicat-ed in Figs. 4 to 6 for various types.

For sea pressure at minimum design draught which may be de-duced from formulae above, see 202.

Formulae [ 2 ] and [ 3 ] are based on a 2% ullage in largetanks.

Guidance note:With respect to the definition of hs, hatchways may be consid-ered small to the extent that the volume of the hatchway is negli-gible compared to the minimum ullage of the tank. Hatchwaysfor access only may generally be defined as small with respect tothe definition of hs.


Guidance note:If the pressure drop according to Pt.4 Ch.6 Sec.4 K201 is notavailable, pdyn may normally be taken as 25 kN/m2. for ballasttanks and zero for other tanks. If arrangements for the preventionof overpumping of ballast tanks in accordance with Pt.4 Ch.6Sec.4 K200 are fitted, pdyn may be taken as zero.


p = 10 (TM – z) (kN/m2)= minimum 0

pdp pl 135y

B 75+---------------- 1 2 T z–( ) (kN/m

2),–+=

ksCW kf+( ) 0 8, 0 15V

L-------,+

� �� if

V

L------- 1 5,>

3CB2 5,CB

----------- at AP and aft+

3CB4 0,CB--------- at FP and forward.+

p ρ g0 0 67 hs φb+( ), 0 12 Hbtφ,–[ ] (kN/m2) 2[ ]=

p ρ g0 0 67 hs θ l+( ), 0 12 Hltθ,–[ ] (kN/m2) 3[ ]=


DET NORSKE VERITAS

Fig. 4Section in cargo tanks

Fig. 5Section in bulk cargo hold

303 Tanks with lb < 0,13 L and bb < 0,56 B are to have scant-lings for unrestricted filling height.

For strength members located less than 0,25 lb away from washand end bulkheads the pressure is not to be taken less than:

lb = distance in m between transverse tank bulkheads orfully effective transverse wash bulkheads at the heightat which the strength member is located (αt < 0,2).

Fig. 6Section in engine room

For strength members located less than 0,25 bb away from lon-gitudinal wash bulkheads and tank sides the pressure is not tobe taken less than:

bb = distance in m between tank sides or fully effective lon-gitudinal wash bulkheads at the height at which thestrength member is located (αl < 0,2)

If the wash bulkheads are not fully effective (αt > 0,2 αl >0,2). l b and bb may be substituted by ls and bs given in 306.αt and αl are defined in 306.

304 The minimum sloshing pressure on webframes and gird-er panels in cargo and ballast tanks is not to be taken less than20 kN/m2.

In long or wide tanks with many webframes or girders thesloshing pressure on the frames or girders near to the wash orend bulkheads is to be taken as:

pbhd = sloshing pressure on wash or end bulkheads as given in306

s = distance in m from bulkhead to webframe or girderconsidered.

ls and bs as given in 306.

305 Tanks with free sloshing breadth bs > 0,56 B will be sub-ject to specified restrictions on maximum GM. In additionsuch tanks and/or tanks with a sloshing length such that 0,13 L< l s < 0,16 L may be designed for specified restrictions in fill-ing height.

Maximum allowable GM, cargo density and possible restric-tions on filling heights will be stated in the appendix to theclassification certificate.

p ρ 4L

200---------– lb (kN/m

2)=

p ρ 3B

100---------– bb (kN/m

2)=

p pbhd 1sls---–

� ��

2 (kN/m

2) for webframes=

p pbhd 1sbs-----–

� �� 2

(kN/m2) for longitudinal griders.=


DET NORSKE VERITAS

The sloshing pressures (p) given in 306 and 309 are to be con-sidered together with the normal strength formulae given inSec.7, Sec.8 and Sec.9.

The impact pressures (pi) given in 307, 308, 309, and 310 areto be used together with impact strength formulae given inSec.9 E400.

bs and ls as given in 306.

Fig. 7Pressure distribution

306 Sloshing pressure

For strength members located less than 0,25 ls away fromtransverse wash and end bulkheads the pressure is not to betaken less than (see Fig. 7):

For strength members located less than 0,25 bs from longitudi-nal wash bulkheads and tank sides the pressure is not to be tak-en less than:

kf =

h = filling height (m)H = tank height (m) within 0,15 ls or 0,15 bsGM = maximum GM including correction for free surface

effect. GMminimum = 0,12 B (m)

ls = effective sloshing length in m given as:

=

=

bs = effective sloshing breadth in m given as:

=

=

l = tank length in mb = tank breadth in mnt = number of transverse wash bulkheads in the tank

with αt < 0,5αt = ratio between openings in transverse wash bulkhead

and total transverse area in the tank below consid-ered filling height, see Fig.8.

Fig. 8Wash bulkhead coefficient

If no restriction to filling height, h is taken as 0,7 H.

n2 = number of transverse web-ring frames in the tank over thelength:

βt = ratio between openings in web-ring frames and totaltransverse area in the tank below considered fillingheight, see Fig.9.

Fig. 9Webframe coefficient

If no restriction to filling height, h is taken as 0,7 H.

nl = number of longitudinal wash bulkheads in the tankwith αl < 0,5

αl = similar to α t but taken for longitudinal wash bulkheadn4 = number of longitudinal ring-girders in the tank be-

tween the breadth

.

βl = similar to βt taken for longitudinal ring-girders.

p ρ g0 ls kf 0 4, 0 39,1 7 ls,

L--------------–

� �� L

350---------– (kN/m

2)=

p 7 ρ g0 kf

bs

B----- 0 3,–

� �� GM

0 75, (kN/m

2)=

1 2 0 7, hH----–

� ��

2 , maximum = 1 –

hH----

� ��

max1=

1 ntα t+( ) 1 βtn2+( ) l

1 nt+( ) 1 n2+( )----------------------------------------------------- for end bulkheads

1 α t nt 1–( )+[ ] 1 βtn2+( ) l

1 nt+( ) 1 n2+( )------------------------------------------------------------------ for wash bulkheads

1 nlα l+( ) 1 β ln4+( ) b

1 nl+( ) 1 n4+( )---------------------------------------------------------- for tank sides

1 α l nl 1–( )+[ ] 1 βln4+( ) b

1 nl+( ) 1 n4+( )-------------------------------------------------------------------- for wash bulkhead

l1 nt+( )

------------------

b1 nl+( )

------------------


DET NORSKE VERITAS

307 Impact pressure in upper part of tanks.

Tanks with free sloshing length 0,13 L < ls < 0,16 L or withfree sloshing breadth bs > 0,56 B will generate an impact pres-sure on horizontal and inclined surfaces adjacent to verticalsurfaces in upper part of the tank due to high liquid velocitiesmeeting these surfaces. For horizontal or inclined panels(deck, horizontal stringers etc.) the impact pressure on upperparts of the tank may be taken as:

Within 0,15 ls from transverse wash or end bulkheads:

Within 0,15 bs from longitudinal wash bulkheads and tanksides:

Outside 0,15 ls and 0,15 bs the pressure may be reduced to zeroat 0,3 ls and 0,3bs, respectively, see Fig. 7.In tank corners within 0,15 ls and 0,15 bs the impact pressureis not to be taken smaller than pi (transversely) or pi (longitu-dinally) + 0,4 pi (transversely). .The reflected impact pressure on vertical surfaces adjacent tohorizontal or inclined surfaces above will have an impact pres-sure linearly reduced to 50% of the pressure above, 0,1 ls or 0,1bs m below.

ls, bs and GM are as given in 306.

kf =

h = maximum allowable filling height (m)H = tank height (m) within 0,15 ls or 0,15 bsγ = angle between considered panel and the vertical.

308 Impact pressure in lower part of smooth tanks

In larger tanks ( ls > 0,13 L or bs > 0,56 B) with double bottomand which have no internal transverse or longitudinal girdersrestraining the liquid movement at low minimum fillingheights (2 < h < 0,2 ls or 2 < h < 0,2 bs) the impact pressure onvertical and inclined tank surfaces is not to be taken less than:

pi = 1,42 ρ g0 k l s sin2 δ (kN/m2)

on transverse bulkheads up to a height of 0,2 l spi = 1,5 ρ g0 bs sin2 δ (kN/m2)

on longitudinal bulkheads up to a height of 0,2 bs

The impact pressure may be reduced to zero 1 metre above theheights given, see Fig. 7.

In tank corners at outermost side of transverse bulkheads theimpact pressure within 0,15 bs is not to be taken smaller than:

pi (longitudinally) + 0,4 pi (transversely)

If the tank is arranged with a horizontal stringer within theheight h < 0,2 ls or h < 0,2 bs a reflected impact pressure of thesame magnitude as on adjacent transverse or longitudinal bulk-head is to be used on the under side of the stringer panel.

ls and bs are free sloshing length and breadth in m at heightconsidered, as given in 306.

k = 1 for L < 200 = 1,4 – 0,002L for L > 200δ = angle between the lower boundary panel and the hori-

zontal.

309 For tanks with upper panels higher than L/20 m abovelowest seagoing waterline the sloshing and impact pressuresgiven in 306 and 307 are to be multiplied by the followingmagnification factors:

1 + 6 ze/L for longitudinal sloshing

1 + 7,5 ze GM/B2 for transverse sloshing

1 + 18 ze/L for longitudinal impact

1 + 17,5 ze GM/B2 for transverse impact

ze = zt – Ts – L/20 (m)zt = distance from baseline to panel consider (m)TS = lowest seagoing draught (m) = 0,50 T may normally be used.

310 For tanks with smooth boundaries (no internal structuralmembers) with tank bottom higher than the D/2, the low fillingimpact pressure as given in 308 is to be multiplied by the fol-lowing magnification factor:

θ and φ = pitch and rolling angle given in B400 and B500zi = distance from panel considered to D/2 in m.

C 400 Dry cargoes, stores, equipment and accommoda-tion

401 The pressure on inner bottom, decks or hatch covers isto be taken as:

p = ρ (g0 + 0,5 av) H (kN/m2)

av = as given in B600H = stowage height in m.

Standard values of ρ and H are given in Table C1.

If decks (excluding inner bottom) or hatch covers are designedfor cargo loads heavier than the standard loads given in TableC1 the notation DK(+) or HA(+) respectively, will be as-signed. The design cargo load in t/m2 will be given for each in-dividual cargo space in the appendix to the classificationcertificate.

402 When the weather deck or weather deck hatch covers aredesigned to carry deck cargo the pressure is in general to betaken as the greater of p according to 201 and 401.

pi ρ g0 kr

220 lsL

-------------- 7 5,–� �� γsin2 (kN/m

2)=

for lsL--- 350 L+

3550-------------------<

ρ g0 kf 25L13------+

� �� 0 5,

lsL---+

� �� γsin2 (kN/m

2)=

for lsL--- 350 L+

3550------------------->

pi

240 ρ g0 kf

B---------------------------

bs

B----- 0 3,–

� �� GM

1 5, γsin2=

1 4 0 6, hH----–

� ��

2 , maximum =1, –

hH----

� ��

max1=

12 zi θ

ls------------+

� ��

2 in longitudinal direction

12 zi φ

bs------------+

� ��

2 in transverse direction


DET NORSKE VERITAS

In case the design stowage height of weather deck cargo issmaller than 2,3 m, combination of loads may be required afterspecial consideration.

403 The pressure from bulk cargoes on sloping and verticalsides and bulkheads is to be taken as:

p = ρ (g0 + 0,5 av) K hc (kN/m2)

K = sin2α tan2 (45 – 0,5 δ ) + cos2 αα = angle between panel in question and the horizontal

plane in degreesav = as given in B600δ = angle of repose of cargo in degrees, not to be taken

greater than 20 degrees for light bulk cargo (grain etc.),and not greater than 35 degrees for heavy bulk cargo(ore)

hc = vertical distance in m from the load point to the highestpoint of the hold including hatchway in general. Forsloping and vertical sides and bulkheads, hc may bemeasured to deck level only, unless the hatch coamingis in line with or close to the panel considered.

C 500 Deck cargo units. Deck equipment

501 The forces acting on supporting structures and securingsystems for heavy units of cargo, equipment or structural com-ponents (including cargo loads on hatch covers) are normallyto be taken as:

— vertical force alone: PV = (go + 0,5 av) M (kN)

— vertical force in combination with transverse force:P VC = go M (kN)

— transverse force in combination with vertical force:P TC = 0,67 at M (kN)

— vertical force in combination with longitudinal force:P VC = (go + 0,5 av) M (kN),

acting downwards at vessels ends together with downwardpitch, acting in 60° - 90° phasing with PLC amidships,where heave part of PVC is prevailing

— longitudinal force in combination with vertical force:PLC = 0,67 al M (kN)

M = mass of unit in tav = as given in B600at = as given in B700al = as given in B800

— PTC and PLC may be regarded as not acting simultaneous-ly, except when the stress σL C > 0,6 σTC, in which caseσLC + 0,4 σTC is to be substituted for σLC .

502 Regarding forces acting on cargo containers, their sup-ports and lashing systems, reference is made to Pt.5 Ch.2Sec.6.

Table C1 Standard load parameters.

DecksParameters

ρ HSheltered deck, sheltered hatch covers and inner bottom for cargo or stores

0,7 t/m3 1)

vertical distance in m from the load point to the deck above.For load points below hatchways H is to be measured to the top of coaming.

ρ H

Weather deck and weather deck hatch covers in-tended for cargo

1,0 t/m2 for L=100 m1,3 t/m2 for L > 150 m at superstructure deck.1,75 t/m2 for L > 150 m at freeboard deck.For vessels corresponding to 100 m < L < 150 m, the standard value of ρ H is obtained by linear interpolation.

Platform deck in machinery space 1,6 t/m2

Accommodation decks

0,35 t/m2, when not directly calculated, includ-ing deck's own mass.Minimum 0,25 t/m2.

1) If ΣρH for cargo spaces exceeds the total cargo capacity of the vessel, ρ may be reduced after special consideration in accordance with spec-ified maximum allowable load for individual decks. When the deck’s own mass exceeds 10% of the specified maximum allowable loads, the ρH is not to be taken less than the combined load of deck mass and maximum allowable deck load.


DET NORSKE VERITAS

SECTION 5LONGITUDINAL STRENGTH

A. General

A 100 Introduction

101 In this section the requirements regarding the longitudi-nal hull girder scantlings with respect to bending and shear aregiven.

102 The wave bending moments and shear forces are givenas the design values with a probability of exceedance of 10- 8.

These values are applied when determining the section modu-lus and the shear area of the hull girder and in connection withcontrol of buckling and ultimate strength. Reduced values willhave to be used when considering combined local and longitu-dinal stresses in local elements, see B204.

103 The buckling strength of longitudinal members is notcovered by this section. Requirements for such control are giv-en in Sec.14.

104 For ships with small block coefficient, high speed andlarge flare the hull girder buckling strength in the forebodymay have to be specially considered based on the distributionof still water and vertical wave bending moments indicated inB100 and B200 respectively. In particular this applies to shipswith length L > 120 m and speed V > 17 knots.

105 For narrow beam ships the combined effects of verticaland horizontal bending of the hull girder may have to be spe-cially considered as indicated in C300.

106 For ships with large deck openings (total width of hatchopenings in one transverse section exceeding 65% of the ship'sbreadth or length of hatch opening exceeding 75% of holdlength) the longitudinal strength including torsion may be re-quired to be considered as given in Pt.5 Ch.2 Sec.6 B200. Forships with block coefficient < 0,7 the longitudinal/localstrength outside of the midship region may, subject to specialconsideration in each case, be taken according to Pt.5 Ch.2Sec.6 B.

107 In addition to the limitations given in 104 to 106, specialconsiderations will be given to vessels with the following pro-portions:

L/B ≤ 5 B/D ≥ 2,5.

A 200 Definitions

201 Symbols:

IN = moment of inertia in cm4 about the transverse neu-tral axis

IC = moment of inertia in cm4 about the vertical neutralaxis

CW = wave coefficient as given in Sec.4 BSN = first moment of area in cm3 of the longitudinal ma-

terial above or below the horizontal neutral axis,taken about this axis

zn = vertical distance in m from the baseline or decklineto the neutral axis of the hull girder, whichever isrelevant

za = vertical distance in m from the baseline or decklineto the point in question below or above the neutralaxis, respectively

MS = design stillwater bending moment in kNm as givenin B100

QS = design stillwater shear force in kN as given in B100MW = rule wave bending moment in kNm as given in

B200QW = rule wave shear force in kN as given in B200

M WH = rule wave bending moment about the vertical axis asgiven in B205

M WT = rule wave torsional moment as given in B206.

202 Terms:

Effective longitudinal bulkhead is a bulkhead extending frombottom to deck and which is connected to the ship's side bytransverse bulkheads both forward and aft.

Loading manual is a document which describes:

— the loading conditions on which the design of the ship hasbeen based, including permissible limits of still waterbending moment and shear force and shear force correc-tion values and, where applicable, permissible limits relat-ed to still water torsional moment 1) and lateral loads

— the results of calculations of still water bending moments,shear forces and still water torsional moments if unsym-metrical loading conditions with respect to the ships cen-treline

— the allowable local loadings for the structure (hatch cov-ers, decks, double bottom, etc.).

1) Permissible torsional still water moment limits are generally applicablefor ships with large deck openings as given in 106 and class notationContainer or Container Carrier.

For bulk carriers of 150 m in length and above, additional re-quirements as given in Pt.5 Ch.2 Sec.5 A also apply.

A Loading computer system is a system, which unless statedotherwise is digital, by means of which it can be easily andquickly ascertained that, at specified read-out points, the stillwater bending moments, shear forces, and the still water tor-sional moments and lateral loads, where applicable, in any loador ballast condition will not exceed the specified permissiblevalues.

Guidance note:The term "Loading computer system" covers the term "Loadinginstrument" as commonly used in IACS UR S1.


An operation manual is always to be provided for the loadinginstrument. Single point loading instruments are not accepta-ble.

Category I ships. Ships with large deck openings where com-bined stresses due to vertical and horizontal hull girder bend-ing and torsional and lateral loads have to be considered.

Ships liable to carry non-homogeneous loadings, where thecargo and/or ballast may be unevenly distributed. Ships lessthan 120 m in length, when their design takes into account un-even distribution of cargo or ballast, belong to Category II.

Chemical tankers and gas carriers.

Category II Ships. Ships with arrangement giving small possi-bilities for variation in the distribution of cargo and ballast, andships on regular and fixed trading pattern where the LoadingManual gives sufficient guidance, and in addition the excep-tion given under Category I.

B. Still Water and Wave Induced Hull Girder Bending Moments and Shear Forces

B 100 Stillwater conditions101 The design stillwater bending moments and shear forcesare to be taken as the maximum value in each section along the


DET NORSKE VERITAS

ship length as obtained from the calculation for load conditionsspecified in 102.

For these calculations, downward loads are assumed to be tak-en as positive values, and are to be integrated in the forward di-rection from the aft end of L. The sign conventions of QS andMS are as shown in Fig. 1.

Fig. 1Sign Conventions of QS and MS

102 The stillwater bending moments and shear forces are tobe calculated for all relevant homogeneous and non-homoge-neous, full and part load conditions, including tank cleaningconditions for ships intended to carry cargo oil, as well as bal-last conditions and docking condition afloat.

For oil carriers complying with the requirements for the segre-gated ballast tanks as stipulated in Pt.5 Ch.3 Sec.3 B, the bal-last conditions shall in addition to the segregated ballastcondition include one or more relevant conditions with addi-tional ballast in cargo tanks.

For product tankers and chemical tankers conditions with highdensity or segregated cargo are to be included.

For smaller ships the stillwater bending moments and shearforces may have to be calculated for ballast and particular non-homogeneous load conditions after special considerations.

For each condition the calculations are to be based on relevantand realistic amounts of bunker, fresh water and stores at de-parture and arrival.

Also short voyage or harbour conditions including loading andunloading transitory conditions are to be checked where appli-cable.

Guidance note:It is advised that the ballast conditions determining the scantlingsare based on the filling of ballast in as few cargo tanks as practi-cable, and it is important that the conditions will allow cleaningof all cargo tanks with the least possible shifting.


103 The design stillwater bending moments amidships (sag-ging and hogging) are normally not to be taken less than:

MS = MSO (kNm)

M SO = – 0,065 CWU L2 B (CB + 0,7) (kNm) in sagging = CWU L2 B (0,1225 – 0,015 CB) (kNm) in hoggingC WU = CW for unrestricted service.

Larger values of MSO based on cargo and ballast conditions areto be applied when relevant, see 102.

For ships with arrangement giving small possibilities for vari-ation of the distribution of cargo and ballast, MSO may be dis-pensed with as design basis.

104 When required in connection with stress analysis orbuckling control, the stillwater bending moments at arbitrary

positions along the length of the ship are normally not to betaken less than:

MS = ksm MSO (kNm)

M SO = as given in 103ksm = 1,0 within 0,4 L amidships = 0,15 at 0,1 L from A.P. or F.P. = 0,0 at A.P. and F.P.

Between specified positions ksm is to be varied linearly.

Values of ksm may also be obtained from Fig. 2.

Fig. 2Stillwater bending moment

The extent of the constant design bending moments amidshipsmay be adjusted after special consideration.

105 The design values of stillwater shear forces along thelength of the ship are normally not to be taken less than:

QS = ksq QSO (kN)

MSO = design stillwater bending moments (sagging or hog-ging) given in 103.

QSO 5MSO

L------------ (kN)=


DET NORSKE VERITAS

Larger values of QS based on load conditions (QS =QSL) are to be applied when relevant, see 102. Forships with arrangement giving small possibilities forvariation in the distribution of cargo and ballast, QSOmay be dispensed with as design basis

k sq = 0 at A.P. and F.P. = 1,0 between 0,15 L and 0,3 L from A.P. = 0,8 between 0,4 L and 0,6 L from A.P. = 1,0 between 0,7 L and 0,85 L from A.P.

Between specified positions ksq is to be varied linearly.

Sign convention to be applied:

— when sagging condition positive in forebody, negative inafterbody

— when hogging condition negative in forebody, positive inafterbody.

B 200 Wave load conditions201 The rule vertical wave bending moments amidships aregiven by:

MW = MWO (kNm)

MWO = – 0,11 α CW L2 B (CB + 0,7) (kNm) in sagging = 0,19 α CW L2 B C B (kNm) in hoggingα = 1,0 for seagoing conditions = 0,5 for harbour and sheltered water conditions (en-

closed fjords, lakes, rivers).

CB is not be taken less than 0,6.

202 When required in connection with stress analysis orbuckling control, the wave bending moments at arbitrary posi-tions along the length of the ship are normally not to be takenless than:

MW = kwm MWO (kNm)

M WO = as given in 201k wm = 1,0 between 0,40 L and 0,65 L from A.P. = 0,0 at A.P. and F.P.

For ships with high speed and/or large flare in the forebody theadjustments to kwm as given in Table B1, limited to the controlfor buckling as given in Sec.14, apply.

C AV =

C AF =

cv =

A DK = projected area in the horizontal plane of upper deck(including any forecastle deck) forward of 0,2 Lfrom F.P.

A WP = area of waterplane forward of 0,2 L from F.P. atdraught T

zf = vertical distance from summer load waterline todeckline measured at F.P.

Between specified CA-values and positions k wm is to be variedlinearly. Values of k wm may also be obtained from Fig. 3.

Fig. 3Wave bending moment distribution

203 The rule values of vertical wave shear forces along thelength of the ship are given by:

Positive shear force, to be used when positive still water shearforce:

Q WP = 0,3 β kwqp CW L B (C B + 0,7) (kN)

Negative shear force, to be used when negative still watershear force:

Q WN = – 0,3 β kwqn CW L B (C B + 0,7) (kN)

Positive shear force when there is a surplus of buoyancy for-ward of section considered, see also Fig. 1.

Negative shear force when there is a surplus of weight forwardof section considered.

β = 1,0 for seagoing conditions = 0,5 for harbour and sheltered water conditions (en-

closed fjords, lakes, rivers)kwqp = 0 at A.P. and F.P. = 1,59 CB/(CB + 0,7) between 0,2 L and 0,3 L from

A.P. = 0,7 between 0,4 L and 0,6 L from A.P. = 1,0 between 0,7 L and 0,85 L from A.P.kwqn = 0 at A.P. and F.P. = 0,92 between 0,2 L and 0,3 L from A.P. = 0,7 between 0,4 L and 0,6 L from A.P. = 1,73 CB/(CB + 0,7) between 0,7 L and 0,85 L from

A.P.CW = as given in 201.

For ships with high speed and/or large flare in the forebody, theadjustments given in Table B2 apply.

Table B1 Adjustments to kwm

Load condition Sagging and hogging Sagging only

CAV ≤ 0,28 ≥ 0,32 1 )CAF ≤ 0,40 ≥ 0,50

kwmNo

adjust-ment

1,2 between 0,48 L and

0,65 L from A.P. 0,0 at F.P. and A.P.

No adjust-ment

1,2 between 0,48 L and

0,65 L from A.P. 0,0 at F.P. and A.P.

1) Adjustment for CAV not to be applied when CAF ≥ 0,50.

cvV

L---------

cvV

L---------

ADK AWP–

Lzf

------------------------------+

L50

--------- , maximum 0,2

Table B2 Adjustments to kwq

Load condition Sagging and hogging Sagging only

CAV ≤ 0,28 ≥ 0,32 1 )CAF ≤ 0,40 ≥ 0,50

Multiply kwq by 1,0

1,0 aft of 0,6 L from

A.P. 1,2 between

0,7 L and 0,85 L

from A.P.

1,0

1,0 aft of 0,6 L from

A.P. 1,2 between

0,7 L and 0,85 L

from A.P.1) Adjustment for CAV not to be applied whenCAF ≥ 0,50.


DET NORSKE VERITAS

C AV = as defined in 202C AF = as defined in 202.

Between specified positions kwq is to be varied linearly. Val-ues of kwq may also be obtained from Fig. 4.

Fig. 4Wave shear force distribution

204 When hull girder stresses due to wave loads are com-bined with local stresses in girder systems, stiffeners and plat-ing in accordance with Sec.13, the wave bending moments andshear forces may be reduced as follows:

MWR = 0,59 MW

QWR = 0,59 QW

205 The rule horizontal wave bending moments along thelength of the ship are given by:

M WH = 0,22 L9/4 ( T + 0,3 B) CB (1 – cos (360 x/L )) (kNm)

x = distance in m from A.P. to section considered.

206 The rule wave torsional moments along the length of theship due to the horizontal wave- and inertia forces and the ro-tational wave- and inertia moment loads are given by:

M WT = K T1 L5/4 (T + 0,3 B) CB ze

± K T2 L4/3 B2 CSWP (kNm)

K T1 = 1,40 sin (360 x/L)K T2 = 0,13 (1 – cos (360 x/L))CSWP = AWP/(LB)A WP = water plane area of vessel in m2 at draught Tze = distance in m from the shear centre of the midship

section to a level 0,7 T above the base linex = distance in m from A.P. to section considered.

C. Bending Strength and Stiffness

C 100 Midship section particulars

101 When calculating the moment of inertia and sectionmodulus, the effective sectional area of continuous longitudi-

nal strength members is in general the net area after deductionfor openings as given in E.

The effective sectional area of strength members betweenhatch openings in ships with twin or triple hatchways is to betaken as the net area multiplied by a factor 0,6 unless a higherfactor is justified by direct calculations.

Superstructures which do not form a strength deck are not to beincluded in the net section. This applies also to deckhouses,bulwarks and non-continuous hatch side coamings.

For definition of strength deck, see Sec.1 B205.

102 The rule section modulus generally refers to the baselineand the deckline.

103 Continuous trunks, longitudinal hatch coamings andabove deck longitudinal girders are to be included in the longi-tudinal sectional area provided they are effectively supportedby longitudinal bulkheads or deep girders. The deck modulusis then to be calculated by dividing the moment of inertia bythe following distance, provided this is greater than the dis-tance to the deck line at side:

ya = distance in m from the centre line of the ship to the sideof the strength member.

ya and za are to be measured to the point giving the largest val-ue of z.

104 The main strength members included in the hull sectionmodulus calculation are to extend continuously through thecargo region and sufficiently far towards the ends of the ship.

105 Longitudinal bulkheads are to terminate at an effectivetransverse bulkhead, and large transition brackets are to be fit-ted in line with the longitudinal bulkheads.

C 200 Extent of high strength steel (HS-steel)

201 The vertical extent of HS-steel used in deck or bottom isnot to be less than:

f2 = stress factor, for the bottom given in Sec.6 and for thedeck in Sec.8

f3 = material factor (general symbol f1) for the members lo-cated more than zhs from deck or bottom, see Fig. 5.

Fig. 5Vertical extent of HS-steel

z zn za+( ) 0 9, 0 2ya

B-----,+ , minimum zn=

zhs zn

f2 f3–

f2---------------=


DET NORSKE VERITAS

For narrow beam ships the vertical extent of HS-steel mayhave to be increased after special consideration.

202 The longitudinal extent of HS-steel used in deck or bot-tom is not to be less than xhs as indicated in Fig. 6.

Fig. 6Longitudinal extent of HS-steel

xhs (minimum) implies that the midship scantlings are to bemaintained outside 0,4 L amidships to a point where the scant-lings equal those of an identical ship built of normal strengthsteel over the full length. xhs (general) implies that the scant-lings outside 0,4 L may be gradually reduced as if HS-steel wasused over the full length. Where material strength groupchanges, however, continuity in scantlings is to be maintained.

C 300 Section modulus

301 The requirements given in 302 and 303 will normally besatisfied when calculated for the midship section only, provid-ed the following rules for tapering are complied with:

a) Scantlings of all continuous longitudinal strength mem-bers are to be maintained within 0,4 L amidships.

In special cases, based on consideration of type of ship,hull form and loading conditions, the scantlings may begradually reduced towards the ends of the 0,4 L amidshippart, bearing in mind the desire not to inhibit the vessel'sloading flexibility.

b) Scantlings outside 0,4 L amidships are gradually reducedto the local requirements at the ends, and the same materialstrength group is applied over the full length of the ship.

The section modulus at other positions along the length of theship may have to be specially considered for ships with smallblock coefficient, high speed and large flare in the forebody orwhen considered necessary due to structural arrangement, seeA106.

In particular this applies to ships of length L > 120 m and speedV > 17 knots.

302 The midship section modulus about the transverse neu-tral axis is not to be less than:

C WO = 10.75 – [ (300 – L) /100 ] 3/2 for L < 300 = 10.75 for 300 ≤ L ≤ 350 = 10.75 – [ (L – 350) /150 ] 3/2 for L > 350

Values of CWO are also given in Table C1.

CB is in this case not to be taken less than 0.60.

For ships with restricted service, CWO may be reduced as fol-lows:

— service area notation R0: No reduction— service area notation R1: 5%— service area notation R2: 10%— service area notation R3: 15%— service area notation R4: 20%— service area notation RE: 25%.

303 The section modulus requirements about the transverseneutral axis based on cargo and ballast conditions are given by:

σl = 175 f1 N/mm2 within 0,4 L amidship = 125 f1 N/mm2 within 0,1 L from A.P. or F.P.

Between specified positions σl is to be varied linearly.

304 The midship section modulus about the vertical neutralaxis (centre line) is normally not to be less than:

The above requirement may be disregarded provided the com-bined effects of vertical and horizontal bending stresses atbilge and deck corners are proved to be within 195 f1 N/mm2.

The combined effect may be taken as:

σs = stress due to MSσw = stress due to MWσ wh = stress due to MWH, the horizontal wave bending mo-

ment as given in B205.

305 The stress concentration factor due to fatigue control ofscallops e.g. in way of block joints is not to be greater than:

- for scallops in deck

- for scallops in bottom

σd = permissible single amplitude dynamic stress in(N/mm2)

= 110 c, in general

ZO

CWO

f1------------ L

2B CB 0 7,+( ) (cm

3)=

Table C1 Values for CWO

L CWO L CWO L CWO

100110120130140150

7,928,148,348,538,738,91

160170180190200210220230240250

9,099,279,449,609,759,9010,0310,1610,2910,40

260280300350370390410440470500

10,5010,6610,7510,7510,7010,6110,5010,2910,039,75

ZO

MS MW+

σl--------------------------- 10

3 (cm

3)=

ZOH5f1---- L

9 4⁄T 0 3B,+( ) CB (cm

3)=

σs σw2 σwh

2++

Kga

σd Zdeck

240 MW hog, MW sag,–( )-------------------------------------------------------------=

Kga

σd Zbottom

240 MW hog, MW sag,–( )-------------------------------------------------------------=


DET NORSKE VERITAS

c = 1,0 for uncoated cargo and ballast tanks = 1,15 for fully coated tanks and fuel tanks = 1,28 for dry cargo holds and void spacesZdeck = midship section modulus in cm3 at deck as builtZbottom = midship section modulus in cm3 at bottom as

builtMW, hog = the rule vertical wave hogging bending moment

amidship, as defined in B201MW, sag = the rule vertical wave sagging bending moment

amidship, as defined in B201.

Stress concentration factors for scallops are given in Table C2.

C 400 Moment of inertia

401 The midship section moment of inertia about the trans-verse neutral axis is not to be less than:

I = 3 CW L3 B (CB + 0,7) (cm4)

D. Shear Strength

D 100 General

101 The shear stress in ship's sides and longitudinal bulk-heads is not to exceed 110 f1 N/mm2. In addition the plate pan-els are to be checked for adequate shear and combinedbuckling strength as outlined in Sec.14 B300 and B500.

102 The thickness requirements given below apply unlesssmaller values are proved satisfactory by an accepted methodof direct stress calculation, including a shear flow calculationand a calculation of bottom load distribution.

Acceptable calculation methods are outlined in ClassificationNotes on «Strength Analysis of Hull Structures» for variousship types.

103 The thickness requirements for side shell (or combinedthickness of inner and outer shell when double skin) and pos-sible longitudinal bulkhead are given by:

Φ = shear force distribution factor as given in Table D1

For these and other arrangements Φ may be taken from a directshear flow calculation.

∆ QS = shear force correction due to shear carrying longitu-dinal bottom members (girders or stiffeners) anduneven transverse load distribution

= 0 when QS = ksq QSO, as given in B105 = ∆ QSL when QS = QSL, i.e. based on cargo and bal-

last conditions

∆ QSL is given in 300 for ships with two LBHD.

∆ QSL is given in 400 for ships with centre line BHD.

∆ QSL is given in 400 for ships without LBHD.

∆ QSL is given in 200 for bulk and OBO carriers.

For other arrangements ∆ QS will be specially considered.

τ = 110 f1 N/mm2, provided the buckling strength (see101) does not require smaller allowable stress.

IN / SN may normally be taken as 90 D at the neutral axis.

AS = mean shear area in cm2 of the side shell or double skinin the side tank under consideration, taken as the totalcross-sectional area of the plating over the depth D

AL = mean shear area in cm2 of the longitudinal bulkhead inthe side tank under consideration, taken as the totalcross-sectional area of the bulkhead plating betweenbottom and deck for plane bulkheads. For corrugatedbulkheads the area to be reduced with the relation be-tween projected length and expanded length of the cor-rugations

AC = mean shear area in cm2 of the centre line bulkhead inthe tank under consideration, taken as the total cross-sectional area of the bulkhead plating between bottomand deck for plane bulkheads. For corrugated bulk-

Table C2 Stress concentration factors Kga for scallops

Structure Point A Point B

1,67 1,2

1,13 1,2

1,07 1,2

For scallops without transverse welds, the K-factor at B will be governing for the design

Table D1 Shear force distribution factor

ΦS = 0,5

ΦS = 0,5

tΦ QS QW+( ) 0 5∆QS,±

τ-----------------------------------------------------------------

SN

IN------- 10

2 (mm)=

ΦS 0 109, 0 0911ASAL--------,+=

ΦL 0 391, 0 0911ASAL--------,–=

ΦS 0 338, 0 0167ASAC--------,+=

ΦC 0 324, 0 0334ASAC--------,–=


DET NORSKE VERITAS

heads the area is to be reduced with the relation be-tween projected length and expanded length of thecorrugations.

104 Minimum shear area at fore end of machinery spaces(machinery aft) is to be based on fully loaded condition at ar-rival. Minimum shear area at after end of fore peak is to bebased on light ballast condition with fore peak filled, or fullyloaded condition at arrival, whichever gives the largest sheararea. If a deep tank is positioned between the forward cargohold/cargo tank and the fore peak, the shear area at after end ofthe deep tank is to be based on a light ballast condition withboth fore peak and deep tank filled, or fully loaded conditionat arrival, whichever gives the largest shear area.

For ships where fore peak and any deep tank are not intendedto carry ballast when the ship is in light ballast condition, theshear force determining scantlings will be specially consid-ered.

D 200 Ships with single or double skin and without other effective longitudinal bulkheads

201 The thickness of side shell is not to be less than given bythe formula in 103. When QS = QSL, the shear force transmit-ted directly to one transverse bulkhead from the hold in ques-tion may be expressed as follows:

PH = cargo or ballast in t for the hold in questionPN = bunker or ballast (t) in double bottom tank no. N (port

and starboard) situated below considered holdT1 = draught in m at the middle of holdCP = load correction factor in kN/tCD = buoyancy correction factor in kN/m

KN = to be calculated for each filled tank

H = height of hold in mVH = volume of hold in m3

AN = horizontal cross-sectional area (m2) (port and star-board) at level of inner bottom tank N

AN ' = horizontal cross-sectional area (m2) (port and star-board) at level of inner bottom of that part of the dou-ble bottom tank no. N which is situated within thelength of the considered hold

AB ' = sum of all AN ' .

The ∆ Q-value is to be deducted from the peak-values of theconventional shear force curve in way of loaded hold betweenempty holds or empty hold between loaded holds as shown inFig. 7. For other loading conditions the sign convention is tobe applied in a similar manner.

For practical purposes CP and CD may be taken as constants in-dependent of cargo filling height and draught respectively.

The following values may be used:

CD = 10 C BDB LH (kN/m)

B DB = breadth of the flat part of the double bottom in mLH = length of hold in m.

Fig. 7Shear force correction

202 For shell plates completely within a top wing tank or ahopper tank, the thickness requirements calculated from theformula in 103 may be divided by 1,2.

D 300 Ships with two effective longitudinal bulkheads

301 Between fore bulkhead in after cargo tank/hold and afterbulkhead in fore cargo tank/hold, the sum of thickness at 0,5 Dof ship's sides and longitudinal bulkheads is normally not to beless than:

of which the thickness of each longitudinal bulkhead at 0,5 Dis not to be less than:

Above 0,5 D the thickness of the longitudinal bulkhead platingmay be linearly reduced to 90% at deck.

Outside the region between fore bulkhead in after cargo tankand after bulkhead in fore cargo tank, the sum of thicknessesof ship's sides and longitudinal bulkheads can be varied linear-ly to give the shear area required by 104 at fore end of machin-ery spaces and after end of fore peak or adjacent deep tank.

302 The thickness of the double side and the longitudinalbulkhead is not to be less than given by the formula in 103.Above 0,5 D the thickness of the plating may be linearly re-duced to 90% at deck.

When QS = QSL the shear force correction due to load distribu-tion is given by:

— for the double side:

∆QSL Cp PH KNPN( )�+( ) CDT1 (kN)–=

VH AN ′H AN AB ′-------------------------

CP

9 81 C BDB LH H,VH

-------------------------------------------- (kN/t)=

CB

2 2 B LH+( ),------------------------------- (for conventional designs)=

Load in double bottom in centre tank to be included in PC

Σ t2 7 LB( )1 3⁄,

f1------------------------------- Σtk (mm)+=

t0 6 LB( )1 3⁄,

f1--------------------------------- tk (mm)+=


DET NORSKE VERITAS

— for the longitudinal bulkhead:

CT = fraction of the centre tank load going through longi-tudinal girders directly to the transverse bulkheadfound by a direct calculation. A value of NL/(NL+NB) may otherwise be used

PC = resulting force in kN due to difference between tankcontents and buoyancy along the centre tank lengthlc. PC is always to be taken positive. If the loadingPC is variable along the length, the PC term is to becalculated specially for each part loading

lc = distance in m between oiltight transverse bulkheadsin the centre tank

l = distance in m between oiltight transverse bulkheadsin the side tank

s = distance in m between floors in the centre tankNL = number of longitudinal girders in centre tankNB = number of transverse floors in centre tankΦS = as given in 103ΦL = as given in 103.

r expresses the ratio between the part of loading from the washbulkheads and the transverses in the centre tank which is car-ried to the ship's side, and the part which remains in the longi-tudinal bulkhead. For preliminary calculations, r may be takenas 0,5.

r may be derived from the following formula:

b = mean span of transverses in the side tank in m (includ-ing length of brackets)

AT = shear area of a transverse wash bulkhead in the sidetank in cm2, taken as the smallest area in a vertical sec-tion

NS = number of wash bulkheads in the side tank along thelength l.

R is an expression for the total efficiency of the girder framesin the side tank, given by the formula:

n = number of girder frames along the tank length lAR = shear area in cm2 of a transverse girder frame in the

side tank, taken as the sum of the shear areas of trans-verses and cross ties

γ =

IR = moment of inertia in cm4 of a transverse girder framein the side tank, taken as the sum of the moment of in-ertia of transverses and cross ties.

Plus or minus sign before the ∆ QS-term in the expressions forplate thickness depends on whether inclination of the shearforce curve increases or decreases due to the loading in the

centre tank. For the longitudinal bulkheads this relation is in-dicated in Table D2.

For the side shell the change in inclination is contrary to thatgiven in Table D2.

At the middle point of l the shear force curve is supposed to re-main unchanged.

If the turning of the shear force curve leads to an increasedshear force, plus sign is to be used, otherwise minus sign. Anexample where the slope increases for the longitudinal bulk-head and decreases for the side shell, is shown in Fig. 8.

Fig. 8Shear force correction

D 400 Ships with number of effective longitudinal bulk-heads different from two

401 The sum of thicknesses at 0,5 D of ship's sides and lon-gitudinal bulkhead(s) is not to be less than:

n = number of longitudinal bulkheads.

Above 0,5 D the thickness of the longitudinal bulkhead platingmay be linearly reduced to 90% at deck.

The requirement applies to the region between fore bulkheadin after cargo tank and after bulkhead in fore cargo tank. Out-side this region, the sum of thicknesses may be varied linearlyto give the shear area required by 103 at fore end of machineryspaces and after end of fore peak or adjacent deep tank.

402 For ships with double sides and a centre line bulkheadthe thickness of centre line bulkhead and the double side is notto be less than given by the formula in 103. Above 0,5 D the

∆QSL 0 5 PC 1slc----–

� �� 1 CT–( ) r

r 1+----------- 2ΦS– (kN),=

∆QSL 0 5 PC 1slc----–

� ��

1 CT–( )r 1+

--------------------- 2ΦL– (kN),=

r1

AL

AS-------

2 Ns 1+( )bAL

l NsAT R+( )-----------------------------------+

-------------------------------------------------=

Rn2--- 1–

� ��

AR

γ------- (cm

2)=

1300b

2AR

IR-----------------------+

Table D2 Shear force correction for longitudinal bulkheadThe ship has

over the length:

The centre tank has over

the length:

Inclination of the shear force curve:

excess in buoyancy excess in buoyancy increases

excess in buoyancy excess in weight decreases

excess in weight excess in weight increases

excess in weight excess in buoyancy decreases

Σt2 6 LB( )1 3⁄,

f1-------------------------------- 0 8, 0 1n,+( ) Σtk (mm)+=


DET NORSKE VERITAS

thickness of the plating may be linearly reduced to 90% atdeck.

When QS = QSL, the shear force correction due to load distri-bution is given by:


— for the centre line bulkhead:

PC = resulting force in kN due to difference between tankcontents and buoyancy along the the centre tank lengthlc. PC is always to be taken positive. If the loading PCis variable along the length, the PC term is to be calcu-lated specially for each part loading

CT = fraction of the centre tank load going through the sidegirders to the transverse bulkhead found by a directcalculation

A value of NL/(NL+NB) may otherwise be used.lc = distance in m between oiltight transverse bulkheads in

the centre tanks = distance in m between floors in the centre tankNL = number of longitudinal girders in one centre tankNB = number of transverse floors in the centre tankΦS = as given in 103ΦC = as given in 103.

Plus or minus sign before the ∆ QS -term in the expression forplate thickness depends on whether the expression in the ( ) af-ter PC in the formula above is a +value or a -value. A +valuegives increased inclination of the shear force curve and hencean increased shear force in the end of the tank where the shearforce is highest.

403 For ships with double sides and no longitudinal bulk-heads the thickness of the double side is not to be less than giv-en by the formula in 103.

Above 0,5 D the thickness of the double side plating may belinearly reduced to 90% at deck.

When QS = QSL, the shear force correction due to load distri-bution is given by:


∆ QSL = CT PC (kN)

PC = resulting force in kN due to difference between tankcontents and buoyancy along the the centre tanklength lc. PC is always to be taken positive. If theloading PC is variable along the length, the term PCis to be calculated specially for each part loading

CT = fraction of the centre tank load going to the trans-verse bulkhead found by a direct calculation. Avalue of 0,5 b /(b + lc) may otherwise be used

b = breadth in m of the inner bottom between the innersides

lc = distance in m between oiltight transverse bulkheadsin the centre tank

s = distance in m between floors in the centre tank

The shear force correction ∆ QS for the ship side may be takenaccording to the principles outlined in Fig. 7, always giving adecreased inclination of the shear force curve.

D 500 Strengthening in way of transverse stringers501 The local thickness of ship's sides and longitudinal bulk-heads supporting stringers on transverse bulkheads is not to beless than:

PSTR = stringer supporting force in kN based on designloads in accordance with Sec.4. At longitudinalbulkheads PSTR is to be taken as the sum of forces at each sideof the bulkhead when acting simultaneously in thesame direction

bstr = largest depth of stringer in m at support, brackets in-cluded

tr = rule thickness in accordance with 103, with full val-ue of QW.

The strengthened area is to extend not less than 0,5 m forwardand aft of the stringer including brackets, and not less than 0,2bstr above and below the stringer.

E. Openings in Longitudinal Strength Members

E 100 Positions101 The keel plate is normally not to have openings. In thebilge plate, within 0,6 L amidships, openings are to be avoidedas far as practicable. Any necessary openings in the bilge plateare to be kept clear of the bilge keel.

102 Openings in strength deck within 0,6 L amidships (for«open» ships within cargo hold region) are as far as practicableto be located inside the line of large hatch openings. Necessaryopenings outside this line are to be kept well clear of ship's sideand hatch corners. Openings in lower decks are to be kept clearof main hatch corners and other areas with high stresses.

103 Openings in side shell, longitudinal bulkheads and lon-gitudinal girders are to be located not less than twice the open-ing breadth below strength deck or termination of roundeddeck corner.

104 Small openings are generally to be kept well clear of oth-er openings in longitudinal strength members. Edges of smallunreinforced openings are to be located a transverse distancenot less than four times the opening breadth from the edge ofany other opening.

E 200 Deduction-free openings201 When calculating the midship section modulus openingsexceeding 2,5 m in length or 1,2 m in breadth and scallops,where scallop welding is applied, are to be deducted from thesectional areas of longitudinal members.

202 Smaller openings (manholes, lightening holes, singlescallops in way of seams etc.) need not to be deducted providedthat the sum of their breadths or shadow area breadths in onetransverse section does not reduce the section modulus at deckor bottom by more than 3% and provided that the height of

PC = PC1 + PC2Load in the double bottom below the centre tanks to be included in PC

Load in double bottom below centre tank to be included in PC

∆QSL PC 0 3 1slc----–

� �� 1 CT–( ), ΦS–

� �� (kN)=

∆QSL PC 0 4 1slc----–

� �� 1 CT–( ), ΦC–

� �� (kN)=

tPSTR

240 f1 bstr------------------------- 0 75 tr (mm),+=


DET NORSKE VERITAS

lightening holes, draining holes and single scallops in longitu-dinals or longitudinal girders does not exceed 25% of the webdepth, for scallops maximum 75 mm.

203 In longitudinals, the longitudinal distance between sin-gle openings or group of openings is not to be less than 10times the height of opening.

204 A deduction-free sum of smaller openings breadths inone transverse section in the bottom or deck area equal to

0,06 (B – Σ b)

may be considered equivalent to the above reduction in sectionmodulus.

B = breadth of shipΣ b = sum of breadths of large openings.

205 When calculating deduction-free openings, the openingsare assumed to have longitudinal extensions as shown by theshaded areas in Fig. 9, i.e. inside tangents at an angle of 30° toeach other.

Fig. 9Deduction-free openings

Example for transverse section III:

Σ bIII = bl + bll + blll

206 It is assumed that the deduction-free openings are ar-ranged approximately symmetric about the ship's centre line,and that the openings do not cut any longitudinal or girder in-cluded in the midship section area. Openings in longitudinalsare normally to be of elliptical shape or equivalent design andare normally to be kept clear of the connecting weld. Whenflush openings are necessary for drainage purposes, the weldconnections are to end in soft toes.

E 300 Compensations

301 Compensation for not deduction-free openings may beprovided by increased sectional area of longitudinals or gird-ers, or other suitable structure. The area of any reinforcementas required in 400 is not to be included in the sectional area ofthe compensation.

E 400 Reinforcement and shape of smaller openings

401 In strength deck and outer bottom within 0,6 L amid-ships (for «open» ships within the total cargo hold region), cir-cular openings with diameter equal to or greater than 0,325 mare to have edge reinforcement. The cross-sectional area ofedge reinforcements is not to be less than:

2,5 b t (cm2)

b = diameter of opening in mt = plating thickness in mm.

The reinforcement is normally to be a vertical ring welded tothe plate edge. Alternative arrangements may be accepted butthe distance from plating edge to reinforcement is in no case toexceed 0,05 b.

402 In areas specified in 401 elliptical openings with breadthgreater than 0,5 m are to have edge reinforcement if theirlength/breadth ratio is less than 2. The reinforcement is to beas required in 401 for circular openings, taking b as the breadthof the opening.

403 In areas specified in 401 rectangular and approximatelyrectangular openings are to have a breadth not less than 0,4 m.For corners of circular shape the radius is not to be less than:

R = 0,2 b

b = breadth of opening.

The edges of such rectangular openings are to be reinforced asrequired in 401.

For corners of streamlined shape, as given by Fig. 10 and tableE1, the transverse extension of the curvature is not to be lessthan:

a = 0,15 b (m)

Edge reinforcement will then generally not be required. Forlarge hatch openings, see 500.

404 Openings in side shell in areas subjected to large shearstresses are to be of circular shape and are to have edge rein-forcement as given in 401 irrespective of size of opening.

E 500 Hatchway corners

501 For corners with rounded shape, the radius is within 0,6L amidships generally not to be less than:

b = breadth of hatchway in ml = longitudinal distance in m between adjacent hatch-

ways.

(B – b) is not to be taken less than 7,5 m, and need not be takengreater than 15 m.

For local reinforcement of deck plating at circular corners, seeSec.8 A405.

When a corner with double curvature is adopted, further reduc-tion in radius will be considered.

For corners of streamlined shape, as given by Fig. 10 and TableE1, the transverse extension of the curvature is not to be lessthan:

r 0 03 1 5, lb---+

� �� B b–( ) (m),=

lb--- need not be taken greater than 1,0.

a 0 025 1 5, lb---+

� �� B b–( ) (m),=


DET NORSKE VERITAS

Fig. 10Streamlined deck corner

502 Alternative hatch corner designs (e.g. key hole) may beaccepted subject to special consideration in each case.

E 600 Miscellaneous

601 Edges of openings are to be smooth. Machine flame cutopenings with smooth edges may be accepted. Small holes areto be drilled.

Hatch corners may in special cases be required to be groundsmooth. Welds to the deck plating within the curved hatch cor-ner region are as far as possible to be avoided.

602 Studs for securing small hatch covers are to be fastenedto the top of a coaming or a ring of suitable thickness weldedto the deck. The studs are not to penetrate the deck plating.

603 The design of the hatch corners will be specially consid-ered for ships with very large hatch openings («open» ships),where additional local stresses occur in the hatch corner areadue to torsional warping effects and transverse bulkhead reac-tions.

F. Loading Guidance Information

F 100 General

101 All ships covered by Reg. 10 of the Load Line Conven-tion (Ch.5 Sec.2 A100) are to be provided with an approvedloading manual.

The requirements given in this subsection are considered tofulfil Reg. 10(1) of the Load Line Convention for all classedships of 65 m in length and above. However, a loading manual,considering longitudinal strength, is not required for a categoryII ship with length less that 90 m where the maximum dead-weight does not exceed 30% of the maximum displacement.

102 If a loading computer system is installed onboard a ship,the system is to be approved in accordance with requirementsin Pt.6 Ch.9.

103 All ships of category I (see A202) are in addition to theloading manual to be provided with a loading computer systemapproved and certified for calculation and control of hullstrength in accordance with the requirements for the additionalclass notation LCS(S) as given in Pt.6 Ch.9.

F 200 Conditions of approval of loading manuals

201 The approved loading manual is to be based on the finaldata of the ship. The manual is to include the design loadingand ballast conditions upon which the approval of the hullscantlings is based, see B101. Possible limitations are:

— draught limitations (in ballast etc.)— load specifications for cargo decks— cargo mass- and cargo angle of repose restrictions— cargo density- and filling heights for cargo tanks— restrictions to GM-value.

Guidance note:The loading manual should contain the design loading and ballastconditions, subdivided into departure and arrival conditions, andballast exchange at sea conditions, where applicable, upon whichthe approval of hull scantlings is based.

In particular the following loading conditions should normally beincluded in the loading manual:

Cargo ships, Container carriers, Roll-on/Roll-off and Refrigerat-ed carriers, Ore carriers and Bulk carriers:

— homogeneous loading conditions at maximum draught— ballast conditions— special loading conditions, e.g. container or light load con-

ditions at less than the maximum draught, heavy cargo,empty holds or non-homogeneous cargo conditions deckcargo conditions, etc. where applicable

— short voyage or harbour conditions, where applicable— docking condition afloat— loading and unloading transitory conditions, where applica-

ble.

For bulk carriers of 150 m in length and above, additional re-quirements as given in Pt.5 Ch.2 Sec.5 apply.

Oil tankers:

— homogeneous loading (excluding dry and clean ballasttanks) and ballast or part-loaded conditions for both depar-ture and arrival

— any specified non-uniform distribution of loading— mid-voyage conditions relating to tank cleaning or other op-

erations where these differ significantly from the ballastconditions

— docking condition afloat— loading and unloading transitory conditions.

Chemical tankers:

— conditions as specified for Oil Tankers— conditions for high density or heated cargo and segregated

cargo where these are included in the approved cargo list.

Liquefied gas carriers:

— homogeneous loading conditions for all approved cargoesfor both arrival and departure

— ballast conditions for both arrival and departure— cargo condition where one or more tanks are empty or par-

tially filled or where more than one type of cargo having sig-nificantly different densities is carried, for both arrival anddeparture

— harbour condition for which an increased vapour pressurehas been approved

— docking condition afloat.

Table E1 Ordinates of streamlined cornerPoint Abscissa x Ordinate y

1 2 3 4 5 6 7 8 9 10 11 12 13

1,793 a 1,381 a 0,987 a 0,802 a 0,631 a 0,467 a 0,339 a 0,224 a 0,132 a 0,065 a 0,022 a 0,002 a

0

0 0,002 a0,021 a 0,044 a0,079 a 0,131 a 0,201 a 0,293 a 0,408 a 0,548 a 0,712 a 0,899 a 1,000 a


DET NORSKE VERITAS

Combination carriers:

— conditions as specified for Oil tankers and Cargo ships.

For Combination Carriers, additional requirements as given inPt.5 Ch.2 Sec.5 apply.


202 The loading manual must be prepared in a language un-derstood by the users. If this language is not English a transla-tion into English is to be included.

203 In case of modifications resulting in changes to the maindata of the ship, a new approved loading manual is to be issued.

F 300 Condition of approval of loading computer sys-tems301 With respect to the approval of the loading computersystem, see Pt.6 Ch.9.


DET NORSKE VERITAS

SECTION 6BOTTOM STRUCTURES

A. General

A 100 Introduction101 The requirements in this section apply to bottom struc-tures.

102 The formulae given for plating, stiffeners and girders arebased on the structural design principles outlined in Sec.3 B. Inmost cases, however, fixed values have been assumed for somevariable parameters such as:

— aspect ratio correction factor for plating— bending moment factor m for stiffeners and girders.

Where relevant, actual values for these parameters may bechosen and inserted in the formulae.

Direct stress calculations based on said structural design prin-ciples and as outlined in Sec.13 will be considered as alterna-tive basis for the scantlings.


L = rule length in m 1)

B = rule breadth in m 1)

D = rule depth in m 1)

T = rule draught in m 1)

CB = rule block coefficient 1)

V = maximum service speed in knots on draught TL1 = L but need not be taken greater than 300 mt = rule thickness in mm of platingZ = rule section modulus in cm3 of stiffeners and simple

girderska = correction factor for aspect ratio of plate field = (1,1 – 0,25 s/ l)2 = maximum 1,0 for s/ l = 0,4 = minimum 0,72 for s/ l = 1,0s = stiffener spacing in m, measured along the platingl = stiffener span in m, measured along the topflange of

the member. For definition of span point, see Sec.3C100. For curved stiffeners l may be taken as thecord length

wk = section modulus corrosion factor in tanks, see Sec.3C1004

= 1,0 in other compartmentsσ = nominal allowable bending stress in N/mm2 due to

lateral pressurep = design pressure in kN/m2 as given in Bf1 = material factor 2)

= 1,0 for NV-NS steel 2)

= 1,08 for NV-27 steel 2)




f2b = stress factor below the neutral axis of the hull girderdepending on surplus in midship section modulusand maximum value of the actual still water bendingmoments:

ZB = midship section modulus in cm3 at bottom as builtMS = normally to be taken as the largest design still water

bending moment in kNm. MS is not to be taken lessthan 0,5 MSO. When actual design moment is notknown, Ms may be taken equal to MSO

M SO = design still water bending moment in kNm given inSec.5 B

MW = rule wave bending moment in kNm given in Sec.5B. Hogging or sagging moment to be chosen in re-lation to the applied still water moment.

1) For details see Sec.1 B.

2) For details see Sec.2 B to C.

Guidance note:In special cases a more detailed evaluation of the actual still wa-ter moment MSMS to be used may be allowed. The simultaneousoccurence of a certain local load on a structure and the largestpossible -value in the same area of the hull girder may be used asbasis for estimating f2B.

Example: Inner bottom longitudinal in a loaded hold of a bulkcarrier with HC-E-notation. Local load from Table B1: P4. MSmay be taken as maximum hogging still water moment in partic-ular hold for HC-E-condition (maximum local stress in compres-sion at longitudinal flange in middle of hold). MSMSO in no caseto be taken less than 0,5 .


A 300 Documentation

301 Plans and particulars to be submitted for approval or in-formation are specified in Sec.1.

A 400 Structural arrangement and details

401 The engine room is normally to have a double bottom.

402 Double bottoms within the cargo region are normally tobe longitudinally stiffened in ships with length L > 150 m

403 Single bottoms within the cargo region are normally tobe longitudinally stiffened.

404 When the bottom or inner bottom is longitudinally stiff-ened:

— the longitudinals are to be continuous through transversemembers within 0,5 L amidships in ships with length L > 150 m

— the longitudinals may be cut at transverse members within0,5 L amidships in ships with length 50 m < L < 150 m. Inthat case continuous brackets connecting the ends of thelongitudinals are to be fitted.

— the longitudinals may be welded against the floors in shipswith length L < 50 m, and in larger ships outside 0,5 Lamidships.

405 Manholes are to be cut in the inner bottom, floors andlongitudinal girders to provide access to all parts of the doublebottom. The vertical extension of lightening holes is not to ex-ceed one half of the girder height. The edges of the manholesare to be smooth. Manholes in the inner bottom plating are tohave reinforcement rings.

Manholes are normally not to be cut in floors or girders underlarge pillars or stool structures.

Manhole covers in the inner bottom plating in cargo holds areto be effectively protected.

The diameter of the lightening holes in the bracket floors is notto be greater than 1/3 of the breadth of the brackets.

406 To ensure the escape of air and water from each framespace to the air pipes and suctions, holes are to be cut in thefloors and longitudinal girders. The air holes are to be placedas near to the inner bottom as possible.

f2b

5 7 MS MW+( ),ZB

--------------------------------------=


DET NORSKE VERITAS

The drain holes are to be placed as near to the bottom as possi-ble. The total area of the air holes is to be greater than the areaof the filling pipes.

407 The access opening to pipe tunnel is to be visible abovethe floor plates and is to be fitted with a rigid, watertight clo-sure.

A notice plate is to be fitted stating that the access opening tothe pipe tunnel is to be kept closed. The opening is to be re-garded as an opening in watertight bulkhead.

408 The bilge keel and the flat bar to which it is attached, isnot to terminate abruptly. Ends are to be tapered, and internalstiffening is to be provided. Butts in the bilge keel and the flatbar are to be well clear of each other and of butts in the shellplating. The flat bar is to be of the same material strength as thebilge strake to which it is attached and of the steel grade ac-cording to Sec.2 Tables B1 and B2 as a bilge strake. The bilgekeel is to be of the same material strength as the bilge strake towhich it is attached.

409 Weld connections are to satisfy the general requirementsgiven in Sec.12.

410 For end connections of stiffeners and girders, see Sec.3C.

A 500 Bottom arrangement

501 A double bottom is normally to be fitted, extending fromthe collision bulkhead to the afterpeak bulkhead, as far as ispracticable and compatible with the design and proper workingof the ship.

502 The depth of the double bottom is given in D100. The in-ner bottom is to be continued out to the ship's side in such amanner as to protect the bottom to the turn of the bilge.

503 Small wells constructed in the double bottom, in connec-tion with the drainage arrangements of holds, shall not extendin depth more than necessary. A well extending to the outer bot-tom may, however, be permitted at the after end of the shafttunnel of the ship. Other wells may be permitted if the arrange-ment gives protection equivalent to that afforded by a doublebottom complying with this regulation.

504 A double bottom need not be fitted in way of watertightcompartments used exclusively for the carriage of liquids, pro-vided the safety of the ship in the event of a bottom damage isnot thereby impaired.

For oil tankers, see Pt.5 Ch.3 Sec.3, for chemical carriers, seePt.5 Ch.4 Sec.3, and for liquefied gas carriers, see Pt.5 Ch.5Sec.3.

(SOLAS, Reg. II-1/12-1).

B. Design Loads

B 100 Local loads on bottom structures

101 All generally applicable local loads on bottom structuresare given in Table B1, based upon the general loads given inSec.4. In connection with the various local structures, refer-ence is made to this table, indicating the relevant loads in eachcase.

B 200 Total loads on double bottom

201 In connection with direct stress calculations on doublebottom structures, total loads are to be taken as differences be-tween internal and external pressures.

These loads are specified in Sec.13.


DET NORSKE VERITAS

T = rule draught in m, see Sec.1 BTM = minimum design draught in m amidships, normally

taken as 0,35 T for dry cargo vessels and 2 + 0,02 Lfor tankers

pdp = as given in Sec.4 C201y = horizontal distance in m from Ship's centre line to

point considered, minimum B/4CW = wave coefficient as given in Sec.4 B200av = vertical acceleration as given in Sec.4 B600φ = roll angle in radians as given in Sec.4 B400hs = vertical distance in m from load point to top of tankhp = vertical distance in m from the load point to the top

of air pipeH = height in m of tankHC = stowage height in m of dry cargo. Normally the

height to 'tween deck or top of cargo hatchway to beused in combination with a standard cargo densityρc = 0,7 t/m3

ρc = dry cargo density in t/m3, if not otherwise specifiedto be taken as 0,7

ρ = density of liquid cargo in t/m, normally not to betaken less than 1,025 t/m2 (i.e. ρ g0 ≈ 10)

b = the largest athwartship distance in m from the loadpoint to the corner at top of the tank/hold most dis-tant from the load point

bt = breadth in m of top of tank/holdp0 = 25 in general = 15 in ballast hold of dry cargo vessels = pressure valve opening pressure when exceeding

the general value.∆pdyn = as given in Sec.4 C300.

C. Plating and Stiffeners

C 100 General

101 In this subsection requirements to laterally loaded plat-ing and stiffeners are given, and in addition the scantlings andstiffening of double bottom floors and girders. For single bot-tom and peak tank girders, see F and G.

C 200 Keel plate

201 A keel plate is to extend over the complete length of theship. The breadth is not to be less than:

b = 800 + 5 L (mm).

202 The thickness is not to be less than:

The thickness is in no case to be less than that of the adjacentbottom plate.

C 300 Bottom and bilge plating

301 The breadth of strakes in way of longitudinal bulkheadand bilge strake, which are to be of steel grade higher than A-grade according to Ch.1 Sec.2, is not to be less than:

b = 800 + 5 L (mm).

302 The thickness requirement corresponding to lateral pres-sure is given by:

Table B1 Design loadsStructure Load type p (kN/m2)

Outer bottom

Sea pressure p1 = 10 T + pdp (kN/m2) 1)

Net pressure in way of cargo tank or deep tank

p2 = ρ (g0 + 0,5 av) hs – 10 TM

p3 = ρ g0 hs + p0 – 10 TM

Inner bottom

Dry cargo in cargo holds p4 = ρ (g0 + 0,5 av) HC

Ballast in cargo holds

Liquid cargo in tank above

Minimum pressure p 13 = 10 T

Inner bottom, floors and girders

Pressure on tank boundaries in double bottom

p 14 = 0,67 (10 hp + ∆ pdyn)

p 15 = 10 hs + p0

Minimum pressure p 16 = 10 T

1) For ships with service restrictions the last term in p1 may be reduced by the percentages given in Sec.4 B202.

2) p6 and p10 to be used in tanks/holds with largest breadth > 0,4 B.

p5 10 0 5av,+( )hs=

p6 6 7 hs φb+( ), 1 2 H φbt2 )

,–=

p7 0 67 10hp ∆pdyn+( ),=

p8 10hs p0+=

p9 ρ g0 0 5av,+( ) hs=

p10 ρ g0 0 67 hs φb+( ), 0 12 H φbt,–[ ] 2 )

=

p11 0 67 ρ g0 hp ∆pdyn+( ),=

p12 ρg0hs p0+=

t 7 0,0 05L1,

f1

------------------ tk (mm)+ +=

t15 8ka s p,

σ----------------------------- tk (mm)+=


DET NORSKE VERITAS

p = p1 to p3 (when relevant) in Table B1σ = 175 f1 – 120 f2b , maximum 120 f1 when transverse

frames, within 0,4L = 120 f1 when longitudinals, within 0,4 L = 160 f1 within 0,1 L from the perpendiculars.

Between specified regions the σ-value may be varied linearly.

f2b = stress factor as given in A 200

303 The longitudinal and combined buckling strength is tobe checked according to Sec.14.


305 Between the midship region and the end regions there isto be a gradual transition in plate thickness.

306 The thickness of the bilge plate is not to be less than thatof the adjacent bottom and side plates, whichever is the greater.

307 If the bilge plate is not stiffened, or has only one stiffenerinside the curved part, the thickness is not to be less than:

R = radius of curvature (mm)l = distance between circumferential stiffeners, i.e. bilge

brackets (mm)p = 10 (T + B φ/2 + 0,088 CB (B/2 + 0,8 CW)) (kN/m2) = 2 p1 – 10T (minimum)φ = roll angle in radians as given in Sec.4 B400.CW = wave coefficient as given in Sec.4 B200.

In case of longitudinal stiffening positioned outside the curva-ture, R is substituted by:

R1 = R + 0,5 (a + b)

See Fig. 1.

The lengths a and b are normally not to be greater than s/3.

C 400 Inner bottom plating


p = p4 to p13 (whichever is relevant) as given in Table B1σ = 200 f1 – 110 f2b, maximum 140 f1 when transverse

frames, within 0,4 L = 140 f1 when longitudinals, within 0,4 L = 160 f1 within 0,1 L from the perpendiculars.


f2b = stress factor as given in A200.


t0 = 7,0 in holds below dry cargo hatchway opening if ceil-ing is not fitted.

= 6,0 elsewhere in holds if ceiling is not fitted = 5,0 in general if ceiling is fitted. = 5,0 in void spaces, machinery spaces and tanks.

Fig. 1Not stiffened bilge plate

403 The longitudinal and combined buckling strength is tobe checked according to Sec.14.

C 500 Plating in double bottom floors and longitudinal girders

501 The thickness requirement of floors and longitudinalgirders forming boundaries of double bottom tanks is given by:

p = p13 to p15 (when relevant) as given in Table B1p = p1 for sea chest boundaries (including top and partial

bulkheads)σ = allowable stress, for longitudinal girders within 0,4L

given by:

σ = 160 f1 within 0,1L from the perpendiculars and forfloors in general

= 120 f1 for sea chest boundaries (including top and par-tial bulkheads)

f2b = stress factor as given in A200.

Between specified regions of longitudinal girders the σ-valuemay be varied linearly.

502 The thickness of longitudinal girders, floors, supportingplates and brackets is not to be less than:

k = 0,04 L1 for centre girder up to 2 m above keel plate = 0,02 L1 for other girders and remaining part of centre

girder = 0.05 L1 for sea chest boundaries (including top and par-

tial bulkheads).

503 The buckling strength of girders is to be checked accord-ing to Sec.14.

t 5 0,0 04L1,

f1

------------------ tk (mm)+ +=

tR

2l p3

900------------------- tk+=

t15 8kas p,

σ--------------------------- tk (mm)+=

t t0

0 03L1,

f1

------------------ tk (mm)+ +=

Transversely stiffened

Longitudinally stiffened

190 f1 – 120 f2b, maximum 130 f1 130 f1

t15.8 kas p

σ---------------------------- tk (mm)+=

t 6 0, k

f1

--------- tk (mm)+ +=


DET NORSKE VERITAS

C 600 Transverse frames

601 The section modulus requirement of bottom and innerbottom frames is given by:

p = p1 to p12 (when relevant) as given in Table B1.

602 Struts fitted between bottom and inner bottom framesare in general not to be considered as effective supports for theframes.

The requirements given in 601, however, may be reduced afterspecial consideration. When bottom and inner bottom frameshave the same scantlings, a Z-reduction of 35% will be accept-ed if strut at middle length of span.

603 The thickness of web and flange is not to be less than thelarger of:

k = 0,02 L1 = 5,0 maximumh = profile height in mg = 70 for flanged profile webs = 20 for flat bar profiles.

C 700 Bottom longitudinals

701 The section modulus requirement is given by:

p = p1 to p3 (when relevant) as given in Table B1σ = allowable stress (maximum 160 f1) given by:

— within 0,4 L:

For bilge longitudinals the allowable stress σ is to be taken as225 f1 – 130 f2 (zn – za)/zn, where zn, za are taken as defined inSec.7 A201.

— within 0,1 L from perpendiculars: σ = 160 f1

Between specified regions the σ- value may be varied linearly.

σ db = mean double bottom stress at plate flanges, normallynot to be taken less than:

= 20 f1 for cargo holds in general cargo vessels = 50 f1 for holds for ballast = 85 f1 b/B for tanks for liquid cargof 2b = stress factor as given in A200b = breadth of tank at double bottom.

Longitudinals connected to vertical girders on transverse bulk-heads are to be checked by a direct stress analysis, see Sec.13C.

702 The buckling strength of longitudinals is to be checkedaccording to Sec.14.



704 Struts fitted between bottom and inner bottom longitudi-nals are in general not to be considered as effective supportsfor the longitudinals. The requirements given in 701, however,may be reduced after special consideration. When bottom andinner bottom longitudinals have the same scantlings, a Z-re-duction of 35% will be accepted if strut at middle length ofspan.

705 A longitudinal is to be fitted at the bottom where the cur-vature of the bilge plate starts.

C 800 Inner bottom longitudinals


p = p4 to p13 (whichever is relevant) as given in TableB1

σ = 225 f1 – 100 f2B – 0,7 σdbwithin 0,4 L (maximum160 f1)

= 160 f1 within 0,1 L from the perpendiculars.

Between specified regions the σ -value may be varied linearly.

σdb = mean double bottom stress at plate flanges, normal-ly not to be taken less than:

= 20 f1 for cargo holds in general cargo vessels = 50 f1 for holds for ballast = 85 f1 b/B for tanks for liquid cargof2b = stress factor as given in A200b = breadth of tank at double bottom.



803 Struts fitted between bottom and inner bottom longitudi-nals are in general not to be considered as effective supportsfor the longitudinals. The requirements given in 801, however,may be reduced after special consideration. When bottom andinner bottom longitudinals have the same scantlings, a Z-re-duction of 35% will be accepted if strut at middle length ofspan.

804 The buckling strength is to be checked according toSec.14.

Single bottom Double bottom225 f1 – 130 f2b 225 f1 – 130 f2b – 0,7 σdb

Z0 63 l

2s p wk,

f1-------------------------------- (cm

3)=

t 5 0, k

f1

---------- tk (mm)+ +=

hg--- tk+=

Z83 l

2s p wk

σ--------------------------- (cm

3)=

t 5 0, k

f1

---------- tk (mm)+ +=

hg--- tk+=

Z83 l

2s p wk

σ-------------------------- (cm

3)=

t 5 0, k

f1

---------- tk (mm)+ +=

hg--- tk+=


DET NORSKE VERITAS

C 900 Stiffening of double bottom floors and girders

901 The section modulus requirement of stiffeners on floorsand longitudinal girders forming boundary of double bottomtanks is given by:

p = p14 to p16 as given in Table B1p = p1 for sea chest boundaries (including top and partial

bulkheads)σ = 225 f1 – 110 f2b, maximum 160 f1 for longitudinal stiff-

eners within 0,4L = 160 f1 for longitudinal stiffeners within 0,1 L from per-

pendiculars and for transverse and vertical stiffeners ingeneral.

= 120 f1 for sea chest boundaries (including top and par-tial bulkheads).

Between specified regions of longitudinal stiffeners the σ-val-ue may be varied linearly.

f 2b = stress factor as given in A 200.

902 Stiffeners in accordance with the requirement in 901 areassumed to have end connections. When Z is increased by40%, however, stiffeners other than longitudinals may besniped at ends if the thickness of plating supported by the stiff-ener is not less than:

903 The thickness of web and flange is not to be less thangiven in 603.

904 In double bottoms with transverse stiffening the longitu-dinal girders are to be stiffened at every transverse frame.

905 The longitudinal girders are to be satisfactorily stiffenedagainst buckling.

906 In double bottoms with longitudinal stiffening the floorsare to be stiffened at every longitudinal.

D. Arrangement of Double Bottom

D 100 General

101 The height of centre girder and floors at centre line is notto be less than:

250 + 20 B + 50 T (mm), minimum 650 mm

The height is to be sufficient to give good access to all parts ofthe double bottom. For ships with a great rise of floors, theminimum height may have to be increased after special consid-eration.

Guidance note:In the engine room, the height of the tank top above the keelshould be 45% and 30% greater than the required centre girderheight, respectively, with and without a sump in way of the mainengine.


102 Under the main engine, girders extending from the bot-tom to the top plate of the engine seating, are to be fitted. Theheight of the girders is not to be less than that of the floors. Ifthe engine is bolted directly to the inner bottom, the thicknessof the plating in way of the engine is to be at least twice the rulethickness of inner bottom plating.

Engine holding-down bolts are to be arranged as near as prac-ticable to floors and longitudinal girders.

Guidance note:The thickness of the top plate of seatings for main engine and re-duction gear should preferably not be less than:


D 200 Double bottom with transverse framing

201 Side girders are to be fitted so that the distance betweenthe side girders and the centre girder or the margin plate or be-tween the side girders themselves does not exceed 4 metres. Inthe engine room, side girders are in all cases to be fitted outsidethe engine seating girders.

202 The floor spacing is normally not to be greater than giv-en in Table D1. In the engine room floors are to be fitted at eve-ry frame. In way of thrust bearing and below pillars, additionalstrengthening is to be provided.

203 Supporting plates for the transverse bottom frames are tobe fitted at the centre girder and the margin plate on frameswithout floors. The breadth is to be at least one frame spacing,and the free edge is to be provided with a flange.

D 300 Double bottom with longitudinals

301 Side girders are to be fitted so that the distance betweenthe side girders and the centre girder or the margin plate or be-tween the side girders themselves does not exceed 5 metres. Inthe engine room, one side girder is in all cases to be fitted out-side the engine seating girders.

302 The floor spacing is normally not to be greater than 3,6m. In way of deep tanks with height exceeding 0,7 times thedistance between the inner bottom and the main deck, the floorspacing is normally not to exceed 2,5 m. In the engine room,floors are to be fitted at every second side frame. Bracket floorsare to be fitted at intermediate frames, extending to the first or-dinary side girder outside the engine seating. In way of thrustbearing and below pillars additional strengthening is to be pro-vided.

303 Supporting plates are to be fitted at the centre girder. Thefree edge of the supporting plates is to be provided with flange.The breadth of the supporting plate is to be at least one longi-tudinal spacing.

The spacing is normally not to exceed two frame spacings. Be-tween supporting plates on the centre girder, docking bracketsare to be fitted.

Alternative arrangements of supporting plates and dockingbrackets require special consideration of local buckling

Z100 l

2s p wk

σ------------------------------- (cm

3)=

t 1 25 l 0 5s,–( ) s pf1

-------------------------------, tk (mm)+=

PS (kW)1) t (mm)≤ 1000 25

1000 < PS ≤ 1750 301750 < PS ≤ 2500 352500 < PS ≤ 3500 40

PS > 3500 451) PS = maximum continuous output of propulsion machinery.

Table D1 Plate floors

Draught in m Under deep tanks 1 )

Clear of deep tanks and machinery

space 2)

T ≤ 2 Every 4th frame Every 6th frame2 < T ≤ 5,4 Every 3rd frame Every 5th frame

5,4 < T ≤ 8,1 Every 3rd frame Every 4th frameT > 8,1 Every 2nd frame Every 3rd frame

1) With height greater than 0,7 times the distance between the inner bot-tom and the main deck.

2) The distance between plate floors is not to exceed 3 metres.


DET NORSKE VERITAS

strength of cen tre girder/duct keel and local strength of dock-ing longitudinal subject to the forces from docking blocks.

E. Double Bottom Girder System below Cargo Holds and Tanks

E 100 Main scantlings

101 In addition to fulfilling the minimum and local require-ments given in C and D, the main scantlings of the girder sys-tem below cargo holds and tanks for cargo or ballast arenormally to be based on a direct strength analysis as outlinedin Sec.13. The distance between floors and side girders givenin D200 and D300 may then be modified.

Special attention is to be given to the relative deflection be-tween the transverse bulkhead and the nearest floor.

In dry Cargo ships with homogeneous loading only, the scant-lings may be based on the local and minimum requirements inC and D.

F. Single Bottom Girders

F 100 Main scantlings

101 The main scantlings of single bottom girder system intanks for liquid cargo and ballast are to be based on a directstress analysis as outlined in Sec.13. The loads given in B areto be used as basis for such calculations.

F 200 Local scantlings

201 The thickness of web plates, flanges, brackets and stiff-eners is generally not to be less than:

k = 0,04 for centre girder plating up to 2 m above keel plate = 0,02 for other girders and remaining part of centre

girder = 0,01 for stiffeners on girders.

The thickness of girders is in addition not to be less than:

t = 15 s + tk (mm)

s = web stiffener spacing in m.

202 The thickness of the web plates is in addition to bechecked for buckling according to Sec.14, with respect to in-plane compressive and shear stresses.

203 Girder flanges are to have:

a thickness not less than 1/30 of the flange width when theflange is symmetrical, and not less than 1/15 of the flangewidth when the flange width is asymmetrical.

204 The end connections and stiffening of single bottomgirder systems are to be as given in Sec.3 C.

G. Girders in Peaks

G 100 Arrangement

101 Girders in fore and after peaks supporting longitudinalsor transverse frames, are normally to have spacing not exceed-ing 1,8 m. Heavy intersecting girders or bulkheads at distancesgenerally not exceeding the smaller of 0,125 B and 5 m are tosupport the girders mentioned above.

102 In the after peak of single screw ships, the floors are tobe of such a height that their upper edge is well above the stern-tube.

G 200 Scantlings201 The thickness of web plates, brackets and stiffeners isgenerally not to be less than:

k = 0,03 L1 for web plates and brackets (maximum 6) = 0,01 L1 for stiffeners on web plates.

The thickness of girders and floors is in addition not to be lessthan:

t = 12 s + tk (mm)

s = stiffener spacing in m.

202 Girder flanges are to have:

— a thickness not less than 1/30 of the flange width when theflange is symmetrical, and not less than 1/15 of the flangewidth when the flange width is asymmetrical

— a width not less than 1/20 of the distance between trippingbrackets.

G 300 Details301 For end connections and stiffening of girders in general,see Sec.3 C.

302 Stiffeners on floors and girders in the after peak are tohave end connections.

H. Special Requirements

H 100 Vertical struts101 Where bottom and inner bottom longitudinals or framesare supported by vertical struts, the sectional area of the strut isnot to be less than:

k = 0,7 in way of ballast tanks = 0,6 elsewherel = stiffener span in m disregarding the strut.

The moment of inertia of the strut is not to be less than:

I = 2,5 hdb2 A (cm4)

h db = double bottom height in m.

H 200 Strengthening against slamming201 The bottom forward is to be strengthened according tothe requirements given in the following. For ships with servicerestriction notations the strengthening will be specially consid-ered.

The bottom aft in vessels with full deck breadths aft and nearlyhorizontal bottom areas may have to be strengthened after spe-cial consideration.

202 For every oil tanker subject to Regulation 13 of MAR-POL 73/78, Annex I (see Pt.7 Ch.4 App.B B100) the strength-ening of the bottom forward is to be based on the draught usingthe segregated ballast tanks only.

(IACS UR S 13).

203 The design slamming pressure is to be taken as:

t 6 0,k L1

f1

---------- tk (mm)+ +=

t 5 0, k

f1

---------- tk (mm)+ +=

Ak l s T

f1-------------- (cm

2)=


DET NORSKE VERITAS

c1 = L1/3 for L ≤ 150 m

c1 =

c2 =

T BF = design heavy weather ballast draught in m at F.P.BB = the breadth of the bottom in m at the height 0,15TBF

above the baseline measured at the cross sectionconsidered. is not to be taken greater than the smaller of1,35 TBF and

x = longitudinal distance in m from F.P. to cross sectionconsidered, but need not be taken smaller than x1

x1 =

The assumed variation in design slamming pressure is shownin Fig. 2.

204 If the ship on the design ballast draught TBFpsl is intend-ed to have full ballast tanks in the forebody and the load fromthe ballast will act on the bottom panel, the slamming pressuremay be reduced by 14 h kN/m2 where h is the height in m ofthe ballast tank.

205 The thickness of the bottom plating below 0,05 TBFfrom keel is not to be less than:

kr = correction factor for curved plates with stiffening di-rection at right angle to axis of curvature

=

r = radius of curvature in mpls = as given in 203 or 204.

206 Above the area given in 203 the thickness may be grad-ually reduced to the ordinary requirement at side. For vesselswith rise of floor, however, reduction will not be accepted be-low the bilge curvature.

207 The section modulus of longitudinals or transverse stiff-eners supporting the bottom plating defined in 205 and 206 isnot to be less than:

The shear area is not to be less than:

psl = as given in 203 or 204.h = stiffener height in m.

Fig. 2Design slamming pressure

208 The net connection area of continuous stiffeners at gird-ers is to satisfy the following expression:

1,7 AF + AW = 2 AS

AF = connection area at flange in cm2

AW = connection area at web in cm2

AS = as given in 207, to be multiplied by f1 if HTS in stiff-ener and MS in girder.

209 In the bottom below 0,05 TBF the spacing of stiffenerson web plates or bulkheads is near the shell plating not to ex-ceed:

sw = 0,09 t (m)

t = thickness of web or bulkhead plating in mm.

210 The sum of shear areas at end supports of all girderswithin a typical bottom area (between heavy supporting struc-tures such as bulkheads and ship's sides) is not to be less than:

psl = as given in 203 or 204.

l and b is the length and the breadth in m respectively of theloaded area supported by the girder or girder system. psl is tak-en at the middle of the girder system considered.

ps l

c1 c2

TBF----------- BB 0 56, L

1250------------–

xL---–

� �� (kN/m

2)=

225L2---–

� ��

1 3⁄ for L 150m>

1675 120TBF

L----------------–

� ��

BB0 55 L,

1 2, CB( )1 3⁄–

L2500------------–

� �� L

t0 9 ka kr s ps l,

f1

------------------------------------ tk (mm)+=

1 0 5sr--,–

� ��

Z0 15 l

2s psl wk,

f1-------------------------------------- (cm

3)=

AS

0 03 l s–( ) s ps l,f1

--------------------------------------- 10 h tk (cm2)+=

ΣAS

c3

f1----- l b ps l (cm

2)=

c3 0 05 110 l bLB

-------------–� �� , minimum 0,025,=


DET NORSKE VERITAS

211 The design ballast draught forward will be stated in theappendix to the classification certificate.

H 300 Strengthening for grab loading and discharging (special features notation IB(+)301 Vessels with inner bottom and adjacent bulkheads overa width (measured along the plate) of 1,5m strengthened in ac-cordance with the requirement given in 302 may have the no-tation IB(+) assigned.

302 The plate thickness is not to be less than:

H 400 Docking401 The bottom scantlings required in this section are con-sidered to give ample strength for the safe docking of shipswith length less than 120 metres and of normal design.

402 For ships of special design, particularly in the afterbody,and for large vessels (docking weight exceeding 70 t/m) the ex-pected docking conditions and docking block arrangements areto be evaluated and checked by a special calculation. Thedocking arrangement plan, giving calculated forces from dock-ing blocks, is to be submitted for information.

Guidance note:Size and number of docking blocks should be estimated on thebasis of a design pressure in blocks normally not exceeding 2 N/mm2. With centre line girder the docking blocks should be sup-ported by the innermost longitudinals, which are to be dimen-sioned for 1/4 of the reaction force from the blocks. With asymmetric duct keel the distance between the duct keel girdersshould be less than the expected transverse length of the dockingblocks.


t 9 0, 12s

f1

---------- tk (mm)+ +=


DET NORSKE VERITAS

SECTION 7SIDE STRUCTURES

A. General

A 100 Introduction101 The requirements in this section apply to ship's sidestructure.

102 The formula are given for plating, stiffeners and girdersare based on the structural design principles outlined in Sec.3B. In most cases, however, fixed values have been assumed forsome variable parameters such as:


Where relevant, actual values of these parameters may be cho-sen and inserted in the formulae.

Direct stress calculations based on said structural principlesand as outlined in Sec.13 will be considered as alternative basisfor the scantlings.








girderska = correction factor for aspect ratio of plate field = (1,1 – 0,25 s/ l)2 = maximum 1,0 for s/ l = 0,4 = minimum 0,72 for s/ l = 1,0s = stiffener spacing in m, measured along the platingl = stiffener span in m, measured along the top flange of

the member. For definition of span point, see Sec.3C100. For curved stiffeners l may be taken as the cordlength.

For main frames in bulk carriers, see special definitionof l in Fig. 3

S = girder span in m. For definition of span point, see Sec.3C100

zn = vertical distance in m from the baseline or deckline tothe neutral axis of the hull girder, whichever is relevant

za = vertical distance in m from the baseline or deckline tothe point in question below or above the neutral axis,respectively

f1 = material factor = 1,0 for NV-NS steel 2)





f 2b = stress factor below neutral axis of hull girder as definedin Sec.6 A200

f 2d = stress factor above neutral axis of hull girder as definedin Sec.8 A200


= 1,0 in other compartmentsσ = nominal allowable bending stress in N/mm2 due to lat-

eral pressurep = design pressure in kN/m2 as given in B.


2) For details see Sec.2 B and C.

202 The load point where the design pressure is to be calcu-lated is defined for various strength members as follows:

a) For plates: midpoint of horizontally stiffened plate field.


b) For stiffeners: midpoint of span.

When the pressure is not varied linearly over the span, thedesign pressure is to be taken as the greater of:

pm, pa and pb are calculated pressures at the midpoint andat each end respectively.

c) For girders: midpoint of load area.

203 The lower span of the side frame in way of longitudinal-ly stiffened single bottom is defined as follows (see Fig. 1):

l = l 2 – 0,3 r – 1,5 (h – a) (m) l2 = vertical distance in m between the bottom and lowest

side stringerr = bilge radius in mh = largest depth of bilge bracket in m measured at right

angles to the flangea = depth of frame in m

Fig. 1Lower span of side frame

A 300 Documentation



401 The ship's side may be longitudinally or vertically stiff-ened.

Guidance note:It is advised that longitudinal stiffeners are used near bottom andstrength deck in ships with length L> 150 m.


402 Within 0,5 L amidships, in the area 0,15 D above thebottom and 0,15 D below strength deck, the continuity of the

pm and pa pb+

2-----------------


DET NORSKE VERITAS

longitudinals is to be as required for bottom and deck longitu-dinals respectively.



B. Design Loads

B 100 Local loads on side structures101 All generally applicable local loads on side structuresare given in Table B1, based upon the general loads given inSec.4. In connection with the various local structures, refer-ence is made to this table, indicating the relevant loads in eachcase.

h0 = vertical distance in m from the waterline at draughtT to the load point

T = rule draught in m, see Sec.1 Bz = vertical distance from the baseline to the load point,

maximum T (m)pdp, ks = as given in Sec.4 C201L1 = ship length, need not be taken greater than 300 (m)av = vertical acceleration as given in Sec.4 B600hs = vertical distance in m from load point to top of tank,

excluding smaller hatchways.

hp = vertical distance in m from the load point to the topof air pipe

hb = vertical distance in m from the load point to the min-imum design draught, which may normally be takenas 0,35 T for dry cargo vessels and 2 + 0,02 L fortankers. For load points above the ballast waterlinehb = 0

po = 25 in general = 15 in ballast holds in dry cargo vessels

= tank pressure valve opening pressure when exceed-ing the general value

ρ = density of ballast, bunker or liquid cargo in t/m3,normally not to be taken less than 1,025 t/m3 (i.e.ρ g0 ≈ 10)

∆ pdyn = as given in Sec.4 C300H = height in m of tankb = the largest athwartship distance in m from the load

point to the tank corner at the top of tank/ hold mostdistant from the load point, see Fig. 2

bt = breadth in m of top of tank/holdl = the largest longitudinal distance in m from the load

point to the tank corner at top of tank most distantfrom the load point

lt = length in m of top of tankφ = roll angle in radians as given in Sec.4 B400θ = pitch angle in radians as given in Sec.4 B500bb = distance in m between tank sides or effective longi-

tudinal wash bulkhead at the height at which thestrength member is located.

Table B1 Design loadsLoad type P (kN/m2)

External

Sea pressure below summer load waterline p1 = 10 h0 + pdp 1)

Sea pressure above summer load waterline

p2 = ( pdp – (4 + 0,2 ks) h0 ) 1)

minimum 6,25 + 0,025 L1

Internal

Ballast, bunker or liquid cargo in side tanks in general

p3 = ρ (g0 + 0,5 av) hs – 10 hb

p4 = ρ g0 hs – 10 hb + po

p5 = 0,67 (ρ g0 hp + ∆ pdyn – 10 hb)

Above the ballast waterline at ballast, bunker or liquid cargo tanks with a breadth > 0,4 B

Above the ballast waterline and towards ends of tanks for ballast, bunker or liquid cargo with length > 0,15 L

In tanks with no restriction on their filling height 2)

1) For ships with service restrictions, p2 and the last term in p1 may be reduced by the percentages given in Sec.4 B202.

2) For tanks with free breadth bs > 0,56 B the design pressure will be specially considered according to Sec.4 C305.

p6 ρg0 0 67 hs φb+( ), 0 12 H φbt,–[ ]=

p7 ρg0 0 67 hs θl+( ), 0 12 Hθ lt,–[ ]=

p8 ρ 3B

100---------– bb=


DET NORSKE VERITAS

Fig. 2Tank shapes


C 100 Side plating, general101 The thickness requirement corresponding to lateral pres-sure is given by:

p = p1 – p8, whichever is relevant, as given in Table B1σ = 140 f1 for longitudinally stiffened side plating at neu-

tral axis, within 0,4 L amidship = 120 f1 for transversely stiffened side plating at neutral

axis, within 0,4 L amidship.

Above and below the neutral axis the σ-values are to bereduced linearly to the values for the deck and bottomplating, assuming the same stiffening direction andmaterial factor f1 as for the plating considered

= 160 f1 within 0,05 L from F.P. and 0,1 L from A.P.


102 The thickness is not for any region of the ship to be lessthan:

k = 0,04 up to 4,6 m above the summer load waterline. Foreach 2,3 m above this level the k-value may be reducedby 0,01 (k (minimum) = 0,01)

= 0,06 for plating connected to the sternframe.

103 The thickness of the side plating between a section aft ofmidships where the breadth at the load waterline exceeds 0,9 Band a section forward of midships where the load waterlinebreadth exceeds 0,6 B, and taken from the lowest ballast wa-terline to 0,25 T (minimum 2,2 m) above the summer load line,is not to be less than:

σf = minimum yield stress in N/mm2 as given in Sec.2B200.

104 The thickness of side plating is also to satisfy the buck-ling strength requirements given in Sec.14, taking into accountalso combination of shear and compressive in-plane stresseswhere relevant.

105 If the end bulkhead of a superstructure is located within0,5 L amidships, the side plating should be given a smoothtransition to the sheer strake below.

C 200 Sheer strake at strength deck

201 The breadth is not to be less than:

b = 800 + 5 L (mm), maximum 1800 mm.


t1 = required side plating in mmt2 = strength deck plating in mm

t2 is not to be taken less than t1.

203 The thickness of sheer strake is to be increased by 30%on each side of a superstructure end bulkhead located within0,5 L amidships if the superstructure deck is a partial strengthdeck.

204 Cold rolling and bending of rounded sheer strakes arenot accepted when the radius of curvature is less than 15 t.

205 When it is intended to use hot forming for rounding ofthe sheer strake, all details of the forming and heat treatmentprocedures are to be submitted to the Society for approval. Ap-propriate heat treatment subsequent to the forming operationwill normally be required.

Where the rounded sheer strake towards ends forward and afttransforms into a square corner, line flame heating may be ac-cepted to bend the sheer strake.

206 The welding of deck fittings to rounded sheer strakes isto be kept to a minimum within 0,6 L amidships. Subject to thesurveyor's consent, such welding may be carried out provided:

— when cold formed, the material is of grade NV D or agrade with higher impact toughness

— the material is hot formed in accordance with 205.

The weld joints are to be subjected to magnetic particle inspec-tion.

t15 8ka s p,

σ------------------------------ tk (mm)+=

t 5 0,k L1

f1

---------- tk (mm)+ +=

t 31 s 0 7,+( ) BT

σf2

--------� � � �

14---

tk (mm)+=

tt1 t2+

2-------------- (mm)=


DET NORSKE VERITAS

The design of the fittings is to be such as to minimise stressconcentrations, with a smooth transition towards deck level.

207 Where the sheer strake extends above the deck stringerplate, the top edge of the sheer strake is to be kept free fromnotches and isolated welded fittings, and is to be groundsmooth with rounded edges. Drainage openings with smoothtransition in the longitudinal direction may be allowed.

208 Bulwarks are in general not to be welded to the top of thesheer strake within 0,6 L amidships. Such weld connectionsmay, however, be accepted upon special consideration of de-sign (i.e. expansion joints), thickness and material grade.

C 300 Longitudinals301 The section modulus requirement is given by:

p = p1 – p8, whichever is relevant, as given in Table B1σ = allowable stress (maximum 160 f1) given by:

Within 0,4 L amidships:

= maximum 130 f1 for longitudinals supported by side verticals in single deck constructions.

Within 0,1 L from perpendiculars:

σ = 160 f1


For longitudinals σ = 160 f1 may be used in any case in com-bination with heeled condition pressures p6 and p8.

f2 = stress factor f2b as given in Sec.6 A200 below the neu-tral axis

= stress factor f2d as given in Sec.8 A200 above the neu-tral axis.

302 The thickness of web and flange is not to be less than thelarger of

k = 0,01 L1 in general = 0,02 L1 (= 5,0 maximum) in peaks and in cargo oil

tanks and ballast tanks in cargo areah = profile height in mmg = 70 for flanged profile webs = 20 for flat bar profiles.

303 Longitudinals supported by side verticals subject to rel-atively large deflections are to be checked by a direct strengthcalculation, see Sec.13 C. Increased bending stresses at trans-verse bulkheads are to be evaluated and may be absorbed byincreased end brackets.


C 400 Main frames

401 Main frames are frames located outside the peak tanks,connected to the floors, double bottom or hopper tanks and ex-

tended to the lowest deck, stringer or top wing tank on the shipside.


p = p1– p8, whichever is relevant, as given in Table B1C = 0,37 when external pressure (p1 – p2) is used = 0,43 when internal pressure (p3 – p8) is usedl = corresponding to full length of frame including brack-

ets.


404 The requirement given in 402 is based on the assumptionthat effective brackets are fitted at both ends. The length ofbrackets is not to be less than:

— 0,12 l for the lower bracket.— 0,07 l for the upper bracket.

The section modulus of frame, including bracket, at frame endsis not to be less than as given in 402 with l equal to total spanof frame including brackets and applying C-factors as givenbelow.

Upper end:

C = 0,56 when external pressure (p1– p2) is usedC = 0,64 when internal pressure (p3 – p8) is used.

Lower end:

C = 0,74 when external pressure (p1 – p2) is usedC = 0,86 when internal pressure (p3 – p8) is used.

When the length of the free edge of the bracket is more than 40times the plate thickness, a flange is to be fitted, the width be-ing at least 1/15 of the length of the free edge.

For single deck vessels e.g. gas carriers, the end connection ofmain frames may alternatively be based on a direct calculationwhere the rotation of upper and lower ends are taken into ac-count.

405 Brackets may be omitted provided the frame is carriedthrough the supporting member and the section modulus asgiven in 402 is increased by 50% and inserting total span in theformula.

406 The section modulus for a main frame is not to be lessthan for the 'tween deck frame above.

407 In ships without top wing tank, frames at hatch endbeams are to be reinforced to withstand the additional bendingmoment from the deck structure.

408 Main frames made of angles or bulb profiles having aspan l > 5 m are to be supported by tripping brackets at themiddle of the span.

Forward of 0,15 L from F.P., see also E200.

C 500 'Tween deck frames and vertical peak frames

501 'Tween deck frames are frames between the lowest deckor the lowest stringer on the ship's side and the uppermost su-perstructure deck between the collision bulkhead and the afterpeak bulkhead.

502 If the lower end of 'tween deck frames is not welded tothe bracket or the frame below, the lower end is to be bracketedabove the deck. For end connections, see also Sec.3 C200.

503 The section modulus is not to be less than the greater of:

Z83 l

2s p wk

σ---------------------------- (cm

3), minimum 15 cm

3=

σ 225 f1 130 f2

zn za–

zn----------------–=

t 5 0, k

f1

---------- tk (mm)+ +=

hg--- tk+=

ZC l

2s p wk

f1-------------------------=

Z0 55 l

2s p wk,

f1--------------------------------- (cm

3)=


DET NORSKE VERITAS

and

k = 6,5 for peak frames = 4,0 for 'tween deck framesp = p1 – p8, whichever is relevant, as given in Table B1.


D. Girders

D 100 General101 The thickness of web plates, flanges, brackets and stiff-eners of girders is not to be less than:

k = 0,01 L1 in general = 0,02 L1 for girder webs, flanges and brackets in cargo

oil tanks and ballast tanks in cargo area = 0,03 L1 (= 6,0 maximum) for girder webs, flanges and

brackets in peaks.

The thickness of girder web plates in single skin constructionis in addition not to be less than:

t = 12 s + tk (mm)

s =spacing of web stiffening in m.

102 The buckling strength of web plates subject to in- planecompressive and shear stresses is to be checked according toSec.14.

103 In the after peak, engine and boiler room, side verticalsare normally to be fitted at every 5th frame.

104 Verticals in the engine room and verticals less than 0,1L from the perpendiculars are to have a depth not less than:

h = 2 L S (mm), maximum 200 S .

105 Girder flanges are to have a thickness not less than 1/30of the flange width when the flange is symmetrical, and notless than 1/15 of the flange width when the flange is asymmet-rical.

For girders in engine room the total flange width is not to beless than 35 S mm.

106 Transverse bulkheads or side verticals with deck trans-verses are to be fitted in the 'tween deck spaces to ensure ade-quate transverse rigidity.

107 Vertical peak frames are to be supported by stringers orperforated platforms at a vertical distance not exceeding 2,25+ L/400 metres.

108 The end connections and stiffening of girders are to bearranged as given in Sec.3 C.

Stiffeners on girders in the after peak are to have end connec-tions.

D 200 Simple girders201 The section modulus requirement is given by:

p = p1 – p4 = 1,15 p5 = p6 – p8, whichever is relevant, as given in Table B1.

b = loading breadth in m

σ = ,

maximum 160 f1 for continuous longitudinal girderswithin 0,4 L amidships

= 160 f1 for other girders.


For longitudinal girders σ = 160 f1 may be used in any case incombination with heeled condition pressures p6 and p8.



The above requirement applies about an axis parallel to theship's side.

202 The web area requirement (after deduction of cut-outs)at the girder ends is given by:

k = 0,06 for continuous horizontal girders and upper end ofvertical girders

= 0,08 for lower end of vertical girdersb = as given in 201h = girder height in mp = p1 – p7, whichever is relevant, as given in Table B1.

The web area at the middle of the span is not to be less than 0,5A.

The above requirement apply when the web plate is perpendic-ular to the ship's side.

For oblique angles the requirement is to be increased by thefactor 1 / cos θ, where θ is the angle between the web plate ofthe girder and the perpendicular to the ship's side.

D 300 Complex girder systems

301 In addition to fulfilling the general local requirementsgiven in 100, the main scantlings of girders being parts of acomplex system may have to be based on a direct stress analy-sis as outlined in Sec.13.

D 400 Cross ties

401 The buckling strength is to satisfy the requirements giv-en in Sec.14.

402 Cross ties may be regarded as effective supports for sidevertical when:

— the cross tie extends from side to side— the cross tie is supported by other structures which may be

considered rigid when subjected to the maximum expectedaxial loads in the cross tie

— the load condition may be considered symmetrical with re-spect to the cross tie.

403 Side verticals may be regarded as individual simplegirders between cross ties, provided effective cross ties, as de-fined in 402, are positioned as follows:Side verticals with 1 cross tie:The cross tie is located 0,36 l – 0,5 l from the lower end.Side verticals with 2 cross ties:The lower cross tie is located 0,21 l – 0,30 l from the lower end.The upper cross tie is located 0,53 l – 0,58 l from the lower end.

l = total span of side vertical.

Z k Lf1---- (cm

3)=

t 5 0, k

f1

---------- tk (mm)+ +=

Z100 S

2b p wk

σ--------------------------------- (cm

3 )=

190 f1 130 f2

zn za–

zn----------------–

Ak S b p

f1---------------- 10 h tk (cm

2)+=


DET NORSKE VERITAS

Side verticals with more than 2 cross ties or with cross ties notlocated as given above, will be specially considered. On string-ers, the cross ties are assumed to be evenly spaced.

E. Special Requirements

E 100 Bar stem

101 The scantlings are not to be less than:

— width: 90 + 1,2 L below summer load waterline 70 +0,9 L at the stemhead

— thickness: 12 + 0,48 L.

The stem width is to be gradually tapered from the waterline tothe stem head.

E 200 Tripping brackets

201 Forward of 0.15 L from F.P., flanged transverse sideframes (i.e. all frame cross sections except flat bars) with webnon-orthogonal to the perpendicular to the side shell are to bearranged with midspan tripping brackets as shown in Fig. 3,unless the web thickness of the frame complies with the fol-lowing requirement:

h = frame profile height in mmbf = flange breadth of profile in mmtf = flange thickness of frame in mml = span length of frame in m


The thickness of tripping brackets may be taken as the smallerof the web thickness of the frames and 10 mm.

E 300 Strengthening against bow impact

301 The bow region as referred to in the following is normal-ly to be taken as the region forward of a position 0,1 L abaftF.P. and above the summer load waterline.

302 The effect of bow impact loads is in general to be eval-uated for all ships. Normally only ships with well rounded bowlines and/or flare will need strengthening.

The impact pressure given in 303 applies to areas away fromknuckles, anchor bolster etc. that may obstruct the water flowduring wave impacts. In way of such obstructions, additionalreinforcement of the shell plate by fitting carlings or similarshall generally be considered.

303 The design bow impact pressure is to be taken as:

C = 0.18 (CW – 0.5 ho), maximum 1,0CW = wave coefficient as given in Sec.4 B200ho = vertical distance (m) from the waterline at draught T to

point consideredCf = 1.5 tan (α + γ) = 4.0, maximumγ = 0.4 (φ cosβ + θ sinβ)φ, θ = as given in Sec.4 Bα = flare angle in radians taken as the angle between the

side plating and a vertical line, measured at the pointconsidered

β = angle in radians between the waterline and a longitudi-nal line, measured at the point considered. With refer-

ence to Fig. 4, the flare angle may normally be taken inaccordance with:

If there is significant difference between a1 and a2, more thanone plane between the design waterline and upper deck (fore-castle deck if any) may have to be considered.

Fig. 3Tripping bracket

Fig. 4Bow region

304 The thickness of shell plating in the bow region is not tobe less than:

ka =

= maximum 1.0 for s/l = 0.4 = minimum 0.72 for s/l = 1.0

tw

0.004 bf tf h

l----------------------------------- tk (mm)+=

psl C 2.2 Cf+( ) 0.4V βsin 0.6 L+( )2 (kN/m

2)=

αtana1 a2+

hd----------------=

t13.8 ka s ps l

σf

------------------------------------ tk (mm)+=

1.1 0.25sl--–

� ��

2


DET NORSKE VERITAS

σf = minimum upper yield stress of material in N/mm2 andis not to be taken less than the limit to the yield pointgiven in Sec.2 B201

psl = as given in 303s = stiffener spacing in m

305 In curved bow shell regions designed in compliancewith 304 and stiffened by radial or vertical stiffeners, the as-pect ratio of each plate field should generally not to be less than0.5. The plate fields within each stiffener span are to be sepa-rated by rows of tangential stiffeners extending into the adja-cent plane shell area.

306 The plastic section modulus of horizontal or verticalstiffeners supporting the shell plating in the bow region is notto be less than:

= 0.0 minimum

= 0.0 minimum

l = stiffener span (m)ns = number of bending effective end supports of stiffener = 2, 1 or 0 (see Guidance note)tp = shell plate thickness (mm)φw = angle between stiffener web and shell plateh = is the stiffener height (mm)hw = profile web height = h – tftw = profile web thickness (mm)tf = flange thickness (mm).


The shear area is not to be less than:

Guidance note:Stiffener end supports may be considered bending effective ex-cept where the stiffener is terminated at the support without beingattached to an aligned member or a supported end bracket.


307 Outside the bow region the requirements as calculated in304 and 306 are to be gradually decreased to the ordinary re-quirements at 0,15 L from F.P. and at the ballast waterline.

308 For unsymmetrical shell stiffeners, midspan trippingbrackets are generally to be fitted. Tripping brackets need notbe fitted if the stiffener web thickness complies with the fol-lowing requirement:

Af = flange area of frameAw = web area of framebfo = width of flange in mm measured from the edge to the

surface of the stiffener web. For bulbs the width may betaken as the mean width of the bulb.

Tripping brackets are to be fitted in way of end brackets ofstiffeners where the stiffener flange has been knuckled orcurved.

For flanged shell stiffeners (i.e. all stiffeners except flat bars),midspan tripping brackets are to be fitted if the angle betweenthe stiffener web and the shell plating is less than 80 degrees,unless the stiffener web thickness complies with the followingrequirement:

psl = as given in 303h = frame profile height in mmbf = flange breadth in mmtf = flange thickness in mm


309 Frames are to be connected to supports, e.g. girders ordecks.

End brackets of shell frames are to be arranged with edge stiff-ener unless the web thickness of the bracket complies with thefollowing requirement:

0.05 d + tk , minimum (mm)

d = smallest bracket depth measured from root to edge inmm.

310 Girder systems in the bow are to be designed to havestructural continuity.

The main stiffening direction of girder webs, platforms andbulkheads supporting shell frames is generally to be parallel tothe web direction of the supported shell frames.

End brackets are generally to be arranged with edge stiffener.

Tripping brackets are to be fitted in way of end brackets ofgirders and where the girder flange has been knuckled orcurved.

One-sided girder flanges are generally to be arranged straightbetween supported knuckle points. Girders and breast hooks ofthe bow shell with one-sided flange, and/or with web inclinedrelative to the perpendicular to the shell are at least to be fittedwith a midspan tripping bracket.

311 The web thickness of shell frames and breast hooks isnot to be less than:

psl = as given in 303s = load breadth of considered member in mφw = angle between member web and shell platehw = web height in mm.

ZP

80psl s l2

1ns2-----+

� �� φw σfsin

---------------------------------------------ns kshear hw tw hw tp+( )

8000------------------------------------------------------------------- cm

3( )+=

kshear

σf kτ–

σf---------------------=

kτ σf2 550ps lsl

φw tw hsin-------------------------

� ��

2–=

AS

6 5 l 0 5s,–( ) s ps l,φw σfsin

-----------------------------------------------h tk

100--------- cm

2( )+=

tw

ps l s bfo

1Aw

2Af---------+

� �� σf φwsin

----------------------------------------------- tk (mm)+=

tw

0.004bf tf h

l--------------------------------- tk (mm)+=

tw1.4d

Eσf-----

----------- tk mm( )+=

tw 0.02psl s hw

2

φwsin----------------------

� � � �

0.33

tk mm( )+=


DET NORSKE VERITAS

Fig. 5Bow stringer or breast hook

312 The thickness of webs/diaphragms supporting shellframes is not to be less than:

σ = 0.9 σ f , but should not be taken larger than the criticalbuckling stress, sc as given in Sec.14 B102 with respectto normal stress acting in the direction of the supportedframe webs.

psl = as given in 303sb = load breadth supported by considered web / diaphragm

in mγ = angle between the axis of the frames and its intersection

with the supporting web/diaphragm.

In way of end support areas the web thickness of stringers andweb frames supporting shell frames is not to be less than asgiven by:

= 20 s + tk (mm), minimums = spacing of web stiffeners in m.

313 The section modulus of local girders supporting shellstiffeners is not to be less than:

The web area at each end of local girders supporting shell stiff-eners is not to be less than:

s = spacing of shell stiffeners supported by girder in m.φw1 = angle between stiffener web and shell plate.φw2 = angle between girder web and shell plate.b = breadth of area supported by the girder in mpsl = as given in 303h = girder height in m.

314 Alternative to the requirements in 312 and 313, the gird-er structures in the bow may be required to be based on directstrength analysis.

When direct calculation of the bow structure subjected to im-pact loading is undertaken, a mean impact pressure = 0.5 pslmay generally be assumed. This pressure should alternativelybe applied on one or both shell sides. In the structure analysis,the nominal equivalent stress, σe, as given in Sec.13 B400 isnot to exceed the yield stress, σf, as given in Sec.14 A200. Inthe buckling control, the usage factors, ηx and ηy as given inSec.14 B400 and B500 may be taken equal to 1.0.

E 400 Strengthening against liquid impact pressure in larger tanks

401 If the ship side forms boundary of larger ballast or cargotanks with free sloshing length ls > 0,13 L and/or breadth bs > 0,56 B, the side structure is to have scantlings accordingto Sec.9 E400 for impact loads referred to in Sec.4 C305.

E 500 Fatigue control of longitudinals, main frames and 'tween deck frames

501 Longitudinals in tanks are to have a section modulus notless than:

pd = single amplitude dynamic pressure in kN/m2

= 5 [ κ + ( T – z) ] (T – z)max = κ

κ =

σd = permissible single amplitude fluctuating dynamic stress

=

c = 1,0 for uncoated cargo and ballast tanks = 1,1 for fully coated tanks and fuel tanksz = distance from base-line to considered longitudinal (m)K = stress concentration factor as given in Fig. 6φ = rolling angle in radians.

For designs giving larger deflections between transverse bulk-heads and the side verticals smooth two-sided brackets (arm-length = 1,2 – 1,5 times profile height) are to be arranged onthe top of the longitudinals at the transverse bulkheads unlessthe strength is verified by a special fatigue analysis. Such ananalysis is to be based on calculating the additional stress:

σδ = fluctuating single amplitude dynamic stresses in thelongitudinal due to relative deflection between the sup-ports calculated for the dynamic pressure pd.

This stress is to be deducted from 110 c/K to obtain the allow-able stress σd in the formula for Z.

502 Main frames in tanks are at their welded end support tohave a section modulus not less than:

pd, σd and K are as given in 501.

503 'Tween deck frames in tanks are to have a section mod-ulus at their welded end supports not less than:

pd, σd and K are as given in 501.

t0.5 psl sb

γ σsin----------------------- tk mm( )+=

t500s

Eσf-----

----------- tk mm( )+=

Z45 S

2b ps l wk

φw1φw2

σfsinsin-------------------------------------------- cm

3( )=

A5.0 S s–( )b psl

φw1φw2

σfsinsin--------------------------------------------

h tk

100---------+ cm

2( )=

Z83 s l

2pd wk

σd----------------------------- (cm

3)=

B2---- φ

2--- B

32------ 1

zT---+

� �� zmax T for κ=+

110cK

------------ (N/mm2)

Z83 s l

2pd wk

σd------------------------------ (cm

3)=

Z83 s l

2pd wk

σd------------------------------ (cm

3)=


DET NORSKE VERITAS

Fig. 6Stress concentration factors


DET NORSKE VERITAS

SECTION 8DECK STRUCTURES

A. General

A 100 Introduction

101 The requirements in this section apply to ship's deckstructure.



Where relevant, actual values for these parameters may bechosen and inserted in the formulae.

Direct stress calculations based on said structural principlesand as outlined in Sec.13 will be considered as alternative basisfor the scantlings.

A 200 Definitions

201 Symbols:







girders ka = correction factor for aspect ratio of plate field = (1,1 – 0,25 s/ l)2 = maximum 1,0 for s/ l = 0,4 = minimum 0,72 for s/ l = 1,0s = stiffener spacing in m, measured along the plating l = stiffener span in m, measured along the topflange of

the member. For definition of span point, see Sec.3C100. For curved stiffeners l may be taken as thecord length

S = girder span in m. For definition of span point, seeSec.3 C100

zn = vertical distance in m from the baseline or decklineto the neutral axis of the hull girder, whichever isrelevant

za = vertical distance in m from the baseline or decklineto the point in question below or above the neutralaxis, respectively


σ = nominal allowable bending stress in N/mm2 due tolateral pressure

p = design pressure in kN/m2 as given in Bf1 = material factor = 1,0 for NV-NS steel 2)





f 2d = stress factor above the neutral axis of the hull girder,depending on surplus in midship section modulusand maximum value of the actual still water mo-ments:

ZD = midship section modulus in cm3 at deck as builtMS = normally to be taken as the largest design still water

bending moment in kNm. MS is not to be taken lessthan 0,5 MSO. When actual design moment is notknown, MS may be taken equal to MSO

M SO = design still water bending moment in kNm given inSec.5 B

MW = rule wave bending moment in kNm given in Sec.5B. Hogging or sagging moment to be chosen in re-lation to the applied still water moment.



Guidance note:In special cases a more detailed evaluation of the actual still wa-ter moment MS to be used may be allowed. The simultaneous oc-currence of a certain local load on a structure and the largestpossible MS-value in the same area of the hull girder may be usedas basis for estimating f2d.

Example: Deck longitudinals. External load (p1 or p2 in TableB1) gives maximum local stress in compression, and MS may betaken as maximum sagging moment. Internal load (p7 to p10 inTable B1) gives maximum load stress in tension, and MS may betaken as maxim hogging moment.


A 300 Documentation



401 Dry cargo ships with length L > 150 m are normally tohave deck longitudinals in the strength deck clear of hatchwayopenings.

402 In tankers the deck is normally to be longitudinally stiff-ened in the cargo tank region.

403 When the strength deck is longitudinally stiffened:

— the longitudinals are to be continuous at transverse mem-bers within 0,5 L amidships in ships with length L > 150 m

— the longitudinals may be cut at transverse members within0,5 L amidships in ships with length corresponding to 50m < L < 150 m. In that case continuous brackets connect-ing the ends of the longitudinals are to be fitted

— the longitudinals may be welded against the transversemembers in ships with length L ≤ 50 m and in larger shipsoutside 0,5 L amidships.

404 Transverse beams are preferably to be used in deck areasbetween hatches. The beams are to be efficiently supported bylongitudinal girders. If longitudinals are used, the plate thick-ness is to be increased so that the necessary transverse bucklingstrength is achieved, or transverse buckling stiffeners are to befitted intercostally. The stiffening of the upper part of a planetransverse bulkhead (or stool tank) is to be such that the neces-sary transverse buckling strength is achieved.

Transverse beams are to extend to the second deck longitudinalfrom the hatch side. Where this is impracticable, stiffeners orbrackets are to be placed intercostally in extension of beams.

f2d

5 7 MS MW+( ),ZD

--------------------------------------=


DET NORSKE VERITAS

405 If hatch coaming corners with double curvature or hatchcorners of streamlined shape are not adopted, the thickness ofdeck plates in strength deck at hatch corners is to be increasedby 25%, maximum 5 mm.

The longitudinal extension of the thicker plating is not to beless than 1,5 R and not more than 3 R on both sides of the hatchend. The transverse extension outside line of hatches is to be atleast 2 R.

For shape and radius of corners in large hatch openings, seeSec.5.

R = corner radius.

406 The seam between the thicker plating at the hatch cornerand the thinner plating in the deck area between the hatches isto be located at least 100 mm inside the point at which the cur-vature of the hatch corner terminates.

If the difference between the deck plate thickness at the hatchcorners and in the deck area between hatches is greater than 1/3 of the thickest plate, a transition plate is to be laid betweenthe thick plating and the thin deck area plating. The quality ofthe transition plate is not to be more than one grade below thatof the plating at the hatch corner.



A 500 Construction and initial testing of watertight decks, trunks etc.

.1 Watertight decks, trunks, tunnels, duct keels and ventila-tors are to be of the same strength as watertight bulkheadsat corresponding levels (see Table B1, p13) The means for

making them watertight, and the arrangements adopted forclosing openings in them are to satisfy the requirements ofthis section and Sec.11. Watertight ventilators and trunksare to be carried at least up to the bulkhead deck in pas-senger ships and up to the freeboard deck in cargo ships.

.2 Where a ventilation trunk passing through a structure pen-etrates the bulkhead deck, the trunk shall be capable ofwithstanding the water pressure that may be present withinthe trunk, after having taken into account the maximumheel angle allowable during intermediate stages of flood-ing, in accordance with regulation 8.5. (Pt.5 Ch.2 Sec.2K506)

.3 Where all or part of the penetration of the bulkhead deck ison the main ro-ro deck, the trunk shall be capable of with-standing impact pressure due to internal water motions(sloshing) of water trapped on the ro-ro deck.

.4 In ships constructed before 1 July 1997, the requirementsof paragraph 2 shall apply not later than the date of the firstperiodical survey after 1 July 1997.

.5 After completion, a hose or flooding test is to be applied towatertight decks and a hose test to watertight trunks, tun-nels and ventilators.

(SOLAS Reg. II-1/19)

B. Design Loads

B 100 Local loads on deck structures

101 All generally applicable local loads on deck structuresare given in Table B1, based upon the general loads given inSec.4. In connection with the various local structures referenceis made to this table, indicating the relevant loads in each case.


DET NORSKE VERITAS

a = 1,0 for weather decks forward of 0,15L from FP, orforward of deckhouse front, whichever is the fore-most position

= 0,8 for weather decks elsewherepdp, ks = as given in Sec.4 C201h0 = vertical distance in m from the waterline at draught

T to the deckav = vertical acceleration as given in Sec.4 B600q = deck cargo load in t/m2 as specified.Weather decks

above cargo holds in dry cargo ships are normally tobe designed for a minimum cargo load:

qmin = 1,0 for ships with L = 100 m = 1,3 for ships with L > 150 m when superstructure

deck = 1,75 for ships with L > 150 m when freeboard deck.

For ships with length between 100 and 150 m the q-value may be varied linearly.When it is specially stated that no deck cargo is tobe carried, the qmin may be discarded

ρc = dry cargo density in t/m3, if not otherwise specifiedto be taken as 0,7, see also also Sec.4 C401

ρ = density of ballast, bunker or liquid cargo in t/m3,normally not to be less than 1,025 (i.e. ρ g0 ≈ 10)

HC = stowage height in m of dry cargo. Normally the'tweendeck height or height to top of cargo hatch-way to be used

hs = vertical distance in m from the load point to top oftank, excluding smaller hatchways


hb = vertical distance in metres from the load point to thedeepest equilibrium waterline in damaged conditionobtained from applicable damage stability calcula-tions. The deepest equilibrium waterline in dam-aged condition should be indicated on the drawingof the deck in question.The vertical distance is not to be less than up to themargin line (a line drawn at least 76 mm below theupper surface of the bulkhead at side)

∆ pdyn = as given in Sec.4 C300p0 = 25 in general = 15 in ballast holds in dry cargo vessels = tank pressure valve opening pressure when exceed-

ing the general valueH = height in m of tankb = the largest athwartship distance in m from the load

point to the tank corner at the top of tank/ hold mostdistant from the load point

bt = breadth in m of top of tank/hold


Weather decks 1)Sea pressure 2) , minimum 5,0

Deck cargo p2 = (g0 + 0,5 av) q

Cargo 'tweendecks Deck cargo p3 = ρc (g0 + 0,5 av) HC

Platform deck in machinery spaces Machinery and equipment p4 = 1,6 (g0 + 0,5 av)

Accommodation decks Accommodation in general

p5 = 0,35 (g0 + 0,5 av), see also Sec.4 C401

Deck as tank bottom in general

Ballast, bunker or liquid cargo

p6 = ρ (g0 + 0,5 av) hs

p7 = 0,67 (ρ g0 hp + ∆ pdyn)

p8 = ρ g0 hs + p0

Deck as tank top in general

p7 = 0,67 (ρ g0 hp + ∆ pdyn)

p8 = ρ g0 hs + p0

Deck as tank boundary in tanks with breadth > 0,4 B

Deck as tank boundary towards ends of tanks with length > 0,15 L

Deck as tank boundary in tanks with breadth > 0,4 B 3)

Deck as tank boundary in tanks with length > 0,1 L 4)

Watertight decks submerged in damaged condition 5) Sea pressure p 13 = 10 hb

1) On weather decks combination of the design pressures p1 and p2 may be required for deck cargo with design stowage height less than 2,3 m.

2) For ships with service restrictions p1 may be reduced with the percentages given in Sec.4 B202. CW should not be reduced

3) To be used for strength members located less than 0,25 bb away from tank sides in tanks with no restrictions on their filling height. For tanks with free breadth (no longitudinal wash bulkheads) bb > 0,56 B the design pressure will be specially considered according to Sec.4 C305

4) To be used for strength members located less than 0,25 lb away from tank ends in tanks with no restrictions on their filling height. For tanks with free length (no transverse wash bulkheads or transverse web frames in narrow tanks) lb > 0,13 L the design pressure will be specially considered according to Sec.4 C305

5) The strength may be be calculated with allowable stresses for plating, stiffeners and girders increased by 60 f1.

p1 a pdp 4 0 2ks,+( ) h0–( )=

p9 ρg0 0 67 hs φb+( ), 0 12 Hφbt,–[ ]=

p10 ρg0 0 67 hs θl+( ), 0 12 Hθlt,–[ ]=

p11 ρ 3B

100---------–

� �� bb=

p12 ρ 4L

200---------–

� �� lb=


DET NORSKE VERITAS

bb = distance in m between tank sides or effective longi-tudinal wash bulkhead at the height at which thestrength member is located

l = the largest longitudinal distance in m from the loadpoint to the tank corner at top of tank most distantfrom the load point

lt = length in m of top of tanklb = distance in m between transverse tank bulkheads or

effective transverse wash bulkheads at the height atwhich the strength member is located. Transversewebframes covering part of the tank cross section(e.g. wing tank structures in tankers) may be regard-ed as wash bulkheads

φ = roll angle in radians as given in Sec.4 B400θ = pitch angle in radians as given in Sec.4 B500.


C 100 Strength deck plating101 The breadth of stringer plate and strakes in way of pos-sible longitudinal bulkheads which are to be of grade B, D orE is not to be less than:

b = 800 + 5 L (mm), maximum 1800 mm.


p = p1 – p13, whichever is relevant, as given in Table B1σ = allowable stress within 0,4 L, given by:

σ = 160 f1 within 0,1 L from the perpendiculars and withinline of large deck openings.


f2D = stress factor as given in A 200.

103 The longitudinal buckling strength is to be checked ac-cording to Sec.14.


t0 = 5,5 for unsheathed weather and cargo decks = 5,0 for accommodation decks and for weather and car-

go decks sheathed with wood or an approved composi-tion

k = 0,02 in vessels with single continuous deck = 0,01 in vessels with two continuous decks above 0,7 D

from the baseline = 0,01 as minimum for weather decks forward of 0,2 L

from F.P. = 0 in vessels with more than two continuous decks

above 0,7 D from the baseline.

105 If the end bulkhead of a long superstructure is locatedwithin 0,5 L amidships, the stringer plate is to be increased inthickness for a length of 3 m on each side of the superstructureend bulkhead. The increase in thickness is to be 20%.

C 200 Plating of decks below or above strength deck201 The thickness requirement corresponding to lateral pres-sure is given by the formula in 102 when σ = 160 f1.

202 The thickness of steel decks is not to be less than:

t0 = as given in 104k = 0,01 for 'tween deck above 0,7 D in vessels with two

continuous decks above 0,7 D from the baseline andfirst tier of superstructure or deckhouse in vessels withsingle continuous deck when more than 50% of 0,4 Lamidships is covered

= 0,01 for forecastle decks forward of 0,2 L from F.P. = 0 for other decks.

C 300 Longitudinals


p = p1 – p13, whichever is relevant, as given in Table B1.σ = allowable stress, within 0,4 L given in Table C1 = 160 f1 for continuous decks within 0,1 L from the per-

pendiculars and for other deck longitudinals in general.

Between specified regions the σ-value may be varied linearly.For longitudinals σ = 160 f1 may be used in any case in com-bination with heeled condition pressures p9, p11 and sloshingload pressure p12.

f2d = stress factor as given in A200.


303 The web and flange thickness is not to be less than thelarger of:

k = 0,01 L1 in general = 0,02 L1 (= 5,0 maximum) in peaks and in cargo oil


304 Longitudinals supported by deck transverses subject torelatively large deflections are to be checked by direct strengthcalculation, see Sec.13 C. Increased bending stresses at trans-verse bulkheads are to be evaluated and may be absorbed byincreased end brackets.

C 400 Transverse beams.


p = p1 – p13, whichever is relevant, as given in Table B1.


403 For end connections, see Sec.3 C200.

Transversely stiffened

Longitudinally stiffened

175 f1 – 120 f2d, maximum 120 f1 120 f1

t15 8ka s p,

σ------------------------------ tk (mm)+=

t t0

k L1

f1

---------- tk (mm)+ +=

t t0

k L1

f1

---------- tk (mm)+ +=

Z83 l

2s p wk

σ---------------------------- (cm

3), minimum 15 cm

3=

t 5 0, k

f1

-------- tk (mm)+ +=

hg--- tk+=

Z0 63 l

2s p wk,

f1--------------------------------- (cm

3), minimum 15 cm

3=


DET NORSKE VERITAS

404 For beam-panel buckling, see Sec.14 C501.

D. Girders

D 100 General

101 The thickness of web plates, flanges, brackets and stiff-eners of girders is not to be less than:

k = 0,01 L1 in general = 0,02 L1 for girder webs, flanges and brackets in cargo


brackets in peaks.

The thickness of girder web plates is in addition not to be lessthan:

t = 12 s + tk (mm)

s =spacing of web stiffening in m.


103 Longitudinal deck girders above tanks are to be fitted inline with transverse bulkhead verticals.

The flange area is to be at least 1/7 of the sectional area of theweb plate, and the flange thickness is to be at least 1/30 of theflange width. For flanges subject to compressive stresses thethickness is to be taken as 0,1 bf, bf being the flange widthwhen asymmetric and half the flange width when symmetric.

104 Deck transverses are to be fitted in the lowest deck in en-gine room, in line with the side verticals. The depth of the decktransverses is to be at least 50% of the depth of the side verti-cals, web thickness and face plate scantlings being as for sideverticals.

105 The thickness of girder stiffeners and brackets is not tobe less than given in 102.


D 200 Simple girders

201 The section modulus requirement for simple girders isgiven by:

p = p1– p6 = 1,15 p7 = p8 – p13, whichever is relevant, as given in Table B1.b = loading breadth in m

σ =

for continuous longitudinal girders within 0,4 L amid-ships

= 160 f1 for transverse girders and longitudinal girderswithin 0,1 L from perpendiculars.

Between specified regions the σ-value may be varied linearly.For longitudinal girders σ = 160 f1 may be used in any case incombination with heeled condition pressures p9 and p11.

f2d = stress factor as given in A 200.


p = as given in 201b = as given in 201h = girder height in m.


203 For stiffness in connection with panel buckling, seeSec.14 C502.


301 In addition to fulfilling the general local requirementsgiven in 100, the main scantlings of deck girders being part ofcomplex girder systems in holds or tanks for heavy cargo orliquids may have to be based on a direct stress analysis as out-lined in Sec.13.


E 100 Transverse strength of deck between hatches101 In ships with large hatch openings, it is to be examinedthat the effective deck area between hatches is sufficient towithstand the transverse load acting on the ship's sides. Bend-ing and shear stresses may also arise as result of loading on thetransverse bulkhead supported by the deck area, and also as re-sult of displacements caused by torsion in the hull girder. Re-inforcements to reduce the additional stresses will beconsidered in each case. The effective area is defined as:

— deck plating— transverse beams— deck transverses— hatch end beams (after special consideration)— cross section of stool tank at top of transverse bulkhead— cross section of transverse bulkhead (if plane or horizon-

tally corrugated) down to base of top wing tank, or to 0,15D from deck.

When calculating the effective area, corrosion additions are tobe deducted.

The compressive stress is not to exceed 120 f1 N/mm2 nor 80%of the critical buckling stress of the deck, bulkhead and stooltank plating.

The buckling strength of stiffeners and girders is to be exam-ined.

E 200 Strength of deck outside large hatches

201 The strength of deck and ship's side in way of long andwide hatches as given in Sec.5 A106 is, as applicable, to be ex-amined by direct calculation of bending moments, torsionalmoments, shear forces and deflections due to loads caused bythe sea and the deck cargo as given in Pt.5 Ch.2 Sec.6 C.

Table C1Deck σStrength deck, long superstructures and effective deckhouses above strength deck

225 f1 – 130 f2d,

maximum 160 f1

Continuous decks below strength deck

maximum 160 f1

225f1 130f2d

zn za–

zn----------------–

t 5 0, k

f1

-------- tk (mm)+ +=

Z100 S

2b p wk

σ--------------------------------- (cm

3)=

190f1 130f2d

zn za–

zn---------------- , maximum 160 f1–

A0 07 S b p,

f1-------------------------- 10 h tk (cm

2)+=


DET NORSKE VERITAS

E 300 Pillars in tanks

301 Solid pillars are to be used.

302 Where the hydrostatic pressure may give tensile stressesin the pillars, their sectional area is not to be less than:

A = 0,07 ADK pt (cm2)

ADK = deck area in m2 supported by the pillarpt = design pressure p in kN/m2 giving tensile stress in

the pillar.

Doubling plates at ends are not allowed.

E 400 Strengthening against liquid impact pressure in larger tanks

401 If the deck forms boundary of larger ballast or cargotanks with free sloshing length ls > 0,13 L and/or breadth bs >0,56 B, the deck structure is to have scantlings according toSec.9 E400 for impact loads referred to in Sec.4 C305.

E 500 Foundations for deck machinery, cranes and masts

501 The support of winches, cranes, masts etc. is to be con-sidered. Drawings showing the deck structure below the foun-dation are to be submitted for approval when the static forcesexceed 50 kN or when the resulting bending moments at deckexceed 100 kNm. The drawings should clearly indicate the rel-evant forces and bending moments acting on the structure.

502 When considering the structural strength of the deckstructure the static loads are to be multiplied by a dynamic fac-tor equal to 1,3 for general cargo vessels and 1,5 for offshorevessels, 2 for offshore vessels when the crane cabin is locatedabove the slewing ring.

503 Acceptable stress levels may be taken as follows:

Bending stresses: 160 f1 N/mm2.Shear stresses: 90 f1 N/mm2.

504 To obtain satisfactory transfer of forces the structure be-low deck is to be in line with the foundation above deck. Thismay be obtained by fitting adequate brackets, intercostals,rings or similar.

505 Crane columns and similar structure should preferablybe extended to the deck below. Reference is made to Ch.3Sec.5 A.

506 For windlass foundations reference is made to Ch.3Sec.5 B.

507 Regarding material qualities reference is made to Sec.2B 300 and Sec.2 B500.

508 The welding is to be considered with respect to the actu-al stress level.

E 600 Emergency towing arrangements for tankers601 Tankers of 20 000 tonnes deadweight and above, includ-ing oil tankers, chemical tankers and gas carriers are to be fit-ted with an emergency towing arrangement in accordance withIMO resolution MSC.35(63).

602 Drawings showing the towing arrangement, includingthe towing brackets, fairleads, towing pennant, pick-up gearand supporting structure are to be submitted for approval.Towing arrangements are to be arranged both forward and aft.Supports shall be adequate for towing angles up to 90° fromthe ship's centreline to both port and starboard and 30° verti-cally downwards.

603 Emergency towing arrangements are to have a workingstrength (SWL) of:

— 1 000 kN for vessels less than 50 000 tonnes deadweight— 2 000 kN for vessels of 50 000 tonnes deadweight and

above.

The minimum breaking load (MBL) of the major componentsof the towing arrangements, as defined in MSC.35(63), is to be2 times the SWL.

604 The strong point and supporting structure for the towingarrangement is to be designed for a load of 1,3 times the SWLwith allowable stresses as given in 503.

605 Material used in the strong point is to be in accordancewith Ch.3 Sec.3 F200.

606 The pick-up gear shall be a floating line of minimumlength 120 m and with a minimum breaking load (MBL) of 200kN.


DET NORSKE VERITAS

SECTION 9BULKHEAD STRUCTURES

A. General

A 100 Introduction101 The requirements in this section apply to bulkhead struc-tures.



Where relevant, actual values for these parameters may bechosen and inserted in the formulae. Direct stress calculationsbased on said structural principles and as outlined in Sec.13will be considered as alternative basis for the scantlings.

A 200 Definitions

201 Symbols:






L1 = L, but need not be taken greater than 300 mt = rule thickness in mm of platingZ = rule section modulus in cm3 of stiffeners and simple

girderska = correction factor for aspect ratio of plate field = (1,1 – 0,25 s/ l)2 = maximum 1,0 for s/ l = 0,4 = minimum 0,72 for s/ l = 1,0s = stiffener spacing in m, measured along the plating. For

corrugations, see 203l = stiffener span in m, measured along the topflange of

the member. For definition of span point, see Sec.3C100. For curved stiffeners l may be taken as the cordlength









f 2b = stress factor below neutral axis of hull girder as definedin Sec.6 A200

f 2d = stress factor above neutral axis of hull girder as definedin Sec.8 A200


= 1,0 in other compartmentsσ = nominal allowable bending stress in N/mm2 due to lat-

eral pressurep = design pressure in kN/m2 as given in B.

1) For details see Sec.1 B .

2) For details see Sec.2 B and C .

202 The load point where the design pressure is to be calcu-lated is defined for various strength members as follows:

— For plates: Midpoint of horizontally stiffened plate field.


— For stiffeners: Midpoint of span.

When the pressure is not varied linearly over the span, thedesign pressure is to be taken as the greater of:

pm, pa and pb are calculated pressures at the midpoint and ateach end respectively.

— For girders: Midpoint of load area.

203 For corrugated bulkheads the following definition ofspacing applies (see Fig. 1):

Fig. 1Corrugated bulkhead

s = s1 for section modulus calculations = 1,05 s2 or 1,05 s3 for plate thickness calculations in

general = s2 or s3 for plate thickness calculation when 90 degrees

corrugations.

A 300 Documentation301 Plans and particulars to be submitted for approval or in-formation are specified in Sec.1.

A 400 Structural arrangement and details401 Number and location of transverse watertight bulkheadsare to be in accordance with the requirements given in Sec.3.

402 The peak tanks are to have centre line wash bulkheadswhen the breadth of the tank is greater than 2/3 of the mouldedbreadth of the ship.

403 Within 0,5 L amidships, in the areas 0,15 D above thebottom and 0,15 D below the strength deck, the continuity ofbulkhead longitudinals is to be as required for bottom and decklongitudinals respectively.



406 Stern tubes are to be enclosed in a watertight space (orspaces) of moderate volume. In case the stern tube terminatesat an afterpeak bulkhead also being a machinery space bulk-head, a pressurized stern tube sealing system may be acceptedas an alternative to the watertight enclosure.

(SOLAS, Reg. II-1/11.9)

pm and pa pb+

2-----------------


DET NORSKE VERITAS

B. Design Loads

B 100 Local loads on bulkhead structures101 All generally applicable local loads on bulkhead struc-tures are given in Table B1, based upon the general loads given

in Sec.4. In connection with the various local structures refer-ence is made to this table, indicating the relevant loads in eachcase.

hb = vertical distance in metres from the load point to thedeepest equilibrium waterline in damaged conditionobtained from applicable damage stability calcula-tions. The deepest equilibrium waterline in dam-aged condition should be indicated on the drawingof the bulkhead in question.The vertical distance is not to be less than up to themargin line (a line drawn at least 76 mm below theupper surface of the bulkhead at side)

av = vertical acceleration in m/s2 as given in Sec.4 B600ρc = dry cargo density in t/m3 if not otherwise specified

to be taken as 0,7ρ = density of ballast, bunker or liquid cargo in t/m3,

normally not to be taken less than 1,025 (i.e. ρ g 0 ≈10)

K = sin2 α tan 2 (45 – 0,5 δ) + cos2 α = cos α minimumα = angle between panel in question and the horizontal

plane in degreesδ = angle of repose of cargo in degrees, not to be taken

greater than 20 degrees for light bulk cargo (coal,grain) and not greater than 35 degrees for heavybulk cargo (ore)

hs = vertical distance in m from the load point to the topof tank or hatchway excluding smaller hatchways

hc = vertical distance in m from the load point to thehighest point of the hold including hatchway in gen-eral. For sloping and vertical sides and bulkheads,

hc may be measured to deck level only, unless thehatch coaming is in line with or close to the panelconsidered.In dry cargo 'tweendecks, hc may be taken to thenearest deck above


∆ pdyn = as given in Sec.4 C300H = height in m of tankp0 = 25 in general = 15 in ballast holds in dry cargo vessels = tank pressure valve opening pressure when exceed-

ing the general valueb = the largest athwartship distance in m from the load




lt = length in m of top of tankφ = roll angle in radians as given in Sec.4 B400θ = pitch angle in radians as given in Sec.4 B500bb = distance in m between tank sides or effective longi-

tudinal wash bulkhead at the height at which thestrength member is located

lb = distance in m between transverse tank bulkheads oreffective transverse wash bulkheads at the height at


Watertight bulkheadsSea pressure when flooded or general dry cargo minimum

p1 = 10 hb

Cargo hold bulkheads Dry bulk cargo p2 = ρc (g0 + 0,5 av) K hc

Tank bulkheads in general

Ballast, bunker or liquid cargo

p3 = ρ (g0 + 0,5 av) hs

p4 = 0,67 (ρ g0 hp + ∆ pdyn)

p5 = ρ g0 hs + p0

Longitudinal bulkheads as well as transverse bulkheads at sides in wide tanks

In tanks with breadth > 0,4 B

Note 1)

Transverse bulkheads and longitudinal bulkheads at ends in long tanks

In tanks with length > 0,15 L

Note 2)

Longitudinal wash bulkheads

Transverse wash bulkheads

1) To be used for strength members located less than 0,25 bb away from tank sides in tanks with no restrictions on their filling height. For tanks with free breadth (no longitudinal wash bulkheads) bb > 0,56 B the design pressure will be specially considered according to Sec.4 C305.

2) To be used for strength members located less than 0,25 lb away from tank ends in tanks with no restrictions on their filling height. For tanks with free length (no transverse wash bulkheads or transverse web frames in narrow tanks) lb > 0,13 L the design pressure will be specially considered according to Sec.4 C305.

p6 ρ g0 0 67 hs φb+( ), 0 12 H φ bt,–[ ]=

p7 ρ 3B

100---------– bb=

p8 ρ g0 0 67 hs θl+( ), 0 12 H θ lt,–[ ]=

p9 ρ 4L

200---------– lb=

p7 ρ 3B

100---------– bb=

p9 ρ 4L

200---------– lb=


DET NORSKE VERITAS

which the strength member is located. Transversewebframes covering part of the tank cross section(e.g. wing tank structures in tankers) may be regard-ed as wash bulkheads.


C 100 Bulkhead plating101 The thickness requirement corresponding to lateral pres-sure is given by:

p = p1– p9, whichever is relevant, as given in Table B1σ = 160 f1 for longitudinally stiffened longitudinal bulk-

head plating at neutral axis irrespective of ship length = 140 f1 for transversely stiffened longitudinal bulkhead

plating at neutral axis within 0,4 L amidships, mayhowever be taken as 160 f1 when p6 or p7 are used.

Above and below the neutral axis the σ-values are to bereduced linearly to the values for the deck and bottomplating, assuming the same stiffening direction andmaterial factor as for the plating considered

= 160 f1 for longitudinal bulkheads outside 0,05 L fromF.P. and 0,1 L from A.P. and for transverse bulkheadsin general

= 220 f1 for watertight bulkheads except the collisionbulkhead, when p1 is applied.


In corrugated bulkheads formed by welded plate strips, thethickness in flange and web plates may be differing.

The thickness requirement then is given by the following mod-ified formula:

tn = thickness in mm of neighbouring plate (flange or web),not to be taken greater than t.


k = 0,03 for longitudinal bulkheads except double skinbulkheads in way of cargo oil tanks and ballast tanks inliquid cargo tank areas

= 0,02 in peak tanks and for transverse and double skinlongitudinal bulkheads in way of cargo oil tanks andballast tanks in liquid cargo tank areas

= 0,01 for other bulkheads.

103 The thickness of longitudinal bulkhead plating is also tosatisfy the buckling strength requirements given in Sec.14, tak-ing into account combined shear and in- plane compressivestresses where relevant.

104 In longitudinal bulkheads within the cargo area thethickness is not to be less than:

105 The buckling strength of corrugation flanges at the mid-dle length of corrugations is to be controlled according toSec.14, taking kl in Sec.14 B201 equal to 5.

Usage factors to be applied:

η = 0,80 for cargo tank bulkheads, cargo hold bulkheadswhen exposed to dry cargo or ballast pressure, and col-lision bulkheads

= 1,0 for watertight bulkheads.

106 For plates in afterpeak bulkhead in way of sterntube, in-creased thickness or doubling may be required.

107 For wash bulkhead plating, requirement for thicknessesmay have to be based on the reaction forces imposed on thebulkhead by boundary structures.

C 200 Longitudinals

201 The section modulus requirement for stiffeners and cor-rugations is given by:

p = p1– p9, whichever is relevant, as given in Table B1

σ =

within 0,4 L amidships = 160 f1 within 0,1 L from perpendiculars.

Between specified regions the σ-value may be varied linearly.For longitudinals σ = 160 f1 may be used in any case in com-bination with heeled condition pressures p6 to p7 and withsloshing pressure p9.

The allowable stress may be increased by 60 f1 for watertightbulkheads, except the collision bulkhead, when p1 is applied.



202 The web and flange thickness is not to be less than thelarger of:

k = 0,01 L1 in general = 0,02 L1 (= 5,0 maximum) in peak tanks and in cargo oil


203 Longitudinals supported by vertical girders subject torelatively large deflections are to be checked by a directstrength calculation, see Sec.13 C. Increased bending stressesat transverse bulkheads are to be evaluated and may be ab-sorbed by increased end brackets.


C 300 Vertical and transverse stiffeners on tank, wash, dry bulk cargo, collision and watertight bulkheads301 Transverse bulkheads for ballast and bulk cargo holdsare normally built with strength members only in the verticaldirection (corrugations or double plane bulkheads), having un-supported spans from deck to inner bottom. In larger ships,

t15 8kas p,

σ----------------------------- tk (mm)+=

t500 s

2p

σ------------------- tn

2– tk (mm)+=

t 5 0,k L1

f1

---------- tk (mm)+ +=

t1000s

120 3 L1–------------------------------ tk (mm)+=

Z83 l

2s p wk

σ---------------------------- (cm

3), minimum 15 cm

3=

225f1 130f2

zn za–

zn----------------, minimum 160 f1–

t 5 0, k

f1

---------- tk (mm)+ +=

hg--- tk +=


DET NORSKE VERITAS

stool tanks are often arranged at the lower and upper end of thebulkhead. The scantlings of such bulkheads are normally to bebased on a direct calculation, taking into account the reactionsand supporting effect from double bottom and deck structure,see Sec.13.

302 The section modulus requirement for simple stiffenersand corrugations is given by:

p = p1– p9, whichever is relevant, as given in Table B1σ = 160 f1 for tank, cargo and collision bulkheads (see also

105) = 220 f1 for watertight bulkheads (see also 105)m = 7,5 for vertical stiffeners simply supported at one or

both ends = 10 for transverse stiffeners and vertical stiffeners

which may be considered fixed at both ends = 10 for horizontal corrugations fixed at ends = 13 for vertical corrugation, upper end if fixed = 20 for vertical corrugation, upper end if flexible = ms for vertical corrugation, lower end to stool

= for vertical corrugation at middle of span

m(max) = 13

ms =

bc = breadth of stool in m where corrugation is welded inbs = breadth of stool in m at inner bottomHS = height of stool in mh db = height of double bottom in ml db = length of cargo hold double bottom between stools in

m not to be taken larger than 6 HS or 6 hdb if no stool.

The m-value may be adjusted for members with boundary con-dition not corresponding to the above specification or a directcalculation including the supporting boundary structure maybe done, see Sec.13.

303 The thickness of web and flanges is not to be less thangiven in 202. For corrugations the flanges are to have thicknesssatisfying buckling as given in 105.

304 Brackets are normally to be fitted at ends of non-contin-uous stiffeners. For end connections, see also Sec.3 C200.

305 For end connection of corrugations welded to stools orinner bottom the throat thickness is to satisfy Sec.12 C202 onboth sides of the end plating. The end plating in upper and low-er stool (preferably with Z-quality steel) is to have a thicknessnot less than 0,8 times the corrugation flange thickness ifbrackets are not welded in line with the corrugation webs. Thesection modulus is then to be based on the corrugation flangeonly as the web will not be supported. For corrugations ar-ranged with a slanting plate the effect of the slanting plate maybe taken into consideration. This effect will increase the sec-tion modulus Z of the corrugation on the side where the slant-ing plate is fitted and hence reduce the nominal stresses. Amaximum increased Z of 15% may be accepted. Tank bulk-heads in oil and chemical carriers normally need brackets inline with corrugation webs. The stool sides or floors in the dou-ble bottom are to have thickness corresponding to the forcescoming from the corrugation flanges with the allowable stress-es as given in 302 and controlled for buckling as given inSec.14.

D. Girders

D 100 General101 The thickness of web plates, flanges, brackets and stiff-eners of girders is not to be less than:

k = 0,01 L1 in general = 0,02 L1 for girder webs, flanges and bracketsin cargo


brackets in peaks

The thickness of girder web plates is in addition not to be lessthan:

t = 12 s + tk (mm)

s = spacing of web stiffening in m.



D 200 Simple girders201 The section modulus requirement for simple girders isgiven by:

p = p1 – p3 = 1,15 p4 = p5 – p9, whichever is relevant, as given in Table B1.b = loading breadth in m

σ =

for continuous longitudinal girders within 0,4 L amid-ships

= 160 f1 for other girders.

The allowable stress may be increased by 60 f1 (40 f1 for lon-gitudinal girders within 0,4 L amidships) for watertight bulk-heads, except the collision bulkhead, when p1 is applied.

Between specified regions the σ-value may be varied linearly.For longitudinal girders σ = 160 f1 may be used in any case incombination with heeled condition pressures p6 and p7.




p = as given in 201k = 0,06 for stringers and upper end of vertical girders = 0,08 for lower end of vertical girdersc = 0,75 for watertight bulkheads, except the collision

bulkhead, when p1 is applied = 1,0 in all other casesb = as given in 201

Z1000 l

2s p wk

σ m--------------------------------- (cm

3)=

8ms

ms 4–---------------

7 5 14 bc HS

hdb

2--------+

� ��

bsldb--------------------------------------+,

t 5 0, k

f1

---------- tk (mm)+ +=

Z100 S

2b p wk

σ---------------------------------- (cm

3)=

190f1 130f2

zn za–

zn----------------, minimum 160 f1–

Ac k S b p

f1--------------------- 10 h tk (cm

2)+=


DET NORSKE VERITAS

h = girder height in m.



301 In addition to fulfilling the general local requirementsgiven in 100, the main scantlings of bulkhead girders beingparts of complex girder systems in holds or tanks for heavycargo or liquids, may have to be based on a direct stress anal-ysis as outlined in Sec.13.


E 100 Shaft tunnels

101 In ships with engine room situated amidships, a water-tight shaft tunnel is to be arranged. Openings in the forwardend of shaft tunnels are to be fitted with watertight slidingdoors capable of being operated from a position above the loadwaterline.

102 The thickness of curved top plating may be taken as 90%of the requirement to plane plating with the same stiffenerspacing.

103 If ceiling is not fitted on top plating under dry cargohatchway openings, the thickness is to be increased by 2 mm.

104 The shaft tunnel may be omitted in ships with service re-striction notation R2, R3 and R4 provided the shafting is oth-erwise effectively protected. Bearings and stuffing boxes are tobe accessible.

E 200 Corrugated bulkheads

201 The lower and upper ends of corrugated bulkheads andthose boundaries of vertically corrugated bulkheads connectedto ship sides and other bulkheads are to have plane parts of suf-ficient width to support the adjoining structures.

202 Girders on corrugated bulkheads are normally to be ar-ranged in such a way that application of the bulkhead as girderflange is avoided.

203 End connections for corrugated bulkheads terminatingat deck or bottom are to be carefully designed. Supportingstructure in line with corrugation flanges are to be arranged be-low an inner bottom.

E 300 Supporting bulkheads

301 Bulkheads supporting decks are to be regarded as pillars.The compressive loads and buckling strength are to be calcu-lated as indicated in Sec.14 assuming:

i = radius of gyration in cm of stiffener with adjoiningplate. Width of adjoining plate is to be taken as 40 t,where t = plate thickness

Local buckling strength of adjoining plate and torsional buck-ling strength of stiffeners are to be checked

302 Section modulus requirement to stiffeners:

Z = 2 l2 s (cm3)

303 The distance between stiffeners is not to be greater than2 frame spacings, and is not to exceed 1,5 m.

304 The plate thickness is not to be less than 7,5 mm in thelowest hold and 6,5 mm in 'tween decks.

305 On corrugated bulkheads, the depth of the corrugationsis not to be less than 150 mm in the lower holds and 100 mmin the upper 'tween deck.

E 400 Strengthening against liquid impact pressure in larger tanks401 Tanks with free sloshing length ls > 0,13 L and/orbreadth bs > 0,56 Bpi are to be strengthened for the impactpressure as given in Sec.4 C305.

402 Plating subjected to impact pressure pi. The thickness isnot to be less than:

403 Stiffeners supporting plating subjected to impact pres-sure pi. The section modulus is not to be taken less than:

The shear area at each end is not to be less than:

lp = loaded length of stiffener, maximum l, but need not betaken greater than 0,1 ls or 0,1 bs, respectively, for lon-gitudinal or transverse impact pressure

kp = correction factor for resulting impact pressure

= , minimum 0,35.

l 's = ls or bs as defined in Sec.4 C306h = height in m of stiffener.

If the impact pressure is acting on the stiffener side, the stiff-ener web thickness is not to be less than:

The throat thickness of continuous fillet welding of the stiffen-er to the plating when impact pressure is acting on the stiffenerside is not to be less than:

A proper fit up between stiffener and plating is assumed.

The net connection area of continuous stiffeners at girders is tosatisfy the following expression:

1,7 AF + AW = 2 AS

AF = connection area at flange in cm2

AW = connection area at web in cm2.

404 Girders supporting stiffeners subjected to impact pres-sure pi.

The section modulus is not to be less than:

The shear area at each end is not to be taken less than:

Sp = loaded length of girder, maximum S, but need not betaken greater than 0,1 ls or 0,1 bs, respectively, for lon-gitudinal or transverse impact pressure

kp = correction factor for impact pressure

t0 9 ka s pi,

f1

---------------------------- tk (mm)+=

Z0 5 l lp s pi kp wk,

f1------------------------------------------- (cm

3)=

AS

0 05 l lp s–( ) s pi kp,lpf1

-------------------------------------------------- 10 h tk (cm2)+=

1 1, 10l

l ′ s-----–

t 5s pi

100f1------------- tk (mm)+ +=

ts pi

120---------

tk

2---- (mm) +=

Z0 5 S Sp b pi kp wk,

f1----------------------------------------------- (cm

3)=

AS

0 05 S b pi kp,f1

---------------------------------- 10 h tk (cm2)+=


DET NORSKE VERITAS

= , minimum 0,25 for horizontals

= , minimum 0,25 for verticals

l 's = l s or bs as defined in Sec.4 C306h = height in m of girder webb = loading breadth of girder in m.

The web thickness is in no case to be less than:

The throat thickness of continuous fillet welding of girderwebs to the plating subjected to impact pressure is acting onthe girder web side is not to be less than:

A proper fit up between stiffener and plating is assumed.

The spacing of stiffeners on the web plate for girders in thetank where impact pressure occurs is not to be taken greaterthan:

pi = impact pressure at panel near girder.

1 1, 10bl ′ s-----–

1 1, 10Sp

l ′ s-----–

t 6 5,0 2 pi,

f1

------------------ tk (mm)+ +=

ts pi

120---------

tk

2---- (mm) +=

s1 2 t tk–( ),

pi

-------------------------- (m)=


DET NORSKE VERITAS

SECTION 10SUPERSTRUCTURE ENDS, DECKHOUSE SIDES AND ENDS, BULWARKS

A. General

A 100 Introduction101 In this section the requirements applicable to superstruc-ture end bulkheads, deckhouse sides and ends and bulwarksare collected. The requirements for sides of superstructuresand decks above superstructures and deckhouses are given inSec.7 and 8 respectively.

Requirements for protection of crew as given by ICLL Regu-lation 25 supplemented by relevant IACS interpretations arealso included (see E). Other relevant requirements given in theICLL regulations are included in Sec.11 and in Ch.5.

Where the ICLL-text is directly quoted it is printed in italics.


L = rule length in m, see Sec.1 BB = rule breadth in m, see Sec.1 BCB = rule block coefficient, see Sec.1 Bt = rule thickness in mm of platingZ = rule section modulus in cm3 of stiffeners and simple

girdersL1 = L, but need not be taken greater than 300 mka = correction factor for aspect ratio of plate field = (1,1 – 0,25 s/ l)2 = maximum 1,0 for s/ l = 0,4 = minimum 0,72 for s/ l = 1,0s = stiffener spacing in m, measured along the platingl = stiffener span in m, measured along the topflange of







σ = nominal allowable bending stress in N/mm2 due to lat-eral pressure

p = design pressure in kN/m2 as given in C.


202 Superstructure is defined as a decked structure on thefreeboard deck, extending from side to side of the ship or withthe side plating not inboard of the shell plating more than 4%of the breadth (B).

203 Deckhouse is defined as a decked structure above thestrength deck with the side plating being inboard of the shellplating more than 4% of the breadth (B).

Long deckhouse = deckhouse having more than 0,2 L of itslength within 0,4 L amidships.

Short deckhouse = deckhouse not defined as a long deckhouse.

B. Structural Arrangement and Details

B 100 Structural continuity101 In superstructures and deckhouses aft, the front bulk-head is to be in line with a transverse bulkhead in the hull be-low or be supported by a combination of partial transversebulkheads, girders and pillars. The after end bulkhead is also to

be effectively supported. As far as practicable, exposed sidesand internal longitudinal and transverse bulkheads are to be lo-cated above tank bulkheads and/or deep girder frames in thehull structure and are to be in line in the various tiers of accom-modation. Where such structural arrangement in line is notpossible, there is to be other effective support.

102 Sufficient transverse strength is to be provided by meansof transverse bulkheads or girder structures.

103 At the break of superstructures, which have no set-infrom the ship's side, the side plating of poop and bridge is toextend beyond the ends of the superstructure, and is to be grad-ually reduced in height down to the sheer strake. The transitionis to be smooth and without local discontinuities. A substantialstiffener is to be fitted at the upper edge of plating, which ex-tends beyond the superstructure. The plating is also to be addi-tionally stiffened.

104 The end bulkheads of long superstructures are to be ef-fectively supported by bulkheads or heavy girders below deck.

105 In long deckhouses, openings in the sides are to havewell rounded corners. Horizontal stiffeners are to be fitted atthe upper and lower edge of large openings for windows.

Openings for doors in the sides are to be substantially stiffenedalong the edges, and the side plates forming coamings belowand above the doors, are to be continuous and extended wellbeyond the door openings. The thickness is to be increased lo-cally or doubling plates are to be fitted.

The connection area between deckhouse corners and deck plat-ing is to be increased locally.

Deck girders are to be fitted below long deckhouses in linewith deckhouse sides. The girders are to extend three framespaces forward and aft of the deckhouse ends. The depth of thegirders is not to be less than that of the beams plus 100 mm.Girders are to be stiffened at the lower edge. The girder depthat ends may be equal to the depth of the beams.

Guidance note:Expansion of long deckhouse sides should be taken into accountby setting in parts of the sides towards the centre line of the ship.


106 Casings situated within 0,5 L amidships are to be stiff-ened longitudinally at the strength deck (e.g. at the lower edgeof the half beams) to avoid buckling due to longitudinal com-pression forces.

B 200 Connections between steel and aluminium

201 To prevent galvanic corrosion a non-hygroscopic insula-tion material is to be applied between steel and aluminiumwhen bolted connection.

202 Aluminium plating connected to steel boundary bar atdeck is as far as possible to be arranged on the side exposed tomoisture.

203 A rolled compound (aluminium/steel) bar may be usedin a welded connection after special approval.

204 Direct contact between exposed wooden materials, e.g.deck planking, and aluminium is to be avoided.

205 Bolts with nuts and washers are either to be of stainlesssteel or cadmium plated or hot galvanized steel. The bolts areto be fitted with sleeves of insulating material. The spacing isnormally not to exceed 4 times the bolt diameter.

206 For earthing of insulated aluminium superstructures, seePt.4 Ch.8.


DET NORSKE VERITAS

B 300 Miscellaneous301 Companionways situated on exposed decks are to be ofsteel and efficiently stiffened.

302 Bulwark plates are in general not to be welded to sideplating or deck plating (see also Sec.7 C208).

Long bulwarks are to have expansion joints within 0,6 L amid-ships.

303 Where bulwarks on exposed decks form wells, ampleprovision is to be made for freeing the decks of water.


C. Design Loads

C 100 External pressure101 The design sea pressure for the various end and sidestructures is given in Table C1.

a =

=

=

k =

k =

x = longitudinal distance in m from A.P. to the load pointho = vertical distance in m from the waterline at draught T

to the load point

c =

b1 = breadth of deckhouse at position consideredB1 = maximum breadth of ship on the weather deck at posi-

tion considered

is not to be taken less than 0,25.

For unprotected parts of machinery casings c is not to be takenless than 1,0.

CW = wave coefficient as given in Sec.4 B200pdp, ks = as given in Sec.4 C201

For ships with service restrictions, p1 and p4 may be reducedwith the percentages given in Sec.4 B202. CW should not be re-duced.

The minimum design pressure for sides and aft end of deck-houses 1,7 CW (m) above S.W.L. may be reduced to 2,5 kN/m2.

D. Scantlings

D 100 End bulkheads of superstructures and deck-houses, and exposed sides in deckhouses

101 The thickness requirement for plating corresponding tolateral external pressure is given by:

p = p1 – p5, whichever is relevant, as given in Table C1σ = 160 f1 N/mm2.


— for the lowest tier:

t = 5 + 0,01 L (mm), maximum 8 mm — for higher tiers:

t = 4 + 0,01 L (mm), maximum 7 mm, minimum 5 mm.

103 The section modulus requirement for stiffeners is givenby:

p = as given in 101σ = 160 f1 for longitudinals, vertical and transverse stiffen-

ers in general = 90 f1σ for longitudinals at strength deck in long deck-

house within 0,4 L amidships. The -value may be in-creased linearly to the general value at the first deckabove the strength deck and at 0,1 L from the perpen-diculars.

104 Front stiffeners are to be connected to deck at both endswith a connection area not less than:

Sniped ends may be allowed, however, for stiffeners above the3rd tier provided the formula in Sec.3 C204 is fulfilled.

Side and after end stiffeners in the lowest tier of erections areto have end connections.

105 Deck beams under front and aft ends of deckhouses arenot to be scalloped for a distance of 0,5 m from each side of thedeckhouse corners.

D 200 Protected casings

201 The thickness of plating is not to be less than:

t = 8,5 s minimum 6,0 mm in way of cargo holds = 6,5 s minimum 5,0 mm in way of accommodation.

202 The section modulus of stiffeners is not to be less than:

l = length of stiffeners in m, minimum 2,5 m.

203 Casings supporting one or more decks above are to beadequately strengthened.

D 300 Bulwarks

301 The thickness of bulwark plates is not to be less than re-quired for side plating in a superstructure in the same position,if the height of the bulwarks is 1,8 m.

Table C1 Design loadsStructure p (kN/m2)

Unpro-tected front bulk-heads

General p1 = 5,7 a (k CW – ho) cMinimum lowest tier p2 = 12,5 + 0,05 L1

Minimum elsewhere p3 = 6,25 + 0,025 L1

Unprotected sides in deckhouses

p4 = pdp – (4 + 0,2 ks) ho, minimum p3

Unprotected aft end bulkheads

p5= 0,85 p4, minimum p3

2 0, L120--------- maximum 4,5 for the lowest tier front+

1 0, L120--------- maximum 3,5 for 2nd tier front+

0 5, L150--------- maximum 2,5 for 3rd tier front and above+

1 3, 0 6xL--- for

xL--- 0 5,≤,–

0 3, 1 4xL--- for

xL--- 0 5,>,+

0 3, 0 7b1

B1------,+

b1

B1------

t15 8ka s p,

σ----------------------------- (mm)=

Z100 l

2s p

σ---------------------- (cm

3)=

a0 07,

f1------------ l s p (cm

2)=

Z3 l

2s

f1----------- (cm

3)=


DET NORSKE VERITAS

If the height of the bulwark is 1 metre or less the thickness neednot be greater than 6,0 mm.

For intermediate heights, the thickness of the bulwark may befound by interpolation.

302 A strong bulb section or similar is to be continuouslywelded to the upper edge of the bulwark. Bulwark stays are tobe spaced not more than 2 m apart, and are to be in line withtransverse beams or local transverse stiffening, alternativelythe toe of stay may be supported by a longitudinal member.The stays are to have sufficient width at deck level. The deckbeam is to be continuously welded to the deck in way of thestay. Bulwarks on forecastle decks are to have stays fitted atevery frame where the flare is considerable.

Stays of increased strength are to be fitted at ends of bulwarkopenings. Openings in bulwarks should not be situated near theend of superstructures.

D 400 Aluminium deckhouses401 The strength of aluminium deckhouses is to be related tothat required for steel deckhouses, see below.

The scantlings are to be based on the mechanical properties ofthe applied alloy. See Sec.2 C.

402 The minimum thicknesses given in 102 and 201 are to beincreased by 1 mm.

403 For the section moduli requirements given in 100 and200, f1 need not be taken less than 0,6.

E. Protection of the Crew

E 100 Regulation 25

1) The strength of the deckhouses used for the accommoda-tion of the crew shall be to the satisfaction of the Adminis-tration (see subsections A to D in this section).

2) Efficient guard rails or bulwarks shall be fitted on all ex-posed parts of the freeboard and superstructure decks.The height of the bulwarks or guard rails shall be at least 1metre from the deck, provided that where this height wouldinterfere with the normal operation of the ship, a lesserheight may be approved if the Administration is satisfiedthat adequate protection is provided.

3) The openings below the lowest course of the guard railsshall not exceed 230 millimetres. The other courses shallbe not more than 380 millimetres apart. In the case of shipswith rounded gunwales the guard rail supports shall beplaced on the flat of the deck.

4) Satisfactory means (in the form of guard rails, life lines,gangways or under deck passages etc.) shall be providedfor the protection of the crew in getting to and from theirquarters, the machinery space and all other parts used inthe necessary work of the ship.

5) Deck cargo carried on any ship shall be so stowed that anyopening which is in way of the cargo and which gives ac-cess to and from the crew's quarters, the machinery spaceand all other parts used in the necessary work of the ship,can be properly closed and secured against the admissionof water. Effective protection for the crew in the form ofguard rails or life lines shall be provided above the deckcargo if there is no convenient passage on or below thedeck of the ship.

(ICLL Reg.25)

E 200 Interpretations201 A guard rail shall also be required for first tier deckhous-es and for superstructures' ends.

(IACS LL14 to Reg. 25.2)

202

a) Fixed, removable or hinged stanchions shall be fittedabout 1,5 m apart.

b) At least every third stanchion shall be supported by abracket or stay.

c) Wire ropes may only be accepted in lieu of guard rails inspecial circumstances and then only in limited lengths.

d) Lengths of chain may only be accepted in lieu of guardrails if they are fitted between two fixed stanchions and/orbulwarks.

e) The openings between courses should be in accordancewith Regulation 25(3) of the Convention.

f) Wires shall be made taut by means of turnbuckles.

g) Removable or hinged stanchions shall be capable of beinglocked in the upright position.

(IACS LL47 to Reg. 25.2 and 25.3)

203 When applying Regulation 25(4), 26(2) and 27(7) of theICLL, as well as Regulation II-1/3-3 of the SOLAS conven-tion, the protection of the crew should be provided by at leastone of the means denoted in the Table E1.

204 Acceptable arrangements referred to in Table E1 are de-fined as follows:

a) A well lit and ventilated under-deck passageway (clearopening 0.8 m wide, 2.0 m high) as close as practicable tothe freeboard deck, connecting and providing access to thelocations in question.

b) A permanent and efficiently constructed gangway fitted ator above the level of the superstructure deck on or as nearas practicable to the centre line of the ship, providing acontinuous platform at least 0.6 m in width and a non-slipsurface, with guard rails extending on each side through-out its length. Guardrails shall be at least 1 m high withcourses as required in Load Line Regulation 25(3), andsupported by stanchions spaced not more than 1.5 m; afoot-stop shall be provided.

c) A permanent walkway at least 0.6 m in width fitted at free-board deck level consisting of two rows of guard rails withstanchions spaced not more than 3 m. The number ofcourses of rails and their spacing are to be as required byRegulation 25(3). On Type B ships, hatchway coamingsnot less than 0.6 m in height may be regarded as formingone side of the walkway, provided that between the hatch-ways two rows of guardrails are fitted.

d) A 10 mm minimum diameter wire rope lifeline supportedby stanchions about 10 m apart,

or

A single handrail or wire rope attached to hatch coamings,continued and adequately supported between hatchways.

e) A permanent and efficiently constructed gangway fitted ator above the level of the superstructure deck on or as nearas practicable to the centre line of the ship:

— located so as not to hinder easy access across theworking areas of the deck;

— providing a continuous platform at least 1.0 m inwidth;

— constructed of fire resistant and non-slip material;— fitted with guard rails extending on each side through-

out its length; guard rails should be at least 1.0 m highwith courses as required by Regulation 25(3) and sup-ported by stanchions spaced not more than 1.5 m.

— provided with a foot stop on each side;— having openings, with ladders where appropriate, to

and from the deck. Openings should not be more than40 m apart;


DET NORSKE VERITAS

— having shelters of substantial construction set in wayof the gangway at intervals not exceeding 45 m if thelength of the exposed deck to be traversed exceeds 70m. Every such shelter should be capable of accommo-dating at least one person and be so constructed as toafford weather protection on the forward, port andstarboard sides.

f) A permanent and efficiently constructed walkway fitted atfreeboard deck level on or as near as practicable to the cen-tre line of the ship having the same specifications as thosefor a permanent gangway listed in (e) except for foot-stops. On Type B ships (certified for the carriage of liquidsin bulk), with a combined height of hatch coaming and fit-ted hatch cover of together not less than 1m in height thehatchway coamings may be regarded as forming one sideof the walkway, provided that between the hatchways tworows of guard rails are fitted.

Alternative transverse locations for (c), (d) and (f) above,where appropriate:

(1) At or near centre line of ship; or fitted on hatchways at ornear centre line of ship.

(2) Fitted on each side of the ship.

(3) Fitted on one side of the ship, provision being made forfitting on either side.

(4) Fitted on one side only.(5) Fitted on each side of the hatchways as near to the centre

line as practicable.

Additional requirements:

1. In all cases where wire ropes are fitted, adequate devicesare to be provided to ensure their tautness.

2. Wire ropes may only be accepted in lieu of guardrails inspecial circumstances and then only in limited lengths.

3. Lengths of chain may only be accepted in lieu of guard-rails if fitted between two fixed stanchions.

4. Where stanchions are fitted, every 3rd stanchion is to besupported by a bracket or stay.

5. Removable or hinged stanchions shall be capable of beinglocked in the upright position.

6. A means of passage over obstructions, if any, such aspipes or other fittings of a permanent nature, should beprovided.

7. Generally, the width of the gangway or deck-level walk-way should not exceed 1.5 m.

(IACS LL50 Rev.4.1 to Reg. 25(4), 26(2), 27(7) and SOLASreg. II-1/3-3.)


DET NORSKE VERITAS

Guidance note:Deviations from some or all of these requirements or alternativearrangements for such cases as ships with very high gangways

(i.e. certain Gas Carriers) may be allowed subject to agreementcase by case with the relevant flag Administration.


Table E1 Protection of the crew

Type of ship Locations of access in ShipAssigned Summer Freeboard

Acceptable arrangements according to type of freeboard assigned

Type A Type B-100 Type B-60 Type B and B+

All shipsother than

Oil Tankers*Chemical

Tankers* andGas Carriers*

1.1 Access to midship quarters1.1.1 Between poop and bridge, or1.1.2 Between poop and deckhouse

containing living accommoda-tion or navigating equipment, or both.

≤ 3 000 mmabe

abe

ab

c(1)e

f(1)

ab

c(1)c(2)c(4)d(1)d(2)d(3)

ef(1)f(2)f(4)

> 3 000 mmabe

abe

ab

c(1)c(2)

ef(1)f(2)

1.2 Access to ends1.2.1 Between poop and bow (if there

is no bridge)1.2.2 Between bridge and bow, or1.2.3 Between a deckhouse contain-

ing living accommodation or navigating equipment, or both, and bow, or

1.2.4 In the case of a flush deck ves-sel, between crew accommoda-tion and the forward and after ends of ship.***

≤ 3 000 mm

ab

c(1)e

f(1)

ab

c(1)c(2)

ef(1)f(2)

ab

c(1)c(2)

ef(1)f(2)

> 3 000 mm

ab

c(1)c(2)d(1)d(2)

ef(1)f(2)

ab

c(1)d(1)

ef(1)

ab

c(1)c(2)c(4)d(1)d(2)d(3)

ef(1)f(2)f(4)

Oil Tankers*Chemical

Tankers* andGas Carriers*

2.1 Access to bow2.1.1 Between poop and bow, or2.1.2 Between a deckhouse contain-

ing living accommodation or navigating equipment, or both, and bow, or

2.1.3 In the case of a flush deck ves-sel, between crew accommoda-tion and the forward end of ship.

≤ (Af+Hs)**

ae

f(1)f(5)

> (Af+Hs)**

ae

f(1)f(2)

2.2 Access to after endIn the case of a flush deck ves-sel, between crew accommoda-tion and the after end of ship.***

as required in 1.2.4 for other types of ships

* Oil Tankers, Chemical Tankers and Gas Carriers as defined in SOLAS Reg. II-1/2.12, VII/8.2 and VII/11.2, respectively.** Af: the minimum summer freeboard calculated as type A ship regardless of the type of freeboard actually assigned. Hs: the standard height of superstructure as defined in ICLL Regulation 33*** Access to after end of ships is not applicable when crew accommodation is located aft.

Acceptable arrangements referred to in this table are given in 204.


DET NORSKE VERITAS

SECTION 11OPENINGS AND CLOSING APPLIANCES

A. General

A 100 Introduction101 In this section the requirements for the arrangement ofopenings and their closing appliances are collected. The clos-ing appliances are in general to have strength at least corre-sponding to the required strength of that part of the hull inwhich they are fitted.

102 The requirements of this section are in accordance withICLL, Reg.11 to 26, as amended 1981, which are given as con-ditions for the assignment of freeboard.

The rules apply to all ships above 24 m in length, with the fol-lowing exceptions:

— ships of war— pleasure yachts not engaged in trade— fishing vessels.

103 In cases where ICLL or SOLAS texts are directly quotedthey are printed in italics types.

104 Where any regulation refers to "the satisfaction of theAdministration", DNV's/IACS' interpretations are given inconnection with the item in question.

105 If any parts of these rules are subject to discussion ormisunderstanding the ICLL text shall apply.

106 References to ICLL and IACS are given by RegulationNo. and LL No. respectively.

SOLAS references are given as SOLAS Reg. No.





t = plate thickness in mm. 1)

Z = rule section modulus in cm3 of stiffeners and simplegirders

ka = correction factor for aspect ratio of plate field = (1,1 – 0,25 s/ l)2 = maximum 1,0 for s/ l = 0,4 = minimum 0,72 for s/ l = 1,0s = stiffener spacing in m, measured along the platingl = stiffener span in m, measured along the topflange of








wk = section modulus correction factor in tanks, see Sec.3C1004.

σ = nominal allowable bending stress in N/mm2 due to lat-eral pressure

τ = nominal allowable shear stress in N/mm2 due to lateralloads

p = design pressure in kN/m2 as given for the variousstructures.

1) See Sec.1 B.


202 Terms

Position

For the purpose of the Regulations, two positions of hatchways,doorways and ventilators are defined as follows:

Position 1 - Upon exposed freeboard and raised quarterdecks, and upon exposed superstructure deckssituated forward of a point located a quarter ofthe ship's length from the forward perpendicular.

Position 2 - Upon exposed superstructure decks situatedabaft a quarter of the ship's length from the for-ward perpendicular.

(ICLL Reg.13)

Ship types

The basic ship types are as follows:

Type "A" Ships designed solely for the carriage ofliquid cargo

Type "B" Cargo ship other than "A", with steelweathertight hatch covers

Type "B-100" "B-60"Cargo ship of type "B" with reducedfreeboard on account of their ability tosurvive damage

Type "B+" Cargo ship with increased freeboard onaccount of hatch cover arrangement

Weathertight means that in any sea condition water will notpenetrate into the vessel.

Watertight means capable of preventing the passage of waterthrough the structure under a head of water for which the sur-rounding structure is designed.

Freeboard, freeboard deck and superstructure, see Sec.1B200.

A 300 Documentation

301 The following plans covering items treated in this sec-tion are normally to be submitted for approval:

Arrangement and design of:

— small hatches and manholes— watertight hatches— watertight doors— weathertight doors— ventilators— side scuttles, windows— freeing ports— cargo hatchway with covers and securing appliances— horizontal stopper arrangement for hatch covers.— doors in side shell, bow and stern with securing appliances— tank access, ullage and ventilation openings— scuppers and sanitary discharges— air pipes above deck with vent heads— engine room skylights and their closing appliances

Several of these items are covered by the freeboard plan as re-quired in Ch.5 Sec.1 B100.

302 An operating and maintenance manual for the side shell,bow and stern doors is to be provided on board and containnecessary information on:

— main particulars and design drawings


DET NORSKE VERITAS

— service conditions, e.g. service restrictions, emergency op-erations, acceptable clearances for supports

— maintenance and function testing— register of inspections and repairs.

The manual is to be submitted for approval limited to the itemsgiven in Pt.5 Ch.2 Sec.3 A301 c).

Guidance note:It is recommended that recorded inspections of the door support-ing and securing devices be carried out by the ship's staff atmonthly intervals or following incidents that could result in dam-age, including heavy weather or contact in the region of side shellor stern doors.Any damage recorded during such inspections is tobe reported to the Society.


303 Documented operating procedures for closing and se-curing of side shell, bow and stern doors are to be kept onboard and posted at the appropriate places.

A 400 Testing

401 All weathertight/watertight doors and hatch covers areto be function tested.

402 For ships exclusively intended for the carriage of con-tainers in the cargo holds, for which an exemption to the ICLL,Reg.16 (see E and F) has been granted by the Flag Administra-tion, and which complies with the requirements given in Pt.5Ch.2 Sec.6 K, the required testing for weathertightness givenin Sec.1 D may be dispensed with.

403 If non weathertight hatch covers are fitted in accordancewith 402, this will be noted in the main letter of approval withthe implication that hose testing for weathertightness in ac-cordance with Sec.1 D will not be carried out.

B. Access Openings in Superstructures and Freeboard Deck.

B 100 Doors

101

1) All access openings in bulkheads at ends of enclosed su-perstructures shall be fitted with doors of steel or otherequivalent material, permanently and strongly attached tothe bulkhead, and framed, stiffened and fitted so that thewhole structure is of equivalent strength to the unpiercedbulkhead and weathertight when closed. The means for se-curing these doors weathertight shall consist of gasketsand clamping devices or other equivalent means and shallbe permanently attached to the bulkhead or to the doorsthemselves, and the doors shall be so arranged that theycan be operated from both sides of the bulkhead.

2) Except as otherwise provided in these Regulations, theheight of the sills of access openings in bulkheads at endsof enclosed superstructures shall be at least 380 millime-tres above the deck.

(ICLL Reg.12)

102

a) Doors should generally open outwards to provide addi-tional security against the impact of the sea. Doors whichopen inwards are to be especially approved.

b) Portable sills should be avoided. However, in order to fa-cilitate the loading/unloading of heavy spare parts or sim-ilar, portable sills may be fitted on the followingconditions:

i) They must be installed before the ship leaves port.

ii) Sills are to be gasketed and fastened by closely spacedthrough bolts.

iii) Whenever the sills are replaced after removal, theweathertightness of the sills and the related doorsmust be verified by hose testing. The dates of removal,replacing and hose testing shall be recorded in theship's log book.

(IACS LL5)

103 Weathertight doors as specified above are to be fitted inall access openings in:

— bulkheads at ends of superstructures— bulkheads of deckhouses on freeboard deck protecting

openings in the freeboard deck— companionways on freeboard deck and superstructure

deck— bulkheads of deckhouses on superstructure deck protect-

ing openings in the superstructure deck— companionways and bulkheads of deckhouse upon anoth-

er deckhouse on freeboard deck protecting openings in thefreeboard deck.

B 200 Sill heights

201 Openings as mentioned in 100 are in general to have sillheights not less than 380 mm.

The following openings in position 1 are to have sill heightsnot less than 600 mm:

— Companionways— where access is not provided from the deck above: Open-

ings in poop frontbulkhead, bulkheads at ends of midshipssuperstructures and bulkheads at ends and sides of deck-houses

— openings in forecastle end bulkhead covering entrance tospace below the deck

— openings in engine casings.

202 In ships which have their freeboard assignment basedupon a flooding calculation (type «A», «B-60» or «B-100»),the sill heights for the superstructure bulkhead openings mayrequire to be adjusted according to the calculated damage wa-terline. In such ships were engine casings are not protected byouter structures, two weathertight doors in series are required,the sill height of the inner door shall not be less than 230 mm.

203 Openings which are used only when the ship is in har-bour (for handling of spare parts, etc.), may have a reduced sillheight.

B 300 Access openings in freeboard and superstructure decks

301

1) Manholes and flush scuttles in position 1 or 2 or within su-perstructures other than enclosed superstructures shall beclosed by substantial covers capable of being made water-tight. Unless secured by closely spaced bolts, the coversshall be permanently attached.

2) Openings in freeboard decks other than hatchways, ma-chinery space openings, manholes and flush scuttles shallbe protected by an enclosed superstructure, or by a deck-house or companionway of equivalent strength and weath-ertightness. Any such opening in an exposedsuperstructure deck or in the top of a deckhouse on thefreeboard deck which gives access to a space below thefreeboard deck or a space within an enclosed superstruc-ture shall be protected by an efficient deckhouse or com-panionway. Doorways in such deckhouses orcompanionways shall be fitted with doors complying withthe requirements of Regulation 12(1)(101).


DET NORSKE VERITAS

3) In position 1 the height above the deck of sills to the door-ways in companionways shall be at least 600 millimetres.In position 2 it shall be at least 380 millimetres.

(ICLL Reg.18)

302 Regarding the requirement to protect openings in super-structures (Regulation 18(2)) it is considered that openings inthe top of a deckhouse on a raised quarterdeck having a heightequal to or greater than a standard height raised quarterdeck areto be provided with an acceptable means of closing but neednot be protected by an efficient deckhouse or companionwayas defined in the regulation provided the height of the deck-house is at least the height of a full superstructure.

(IACS LL46)

303 Only those doorways in deckhouses leading to or givingaccess to companionways leading below, need to be fitted withdoors in accordance with Regulation 12(101).

Alternatively, if stairways within a deckhouse are enclosedwithin properly constructed companionways fitted with doorscomplying with Regulation 12(101), the external doors neednot be weathertight.

Where an opening in a superstructure deck or in the top of adeckhouse on the freeboard deck which gives access to a spacebelow the freeboard deck or to a space within an enclosed su-perstructure is protected by a deckhouse, then it is consideredthat only those side scuttles fitted in spaces which give directaccess to an open stairway need be fitted with deadlights in ac-cordance with Regulation 23 (L100). A cabin is considered toprovide adequate protection against the minimal amount ofwater which will enter through a broken side scuttle glass fittedon the second tier.

In the application of Regulation 18 it is understood that:

i) Where access is provided from the deck above as an alter-native to access from the freeboard deck in accordancewith Regulation 3(10)(b) (Ch.5 Sec.1 D100) then theheight of sills into a bridge or poop should be 380 mm. Thesame consideration should apply to deckhouses on thefreeboard deck.

ii) Where access is not provided from above the height of thesills to doorways in a poop bridge or deckhouse on thefreeboard deck should be 600 mm.

iii) Where the closing appliances of access openings in super-structures and deckhouses are not in accordance with Reg-ulation 12(101), interior deck openings are to beconsidered exposed, i.e. situated in the open deck.

(IACS LL8)

C. Side and Stern Doors

C 100 General.

101 These requirements cover cargo and service doors in theship side (abaft the collision bulkhead) and stern area, belowthe freeboard deck and in enclosed superstructures. For re-quirements for bow doors, see Pt.5 Ch.2 Sec.3.

102 The side and stern doors are to be fitted as to ensuretightness and structural integrity commensurate with their lo-cation and the surrounding structure.

The number of such openings shall be the minimum compati-ble with the design and proper working of the ship.

103 Where the sill of any cargo or service door is above theuppermost loadline, special consideration is to be given to pre-venting the spread of any leakage water over the deck. A flat-bar welded to the deck and provision of scuppers would be anacceptable arrangement.

104 Where the sill of any cargo or service door is below theuppermost load line, the arrangements will require to be spe-cially considered to ascertain that the safety of the ship is in noway impaired. It is considered that the fitting of a second doorof equivalent strength and watertightness is one acceptable ar-rangement. In that case leakage detection device should beprovided in the compartment between the two doors. Further,drainage of this compartment to the bilges controlled by aneasily accessible screw down valve, should be arranged. Theouter door should preferably open outwards.

(IACS LL21)

105 Doors should preferably open outwards.

106 Terms:

Cleats: Devices for pre-compression of packings and steel tosteel contact.

Supports: Load carrying devices designed for transfer of act-ing forces from door structures to hull structures.

Locking arrangement: Preventive measures ensuring thatcleats and supports as applicable always remain in positionwhen engaged.

C 200 Structural arrangement201 Door openings in the shell are to have well rounded cor-ners and adequate compensation is to be arranged with webframes at sides and stringers or equivalent above and below.

202 Doors are to be adequately stiffened, and means is to beprovided to prevent movement of the doors when closed. Ad-equate strength is to be provided in the connections of the lift-ing/manoeuvring arms and hinges to the doors structures andto the ship structure.

203 A ≥ 12 m2 Doors with light opening area are to be suchthat the sea pressure is transferred directly to the hull coam-ings.

204 For doors with light opening area A < 12 m2 securingbolts or similar devices may be accepted as carriers of sea pres-sure to the coamings, if an arrangement as required in 203 isnot feasible.

205 If a door is divided into separate sections, each section isto have full strength independent of the other sections.

206 Where doors also serve as vehicle ramps, the design ofthe hinges should take into account the ship angle of trim andheel, which may result in uneven loading on the hinges.

C 300 Design loads301 The design sea pressure is given by:

p = ( pdp – (4 + 0,2 ks) h0 ) 1)

minimum 6,25 + 0,025 L (kN/m2)

pdp, ks = as given in Sec.4 C201h0 = vertical distance in m from the load point to the wa-

terline at draught T.

1) For ships with service restrictions p may be reduced with the percentagesgiven in Sec.4 B202. CW should not be reduced.

302 The design force for securing bolts and other closing de-vices, supporting members and surrounding structure is givenby:

F1 = A pe 103 + FP (N)

or

F2 = F0 + 10 W + FP (N)

F1 is applicable for ports opening inwards.

F2 is applicable for ports opening outwards.

pe = external design pressure p according to 301, minimum25kN/m2.


DET NORSKE VERITAS

FP = total packing force in NF0 = FCthe greater of and 5000 A (N)FC = accidental force (N) due to loose cargo etc., to be uni-

formly distributed over the area A and not to be takenless than 300 000 N.

For small doors such as bunker doors and pilot doors,the value of FC may be appropriately reduced. Howev-er, the value of FC may be taken as zero, provided anadditional structure such as an inner rampway is fitted,which is capable of protecting the door from accidentalforces due to loose cargo etc.

A = area of door opening (m2) to be determined on the ba-sis of the loaded area taking account of the direction ofthe pressure

W = mass of door (kg).

pe is normally to be calculated at the midpoint of A.

Packing force is to be decided depending on type and hardnessof packing. For calculation purpose, however, the packing linepressure should not be taken less than 5 N/mm. The packingline pressure is to be specified.

C 400 Plating


p = as given in 300.

The thickness is in no case to be less than the minimum shellplate thickness.

402 Where doors also serve as vehicle ramps, the plating isnot to be less than required for vehicle decks.

C 500 Stiffeners


assuming simply supported ends.

p = as given in 300

502 The stiffener web plate at the ends is to have a net sec-tional area not less than:

A = 0,08 l s p (cm2)

p = as given in 300.

503 Edge stiffeners of doors are to have a moment of inertianot less than:

I = 8 pl d4 (cm4)

for cover edges connected to a rigid ship structure member oradjacent door coaming.

d = distance between closing devices in mpl = packing line pressure along edges in N/mm, see 302.

504 For edge stiffeners supporting main door stiffeners be-tween securing devices, the moment of inertia is to be in-creased corresponding to the extra force.

505 Where doors also serve as vehicle ramps, the stiffenerscantlings are not to be less than required for vehicle decks.

C 600 Girders

601 The section modulus requirement for simple girders as-suming simply supported ends is given by:

S = girder span in mb = loading breadth in mp = design pressure according to 300.


S, b and p as in 601.

603 For large doors with a grillage girder system, a directstress analysis as outlined in Sec.13 may be necessary. Designloads are to be as given in 300, and the allowable stresses areas follows:

— bending or normal stress:

s = 120 f1 N/mm2

— Shear stress:

τ = 80 f1 N/mm2

— Equivalent stress:

The material factor f1 is not to be taken greater than 1,39 unlessa direct stress analysis with regard to relevant modes of failures(e.g. fatigue) is carried out.

604 The webs of girders and stringers are to be adequatelystiffened, preferably in a direction perpendidular to the shellplating.

605 The girder system is to be given sufficient stiffness toensure integrity of the boundary support of the door. Edgegirders should be adequately stiffened against rotation and areto have a moment of inertia not less than:

I = 8 pl d4 (cm4)

d = distance between closing devices in mpl = packing line pressure in N/mm, see 302.

For edge girders supporting main door girders between secur-ing devices, the moment of inertia is to be increased in relationto the additional force.

C 700 Closing arrangement, general

701 Closing devices are to be simple to operate and easily ac-cessible. Where hinges are used as closing devices they shouldbe well integrated into the door structure.

702 Packing material is to be of a comparatively soft type,and the supporting forces are to be carried by the steel structureonly. Other types of packing will be specially considered.

703 Flat bars or similar fastening devices for packings are tohave scantlings and welds determined with ample considera-tions to wear and tear.

704 Devices are to be arranged for the doors to be secured inopen position.

t1 58ka s p,

f1

------------------------------ (mm)=

Z0 8 l

2s p,

f1---------------------- (cm

3)=

Z1 05 S

2b p,

f1---------------------------- (cm

3)=

A0 08 S b p,

f1-------------------------- (cm

2)=

σe σ23τ2

+ 150 f1 N mm2⁄= =


DET NORSKE VERITAS

C 800 Closing arrangement, strength

801 Side and stern doors are to be fitted with adequate meansof closing and securing, commensurate with the strength of thesurrounding structure.

802 The closing and/or supporting devices are to be fitted notmore than 2,5 metres apart and as close to corners as possible.The number of devices are generally to be the minimum prac-tical whilst taking into account the requirement for redundantprovision given in 806 and the available space for adequatesupport in the surrounding hull structure which may limit thesize of each device.

803 Only supports having an effective stiffness in a given di-rection are to be included in a calculation of the load carryingcapacity of the devices. The total external or internal force, asgiven in 302, may normally be considered as equally distribut-ed between the devices. However, the distribution of the totalforces acting on the supports may, for doors with a complexclosing arrangement, be required calculated by a direct calcu-lation taking into account the flexibility of the door and sur-rounding hull structure and the position of the supports.Maximum design clearance for effective supports should nor-mally not exceed 3 mm. Design clearances are to be includedin the Operating and Maintenance Manual as given in A302.Allowable normal, shear and equivalent stresses in closing andsupporting elements are as given in 603.

804 The nominal tensile stress in way of threads of bolts isnot to exceed 105 f1 N/mm2. The arrangement of securing andsupporting devices is to be such that threaded bolts do not carrysupport forces.

805 For steel to steel bearings in closing and supporting de-vices, the nominal bearing pressure calculated by dividing thedesign force by the projected area is not to exceed 0,8σf, whereσf is the yield stress of the bearing material. For other bearingmaterials, the permissible bearing pressure is to be determinedaccording to the manufacturer's specification.

806 For side and stern doors effective supports includingsurrounding door and hull structural members are, in the caseof failure of any single support, to have sufficient capacity towithstand the total design forces.In this case the allowablestresses as given in 603 may be increased by 20%.

807 All load transmitting elements in the design load path,from the door through securing and supporting devices into theship structure, including welded connections, are to be to thesame strength standard as required for the securing and sup-porting devices.

C 900 Closing arrangement, system for operation and indication/monitoring

901 Cleats and support devices are to be equipped with me-chanical locking arrangement (self locking or separate ar-rangement) or to be of the gravity type.

902 Where hydraulic operating systems are applied, cleatsand support devices are to remain locked in closed position incase of failure in the hydraulic system.

903 Systems for opening and closing of the door, operationof cleats and support devices and, where applicable, for lock-ing arrangement are to be interlocked in such a way that theycan only operate in the proper sequence. Hydraulic operatingsystems are to be isolated from other circuits and to be blockedwhen doors and closing arrangement are in closed/locked po-sition.

904 Signboards giving instructions to the effect that thedoors are to be closed and all the closing devices locked beforeleaving quay side (or terminal), are to be placed at the operat-ing panel (or for small doors at the door when no operatingpanel) and on the bridge, and are to be supplemented by warn-ing indicator lights on the panel and on the bridge.

905 Doors with clear opening area greater than 6 m2 are tobe provided with an arrangement for remote control, from aconvenient position above the freeboard deck, of:

— the closing and opening of the doors— associated cleats, support and locking devices.

For doors which are required to be equipped with a remotecontrol arrangement, the open/closed position of the door andevery closing decive (cleats, support and locking device) is tobe indicated at the remote control station.

The operating panel for remote controlled doors is to be inac-cessible to unauthorised persons.

906 The requirements given in 907 to 911 apply to doors inthe boundary of special category spaces or ro-ro spaces, as de-fined in Pt.4 Ch.10 Sec.1 C, through which such spaces may beflooded.

For cargo ships, where no part of the door is below the upper-most waterline and the area of the door opening is not greaterthan 6 m2, then the requirements in 907 to 911 need not be ap-plied.

907 Separate indicator lights are to be provided on each op-erating panel to indicate that the doors are closed and that theircleats, support and locking devices as applicable are properlypositioned.

Indication panels are to be provided with a lamp test function.

908 Separate indicator lights and audible alarms are to beprovided on the navigation bridge to show and monitor thatany of the doors are properly positioned and that cleats, sup-port and locking devices as applicable are properly positioned.

The indication panel on the navigation bridge is to be equippedwith a mode selection function "harbour/sea voyage", so ar-ranged that audible alarm is given if the vessel leaves quay side(or terminal) with side shell or stern doors not closed or withany of the cleats, support and locking devices, as applicable,not in the correct position.

When the mechanical lock is placed inside the hydraulic cylin-der moving the cleat, and this is non-duplicated, indication ofthe open/closed position of any of the cleats, support and lock-ing device is to be made on the lock inside the cylinder.

909 The indicator and alarm system on the navigation bridgeis to be designed on the fail to safe principle. The panel is to beprovided with a function test facility and a separate alarm forpower failure to the indicator lights and audible alarm system.

910 The power supply for indicator and alarm systems is tobe independent of the power supply for the operating and clos-ing arrangements and is to be provided with a backup powersupply. It shall not be possible to turn off the indicator lights.

Sensors for the indicator system are to be protected from water,ice formation and mechanical damage.

911 For passenger ships, a water leakage detection systemwith audible alarm and television surveillance is to be arrangedto provide an indication to the navigation bridge and to the en-gine control room of any leakage through the doors.

For cargo ships, a water leakage detection system with audiblealarm is to be arranged to provide an indication to the naviga-tion bridge.

D. Hatchway Coamings

D 100 General

101 Side coamings of hatchways are to extend to lower edgeof deck beams. Side coamings not forming part of continuousgirders, are below deck to extend two frame spaces beyond thehatch ends.


DET NORSKE VERITAS

102 Hatch end coamings not in line with ordinary deck trans-verses are below deck to extend at least three longitudinalframe spaces beyond the side coamings.

103 Continuous hatchway coamings on strength deck are tobe made from steel of the same strength group as the deck plat-ing. The same apply to non-continuous coamings effectivelysupported by longitudinal strength member or being an effec-tive part of the deck girder system.

104 If the junction of hatch coamings forms a sharp corner,well rounded brackets are to be fitted towards the deck bothlongitudinally and transversely. The longitudinal brackets areto be welded by full penetration welding.

The hatch end beam is to be given a smooth transition to thedeck transverse.

If the hatch end beam is replaced by a stool tank, this is to bein line with structures outside the hatch.

105 The web plate of low hatch side coamings is to be stiff-ened over the entire height at each frame or with a stiffenerspacing of about 60 x web thickness. Tripping brackets are tobe fitted on every 2nd frame.

106 Cut-outs in the top of hatch coamings are normally to beavoided. Unavoidable cut-outs are to be circular or elliptical inshape. Local reinforcements should be given a soft transitionin the longitudinal direction.

Unavoidable cutouts in longitudinal coaming end brackets areto be as small as possible and with edge reinforcement.

D 200 Coaming heights201 The minimum height of coamings for hatches withweathertight covers is normally not to be less than:

600 mm in position 1

450 mm in position 2

202 Manholes and small scuttles with coaming height lessthan given in 201, and flush scuttles may be allowed when theyare closed by substantial watertight covers. Unless secured byclosely spaced bolts, the covers are to be permanently attached.

203 Coamings with heights less than given in 201 may be ac-cepted after special consideration of arrangement and integrityof the vessel. When such acceptance is given, the stiffness ofdeck girders supporting the covers is given by the following re-quirement to moment of inertia:

p = design pressure for deck girder in kN/m2 as given inE200

b = breadth in m of load area for deck girderl = total length in m of hatch coaming between supportsn = number of cover elements along length l of coaming.

204 Coamings with increased height may be required onships of «type B-100» and «B-60» if found necessary by thefloatability calculation.

D 300 Scantlings301 Hatchway coamings to holds also intended to carry wa-ter ballast or oil in bulk, are to satisfy the requirements for tankbulkheads given in Sec.9.

302 The scantlings of coamings acting as deck girders are tosatisfy the requirements in Sec.8.

303 The plate thickness of large hatchway coamings onweather deck is not to be less than 11 mm.

304 Hatchway coamings of conventional design are to bestiffened by a horizontal section of substantial strength nor-mally not more than 0,25 m from the upper edge of the coam-ing. Coaming brackets spaced not more than 3 m apart, are tobe fitted. The brackets are not to end on unstiffened plating.The coamings are to be satisfactorily stiffened against buck-ling.

305 Stiffeners, brackets and coamings are to be able to with-stand the local forces set up by the clamping devices and/or thehandling facilities necessary for securing and moving the hatchcovers as well as vertical and horizontal mass forces from car-go stowed on the hatch covers, e.g. containers, see E200.

306 Hatchway coamings are to satisfy relevant requirementsfor deckhouses given in Sec.10.

E. Hatch Covers

E 100 General

101 The requirements below are valid for steel hatch coversin holds intended for dry cargo, liquid cargo and ballast.

102 Steel hatch covers are to be fitted to hatch openings onweather decks so as to ensure tightness consistent with opera-tional conditions and type of cover and to give effective pro-tection to the cargo in all sea conditions.

103 Requirements for small cargo tank hatch covers used foraccess and ventilation only, are given in I.

104 Materials for steel hatch covers are to satisfy the require-ments given for hull material.

Other material than steel may be used, provided the strengthand stiffness of covers are equivalent to the strength and stiff-ness of steel covers.

For aluminium alloys, see Ch.1 Sec.2 C.

105 Tank hatch covers of closed box type construction are tobe provided with effective means for ventilation and gasfree-ing.

106 Hatch covers are to be mechanically lockable in openposition.

107 Upon completion of installation of hatch covers, a chalktest is to be carried out. For tightness testing, see A400.

Guidance note:It is recommended that ships with steel hatch covers are suppliedwith an operation and maintenance manual including:

— opening and closing instructions— maintenance requirements for packing, securing devices

and operating items— cleaning instructions for the drainage system— corrosion prevention instructions— list of spare parts.


I7 p b l

4

n2E

-----------------105 (cm

4)=


DET NORSKE VERITAS

E 200 Design loads201 All generally applicable lateral loads on hatch covers aregiven in Table E1, based upon the general loads given in Sec.4.

a = 1,0 for weather decks forward of 0,15 L from FP, orforward of deckhouse front, whichever is the fore-most position

= 0,8 for weather decks elsewherepdp, ks = as given in Sec.4 C201h0 = vertical distance in m from the waterline at draught

T to the cover topav = vertical acceleration as given in Sec.4 B600q = deck cargo load in t/m2, as specified. Weather decks

above cargo holds in dry cargo ships are normally tobe designed for a minimum cargo load:

qmin = 1,0 for ships with L = 100 m = 1,3 for ships with L > 150 m when superstructure

deck = 1,75 for ships with L > 150 m when freeboard deck.

For ships with length between 100 and 150 m the q-value may be varied linearly.When it is specially stated that no deck cargo is tobe carried, the qmin may be discarded

ρc = dry cargo density in t/m3, if not otherwise specifiedto be taken as 0,7, see also Sec.4 C401

ρ = density of ballast, bunker or liquid cargo in t/m3,normally not to be less than 1,025 (i.e. ρ g0 ≈ 10)

HC = stowage height in m of dry cargo. Normally the'tweendeck height or height to top of cargo hatch-way to be used.

hs = vertical distance in m from the load point to top oftank, excluding smaller hatchways


hb = vertical distance in metres from the load point to thedeepest equilibrium waterline in damaged conditionobtained from applicable damage stability calcula-

tions. The deepest equilibrium waterline in dam-aged condition should be indicated on the drawingof the deck in question

∆ pdyn = as given in Sec.4 C300p0 = 25 in general = 15 in ballast holds in dry cargo vessels = pv when exceeding the general valuepv = pressure valve opening pressureH = height in m of tankb = the largest athwartship distance in m from the load




lt = length in m of top of tankφ = roll angle in radians as given in Sec.4 B400θ = pitch angle in radians as given in Sec.4 B500.

202 Horizontal loads from cargo stored on hatch covers aregiven by:

— Total transverse force:

PT = C at q lh bh (kN)

— Total longitudinal force:

PL = C al q lh bh (kN)

at = transverse acceleration as given in Sec.4 B 700al = longitudinal acceleration as given in Sec.4 B

800

Table E1 Design loadsHatch cover at Load type p (kN/m2)

Weather decks 1)Sea pressure

Deck cargo

p2 = (g0 + 0,5 av) q

Cargo 'tweendecks p3 = ρc (g0 + 0,5 av) HC

Deck as tank top in general

Ballast or liquid cargo

p4 = ρ g0 hp + ∆ pdyn

p5 = ρ g0 hs + p0

Deck as tank top in tanks with breadth > 0,4 B

Deck as tank top towards ends of tanks with length > 0,15 L

Deck as tank top in tanks with unrestricted filling and with free breadth bt < 0,56B 4)

Watertight decks submerged in damaged condition 6) Sea pressure p9 = 10 hb

1) On weather decks combination of the design pressures p1 and p2 may be required for deck cargo with design stowage height less than 2,3 m.

2) For ships with service restrictions p1 may be reduced with the percentages given in Sec.4 B202. CW should not be reduced.

3) Distribution across hatch: Maximum value at one side linearly reduced to pv at other side.

4) For tanks with free breadth above 0,56 B the design pressure will be specially considered, see Sec.4 C305.

5) Distribution across hatch: Maximum value constant for 0,25 bt from one side, reduced to pv elsewhere.

6) The strength may be calculated with allowable stresses for plating, stiffeners and girders increased by 60 f1.

p1 a pdp 4 0 2ks,+( )h0–( )2 ) minimum 5,0=

p6 ρg0 0 67 hs φb+( ), 0 12 H φbt,–[ ] pV3 )

+=

7 ρg0 0 67 hs θl+( ), 0 12 Hθ lt,–[ ] pV+=

p8 ρ 3B

100---------–

� �� bt pV

5 )+=


DET NORSKE VERITAS

q = deck cargo load in t/m2, see Table E1lh = length of hatch in mbh = breadth of hatch in mq lh bh = total cargo mass (M) on hatch cover in tC = 0,5 when horizontal forces are combined with

vertical forcesC = 0,67 when horizontal forces are considered

alone.

If the cargo is secured (lashed etc.) to the deck outside thehatch cover, the horizontal load on covers may be reduced.

203 In addition to the distributed design loads specified in201, forces acting on hatch covers from heavy cargo units areto be taken into account as given in Sec.4 C500.

Deflections and loads due to movements and thermal effectsare also to be considered, see F 203.

204 Hatch covers subjected to wheel loading are to satisfythe strength requirements given in Pt.5 Ch.2 Sec.4 C.

E 300 Plating

301 The thickness corresponding to lateral pressure is givenby:

p = p1– p9, whichever is relevant, as given in Table E1σ = 0,58 σf N/mm2 for hatchways in position 1 or 2 when

p = p1 or p2 = 0,67 σf N/mm2 in all other casesσf = minimum upper yield stress in N/mm2. NV-NS-steel

may be taken as having σf = 235 N/mm2.

σf is not to be taken greater than 70% of the ultimatetensile strength.

302 The thickness of top plating is not to be less than:

t = 10 s (mm) , min. 6 mm.

303 The thickness of bottom plating of closed box construc-tion is not to be less than 6 mm.

304 Top or bottom plating acting as compression flanges inhatch cover main stiffening members (girders) is to be effec-tively stiffened against buckling.

In the middle half part of simply supported span the criticalbuckling stress is normally not to be less than:

— for hatchways in position 1 or 2:

— for hatchways in position 3:

η = stability factor (usage factor) = 0,77 for sea loads and wave induced internal liquid

loads = 0,87 for other loadsZR = Z according to 401 or 0,7 Z according to 402 (position

1 or 2), whichever gives the highest stress valueZA = actual section modulus in plate flange.

The critical buckling stress may be taken as:

or

σel =

k = 4 for plating with local stiffeners parallel to main stiff-ening members

=

for plating with local stiffeners perpendicular to mainstiffening members

c = 1,21 when local stiffeners are angles or T-sections = 1,10 when local stiffeners are bulb flats = 1,05 when local stiffeners are flat bars.

E 400 Stiffeners401 The section modulus is given by:

p = p1– p9, whichever is relevant, as given in Table E1m = 8 for stiffeners simply supported at both ends, or sim-

ply supported at one end and fixed at the other end = 12 for stiffeners fixed at both endsσ = 0,58 σf N/mm2 for hatchways in position 1 or 2 when

p = p1 or p2 = 0,67 σf N/mm2 in all other cases.

Stiffeners subject to point loads from heavy cargo units (see203) are to be specially considered.

402 The section modulus for stiffeners of normal strengthsteel in position 1 or 2 is in no case to be less than:

m = as defined in 401

ql =

=

For other materials the requirement will be specially consid-ered. The allowable nominal tensile stress is normally given byσb /4,25, where σb is the ultimate tensile strength of the mate-rial.

403 The moment of inertia of steel members in position 1 or2, supported at side or end coamings only, is not to be less than:

I = 22 l 3 s ql (cm4)

ql = as defined in 402.

For other materials the requirement will be specially consid-ered. The requirement corresponds to a maximum allowabledeflection of 0,0028 l.

404 The requirements for section modulus and moment ofinertia given above are valid for strength members with a con-stant cross section over the entire span. Covers with graduallyreduced Z and I towards the ends of the span are to be designedso that the maximum bending stresses and deflections are notincreased.

With a Z-reduction towards ends, the rule section modulus atmiddle of span is to be multiplied by a factor:

t15 8ka s p,

σ------------------------------ tk (mm)+=

σc

0 58σf,η

-----------------ZR

ZA------- N/mm

2( )=

σc

0 67σf,η

-----------------ZR

ZA------- N/mm

2( )=

σc σel when σel

σf

2-----≤=

σc σf 1σf

4σel-----------–

� �� when σel

σf

2----->=

185000 kt tk–

1000s--------------

� ��

2N/mm

2( )

c 1sl--

� ��

2+

2

Z1000 l

2s p wk

mσ---------------------------------- (cm

3)=

Z103m

--------- l2

s ql wk (cm3)=

0 76, 0 75,76

------------ L+� �� , maximum 1,75 t/m

2 in position 1

0 58, 0 55,76

------------ L+� �� , maximum 1,30 t/m

2 in position 2

C1 13 2α, β– 0 8,–

7β 0 4,+-------------------------------------+=


DET NORSKE VERITAS

α =

β =

l 1, l 0, Z1, and Z0 are given in Fig.1.

C1 is not to be taken less than 1,0.

With an I-reduction towards ends, the rule moment of inertia isto be multiplied by a factor:

δ =

I1 and I0 are given in Fig.1.

405 The net web area is not to be less than:

Fig. 1Hatch cover with variable cross-section

x = distance in m from the end of span to section consid-ered, and is not to be taken greater than 0,25 l

h = web height in m.

(IACS LL20)

406 The cover edges are to be adequately stiffened to with-stand the forces imposed upon them during opening and clos-ing of the hatches. For stiffness of cover edges, see also 600.

407 Stiffeners are to be connected to supporting girders orcover edges by an area not less than:

a = 5 + 0,07 (l 1 + l 2) s p + ak (cm2)

l 1 and l 2 are stiffener spans in m on each side of support.

ak = corrosion addition in tanks corresponding to tk.

408 Weld attachment other than given in 407, are to be in ac-cordance with Sec.12.

For covers above cargo- and ballast tanks, chain or staggeredfillet welds on the tank side are not acceptable.

409 The web and flange thickness is not to be less than:

t = 5,0 + tk (mm)

tk as defined in Sec.2 Table D1, but assuming that the hatchcover is a part of the hold, or tank, as appropriate.

E 500 Girders

501 When calculating the actual Z for strength members sup-porting other stiffeners, the effective flange is to be determinedin accordance with Sec.3 C400. When the hatch cover is ofclosed box girder construction, the flange may be taken as 100% effective.

502 The section modulus and moment of inertia are not to beless than according to the requirement given in 400, when s isreplaced by b.

b = half the sum in m of stiffener span on either side of thegirder.

503 The net web area at ends is not to be less than:

A = 0,07 l b p + 10 h tk (cm2)

b = as defined in 502h = as defined in 405.

At each intersection with supported members, A may be re-duced by the value 0,14 s b p towards the middle of the span, sbeing the distance in m between supported members. A is notto be taken less than 50% of the value at ends.

Web plates are to be effectively stiffened against buckling.

504 Double continuous fillet welds are normally to be usedwithin areas with shear stress greater than 75 N/mm2, and notless than 150 mm from each end of the girder. The throat thick-ness of the weld attachment between web plates and flanges inthese areas is normally not to be less than 0,4 t, where t = webplate thickness.

E 600 Stiffness of cover edges

601 To ensure sufficient packing pressure for the whole dis-tance between the securing devices, the moment of inertia ofthe side elements of the covers is to be at least:

I = 6 pl a4 (cm4)

for cover edges connected to a rigid hatch coaming and

I = 12 pl a4 (cm4)

between cover edges of equal stiffness.

pl = packing line pressure along edges in N/mm, minimum5 N/mm

a = spacing in m of bolts or other securing devices.

602 When determining the moment of inertia of tank coverside elements supporting primary cover stiffening elements be-tween securing devices, the internal pressure in the tank is tobe taken into consideration.

E 700 Structural analysis

701 For hatch covers of special construction or arrangement(e.g. covers constructed as a grillage, covers supported alongmore than two opposite edges, covers supporting other covers)a separate strength calculation may be required, in which thearrangement of girders and supports is taken into account. Thisis specially valid for hatch covers in open bulk carriers andcombination carriers where deflections are important to tight-ness, see F203.

702 Load conditions are to be established in accordance withthe loads given in 200. For calculations according to beam the-ory the following stresses will be accepted:

a) Bending stress:

σ = 0,58 σf N/mm2 for hatchways in position 1 or 2when p = p1 or p2

= 0,67 σf N/mm2 in all other cases

b) Shear stress:

τ = 0,33 σf N/mm2 for hatchways in position 1 or 2when p = p1 or p2

= 0,37 σf N/mm2 in all other cases.

σf as defined in 301

l1

l0----

Z1

Z0------

C2 1 8α3 1 δ–

0 2, 3 δ+-------------------------+=

I1

I0----

A 0 14 0 5, xl---–

� �� l s p, 10 h tk (cm

2)+=


DET NORSKE VERITAS

The sum of girder bending stress and local bending stress in stiffeners being part of the girder is not to exceed 0,8 σf N/mm2

c) critical buckling stress:

η = 0,77 for sea loads and wave induced internal liquidloads (weather deck hatch covers)

= 0,87 for other loadsσa = actual calculated stress.

σc to be calculated as shown in 304.

703 For hatchway in position 1 or 2 additional conditionscorresponding to pressure 9,81 ql kN/m2ql are to be checked ( as defined in 402). For these conditions the following bend-ing stress for normal strength steel will be accepted:

σ = 95 N/mm2.

For other materials a bending stress of σb / 4,25 will normallybe accepted, σb being the ultimate tensile strength of the mate-rial.

Maximum deflection at the middle of hatch cover:

δ = 0,0028 ll = the smaller of hatch breadth and hatch length.

704 In way of holds/tanks for cargo oil and/or water ballast,the calculated scantlings for the hatch covers are to be in-creased by a corrosion addition tk as specified in Sec.1.

F. Hatchway Tightness Arrangement and Clos-ing Devices

F 100 General101 The requirements below are valid for steel hatch coverson weather decks and above tanks, with ordinary packing ar-rangement between hatch cover and coaming, and packing ar-ranged for vertical packing pressure in joints between coverelements. Other packing arrangements will be specially con-sidered.

102 Closing of hatches by portable hatch beams, covers andtarpaulins will be specially considered.

103 Packing and drainage arrangements of hatch covers forcargoes which are not sensitive to moisture from small leakag-es may be specially considered.

F 200 Design and tightness requirements201 The weight of covers and any cargo stowed thereon, to-gether with inertial forces generated by ship motions, are to betransmitted to the ship structure through steel to steel contact.This may be achieved by continuous steel to steel contact ofthe cover skirt plate with the ships structure or by means of de-fined bearing pads. A proper alignment between coaming andcover is very important in this respect.

202 The sealing is to be obtained by a continuous gasket ofrelatively soft, elastic material compressed to achieve the nec-essary weathertightness. Similar sealing is to be arranged be-tween cross-joint elements. Where fitted, compression flat barsor angles are to be well rounded where in contact with the gas-ket and are to be made of a corrosion-resistant material.

203 Special consideration is to be given to the gasket and se-curing arrangements in ships with large relative movementsbetween cover and ship structure or between cover elements.For such ships, relative deflections both in the vertical and thehorizontal planes should be calculated and submitted with the

hatch cover plans. Also vertical deflections due to thermal ef-fects and internal pressure loads are to be considered.

For ships with large deck openings as defined in Sec.5, the tor-sional deformation of the hatch opening is to be calculatedbased on a torsional moment

Mt = M ST + MWT

M ST , M WT = as given in Pt.5 Ch.2 Sec.6.

The necessary compression of the gasket to obtain sufficientsealing is to be estimated on the basis of the vertical deflectionscalculated, including building/installation tolerances, seen inrelation to results from compression/ leakage tests performed.

204 It is assumed that the gasket material and any gluing ma-terial used in gasket junctions or to fasten the gasket to the cov-er are of a quality suitable for all environmental conditionslikely to be experienced by the ship, and are compatible withthe cargoes carried. The material and form of gasket selectedis to be considered in conjunction with the type of cover, thesecuring arrangement and the expected relative movement be-tween cover and ship structure. The gasket is to be effectivelysecured to the cover.

205 There is to be a metallic contact between hatch cover andhull (earthing connection). If necessary, this is to be achievedby a special connection.

Guidance note:

1) As practical limits for the hatch opening horizontal defor-mations in ships with hatch openings less than given inSec.5 A106 (calculated with rule design loads) are indicat-ed:

— single amplitude diagonal deformation: ld/1000— bending deflection of coamings: lc/1000

l d = length of hatch opening diagonall c = length of side or end coaming.

2) Deflections due to temperature differences should bechecked, especially for closed (double-skin) hatch coverpontoons. The deflections should be calculated both for hotcargo (80°C) and cold air (–5°C) resulting in upward bend-ing of pontoon corners, and for hot air (60°C) and cold cargo(0°C) resulting in upward bending of middle of pontoon andpontoon edges. Securing devices are to be given sufficientstrength and pre-tension to reduce deflections to acceptablefigures.

Designing the pontoons as open panels (one continuousplate flange only) will normally reduce the temperature de-flections effectively.

Combination of loads and deflections should be based on aconsideration of the probability of simultaneous occurrence.

3) Laboratory compression tests should be performed on testpanels arranged for observing leakage for various combina-tions of internal liquid pressure and compression of gasket.By this a minimum compression/internal pressure curve forno leakage may be obtained. Necessary compression of gas-kets may thus be estimated by adding minimum compres-sion to maximum vertical deflections calculated.


F 300 Securing devices in general301 Panel hatch covers on weather decks above dry cargoholds or on top of deep tanks are in general to be secured byappropriate devices (bolts, wedges or similar) suitably spacedalongside the coamings and between cover elements. Arrange-ment and spacing are to be determined with due attention to theeffectiveness for tightness, depending upon the type and thesize of the hatch cover, as well as the stiffness of the cover edg-es between the securing devices, see E600. Scantlings of secur-ing devices are given in 400 to 600.

σc

σa

η----- (N/mm

2)≥


DET NORSKE VERITAS

302 Securing means of other material than mild steel or othermeans than bolts are to be of strength equivalent to the require-ments given in 400 and 600, and so arranged that the correctpressure on the packing between the covers and the coamings,and adjacent covers as well, is obtained.

Bolts with nuts, wedges and other parts for securing the covers,are to be of reliable construction and securely attached to thehatchway coamings, decks or covers.

The individual securing elements are to have approximatelythe same deflection characteristics.

Bolts and adjusting screws are to be secured in position by ap-propriate means.

Where rod cleats are fitted, resilient washers or cushions are tobe incorporated.

Where hydraulic cleating is applied, the system is to remainmechanically locked in closed position in the event of failureof the hydraulic system.

303 Spare securing elements are to be kept on board, thenumber depending on the total number fitted, as well as type ofelement, special material used, etc.

F 400 Securing arrangement for weathertight hatch covers401 Ordinary packed hatch covers are to be secured to thecoaming by a net bolt area for each bolt not less than:

a = spacing of bolts in m

f1e =

σf = minimum upper yield stress in N/mm2, not to be takengreater than 70% of the ultimate tensile strength

e = 0,75 for σf > 235 = 1,0 for σf < 235.

402 Between cover and coaming and at cross-joints, a pack-ing line pressure sufficient to obtain weathertightness is to bemaintained by a bolt area as given in 401.

403 For packing line pressures exceeding 5 N/mm, the areais to be increased accordingly. The packing line pressure is tobe specified.

404 The net bolt diameter is not to be less than 19 mm forhatchways exceeding 5 m2 in area.

405 Closing appliances of covers to hatches on exposeddecks (position 1 and 2) where reduced coaming heights areaccepted (see D 200) will be specially considered.

In this case each cover element is to be equipped with at least2 securing devices along each side, and the maximum distanceis not to exceed amax = 2,5 metres.

F 500 Securing arrangement for deep tank or cargo oil tank hatch covers501 In addition to the requirements given in 400, deep tankor cargo oil tank hatch covers have to fulfil the following re-quirements.

The net securing bolt area for each bolt is not to be less than:

a = spacing of bolts in ml = span in m of hatch cover girder or stiffener perpendic-

ular to coaming, if any — or distance from cover edgeto the first parallel stiffener

p = p4 – p9, whichever is relevant, as given in Table E1pl = packing line pressure in N/mm. For calculation pur-

pose, however, the packing pressure is not to be takenless than 5 N/mm

f1e = as given in 401.

502 Between cover elements the packing line pressure is tobe maintained by a net bolt area for each bolt not less than:

a = spacing of bolts in m.

Corrections to be applied as given in 403 and 404.

503 Covers particularly calculated, as mentioned in E700,are to be fitted with closing devices corresponding to the reac-tion forces found by the calculation. The maximum tension inway of threads of bolts is not to exceed 125 f1e N/mm2 .. Themaximum stresses in closing devices of other types than boltsare:

— normal stress:

σ = 120 f1e N/mm2

— shear stress:

τ = 80 f1e N/mm2

— equivalent stress:

Guidance note:In order to satisfy the tightness requirements the following de-sign recommendations are given:

1) The horizontal distance between the gaskets and the secur-ing devices should be as small as possible.

2) Securing devices should be arranged as close to the panelcorners as possible.

3) Securing devices with a vertical clearance (passive cleating)should be avoided, i.e. active cleating with a certain pre- ten-sion should be used.


F 600 Securing arrangement for hatch covers carrying deck cargo

601 In addition to the requirements given in 400 or 500, allhatch covers, especially those carrying deck cargo are to be ef-fectively secured against horizontal shifting due to the hori-zontal forces given in E202, which may be reduced by 10%due to friction.

The maximum allowable stresses in stoppers are as given in503.

602 To prevent damage to hatch covers and ship structure,the location of stoppers is to be compatible with the relativemovements between hatch covers and ship structure. Thenumber of stoppers is to be as small as possible, preferablyonly one stopper at each end of each cover element.

In case of twin hatches supported by a narrow box girder atcentre-line, two-way stopper at outboard coaming may be re-quired.

603 Towards the ends of the ship vertical acceleration forcesmay exceed the gravity force. The resulting lifting forces mustbe considered when dimensioning the securing devices. Alsolifting forces from cargo secured on the hatch cover during

A1 4a,f1e

------------ (cm2

)=

σf

235---------

� ��

e

A0 08a,

f1e--------------- 0 5 lp, pl+( ) (cm

2 )=

A3af1e------- (cm

2 )=

σe σ23τ2

+ 150 f1e N/mm2

= =


DET NORSKE VERITAS

rolling are to be taken into account. The allowable stresses inbolts and other types of securing devices are as given in 503.

604 Hatch coamings and supporting structure are to be ade-quately stiffened to accommodate the loading from hatch cov-ers.

605 At cross-joints of multi-panel covers vertical guides(male/female) are to be fitted to prevent excessive relative ver-tical deflections between loaded/unloaded panels.

F 700 Drainage arrangement701 On weather deck hatch covers drainage is to be arrangedinside the line of gasket by means of a gutter bar or vertical ex-tension of the hatch side and end coaming.

702 Drain openings are to be arranged at the ends of drainchannels and are to be provided with effective means for pre-venting ingress of water from outside, such as non-returnvalves or equivalent.

703 Cross-joints of multi-panel covers are to be arrangedwith drainage of water from the space above the gasket and adrainage channel below the gasket.

704 If a continuous outer steel contact between cover andship structure is arranged, drainage from the space between thesteel contact and the gasket is also to be provided for.

G. Internal Doors and Hatches for Watertight Integrity

G 100 General101 General requirements to internal openings in connectionwith watertight integrity are given in Sec.3 A600. For pipe tun-nel openings, see also Sec.6 A407.

102 Watertight doors or hatches may be of the followingtypes:

— hinged doors or hatches of approved type with mechanicalsecuring devices. May be fitted in 'tween decks in ap-proved positions. Such doors are not to be used where re-mote control is required.

— rolling doors, guided and supported by steel rollers, andwith mechanical or hydraulic securing devices

— sliding doors, moving along and supported by trackwaygrooves and with mechanical locking due to taper and fric-tion. A positive force is required to re-open the doors. Maybe only hand operated or both power and hand operated.

G 200 Operation201 All watertight doors and access hatches are to be opera-ble from both sides of the bulkhead or deck.

202 Remotely controlled doors are also to be locally opera-ble. Indicators are to be provided at the control position to in-dicate whether the doors are open or closed.

G 300 Strength301 Watertight doors and hatches are to be designed with astrength equivalent to that of the structure in which they are po-sitioned. They are to withstand the design pressure from bothsides.

302 The thickness corresponding to lateral pressure is givenby:

p = design pressure p, as given in Sec.9, Table B1c = 1,58 for collision bulkhead

= 1,35 for all other bulkheads and decks.

The thickness is in no case to be less than the minimum bulk-head thickness.

303 The stiffener section modulus requirement is given by:

p = as given in 302c1 = 0,8 for collision bulkhead = 0,6 for all other bulkheads and decks.

304 Edge stiffeners of doors are to have a moment of inertianot less than:

I = 8 pe d4 (cm4)

d = distance between closing devices in m, to be measuredalong door edge

pe = packing line pressure along edges, not to be taken lessthan 5 N/mm

= pb, whichever is the greaterp = design pressure p1 as given in Sec.9, Table B1b = load breadth, normally taken as h/3 or w/2, whichever

is the less.

h and w are height and width of door in m.

305 The coaming of watertight doors (door frame) is to bedesigned with due care to necessary stiffness in order to avoidlarge deflections resulting in leakage in the damaged condi-tion. The door frames shall have no groove at the bottom inwhich dirt might lodge and prevent the door from closing prop-erly.

306 Securing devices are to be designed for the load actingalso on the opposite side of where they are positioned. Allow-able stresses in securing devices are as follows:

normal stress: σ = 165 f1 N/mm2

shear stress: τ = 110 f1 N/mm2

equivalent stress:

H. Ventilators

H 100 Regulation 19101

1) Ventilators in position 1 or 2 to spaces below freeboarddeck or decks of enclosed superstructures shall havecoamings of steel or other equivalent material, substantial-ly constructed and efficiently connected to the deck. Wherethe coamings of any ventilators exceed 900 millimetres inheight it shall be specially supported.

2) Ventilators passing through superstructures other than en-closed superstructures shall have substantially construct-ed coamings of steel or other equivalent material at thefreeboard deck.

3) Ventilators in position 1 the coamings of which extend tomore than 4.5 metres above the deck, and in position 2 thecoamings of which extend to more than 2.3 metres abovethe deck, need not be fitted with closing arrangements un-less specifically required by the Administration.

4) Except as provided in paragraph (3) of this Regulation ven-tilator openings shall be provided with efficient weathertightclosing appliances. In ships of not more than 100 metres inlength the closing appliances shall be permanently at-

tckas p

f1

------------------ tk (mm)+=

Zc1 l

2s p wk

f1--------------------------- (cm

3 )=

σe σ23τ2

+ 200f1e N/mm2

= =


DET NORSKE VERITAS

tached; where not so provided in other ships, they shall beconveniently stowed near the ventilators to which they areto be fitted. Ventilators in position 1 shall have coamings ofa height of at least 900 millimetres above the deck; in posi-tion 2 the coamings shall be of a height of at least 760 mil-limetres above the deck.

5) In exposed positions, the height of coamings may be re-quired to be increased to the satisfaction of the Administra-tion.

(ICLL Reg.19)

H 200 Thickness of coamings

201 The thickness of ventilator coamings is not to be lessthan given in the following table:

For intermediate external diameter the wall thickness is ob-tained by linear interpolation.

(IACS LL36)

H 300 Arrangement and support

301 Where required by Regulation 19 (101), weathertightclosing appliances for all ventilators in positions 1 and 2 are tobe of steel or other equivalent materials.

Wood plugs and canvas covers are not acceptable in these po-sitions.

(IACS LL52)

302 The deck plating in way of deck openings for ventilatorcoamings is to be of sufficient thickness, and efficiently stiff-ened between ordinary beams or longitudinals. Coamings withheights exceeding 900 mm are to be additionally supported.

303 Where ventilators are proposed to be led overboard in anenclosed superstructure deck house or shipside the closing ar-rangement is to be submitted for approval. If such ventilatorsare lead overboard more than 4,5 m above the freeboard deck,closing appliances may be omitted, provided that satisfactorybaffles and drainage arrangements are provided.

304 To ensure satisfactory operation in all weather condi-tions, machinery spaces and emergency generator room venti-lation inlets and outlets are to be located in such positions thatclosing appliances will not be necessary.

Alternatively, depending on vessel's size and arrangement,lesser coaming heights may be accepted if weathertight closingappliances are provided, in accordance with 100 (Reg.19) andin combination with suitable means arranged to ensure uninter-rupted and adequate supply of air to these spaces.

Guidance note:The term suitable means is meant e.g. that direct and sufficientsupply of air is provided through open skylights, hatches or doorsat a higher level than the heights required by the Reg.19 of theLoad Line Convention.


I. Tank Access, Ullage and Ventilation Openings

I 100 General

101 The number of hatchways and other openings in thetank deck are not to be larger than necessary for reasonable ac-cess to and ventilation of each compartment.

102 Hatchways, openings for ventilation, ullage plugs orsighting ports, etc. are not to be placed in enclosed compart-ments where there is a danger of accumulation of gases.

Ullage plugs or sighting ports should be fitted as high abovethe deck as practicable, for instance in the cover of accesshatches.

Access hatches to holds or other openings, for example fortank cleaning devices, are to be of substantial construction, andmay be arranged in the main hatch covers.

I 200 Hatchways

201 The thickness of the hatch coaming is not to be less thangiven in Sec.10 for a deckhouse in the same position.

202 The thickness of covers is not to be less than:

— 12,5 mm for cover area exceeding 0,5 m2

— 10,0 mm for cover area less than 0,25 m2.

For intermediate areas the thickness may be linearly varied.

203 Where the area of the hatchway exceeds 1,25 m2, thecovers are to be stiffened.

204 Covers are to be secured to the hatch coamings by fas-tenings spaced not more than 380 mm apart and not more than250 mm from the corners. For circular covers the fasteningsare not to be spaced more than 450 mm apart.

205 Other types of covers may be approved, provided theirconstruction is considered satisfactory.

I 300 Air Pipes

301

Where air pipes to ballast and other tanks extend above thefreeboard or superstructure decks, the exposed parts of thepipes shall be of substantial construction; the height from thedeck to the point where water may have access below shall beat least 760 millimetres on the freeboard deck and 450 millime-tres on the superstructure deck. Where these heights may in-terfere with the working of the ship, a lower height may beapproved, provided the Administration is satisfied that the clos-ing arrangements and other circumstances justify a lowerheight. Satisfactory means permanently attached, shall be pro-vided for closing the openings of the air pipes.

(ICLL Reg.20)

302 For ships assigned timber freeboards the air pipes shouldbe provided with automatic closing appliances.

(IACS LL10)

303 Where required by Regulation 20 (301) air pipe closingdevices shall be weathertight. Closing devices shall be auto-matic if, while the vessel is at its draught corresponding tosummer load line, the openings of air pipes to which these clo-sures are fitted submerge at angles up to 40° or up to a lesserangle which may be agreed on the basis of stability require-ments. Pressure- vacuum valves (PV valves) may, however, beaccepted on tankers.

Wooden plugs and trailing canvas hoses shall not be acceptedin position 1 and position 2.

Guidance note:The member Societies in formulating this interpretation realisethat pressure-vacuum valves (PV valves) presently installed ontankers do not theoretically provide complete watertightness. Inview, however, of experience of this type of valve and the posi-tion in which they are normally fitted it was considered theycould be accepted.


(IACS LL49)

External diameter in mm

Wall thickness in mm

≤80 6,0≥165 8,5


DET NORSKE VERITAS

304 The thickness of air pipe coamings is not to be less thangiven in the following table:

For intermediate external diameter the wall thickness is ob-tained by linear interpolation. Coamings with heights exceed-ing 900 mm are to be additionally supported. (IACS LL36)

305 Openings of air pipes are to be provided with perma-nently attached efficient means of closing. The closing appli-ances are to be so constructed that damage to the tanks byoverpumping or occasionally possible vacuum by dischargingis prevented.

306 In cases where air pipes are led through the side of su-perstructures, the height of their openings to be at least 2,3 me-tres above the summer water line. Automatic vent heads ofapproved design are to be provided.

307 The height of air pipes may be required to be increasedon ships of type "A", type "B-100" and type "B-60" where thisis shown to be necessary by the floatability calculation.

308 In a ship to which timber freeboard is assigned, air pipeswhich will be inaccessible when the deck cargo is carried areto be provided with automatic closing appliances.

309 All air pipes in cargo spaces are to be well protected.

310 For arrangement and size of air pipes, see also Pt.4 Ch.6Sec.4 K.

J. Machinery Space Openings

J 100 Regulation 17

101

1) Machinery space openings in position 1 or 2 shall be prop-erly framed and efficiently enclosed by steel casings of am-ple strength, and where the casings are not protected byother structures their strength shall be specially consid-ered. Access openings in such casings shall be fitted withdoors complying with the requirements of Regulation 12(1)(B101), the sills of which shall be at least 600 millimetresabove the deck if in position 1, and at least 380 millimetresabove the deck if in position 2. Other openings in such cas-ings shall be fitted with equivalent covers, permanently at-tached in their proper positions.

2) Coamings of any fiddley, funnel or machinery space venti-lator in an exposed position on the freeboard or superstruc-ture deck shall be as high above the deck as is reasonableand practicable. Fiddley openings shall be fitted with strongcovers of steel or other equivalent material permanently at-tached in their proper positions and capable of being se-cured weathertight.

(ICLL Reg. 17)

J 200 Interpretations

201 Where casings are not protected by other structures,double doors should be required for ships assigned freeboardsless than those based on Table B (See Ch.5 Sec.3 B100). Aninner sill of 230 mm in conjunction with the outer sill of 600mm is recommended.

(IACS LL7)

202 Doorways in engine and boiler casings are to be ar-ranged in positions which afford the greatest possible protec-tion.

203 Skylights are to be of substantial construction and se-curely connected to deck. If the upper part of the skylight con-sists of hinged scuttles, effective means for closing andsecuring are to be provided.

For skylights in position 1 or 2 the coaming height is not to beless than given for hatchway coamings. For skylights in posi-tion 1, deadlights are to be fitted.

204 Side scuttles in engine casings are to be provided withfireproof glass.

K. Scuppers, Inlets and Discharges

K 100 Regulation 22

101

1) Discharges led through the shell either from spaces belowthe freeboard deck or from within superstructures anddeckhouses on the freeboard deck fitted with doors com-plying with the requirements of Regulation 12 (B101) shall,except as provided in paragraph (2), be fitted with efficientand accessible means for preventing water from passinginboard. Normally each separate discharge shall have oneautomatic non-return valve with a positive means of closingit from a position above the freeboard deck. Where, how-ever, the vertical distance from the summer load waterlineto the inboard end of the discharge pipe exceeds 0.01 L,the discharge may have two automatic non-return valveswithout positive means of closing, provided that the inboardvalve is always accessible for examination under serviceconditions; where that vertical distance exceeds 0.02 L asingle automatic non return valve without positive means ofclosing may be accepted subject to the approval of the Ad-ministration. The means for operating the positive actionvalve shall be readily accessible and provided with an indi-cator showing whether the valve is open or closed.

2) Scuppers led through the shell from enclosed superstruc-tures used for the carriage of cargo shall be permitted onlywhere the edge of the freeboard deck is not immersedwhen the ship heels 5 degrees either way. In other casesthe drainage shall be led inboard in accordance with the re-quirements of the International Convention for the Safety ofLife at Sea in force.

3) In manned machinery spaces main and auxiliary sea inletsand discharges in connection with the operation of machin-ery may be controlled locally. The controls shall be readilyaccessible and shall be provided with indicators showingwhether the valves are open or closed.

4) Scuppers and discharge pipes originating at any level andpenetrating the shell either more than 450 millimetres be-low the freeboard deck or less than 600 millimetres abovethe summer load waterline shall be provided with a non-re-turn valve at the shell. This valve, unless required by para-graph (2), may be omitted if the piping is of substantialthickness.

5) Scuppers leading from superstructures or deckhouses notfitted with doors complying with the requirements of Regu-lation 12 (B101) shall be led overboard.

6) All shell fittings, and the valves required by this Regulationshall be of steel, bronze or other approved ductile material.Valves of ordinary cast iron or similar material are not ac-ceptable. All pipes to which this Regulation refers shall beof steel or other equivalent material to the satisfaction ofthe Administration, see Pt.4 Ch.6 Sec.2.

(ICLL Reg.22)

External diameter in mm

Wall thickness in mm

≤ 80 6,0≥ 165 8,5


DET NORSKE VERITAS

K 200 Interpretations

201 It is considered that the position of the inboard end ofdischarges should be related to the timber summer load water-line when timber freeboard is assigned.

(IACS LL22)

202 It is considered that an acceptable equivalent to one au-tomatic non-return valve with a positive means of closing froma position above the freeboard deck would be one automaticnon-return valve and one sluice valve controlled from abovethe freeboard deck. Where two automatic non-return valves arerequired, the inboard valve must always be accessible underservice conditions, i.e., the inboard valve should be above thelevel of the tropical load water line. If this is not practicable,then, provided a locally controlled sluice valve is interposed

between the two automatic non-return valves, the inboardvalve need not to be fitted above the LWL.

Where sanitary discharges and scuppers lead overboardthrough the shell in way of machinery spaces, the fitting toshell of a locally operated positive closing valve, together witha non-return valve inboard, is considered to provide protectionequivalent to the requirements of Regulation 22(1).

It is considered that the requirements of Regulation 22(1) fornon-return valves are applicable only to those dischargeswhich remain open during the normal operation of a vessel.For discharges which must necessarily be closed at sea, such asgravity drains from topside ballast tanks, a single screw downvalve operated from the deck is considered to provide efficientprotection.

Table K1 Acceptable arrangements of discharges with inboard endsDischarges coming from defined enclosed spaces (spaces below freeboard deck, in superstructures

and in deck houses defined by Reg.3 (10) with doors according to Reg.12 and defined by Reg.18 (2)) ***

Discharges coming from open deck and from spaces not defined

General requirements (Reg.22 (1))

In engine rooms only

Alternatives where inboard end is:

(Reg.22 (1))

Outboard end > 450 mm below

FB DECK or < 600 mm above SWL (Reg.22 (3))

Otherwise Reg.22(4)

> 0.01 x L above SWL

> 0.02 x L above SWL

*) The control shall be so sited as to allow adequate time for operation in case of influx of water to the space having regard to the time which could be taken to reach and operate such controls**) Substantial pipe thickness from the shell and up to the freeboard deck and in cases further up in closed superstructure to a height at least 600 mm above the summer water line***) References: Reg.3, see Ch.5 Sec.1 D100, Reg.12, see B100, Reg .18, see B301.


DET NORSKE VERITAS

The inboard end of a gravity discharge which leads overboardfrom an enclosed superstructure or space is to be located abovethe water line formed by a 5 degree heel, to port or starboard,at a draft corresponding to the assigned summer freeboard.

It is considered that the position of the inboard end of discharg-es shoul be related to the timber summer load waterline whentimber freeboard is assigned.

See Table K1 for the acceptable arrangement of scuppers, in-lets, and discharges.

Plastic pipes may be used for sanitary discharges and scuppersas permitted by Pt.4 Ch.1 Sec.2 C700.

The portion of discharge line from the shell to the first valve aswell as shell fittings and valves shall be of steel, bronze or oth-er approved ductile material.

203 The wall thickness of steel piping between hull platingand closeable or non-return valve is not to be less than given inTable K2.


The wall thickness of steel piping inboard of the valve is not tobe less than given in Table K3.


(IACS LL36)

K 300 Discharges

301 Discharges with inboard opening located lower than theship's uppermost load line may be accepted when a loop of thepipe is arranged, extending not less than 0,01L (minimum 0,5m) above the summer load waterline. The top of the loop is tobe regarded as the position of the inboard opening, and thepipeline is to be provided with valves according to Regulation22 (101).

302 Discharges from spaces above the freeboard deck are tobe of steel or material specially resistant to corrosion.

303 Adequate protection is to be provided to protect valvesor pipes from being damaged by cargo, etc.

K 400 Scuppers

401 A sufficient number of scuppers, arranged to provide ef-fective drainage, is to be fitted on all decks.

402 Scuppers on weather portions of decks and scuppersleading from superstructures or deckhouses not provided withclosing appliances required in C, are usually to be led over-board.

403 Scuppers led through the deck or shell, are to complywith requirements to material and thickness as given for dis-charges.

404 Scupper pipes are to be well stayed to prevent any vibra-tions. However, sufficient possibility for expansion of thepipes to be provided when necessary.

405 Scuppers from spaces below the freeboard deck or spac-es within closed superstructures, may be led to bilges. Fordrainage of cargo deck spaces, see Pt.4 Ch.6 Sec.4 D.

406 Scuppers leading overboard from spaces mentioned in405, are to comply with the requirements given for discharges.Scuppers from exposed superstructure deck, led through theship's sides and not having closeable valves, are to have wallthickness as required in 203.

407 Gravity discharges from top wing tanks may be ar-ranged. The drop valves are to be of substantial constructionand of ductile material, and they are to be closeable from an al-ways accessible position. It is to be possible to blank- flangethe discharge or to lock the valves in closed position when thetanks are used for carrying cargo.

The thickness of the pipe or box leading from the tank throughthe shell is to comply with the requirements given for discharg-es.

408 Drainage from refrigerated cargo spaces is to complywith the requirements for class notation Reefer. Drain pipesfrom other compartments are not to be led to the bilges in re-frigerated chambers.

409 Drainage from helicopter decks is to comply with the re-quirements for the class notation HELDK S.

K 500 Periodically unmanned machinery space

501 The location of the controls of any valve serving a sea in-let, a discharge below the waterline or a bilge injection systemshall be so sited as to allow adequate time for operation in caseof influx of water to the space, having regard to the time likelyto be required in order to reach and operate such controls. If thelevel to which the space could become flooded with the ship inthe fully loaded condition so requires, arrangements shall bemade to operate the controls from a position above such level.

(SOLAS Reg. II-1/48.3)

502 If it can be documented by calculation of filling time thatthe water level is not above the tank top floor after 10 minutesfrom the initiation of the uppermost bilge level alarm, it will beaccepted that the valves are operated from the tanktop floor.

Guidance note:Various Flag Administrations have worked out their own inter-pretations of this regulation.


L. Side Scuttles

L 100 Regulation 23

101

1) Side scuttles to spaces below the freeboard deck or tospaces within enclosed superstructures shall be fitted withefficient hinged inside deadlights arranged so that they canbe effectively closed and secured watertight.

2) No side scuttle shall be fitted in a position so that its sill isbelow a line drawn parallel to the freeboard deck at sideand having its lowest point 2.5 per cent of the breadth (B)above the Summer Load Line (or Summer Timber LoadLine, if assigned), or 500 millimetres, whichever is thegreater distance.

3) The side scuttles, together with their glasses, if fitted, anddeadlights, shall be of substantial and approved construc-tion.

(ICLL Reg.23)

Table K2 Wall thickness of steel pipingExternal diameter in mm Wall thickness in mm

≤ 80 7,0= 180 10,0≥ 220 12,5

Table K3 Wall thickness of steel pipingExternal diameter in mm Wall thickness in mm

≤ 155 4,5≥ 230 6,0


DET NORSKE VERITAS

L 200 Interpretations

201 For those vessels where the freeboard is reduced on ac-count of subdivision characteristics, side scuttles fitted outsidethe space considered flooded and which are below the final wa-terline shall be of the non-opening type.

(IACS LL12)

202 By extension of Regulation 23 (101) and InterpretationLL8 (B303), deckhouses situated on a raised quarterdeck maybe treated as being on the second tier as far as the provision ofdeadlights and side scuttles and windows is concerned, provid-ed the height of the raised quarterdeck is equal to or greaterthan the standard quarterdeck height.

(IACS LL46)

L 300 Arrangement

301 Side scuttles in the ship's side and in sides and ends ofenclosed superstructures are to have hinged inside deadlightsarranged so that they can be effectively closed and secured wa-tertight.

302 Deadlights are also to be fitted on side scuttles in deck-houses, casings and companionways on freeboard deck cover-ing entrance to spaces below the freeboard deck.

The same requirement applies to side scuttles in deckhouses,casings and companionways situated on top of the lowest tierof erections if there is direct access from the compartmentwhere the side scuttle is fitted to a compartment within an en-closed superstructure or to a compartment below the freeboarddeck.

303 Deadlights as required in 302 may be hinged outside,provided there is easy access for closing.

Guidance note:Such arrangement will also have to be approved by Maritime Au-thorities.


L 400 Glass dimensions, side scuttles and windows

401 Side scuttles and windows made and tested according toISO 1751 for side scuttles and ISO 3903 for windows, withglass glass according to ISO 1095 for side scuttles and 3254 forwindows and glass tested and marked according to ISO 614will normally be accepted. The same applies to national stand-ards equivalent to the ISO-standards.

402 The glass thickness can be calculated from the followingformulae:

1) For 2nd tier and below the design load for side scuttles andwindows to be in accordance with ISO/DIS 5779 and5780.

For 3rd tier and above the design load to be in accordancewith the rules as given in Sec.10 C100.

2) Minimum design load for windows located 1,7 Cw (m) ormore above S.W.L. is 2,5 kN/m2.

L should not be taken less than 100 m.

The thickness of windows are not to be less than:

— 8 mm for windows with area less than 1,0 m2

— 10 mm for windows of 1,0 m2 or more.

N = nominal diameter/light opening of side scuttle in mm

b = the minor dimension of the window in mmβ = factor obtained from the graph in Fig. 2p = design load in kN/m2

t = glass thickness in mmCw = wave coefficient as given in Sec.4 B200.

Fig. 2Diagram for factor β for windows

M. Freeing Ports

M 100 Regulation 24

101

1) Where bulwarks on the weather portions of freeboard orsuperstructure decks form wells, ample provision shall bemade for rapidly freeing the decks of water and for drainingthem. Except as provided in paragraphs (2) and (3) of thisRegulation, the minimum freeing port area (A) on each sideof the ship for each well on the freeboard deck shall be thatgiven by the following formula in cases where the sheer inway of the well is standard or greater than standard. Theminimum area for each well on superstructure decks shallbe one-half of the area given by the formula.

Where the length of bulwark ( l) in the well is 20 metres orless:

A = 0.7 + 0.035 l (square metres),

where l exceeds 20 metres:

A = 0.07 l (square metres).

l need in no case be taken as greater than 0.7 L.

If the bulwark is more than 1.2 metres in average height therequired area shall be increased by 0.004 square metresper metre of length of well for each 0.1 metre difference inheight. If the bulwark is less than 0.9 metre in averageheight, the required area may be decreased by 0.004square metres per metre of length of well for each 0.1 me-tre difference in height.

2) In ships with no sheer the area calculated according to par-agraph (1) of this Regulation shall be increased by 50 percent. Where the sheer is less than the standard the per-centage shall be obtained by linear interpolation. Where aship fitted with a trunk which does not comply with the re-quirements of Regulations 36 (1)(e)

3) Where a ship fitted with a trunk which does not comply withthe requirements of Regulations 36 (1)(e)(Ch.5 Sec.3 J100)or where continuous or substantially continuous hatchwayside coaming are fitted between detached superstructures

side scuttles: tN

362--------- p=

windows: tb

200--------- β p=


DET NORSKE VERITAS

the minimum area of the freeing port openings shall be cal-culated from the following table:

The area of freeing ports at intermediate breadths shall beobtained by linear interpolation.

4) In ships having superstructures which are open at either orboth ends, adequate provision for freeing the space withinsuch superstructures shall be provided to the satisfactionof the Administration.

5) The lower edges of the freeing ports shall be as near thedeck as practicable. Two-thirds of the freeing port area re-quired shall be provided in the half of the well nearest thelowest point of the sheer curve.

6) All such openings in the bulwarks shall be protected by railsor bars spaced approximately 230 millimetres apart. Ifshutters are fitted to freeing ports, ample clearance shall beprovided to prevent jamming. Hinges shall have pins orbearings of non-corrodible material. If shutters are fittedwith securing appliances, these appliances shall be of ap-proved construction.

(ICLL Reg.24)

M 200 Interpretations

201 (To Reg. 24.1 and 24.5)

On a flush deck ship with a substantial deckhouse amidships itis considered that the deckhouse provides sufficient break toform two wells and that each could be given the required free-ing port area based upon the length of the «well». It would notthen be allowed to base the area upon 0,7 L.

In defining a substantial deckhouse it is suggested that thebreadth of the deckhouse should be at least 80% of the beam ofthe vessel, and that the passageways along the side of the shipshould not exceed 1,5 m in width.

Where a screen bulkhead is fitted completely across the vessel,at the forward end of a midship deckhouse, this would effec-tively divide the exposed deck into wells and no limitation onthe breadth of the deckhouse is considered necessary in thiscase.

It is considered that wells on raised quarterdecks should betreated as previously, i.e. as being on freeboard decks.

With zero or little sheer on the exposed freeboard deck or anexposed superstructure deck it is considered that the freeingport area should be spread along the length of the well. (IACSLL13)

202 (To Reg. 24.3)

The effectiveness of the freeing area in bulwarks required byRegulation 24(1) and (2) depends on free flow across the deckof a ship. Where there is no free flow due to the presence of acontinuous trunk or hatchway coaming, the freeing area in bul-warks is calculated in accordance with Regulation 24(3).

The free flow area on deck is the net area of gaps betweenhatchways, and between hatchways and superstructures anddeckhouses up to the actual height of the bulwark.

The freeing port area in bulwarks should be assessed in relationto the net flow area as follows:

(i) If the free flow area is not less than the freeing area calcu-lated from Regulation 24(3) as if the hatchway coamings werecontinuous, then the minimum freeing port area calculatedfrom Regulation 24(1) and (2) should be deemed sufficient.

(ii) If the free flow area is equal to, or less than the area calcu-lated from Regulations 24(1) and (2) minimum freeing area inthe bulwarks should be determined from Regulation 24(3).

(iii) If the free flow area is smaller than calculated from Reg-ulation 24(3) but greater than calculated from Regulation 24(1)and (2), the minimum freeing area in the bulwark should be de-termined from the following formula:

F = F1 + F2 – fp (m2)

where

F1 = the minimum freeing area calculated from Regulation24(1) and (2),

F2 = the minimum freeing area calculated from Regulation24(3),

fp = the total net area of passages and gaps between hatchends and superstructures or deckhouses up to the actualheight of bulwark.

(IACS LL44)

203 (To Reg. 24.4)

For superstructures that are open at either or both ends the ef-fective freeing area at the end of the superstructure may beadded to the respective freeing port area for the port and star-board side of the superstructure. The effective area of the open-ing at the end of a superstructure will be assessed on a case bycase basis weighing the following factors:

— the athwartship location of the opening— the slope of the deck towards or away from the opening— the length/breadth ratio of the well— the free fore and aft passage for the water to reach the

opening, unobstructed by deck equipment, fittings, or car-go stowage.

M 300 References

301 Requirements for freeing arrangements for Type «A»ships are given in N100.

302 Requirements for freeing arrangements for Type «B-100» ships are given in Ch.5 Sec.3 A100 and for Type «B-60»ships in Ch.5 Sec.3 A300.

N. Special Requirements for Type A Ships

N 100 Regulation 26

101

Machinery Casings

1) Machinery casings on Type A ships as defined in Regula-tion 27 (see A202 and Ch.5 Sec.3 A100) shall be protectedby an enclosed poop or bridge of at least standard height,or by a deckhouse of equal height and equivalent strength,provided that machinery casings may be exposed if thereare no openings giving direct access from the freeboarddeck to the machinery space. A door complying with the re-quirements of Regulation 12 (B101) may, however, be per-mitted in the machinery casing, provided that it leads to aspace or passageway which is as strongly constructed asthe casing and is separated from the stairway to the engineroom by a second weather tight door of steel or other equiv-alent material.

Gangway and Access

2) An efficiently constructed fore and aft permanent gangwayof sufficient strength shall be fitted on Type A ships at thelevel of the superstructure deck between the poop and themidship bridge or deckhouse where fitted, or equivalentmeans of access shall be provided to carry out the purpose

Breadth of hatchway or trunk in relation to the breadth of ship

Area of freeing ports in relation to the total area of the bulwarks

40% or less75% or more

20%10%


DET NORSKE VERITAS

of the gangway, such as passages below deck. Else-where, and on Type A ships without a midship bridge, ar-rangements to the satisfaction of the Administration shallbe provided to safeguard the crew in reaching all partsused in the necessary work of the ship, see Sec.10

3) Safe and satisfactory access from the gangway level shallbe available between separate crew accommodations andalso between crew accommodations and the machineryspace.

Hatchways

4) Exposed hatchways on the freeboard and forecastle decksor on the tops of expansion trunks on Type A ships shall beprovided with efficient watertight covers of steel or otherequivalent material.

Freeing Arrangements

5) Type A ships with bulwarks shall have open rails fitted forat least half the length of the exposed parts of the weatherdeck or other effective freeing arrangements. The upperedge of the sheer strake shall be kept as low as practica-ble.

6) Where superstructures are connected by trunks, open railsshall be fitted for the whole length of the exposed parts ofthe freeboard deck.

(ICLL Reg.26)

N 200 InterpretationIt is considered that a freeing port area, in the lower part of thebulwarks, of 33% of the total area of the bulwarks provides the«other effective freeing arrangements» mentioned in Regula-tion 26(5).

(IACS LL23)


DET NORSKE VERITAS

SECTION 12WELDING AND WELD CONNECTIONS

A. General

A 100 Introduction

101 In this section requirements related to welding and vari-ous connection details are given.

A 200 Definitions

201 Symbols:

tk = see Sec.1 B101.

A 300 Welding particulars

301 Welding of important hull parts is to be carried out byapproved welders only.

302 Welding at ambient air temperature of –5°C or below, isonly to take place after special agreement.

303 The welding sequence is to be such that the parts may asfar as possible contract freely in order to avoid cracks in al-ready deposited runs of weld. Where a butt meets a seam, thewelding of the seam should be interrupted well clear of thejunction and not be continued until the butt is completed.Welding of butt should continue past the open seam and theweld be chipped out for the seam to be welded straight through.

304 Welding procedures and welding consumables ap-proved for the type of connection and parent material in ques-tion, are to be used. See «Register of Type Approved ProductsNo.2, Welding Consumables».

A 400 Radiographic examination.

401 The welds are normally to comply with the requirementto mark 3 (green) of the IIW's Collection of Reference Radio-graphs of Welds.

402 The welds are to be examined by X-ray or by other ap-proved method in positions indicated by the surveyor.

At least all weld crossings in the bottom and deck plating with-in 0,4 L amidships are to be examined.

B. Types of Welded Joints

B 100 Butt joints

101 For panels with plates of equal thickness, the joints arenormally to be butt welded with edges prepared as indicated inFig. 1.

102 For butt welded joints of plates with thickness differenceexceeding 4 mm, the thicker plate is normally to be tapered.The taper is generally not to exceed 1 : 3. After tapering, theend preparation may be as indicated in 101 for plates of equalthickness.

103 All types of butt joints are normally to be welded fromboth sides. Before welding is carried out from the second side,unsound weld metal is to be removed at the root by a suitablemethod.

104 Butt welding from one side only will be permitted afterspecial consideration where a backing run is not practicable orin certain structures when the stress level is low.

Fig. 1Manually welded butt joint edges

B 200 Lap joints and slot welds

201 Various types of overlapped joints are indicated in Fig.2.

Fig. 2Lap joints and slot welds

Type «a» (lap joint) is frequently used in end connection ofstiffeners. Unless the stresses are moderate, such overlaps willnormally not be accepted for connection of plates to panels.Type «b» (slot weld) may be used for connection of plating tointernal webs, where access for welding is not practicable.

For size of slot welds, see C600.

B 300 Tee or cross joints

301 The connection of girder and stiffener webs to plate pan-el as well as plating abutting on another plate panel, is normal-ly to be made by fillet welds as indicated in Fig. 3.


DET NORSKE VERITAS

Fig. 3Tee or cross joints

Where the connection is highly stressed or otherwise consid-ered critical, the edge of the abutting plate may have to be bev-elled to give deep or full penetration welding, see also C203.Where the connection is moderately stressed, intermittentwelds may be used. With reference to Fig. 4, the various typesof intermittent welds are as follows:

— chain weld— staggered weld— scallop weld (closed).

For size of welds, see C500.

Fig. 4Intermittent welds

302 Double continuous welds are required in the followingconnections irrespective of the stress level:

— weathertight, watertight and oiltight connections— connections in foundations and supporting structures for

machinery— all connections in after peak— connections in rudders, except where access difficulties

necessitate slot welds— connections at supports and ends of stiffeners, pillars,

cross ties and girders— centre line girder to keel plate.

303 Where intermittent welds are accepted, scallop weldsare to be used in tanks for water ballast, cargo oil or fresh wa-ter. Chain and staggered welds may be used in dry spaces andtanks arranged for fuel oil only.

When chain and staggered welds are used on continuous mem-bers penetrating oil- and watertight boundaries, the weld termi-nation towards the tank boundary is to be closed by a scallop,see Fig.5.

Fig. 5Weld termination towards tank boundary

C. Size of Weld Connections

C 100 Continuous fillet welds, general101 Unless otherwise stated, it is assumed that the weldingconsumables used will give weld deposit with yield strengthσfw as follows:

σ fw = 355 N/mm2 for welding of normal strength steel = 375 N/mm2 for welding of the high strength steels NV-

27, NV-32 and NV-36 = 390 N/mm2 for welding of high strength steel NV-40.

If welding consumables with deposits of lower yield strengththan specified above are used, the σfw-value is to be stated onthe drawings submitted for approval. The yield strength of theweld deposit is in no case to be less than required in Pt.2 Ch.3.

For welding of the high strength steels NV-32, NV-36 and NV-40, welding consumables with deposits of higher yield strengththan specified above may be used. The weld dimensions forthese steels are, however, in no case to be based on σfw-valueshigher than 1,5 times the yield strength of the material to bewelded.

102 When deep penetrating welding processes are applied,the required throat thicknesses may be reduced by 15% provid-ed sufficient weld penetration is demonstrated.

103 The throat thickness of double continuous fillet welds isnot to be less than:

C = weld factor given in Table C1t0 = net thickness in mm of abutting plate, corrosion addi-

tion not included = t – tk, where:

t = gross thickness of abutting plate in mmtk = corrosion addition in mm, see Sec.2 D

= 0,5 ( 25 + t – tk ) for net plate thicknesses (t – tk) above25 mm

fpm = material factor f1 as defined in Sec.2 B100 for plates tobe joined

fw = material factor for weld deposit

=

σfw = yield strength in N/mm2 of weld deposit

tw

C fpm t0

fw-------------------------- 0 5tk (mm),+=

σfw

235---------

� ��

0 75,


DET NORSKE VERITAS

When welding consumables with deposits as assumed in 101are used, fw may be taken as follows dependent on parent ma-terial:

fw = 1,36 for NV-NS = 1,42 for NV-27, NV-32 and NV-36 = 1,46 for NV-40.

104 The throat thickness of fillet welds is in no case to betaken less than given in Table C2:

C 200 Fillet welds and penetration welds subject to high tensile stresses201 In structural parts where high tensile stresses act throughan intermediate plate (see Fig. 3) increased fillet welds or pen-etration welds are to be used. Examples of such structures are:

— transverse bulkhead connection to the double bottom— vertical corrugated bulkhead connection to the top of

stooltank or directly to the inner bottom— stooltanks to inner bottom and hopper tank— structural elements in double bottoms below bulkhead and

stooltanks— transverse girders in centre tanks to longitudinal bulk-

heads.

202 The throat thickness of double continuous welds is notto be less than:

tw = C1 to + 0,5 tk (mm)

C1 =

σ = calculated maximum tensile stress in abutting plate inN/mm2

r = root face in mmto = net thickness in mm of abutting plate, corrosion addi-

tion not included, as given in 103fw = as given in 103.

Typical design values for C1 are given in Table C3.

203 Full penetration welds are in any case to be used in thefollowing connections:

— rudder horns and shaft brackets to shell structure— rudder side plating to rudder stock connection areas— end brackets of hatch side coamings to deck and coaming— edge reinforcements or pipe penetrations to strength deck

(including sheer strake) and bottom plating within 0,6 Lamidships, when transverse dimension of opening exceeds300 mm, see Fig. 6.

— abutting plate panels (see Fig. 3) forming boundaries tosea (including top and partial bulkheads). For thickness tabove 12 mm, penetration weld with root face r = t/3 maybe accepted.

Fig. 6Deck and bottom penetrations

C 300 End connections of girders, pillars and cross ties301 The weld connection area of bracket to adjoining girdersor other structural parts is to be based on the calculated normaland shear stresses. Double continuous welding is to be used.Where large tensile stresses are expected, welding according to200 is to be applied.

302 The end connections of simple girders are to satisfy therequirements tor section modulus given for the girder in ques-tion. Where high shear stresses in web plates, double continu-ous boundary fillet welds are to have throat thickness not lessthan:

τ = calculated shear stress in N/mm2

Table C1 Weld factor CItem 60% of

span At ends

Local buckling stiffeners 0,14 0,14Stiffeners, frames, beams or longitudinals to shell, deck, o.t. or w.t. girders or bulkhead plating, except in after peaks

0,16 0,26

Web plates of non-watertight girders except in after peaks 0,20 0,32

Girder webs and floors in double bottom Stiffeners and girders in after peaks 0,26 0,43

Watertight centre line girder to bottom and in-ner bottom plating

Boundary connection of ballast and liquid car-go bulkhead:

— longitudinal bulkheads— transverse bulkheads

Hatch coamings at corners and transverse hatch end brackets to deck. Top horizontal profile to coaming Strength deck plating to shell Scuppers and discharges to deck

0,52

Fillet welds subject to compressive stresses only 0,25

All other welds not specified above or in 200 to 400 0,43

Table C2 Minimum throat thicknessPlate thickness

(web thickness) t0 (mm)Minimum throat thickness

(mm) 1)

t0 ≤ 4 2,04 < t0 ≤ 6,5 2,5

6,5 < t0 ≤ 9,0 2,759,0 < t0 ≤ 12,5 3,0

t0 > 12,5 0,21 t0, minimum 3,25 2)

1) Corrosion addition 0,5 tk to be added where relevant, see Sec.2 D.

2) 0,18 t0, minimum 3,0 when automatic deep penetration welding is ap-plied.

Table C3 Values of C1

Plate material σ

C1Fillet weld:

r=toDeep or partial

penetration weld with root face:

r=to/3

Full penetration

weld: r=0

NSNV-32NV-36

160 205222

0,540,680,74

0,31 0,35 0,37

0,200,190,18

1 36,fw

------------ 0 2, σ270--------- 0 25,–

� �� r

t0----+

tw

t0τ200fw--------------- 0 5tk (mm),+=


DET NORSKE VERITAS

to = net thickness of abutting plate, corrosion addition notincluded, as given in 103

fw = as given in 103.

303 End connection of pillars and cross ties are to have aweld area not less than:

A = load area in m2 for pillar or cross tiep = design pressure in kN/m2 as given for the structure in

questionak = corrosion addition corresponding to tkfw = as given in 103k = 0,05 when pillar in compression only = 0,14 when pillar in tension.

C 400 End connections of stiffeners

401 Stiffeners may be connected to the web plate of girdersin the following ways:

— welded directly to the web plate on one or both sides of theframe

— connected by single- or double-sided lugs— with stiffener or bracket welded on top of frame— a combination of the above.

In locations with great shear stresses in the web plate, a double-sided connection or a stiffening of the unconnected web plateedge is normally required. A double-sided connection may betaken into account when calculating the effective web area.

402 The connection area at supports of stiffeners is normallynot to be less than:

ao = c k (l – 0,5 s) s p (cm2)

c = factor as given in Table C4k = r1 r2r1 = 0,125 when pressure acting on stiffener side = 0,1 when pressure acting on opposite sider2 = 1,0/fpm for stiffeners with mainly loading from one

side (pressure ratio less than 0,3 or greater than 3,3) = 1,0 for stiffeners with loading from two sidesf pm = material factor f1 as defined is Sec.2 B100 for platel = span of stiffener in ms = spacing between stiffeners in mp = design pressure in kN/m2.

Corrosion addition as specified in Sec.2 D200 is not includedin the formulae for ao, and is to be added where relevant.

Weld area is not to be less than:

ak = corrosion addition corresponding to tkfw = as given in 103.

Fig. 7End connections

403 Various standard types of connections are shown inFig.7.

Other types of connection will be considered in each case.

Guidance note:In ballast and cargo tanks the connection types b or c should beused for longitudinals on ship sides, unless double-sided bracketsare arranged, see also Sec.7 E500.


404 Connection lugs are to have a thickness not less than75% of the web plate thickness.

405 Lower ends of peak frames are to be connected to thefloors by a weld area not less than:

a = 0,105 l s p + ak (cm2)

l, s, p and ak = as given in 402.

406 For stiffeners which may be sniped at the ends accordingto the requirements given in Sec.3 C202, the required connec-tion area is satisfied by the plating.

407 Bracketed end connections as mentioned below, are tohave a weld area not less than:

Z = net section modulus of stiffener in cm3, corrosion ad-dition not included

h = stiffener height in mmk = 24 for connections between supporting plates in dou-

ble bottoms and transverse bottom frames or reversedframes

= 25 for connections between the lower end of mainframes and brackets (Minimum weld area = 10 cm2)

= 15 for brackets fitted at lower end of 'tween deckframes, and for brackets on stiffeners

= 10 for brackets on 'tween deck frames carried throughthe deck and overlapping the underlying bracket

ak = corrosion addition corresponding to tk.

Table C4 Values of cType of

connection (see figure)

Stiffener/bracket on top of stiffener

None Single- sided

Double- sided

a b c

1,00 0,90 0,80

1,25 1,15 1,00

1,00 0,90 0,80

ak A p

fw-------------- ak (cm

2)+=

a1 15a0 fpm,

fw-------------------------------- ak (cm

2)+=

akZh

------- ak (cm2)+=


DET NORSKE VERITAS

408 Brackets between transverse deck beams and frames orbulkhead stiffeners are to have a weld area not less than:

tb = net thickness in mm of bracketZ = as defined in 407ak = as defined in 407.

409 The weld area of brackets to longitudinals is not to beless than the sectional area of the longitudinal. Brackets are tobe connected to bulkhead by a double continuous weld.

C 500 Intermittent welds

501 The throat thickness of intermittent fillet welds is not tobe less than:

C, t0, fpm and fw are as given in 103. C-values given for 60%of span may be applied.

d = distance, in mm, between successive welds, see Fig. 4l = length, in mm, of weld fillet, not to be less than 75 mm.

502 In addition to the minimum requirements in 501, the fol-lowing apply:

— for chain intermittent welds and scallop welds the throatthickness is not to exceed 0,6 t0

— for staggered intermittent welds the throat thickness is notto exceed 0,75 t0.

C 600 Slot welds601 Slots are to have a minimum length of 75 mm and, nor-mally, a width of twice the plate thickness. The ends are to bewell rounded, see Fig. 2. The distance d between slots is not toexceed 3 l, maximum 250 mm.

602 Fillets welds in slots are to have a throat thickness asgiven by the formula in 501 with:

t0 = net thickness of adjoining web plated = distance between slots, see Fig. 2l = length of slots.

603 Slots through plating subject to large in-plane tensilestresses across the slots may be required to be completely filledby weld. More narrow slots with inclined sides (minimum 15°to the vertical) and a minimum opening of 6 mm at bottomshould then be used. A continuous slot weld may, however, insuch cases be more practical.

a 0 41 Z tb, ak (cm2)+=

tw

C fpm t0

fw------------------------- d

l--- 0 5 tk (mm),+=


DET NORSKE VERITAS

SECTION 13DIRECT STRENGTH CALCULATIONS

A. General

A 100 Introduction101 In the preceding sections the scantlings of various pri-mary and secondary hull structures have been given explicitly,based on design principles outlined in Sec.3 B. In some casesdirect strength or stress calculations have been referred to inthe text.

This section describes loads, acceptance criteria and requireddocumentation of direct strength calculations. Loading condi-tions and specific scope of analysis are given in Pt.5 for the dif-ferent class notations. Instructions related to model and modelextent for such analysis are described in detail in classificationnotes for the considered type of vessel.

A 200 Application201 The application of direct stress analysis is governed by:

— required as part of rule scantling determination.

When simplified formulations do not take into accountspecial stress distributions, boundary conditions or struc-tural arrangements with sufficient accuracy, direct stressanalysis has been required in the rules. These analysesmay be performed by finite element analyses or beamanalyses if finite element analysis has not been specificallyrequired elsewhere in the rules.

— as supplementary basis for the scantlings.

202 For ships where direct calculations for the midship re-gion based on finite element methods are required in the rules,such analysis are to be performed with a scope sufficient for at-taining results as listed below:

— relative deflections of deep supporting members such asfloors, frames and girders

— stresses in transverse bulkheads— stresses in longitudinal bottom, side, bulkhead and deck

girders— stresses in transverse bottom, side, bulkhead and deck

girders— stresses in girders and stringers on transverse bulkheads— stresses in brackets in connection with longitudinal and

transverse or vertical girders located on bottom, side, deckor bulkhead structures

— stresses in stiffeners where the stiffeners' supports are sub-jected to large relative deflections

— stresses in brackets in connection with longitudinal andtransverse stiffeners located on bottom, side, decks orbulkhead structures.

The stresses are not to exceed the acceptance criteria given inB400.

Hull girder normal stresses and hull girder shear stresses arenot to be considered directly from the analysis unless specialboundary conditions and loads are applied to represent the hullgirder shear forces and hull girder bending moments correctly.

Further descriptions of such calculations are given in subsec-tions D, E and F.

A 300 Documentation301 When direct strength analyses are submitted for infor-mation, such analyses are to be supported by documentationsatisfactory for verifying results obtained from the analyses.

302 The documentation for verification of input is to containa complete set of information to show the assumptions made

and that the model complies with the actual structure. The doc-umentation of the structure may be given as references todrawings with their drawing numbers, names and revisionnumbers. Deviations in the model compared with the actualgeometry according to these drawings are to be documented.

303 The modelled geometry, material parameters, platethickness, beam properties, boundary conditions and loads areto be documented preferably as an extract directly from thegenerated model.

304 Reaction forces and displacements are to be presented tothe extent necessary to verify the load cases considered.

305 The documentation of results is to contain all relevantresults such as:

— type of stress (element/nodal, membrane/surface, normal/shear/equivalent)

— magnitude— unit— load case— name of structure— structural part presented.

306 Evaluation of the results with respect to the acceptancecriteria is to be submitted for information.

B. Calculation Methods

B 100 General

101 For girders which are parts of a complex 2- or 3-dimen-sional structural system, a complete structural analysis mayhave to be carried out to demonstrate that the stresses are ac-ceptable when the structure is loaded as described in 300.

102 Detailed requirements for the extent of direct calcula-tions have (as applicable) been given in Pt.5 for the variousclass notations. These requirements may, subject to specialconsideration in each case, be required to be applied also forships of related types, even if the particular class notation hasnot been requested.

103 Calculation methods and computer programs applied areto take into account the effects of bending, shear, axial and tor-sional deformations. The calculations are to reflect the struc-tural response of the 2- or 3-dimensional structure considered,with due attention to:

— boundary conditions— shear area and moment of inertia variation— effective flange— effect of relative support deflections— effects of bending, shear and axial deformations— influence of end brackets.

For deep girders, bulkhead panels, bracket zones, etc. whereresults obtained by applying beam theory are unreliable, finiteelement analysis or equivalent methods are to be applied.

104 The objectives of analyses together with their applicableacceptance criteria are described in C to F for the followinglevels of calculations:

— global analysis— cargo hold/tank analysis— frame and girder analysis— local structure analysis.


DET NORSKE VERITAS

105 For structures as decks, bulkheads, hatch covers, rampsetc., a direct calculation may generally be undertaken as aframe and girder analysis as described in E, supplemented bylocal structure analyses as described in F, if necessary.

106 Corrosion additions, tk, are to be deducted from the ma-terial thickness.

107 Areas representing girder flanges are to be adjusted foreffective width in accordance with Sec.3 C400.

108 The element mesh fineness and element types used in fi-nite element models are to be sufficient to allow the model torepresent the deformation pattern of the actual structure withrespect to matters such as:

— effective flange (shear lag)— bending deformation of beam structures— three-dimensional response of curved regions.

Acceptable calculation methods, including mesh fineness in fi-nite element models are given in relevant classification notes.The acceptance criteria given in 400 are closely related to theprocedures given in the classification notes.

B 200 Computer program

201 The calculations specified in the requirements are to becarried out by computer programs supplied by, or recognisedby the Society. Programs applied where reliable results havebeen demonstrated to the satisfaction of the Society are regard-ed as recognised programs.

B 300 Loading conditions and load application

301 The calculations are to be based on the most severe real-istic loading conditions with the ship:

— fully loaded— partly loaded— ballasted— during loading/discharging.

302 General design loads are given in Sec.4 and design loadsfor specific structures are given in Sec.6 to Sec.10.

303 Local dynamic loads are to be taken at a probability ofexceedance of 10-4, when used together with acceptance crite-ria as given in 400.

304 For sea-going conditions realistic combinations of exter-nal and internal dynamic loads are to be considered.

305 For harbour conditions, only static loads need to be con-sidered. Harbour conditions with asymmetric loading are rele-vant to the extent that they do not result in unrealistic heeling.

306 External sea pressures in the upright seagoing conditionare to be taken in accordance with Sec.4 C200 with h0 definedas follows.

h0 = vertical distance in m from the waterline considered tothe load-point.

307 In harbour conditions, the external sea pressure, p is tobe taken as:

p = 10 h0 (kN/m2)

308 The external sea pressures, p, in heeled conditions arenormally to be taken as:

p = 10 (Ta– z) + 6,7 y tan (ϕ/2) (kN/m2)

on submerged sidep = 10 (Ta– z) – 10 y tan (ϕ/2) (kN/m2)

on emerged side = 0 minimum.

Ta = actual considered draught in mz = vertical distance in m from base line

y = transverse distance in m from centre lineϕ = as given in Sec.4 B.

309 The liquid pressure in tanks in the upright condition isnormally to be taken as given in Sec.4 C300 (5).

310 In heeled condition, the liquid pressure in tanks, p, is tobe taken as:

ρ = liquid density in t/m3

hs = height in m from load point to top of hold (includinghatch coaming) or tank with the vessel on even keel

b = athwartships distance in m with the vessel on even keelfrom load point to the point which represents the top ofthe tank when the ship is heeled to an angle of 0,5 ϕ

H = height of hold (including hatch coaming) or tank in mwith the vessel on even keel

bt = breadth of top of tank or hold in meter with the vesselon even keel

ϕ = as given in Sec.4 B.

311 Pressures and forces from cargo and heavy units are gen-erally to be taken as given in Sec.4, C400 and C500. The pres-sure from dry bulk cargoes is, however, generally to be takenas:

p = ρ (g0 + 0,5 av) K hc (kN/m2)

K = sin2 α tan2 (45 – 0,5 δ ) + cos2 α

ρ = stowage rate of cargo in t/m3

α = angle between panel in question and the horizontalplane in degrees

av = as given in Sec.4 B, generally = 0 in static loading conditionsδ = angle of repose of cargo in degreeshc = vertical distance in m from the load point to the hold

boundary above, in general. When a partly filled holdis considered, the hc is to be measured to the cargo sur-face, taking due consideration of the untrimmed coni-cal shape of the cargo volume within the hold

= as given in Sec.9 B100 for cargo bulkhead structures.

For watertight bulkheads between cargo holds, the pressureload, p, is to be taken as given in Sec.9 B100.

312 The mass of deck structures is generally to be includedwhen greater than 5% of the applied loads. Vertical accelera-tion is to be included when relevant.

B 400 Acceptance criteria401 The expressions related to nominal stress componentsare defined as follows:

Hull girder stresses consist of nominal normal and shearstresses. Hull girder normal stresses are those stresses resultingfrom hull-girder bending and may generally be determined bya simple beam method, disregarding shear lag and effects ofsmall deck openings etc. Hull girder shear stresses are thoseshear stresses caused by the unbalanced forces in the vertical,horizontal and longitudinal directions along the vessel, that aretransferred to the hull girder with the vessel in an equilibriumcondition. The hull girder may be defined as effective longitu-dinal material such as bottom, inner bottom, decks, side andlongitudinal bulkheads.

Transverse or longitudinal bottom, side, bulkhead or deckgirder nominal stresses consist of normal and shear stresses.These stresses are to be determined by performing a 3-dimen-sional finite element analysis or a beam analysis. Transverse orlongitudinal bottom, side, bulkhead or deck girder normalstresses are those stresses resulting from bending of large stiff-ened panels between longitudinal and transverse bulkheadsdue to local loads in a cargo hold or tank. The nominal normal

p g0ρ hs 0 5φb 0 1 ϕHbt,–,+( ) (kN/m2 )=


DET NORSKE VERITAS

stresses of girders are to include the effect of shear lag and ef-fectivity of curved and unsymmetrical flanges. Transverse orlongitudinal bottom, side, bulkhead or deck girder shearstresses are those stresses caused by an unbalanced force with-in a tank or a hold and carried in girders as mentioned, to thegirder supports. The nominal shear stress of girders is general-ly defined as the mean shear stress of the effective shear carry-ing areas of the girder web.

Stiffener nominal stresses are those stresses resulting from lo-cal bending of longitudinals between supporting members, i.e.floors and girders web frames etc. The stresses include thosedue to local load on the stiffener and those due to relative de-flections of the supporting ends. The stiffener stress may be re-garded as a nominal bending stress without consideration ofeffective width of flanges and warping of unsymmetrical stiff-eners.

402 The final thickness of the considered structure is not tobe less than the minimum thickness given in Sec.6 to Sec.10,regardless of the acceptance criteria presented in the following.

403 The equivalent stress σe, taken as the local bendingstresses combined with in plane stresses, in the middle of a lo-cal plate field is not to exceed 245 f1 N/mm2. The local bend-ing in the middle of the plate field is not to exceed 160 f1 N/mm2. σe is defined in 409.

404 The allowable nominal stresses may be taken as given inTable B1. Buckling strength with usage factors as given inSec.14 is generally to be complied with.

405 The allowable nominal girder stresses in a flooded con-dition may be taken as 220 f1 for normal stresses and 120 f1 forshear stresses.

406 The longitudinal combined stress taken as the sum ofhull girder and longitudinal bottom, side or deck girder bend-ing stresses, is normally not to exceed 190 f1 N/mm2. The hullgirder stresses may in general be calculated as given in Sec.5C300, applying relevant combinations of hogging and saggingstresses, and with wave bending moments taken as given inSec.5 B204.

407 During preliminary strength calculations of longitudinalstiffeners in double bottom the values of longitudinal bottomgirder stresses may normally be taken as follows:

Normal stress, light bulk cargoes:

σ = 20 f1 (N/mm2)

Normal stress, ballast condition:

σ = 50 f1 (N/mm2)

Normal stress, liquid cargo condition:

b = breadth of double bottom in m between supporting sideand/or bulkheads.

Higher local normal stresses than given above may be acceptedprovided the combined stress including hull girder stress andlongitudinal bottom girder stress, as given in Table B1 and402, are complied with.

408 The allowable stresses given in Table B1 assume thatappropriate considerations and conditions are taken with re-spect to the model definition and result analysis. In particularthe following should be noted:

1) Calculated stresses based on constant stress elements mayhave to be considered with respect to the stress variationwithin each element length.

2) The allowable nominal stresses, given in Table B1, do notrefer to local stress concentrations in the structure or to lo-cal modelling deficiencies in finite element models. Theallowable stresses do neither refer to areas where the mod-el is not able to describe the structure's response properlydue to geometrical simplifications or insufficiencies of theelement representation.

3) The allowable shear stresses given in Table B1 may beused directly to assess shear stresses in girder webs clearof openings not represented in the model. In way of areaswith openings, the nominal shear stress is normally to bederived as given in Sec.3 C500, based on the integratedshear force over the girder web height.

4) Equivalent stresses for girder webs of longitudinal struc-tures are not to be considered in relation to the allowablelimits given in Table B1, unless global forces and mo-ments are applied.

5) Peak stresses obtained by fine mesh finite element calcu-lations may exceed the values stated above in local areasclose to stress concentration points. The allowable peakstress is subject to special consideration in each case.

409 The equivalent stress is defined as follows:

σx = nominal normal stress in x-directionσy = nominal normal stress in y-directionτ = shear stress in the x-y-plane.

σ85 b f1

B--------------- (N/mm

2 )=

σe σx2 σy

2 σxσy– 3τ2+ +=


DET NORSKE VERITAS

C. Global Analysis

C 100 General101 A global analysis covers the whole ship.

102 A global analysis may be required if the structural re-sponse can otherwise not be sufficiently determined, e.g. forships with large deck openings subjected to overall torsionaldeformation and stress response. A global analysis may also berequired for ships without or with limited transverse bulkheadstructures over the vessel length, e.g. Ro-Ro vessels and carcarriers.

Guidance note:For open type ships with large deck openings with total width ofhatch openings in one transverse section exceeding 65 % ofship's breadth, or length of hatch openings exceeding 75 % ofhold length, a torsional calculation covering the entire ship hulllength may have to be carried out.


103 Global analyses are generally to be based on loadingconditions that are representative with respect to the responsesand failure modes to be evaluated, e.g.: normal stress, shearstress and buckling.

104 If a global analysis is required for the evaluation of thefatigue life of critical members of the hull structure, designload conditions and criteria may be based on ClassificationNote No. 30.7.

105 Design loading conditions and acceptance criteria may,subject to special consideration in each case, be taken in ac-cordance with Sec.16.

C 200 Loading conditions201 The selection of loading conditions and the applicationof loads will depend on the scope of the analysis. Directly cal-culated loads, torsion loads or racking loads may have to be ap-plied.

C 300 Acceptance criteria301 If the applied load condition is relevant for the longitu-dinal hull girder and main girder system, nominal and localstresses derived from a global analysis are to be checked ac-cording to the acceptance criteria given in B400.

Other acceptance criteria may be relevant depending on thetype of analysis and applied loads.

D. Cargo Hold or Tank Analysis

D 100 General101 A cargo tank or hold analysis may be used to analyse de-formations and nominal stresses of primary hull structuralmembers. The model and the analysis are to be designed andperformed in a suitable way for obtaining results as listed be-low. Acceptable methods are described in detail in classifica-tion notes related to the considered type of vessel.

— stresses in transverse bulkheads— stresses in longitudinal bottom, side, bulkhead and deck

girders (see Guidance note)— stresses in transverse bottom, side, bulkhead and deck

girders (see Guidance note)

Table B1 Allowable nominal stresses

StructureSeagoing or

harbour condition

Type of stress

Normal stress σ (N/mm2)

Shear stress τ (N/mm2)

Equivalent stress

σe (N/mm2)

Hul

l gir

der

stre

sses

Tra

nsve

rse

bott

om, s

ide

or d

eck

gird

er s

tres

ses

Lon

gitu

dina

l bot

tom

, sid

e or

dec

k gi

rder

str

esse

s

Loc

al s

tiff

ener

ben

ding

st

ress

es

One plate flange

Two plate flanges

Longitudinalgirders

Seagoing X1) X 190 f1 90 f1 100 f1Harbour X1) X 190 f1 100 f1 110 f1

Transverse and vertical girders

Seagoing X 160 f1 90 f1 100 f1 180 f1Harbour X 180 f1 100 f1 110 f1 200 f1

Girder bracketsSeagoing (X) (X) 200 f1

2)

Harbour (X) (X) 220 f12)

Longitudinal stiffeners

Seagoing and harbour X 160 f1

Seagoing and harbour X X 180 f1 90 f1

Seagoing and harbour X1) X X 245 f1

Transverse and vertical stiffeners

Seagoing and harbour (X) (X) X 180 f1

Stiffener brackets Seagoing and harbour (X) (X) X 225 f1

X Stress component to be included

(X) Stress component to be included when relevant

1) Includes the hull girder stresses at a probability of exceedance of 10-4, see 406.

2) Shows allowable stress in the middle of the the bracket's free edge. For brackets of unproven design, additional stress analysis in way of stress concetration areas may be required. Reference is made to acceptance criteria for local structure analysis, F300.


DET NORSKE VERITAS

— stresses in girders and stringers on transverse bulkheads— relative deflections of deep supporting members as floors,

frames and girders.

Guidance note:Shear stresses of plate flanges of the mentioned girders formingships' sides or longitudinal bulkheads are not to be taken from themodel unless special boundary conditions are applied to repre-sent the global shear forces correctly.



102 A cargo hold or tank analysis, carried out for the midshipregion, will normally be considered applicable also outside ofthe midship region. However, special direct calculations ofgirder structures outside of the midship region may be requiredif the structure or loads are substantially different from that ofthe midship region.

D 200 Loading conditions and load application201 Selection of design loading conditions and applicationof local loads are given in B300.

D 300 Acceptance criteria301 For the main girder system, nominal and local stressesderived from a cargo hold or tank analyses are to be checkedaccording to the acceptance criteria given in B400.

E. Frame and Girder Analysis

E 100 General101 A frame and girder analysis may be used to analysestresses and deformations in the framing and girder systemswithin or outside of the midship region. The model and theanalysis are to be designed and performed in a suitable way forobtaining results as listed below. Acceptable methods are de-scribed in detail in classification notes related to the consideredtype of vessel.

— stresses in longitudinal bottom, side and deck girders(when relevant)

— stresses in transverse bottom, side and deck girders (whenrelevant)

— stresses in girders and stringers on transverse bulkheads(when relevant)

— stresses in brackets in connection with longitudinal, trans-verse or vertical girders located on bottom, side, deck orbulkhead structures.

However, shear stresses in plate flanges of the mentioned gird-ers, forming ships' sides, inner sides or longitudinal bulkheadsare not to be taken from the model unless special boundaryconditions are applied to represent the global shear forces cor-rectly.

102 The analysis may be included as a part of a larger 3- di-mensional analysis, or run separately with prescribed bounda-

ry assumptions, deformations or forces. Prescribed boundarydeformations may be taken from a cargo hold or tank analysisas described in subsection D.

E 200 Loading conditions and load application201 Selection of design loading conditions and applicationof local loads are given in B300.

E 300 Acceptance criteria301 For the main girder system, nominal and local stressesderived from a frame and girder analysis are to be checked ac-cording to the acceptance criteria given in B400.

302 In way of local stress concentrations, and at local struc-tural details where the finite element model does not representthe local response sufficiently, the structure may for provendesign details be accepted based on the nominal stress re-sponse of the adjacent structures.

F. Local Structure Analysis

F 100 General101 A local structure analysis may be used to analyse nomi-nal stresses in laterally loaded local stiffeners and their con-nected brackets, subject to relative deformation betweensupports. The model and the analysis are to be designed andperformed in a suitable way for obtaining results as listed be-low:

— nominal stresses in stiffeners— stresses in brackets' free edge.

Acceptable methods are described in detail in classificationnotes related to the considered type of vessel.

102 The analysis may be included as a part of a larger 3-di-mensional analysis, or run separately with prescribed bounda-ry assumptions, deformations or forces. Prescribed boundarydeformations may be taken from a cargo hold or tank analysisas described in D.

F 200 Loading conditions and load application201 Selection of design loading conditions and applicationof local loads are given in B300.

202 The most severe loading condition among those relevantfor the cargo hold or tank analysis or the frame and girder anal-ysis, are to be applied for the structure in question.

203 If the local structure analysis is run separately, pre-scribed boundary deformations or forces, taken from the cargohold or tank analysis or the frame and girder analysis are to beapplied. Local loads acting on the structure are to be applied tothe model.

F 300 Acceptance criteria301 Allowable nominal stresses are in general given inB400, Table B1.

302 The equivalent nominal allowable stress for bracketsconnected to longitudinal stiffeners may be taken as σe = 245f1, when longitudinal stresses are included.


DET NORSKE VERITAS

SECTION 14BUCKLING CONTROL

A. General

A 100 Introduction101 In this section requirements to buckling control of plat-ing subject to in-plane compressive and/or shear stresses aswell as axially compressed stiffeners and pillars are given.

102 The buckling strength requirements are related to:

— longitudinal hull girder compression and shear stressesbased on design values of still water and wave bendingmoments and shear forces

— axial forces in pillars, supporting bulkheads and pantingbeams based on the rule loads

— axial and shear forces in primary girders based on the ruleloads.


t = thickness in mm of platings = shortest side of plate panel in ml = longest side of plate panel in m = length in m of stiffener, pillar etc.E = modulus of elasticity of the material = 2,06 105 N/mm2 for steelσel = the ideal elastic (Euler) compressive buckling stress in

N/mm2

σf = minimum upper yield stress of material in N/mm2, andis not to be taken less than the limit to the yield pointgiven in Sec.2 B201.

τel = the ideal elastic (Euler) shear buckling stress in N/mm2

σc = the critical compressive buckling stress in N/mm2

τc = the critical shear stress in N/mm2

σa = calculated actual compressive stress in N/mm2

τa = calculated actual shear stress in N/mm2

η = stability (usage) factor =







= 1,43 for NV-40 steel. 1)

1) For details see Sec.2 B and C .

B. Plating

B 100 General101 Local plate panels between stiffeners may be subject touni-axial or bi-axial compressive stresses, in some cases alsocombined with shear stresses. Methods for calculating the crit-ical buckling stresses for the various load combinations aregiven below.

102 Formulae are given for calculating the ideal compressivebuckling stress σ el. From this stress the critical buckling stressσc may be determined as follows:

103 Formulae are given for calculating the ideal shear buck-ling stress τel. From this stress the critical buckling stress τcmay be determined as follows:

τf = yield stress in shear of material in N/mm2

= .

B 200 Plate panel in uni-axial compression

201 The ideal elastic buckling stress may be taken as:

For plating with longitudinal stiffeners (in direction of com-pression stress):

For plating with transverse stiffeners (perpendicular to com-pression stress):

c = 1,21 when stiffeners are angles or T-sections = 1,10 when stiffeners are bulb flats = 1,05 when stiffeners are flat barsc = 1,3 when the plating is supported by floors or deep

girders.

For double bottom panels the c-values may be multiplied by1,1.

ψ is the ratio between the smaller and the larger compressivestress assuming linear variation, see Fig. 1.

Fig. 1Buckling stress correction factor

σa

σc-----

τa

τc----=

σc σel when σe l

σf

2-----<=

σf 1σf

4σel-----------–


σf

2----->=

τc τel when τel

τ f

2----<=

τf 1τ f

4τel----------–

� �� when τel

τ f

2---- >=

σf

3--------

σel 0 9 k Et tk–

1000s--------------

� ��

2 (N/mm

2 ),=

k kl8 4,

ψ 1 1,+------------------- for 0 ψ 1≤ ≤( )= =

k ks c 1sl--

� ��

2+

22 1,

ψ 1 1,+------------------- for 0 ψ 1≤ ≤( )= =


DET NORSKE VERITAS

The above correction factors are not valid for negative ψ-val-ues.

The critical buckling stress is found from 102.

202 For plate panels stiffened in direction of the compressivestress and with circular cut-outs, the ideal buckling stress σ elis to be found by multiplying the factor kl with a reduction fac-tor r given as:

ψ = factor given in 201, Fig. 1d = diameter of cut-out, in m.

With edge reinforcement of thickness t at least equal to platethickness to, factor r may be multiplied by:

h = height of reinforcement, in mm.

203 For plate panels stiffened in direction of the compressivestress and with stadium formed cut-outs (see Fig. 2) the idealbuckling stress σ el is to be found by substituting the expres-sion for factor kl in 201 with the following:

(see Fig. 2)

ψ = as given in 201.

Fig. 2Stiffening in direction of compressive stress

Guidance note:

The formula for k should not be applied when

a/b < 1,5 and b/s < 0,35

An approximation to a circular opening as given in 202 may thenbe applied.


204 For plate panels stiffened perpendicular to the compres-sive stress and with stadium formed cut-outs (see Fig. 3) theideal buckling stress σ el may be found by multiplying the fac-tor ks with the reduction factor:

ψ = as given in 201.

Fig. 3Stiffening perpendicular to compressive stress

205 The critical buckling stress calculated in 201 is to be re-lated to the actual compressive stresses as follows:

σa = σa calculated compressive stress in plate panels. Withlinearly varying stress across the plate panel, is to betaken as the largest stress.

In plate panels subject to longitudinal stresses, σa isgiven by:

= minimum 30 f1 N/mm2 at side

η = 1,0 for deck, single bottom and longitudinally stiffenedside plating

= 0,9 for bottom, inner bottom and transversely stiffenedside plating

= 1,0 for local plate panels where an extreme load levelis applied (e.g. impact pressures)

= 0,8 for local plate panels where a normal load level isapplied

MS = stillwater bending moment as given in Sec.5MW = wave bending moment as given in Sec.5IN = moment of inertia in cm4 of the hull girder.

For reduction of plate panels subject to elastic buckling, see207.

MS and MW are to be taken as sagging or hogging values formembers above or below the neutral axis respectively.

For local plate panels with cut-outs, subject to local compres-sion loads only, σa is to be taken as the nominal stress in panelwithout cut-outs.

An increase of the critical buckling strength may be necessaryin plate panels subject to combined in-plane stresses, see 400and 500.

206 For ships with high speed and large flare in the forebody,the requirement for critical buckling stress σc of the strengthdeck as given in 205 is to be based on the following σ-valueforward of 0,3 L from F.P.:

σl1 = σ al as calculated in 205σl2 = 0 for CAF ≤ 0,4

r 1 0 5, 0 25ψ,+( ) ds---–=

0 8, 0 1ht0---- ,

ht--- 8≤,+

k0 58,

0 35ψ, 1+------------------------- s b–

2a-----------

� ��

2+ 1 2 7

ba---

� ��

2,+=

r 1 0 5, 0 25ψ,+( ) al-- (see Fig.3)–=

σc

σa

η-----≥

σal

MS MW+

IN------------------------ zn za–( )10

5 (N/mm

2)=

σal σl1 σl2 1x

0 3L,-------------–

� �� (N/mm

2)+=


DET NORSKE VERITAS

= 50 f1 N/mm2 for CAF ≥ 0,5x = distance in m from F.P. x need not be taken smaller

than 0,1 LC AF = as defined in Sec.5 B200.

For intermediate values of CAF the σl2 - value is to be variedlinearly.

207 Elastic buckling (σ el < σa/η) in plate panels may be ac-cepted after special consideration. An acceptable method forevaluating ultimate compressive stresses above the criticalbuckling stress in the elastic range (σ el < 0,50 σf) is given inAppendix A.

For plate panels taking part in the longitudinal strength the ef-fective width be is to be calculated according to Appendix Afor those panels sustaining elastic buckling. The area of eachpanel is to be reduced by the ratio be/b when calculating thehull girder moment of inertia inserted in the formula for ∆ MUin App.A B500. The MA-value to be applied is given by:

MA = MS + MW

MS and MW as given in 205.

Appendix A is not to be applied for plate panels subject to thecombined effect of compression and shear.

B 300 Plate panel in shear301 The ideal elastic buckling stress may be taken as:

kt =

The critical shear buckling stress is found from 103.

302 For plate panels with cut-outs the ideal buckling stress σ el is to be found by multiplying the factor kt with a reductionfactor r given as:

a) For circular cut-outs with diameter d:

With edge reinforcement of thickness t at least equal to theplate thickness t0, factor r may be multiplied by:

h = height of reinforcement.

Alternatively, with buckling stiffeners on both sides ofopening, factor r may be multiplied by 1,3

b) For rectangular openings the reduction factor may befound from Fig. 4. With edge reinforcement of thickness tat least twice the plate thickness and height at least equalto 8 t, the factor may be multiplied by 2,1.

Alternatively, with buckling stiffeners along the longeredges the factor may be multiplied by 1,4, with stiffenersalong the shorter edges by 1,5, see Fig. 5.

Fig. 4Buckling stress reduction factor

Fig. 5Buckling stiffeners

τel 0 9 kt Et tk–

1000s--------------

� ��

2 (N/mm

2),=

5 34, 4sl--

� ��

2+

r 1ds---–=

0 94, 0 023ht0---- ,

ht--- 8≤,+


DET NORSKE VERITAS

303 The critical shear stress calculated in 301 and 302 is tobe related to the actual shear stresses as follows:

τa = calculated shear stress. In plate panels in ship's sideand longitudinal bulkheads the shear stresses are givenin Sec.5 D.

For local panels in girder webs with cut-outs, τa is to betaken as the stress in web plate without cut-out

η = 0,90 for ship's side and longitudinal bulkhead subjectto hull girder shear forces

= 0,85 for local panels in girder webs when nominalshear stresses are calculated (τa = Q/A)

= 0,90 for local panels in girder webs when shear stressesare determined by finite element calculations or simi-lar.

An increase of the critical buckling strength may be necessaryin plate panels subject to combined in-plane stresses, see 400and 500.

B 400 Plate panel in bi-axial compression

401 For plate panels subject to bi-axial compression the in-teraction between the longitudinal and transverse bucklingstrength ratios is given by:

σ ax = compressive stress in longitudinal direction (per-pendicular to stiffener spacing s)

σ ay = compressive stress in transverse direction (perpen-dicular to the longer side l of the plate panel)

σ cx = critical buckling stress in longitudinal direction ascalculated in 200

σ cy = critical buckling stress in transverse direction as cal-culated in 200

ηx, ηy = 1,0 for plate panels where the longitudinal stress σ al (as given in 205) is incorporated in σax or σay

= 0,85 in other casesK = c β a

c and a are factors given in Table B1.

β =

n = factor given in Table B1.

For plate panels in structures subject to longitudinal stresses,such stresses are to be directly combined with local stresses tothe extent they are acting simultaneously and for relevant loadconditions. Otherwise combinations based on statistics may beapplied.

In cases where the compressive stress σax or σay is based on anextreme loading condition (dynamic loads at probability level10-8 or less) the corresponding critical buckling stress σcx or-σcy may be substituted by σux or σuy according to Appendix A.This is only relevant in the elastic range

(σc based on σ el < 0,65 σf).

B 500 Plate panel in bi-axial compression and shear

501 For plate panels subject to bi-axial compression and inaddition to in-plane shear stresses the interaction is given by:

σax, σay, σcx, σcy. ηx, ηy,K and n are as given in 401.

τa and τc are as given in 303.

Only stress components acting simultaneously are to be insert-ed in the formula, see also 401.

C. Stiffeners and Pillars

C 100 General

101 Methods for calculating the critical buckling stress forthe various buckling modes of axially compressed stiffenersand pillars are given below. Formulae for the ideal elasticbuckling stress σ el are given. From this stress the critical buck-ling stress σc may be determined as follows:

C 200 Lateral buckling mode

201 For longitudinals subject to longitudinal hull girdercompressive stresses, supporting bulkhead stiffeners, pillars,cross ties, panting beams etc., the ideal elastic lateral bucklingstress may be taken as:

IA = moment of inertia in cm4 about the axis perpendicularto the expected direction of buckling

A = cross-sectional area in cm2.

When calculating IA and A, a plate flange equal to 0,8 timesthe spacing is included for stiffeners. For longitudinals sup-porting plate panels where elastic buckling is allowed, theplate flange is not to be taken greater than the effective width,see B207 and Appendix A.

Where relevant tk is to be subtracted from flanges and webplates when calculating IA and A.

The critical buckling stress is found from 101.

The formula given for σ el is based on hinged ends and axialforce only.

If, in special cases, it is verified that one end can be regardedas fixed, the value of σ el may be multiplied by 2. If it is veri-fied that both ends can be regarded as fixed, the value of σ elmay be multiplied by 4.

In case of eccentric force, additional end moments or addition-al lateral pressure, the strength member is to be reinforced towithstand bending stresses.

202 For longitudinals and other stiffeners the critical buck-ling stress calculated in 201 is to be related to the actual com-pressive stress as follows:

Table B1 Values for c, a, nc a n

1,0 <l/s < 1,5 0,78 minus 0,12 1,01,5 ≤ l/s < 8 0,80 0,04 1,2

τc

τa

η----≥

σax

ηxσcx--------------- K

σaxσay

ηxηyσcxσcy-------------------------------

σay

ηyσcy---------------

� ��

n+– 1≤

1000s

t tk–-----------

σf

E-----

σax

ηxσcxq------------------ K

σaxσay

ηxηyσcxσcyq----------------------------------

σay

ηyσcyq------------------

� ��

n+– 1≤

q 1τa

τc----

� ��

2–=

σc σe l when σel

σf

2-----<=

σf 1σf

4σe l-----------–


σf

2----->=

σel 0 001 EIA

Al2

-------- (N/mm2),=


DET NORSKE VERITAS

σa = calculated compressive stress.

For longitudinals σa = σ al as given in B205. For shipswith high speed and large flare, see also B206

η = 0,85.

203 For pillars, cross ties and panting beams the criticalbuckling stress as calculated in 201 is not to be less than:

η =

P = axial load in kN as given for various strength membersin 204 and 205. Alternatively, P may be obtained fromdirect stress analysis, see Sec.13

l = length of member in m

i = radius of gyration in cm =

IA and A as given in 201k = 0,5 for pillars below exposed weather decks forward of

0,1 L from F.P. = 0,6 for pillars below weather decks when sea loads are

applied = 0,7 in all other cases.

204 The nominal axial force in pillars is normally to be takenas:

P = n F

n = number of decks above pillar. In case of a large numberof decks (n>3) a reduction in P will be consideredbased upon a special evaluation of load redistribution

F = the force contribution in kN from each deck above andsupported by the pillar in question given by:

F = p AD (kN)

p = design pressure on deck as given in Table B1 in Sec.8B

AD = deck area in m2 supported by the pillar, normally takenas half the sum of span of girders supported, multipliedby their loading breadth.

For centre line pillars supporting hatch end beams (seeFigs. 6 and 7):

b1 = distance from hatch side to ship's side.

205 The nominal axial force in cross ties and panting beamsis normally to be taken as:

P = e b p (kN)

e = mean value of spans in m on both sides of the cross tieb = load breadth in mp = the larger of the pressures in kN/m2 on either side of

the cross tie (e.g. for a side tank cross tie, the pressurehead on the ship's side may be different from that onthe longitudinal bulkhead).

Fig. 6Deck with transverse beams

Fig. 7Deck with longitudinals

C 300 Torsional buckling mode

301 For longitudinals and other stiffeners in the direction ofcompressive stresses, the ideal elastic buckling stress for thetorsional mode may be taken as:

K =

m = number of half waves, given by the following table:

IT = St Venant's moment of inertia in cm4 of profile (with-out plate flange)

= for flat bars (slabs)

σc

σa

η-----≥

σc10PAη--------- (N/mm

2 )=

k

1li-+

� �� -------------------- , minimum 0,3

IA

A-----

AD 4 A1 A2+( )b1

B----- when transverse beams=

4 A3 A4 A5+ +( )b1

B----- when longitudinals=

0 < K ≤ 4 4 < K ≤ 36 36 < K ≤ 144 K > 144m 1 2 3 4

σel

π2E IW

104

Ip l2

-------------------- m2 K

m2

-------+� �� 0 385 E

IT

IP----- (N/mm

2),+=

C l4

π4E IW

------------------106

hwtw3

3--------------10

4–


DET NORSKE VERITAS

=

for flanged profilesIP = polar moment of inertia in cm4 of profile about connec-

tion of stiffener to plate

= for flat bars

= for flanged profiles

IW = sectorial moment of inertia in cm6 of profile about con-nection of stiffener to plate

= for flat bars

= for T-profiles

=

for angles and bulb profileshw = web height in mmtw = web thickness in mmbf = flange width in mmtf = flange thickness in mm. For bulb profiles the mean

thickness of the bulb may be usedtp = thickness of supporting plate in mml = span of profile in ms = spacing of profiles in m.

Where relevant tk is to be substracted from all thicknesses (tw,tf and tp).

C = spring stiffness exerted by supporting plate panel

=

k = 1 – ηpa, not to be taken less than zero

ηp =

a = 2 in general = 1 for flat bar profilesσa = calculated compressive stress. For longitudinals, see

B205 and 206σ ep = elastic buckling stress of supporting plate as calculated

in B201.

For flanged profiles k need not be taken less than 0,2.

302 The critical buckling stress as found from 301 and 101 isnot to be less than:

σa = calculated compressive stress. For longitudinals σa =σel as given in B205. For ships with high speed andlarge flare, see also B206

η = 0,9 in general = 0,85 when the adjacent plating is allowed to buckle in

the elastic mode, according to B207.

C 400 Web and flange buckling

401 The σel -value required for the web buckling mode forflanged profiles may be taken as:

The critical buckling stress σc found from 101 is not to be lessthan as given in 302.

402 For flanges on angles and T-sections of longitudinals another highly compressed stiffeners the thickness is not to beless than:

tf = 0,1 bf + tk (mm)

bf = flange width in mm for angles, half the flange width forT-sections.

C 500 Transverse beams and girders

501 For beams and stiffeners supporting plating subject tocompressive stresses perpendicular to the stiffener directionthe moment of inertia of the stiffener section (including effec-tive plate flange) is not to be less than:

l = span in m of beams or stiffenerss = spacing in m of beams or stiffenerst = plate thickness in mmσel = 1,18 σa when less than σf/2

= otherwise

σa = actual compressive stress.

502 For transverse girders supporting longitudinals or stiff-eners subject to axial compression stresses the moment of in-ertia of the girder section (including effective plate flange) isnot to be less than:

S = span in m of girderl = distance in m between girderss = spacing in m of stiffenersIS = moment of inertia in cm4 of longitudinal or stiffener

necessary to satisfy the lateral buckling mode require-ment given in 201—202

=

σel = as given in 501A = as given in 201.

13--- hw tw

3bf tf

31 0 63

tf

bf----,–

� �� + 10

4–

hwtw3

3--------------10

4–

hw3

tw

3-------------- hw

2bf tf+

� � � �

104–

hw3

tw3

36-----------------10

6–

tf bf3

hw2

12---------------------10

6–

bf3hw

2

12 bf hw+( )2------------------------------- tf bf

22bfhw 4hw

2+ +( ) 3twbfhw+[ ] 10

6–

kEtp3

3s 11 33 k hw tp

3,

1000 s tw3

-----------------------------+� � � �

------------------------------------------------------103–

σa

σep--------

σc

σa

η-----≥

σe l 3 8 Etw tk–

hw---------------

� ��

2 (N/mm

2),=

I0 09 σa σel l

4s,

t--------------------------------------- (cm

4)=

σf2

4 σf 1 18σa,–( )--------------------------------------

I 0 3S

4

l3s

------ IS (cm4),=

σe l A l2

0 001 E,--------------------


DET NORSKE VERITAS

SECTION 15STRUCTURES FOR HIGH TEMPERATURE CARGO

A. General

A 100 Introduction

101 The rules in this section apply to ships intended to carryliquid cargo at a temperature higher than 80°C at atmosphericpressure.

102 The liquid cargo may be transported in integral cargotanks or independent cargo tanks, dependent of structure andstrength.

A list of cargoes which may be covered by these rules is givenin F.

103 Cargoes of different temperatures and natures are not tobe carried simultaneously in adjacent tanks or in the cargo areaunless especially investigated and accepted.

104 The temperature stresses in the cargo containment areawith surroundings are to be determined and documented, validboth for part-cargo and full-cargo conditions, see D.

105 Heat balance calculations for part-cargo and full-cargoconditions are also to be available, see D.

106 For a specific gravity of cargo exceeding 1,025 t/m3 ref-erence is made to Sec.4 C300.

107 The definitions of integral tank or independent tank aregiven in Pt.5 Ch.4 Sec.1 D.

108 Ships complying with these rules may be assigned theclass notation Tanker for Asphalt or Tanker for C, which-ever is applicable. See also Pt.5 Ch.3 and Ch.4.

A 200 Special features notations

201 Ships built according to these rules may be given the ad-ditional notation HOT e.g. HOT (...°C cargo tank no....).

202 Ships built for carrying cargoes with specific gravityheavier than sea water the additional notation HL(ρ) (cargotank no....) may be given, see Sec.4 C300.

A 300 Documentation

301 In addition to the required documentation given in Pt.5Ch.3 Sec.1 C or Pt.5 Ch.4 Sec.1 C, whichever is relevant, thefollowing documentation is to be submitted:

— heat balance calculations of the part-cargo or full-cargoconditions, including all the necessary input data

— heat capacity calculations— temperature distribution in the hull girder system for the

part-cargo and full-cargo conditions— stress analysis carried out based on the above temperature

distributions in the hull system. The extent of this calcula-tion is dependent on cargo containment system and cargotemperature. Combination of calculated conditions to rep-resent actual sea conditions is appreciated. Presentation ofresults as isoplot instead of listing is then a must

— specifications and data for insulation materials.

A 400 Survey and testing

401 See Sec.1 D, Pt.5 Ch.3 Sec.1 D or Pt.5 Ch.4 Sec.5 C,whichever is relevant.

A 500 Signboards

501 See Pt.5 Ch.3 Sec.1 E or Pt.5 Ch.4 Sec.1 F, whichever isrelevant.

B. Materials and Material Protection

B 100 Hull and tank material

101 See Sec.2. For mild steel and high strength steel therewill be a reduction in the yield strength at higher temperatures.This reduction is in the order of 20 N/mm2 per 50°C increasein temperature above 80°C and is to be taken into accountwhen calculating the strength.

102 The use of high strength steel in the cargo containmentarea may be advantageous or necessary to absorb the tempera-ture stresses added.

103 When calculating the f2b and f2d factors, see Sec.6 A 201and Sec.8 A 201, the elements in the hull structure intended tobuckle are to be excluded. Such elements may, however, be in-cluded when they are in tension.

B 200 Insulation material

201 Insulation materials used on board to reduce the heattransfer in the cargo area must be approved with regard to theability to withstand dynamic loads from the cargo, sticking, in-sulation etc.

B 300 Corrosion protection301 Ballast tanks within the cargo area or adjacent to the car-go area are to be coated to prevent corrosion.

Guidance note:The coating material must be compatible with expected environ-mental conditions e.g. resistive against heat, elastic against ex-pansion.


Corrosion additions above table values given in Sec.2 D200should be considered.

Particular attention is to be paid to the upper part of side tanks,hot sides of ballast tanks and upper deck subject to the salt at-mosphere.

C. Ship Arrangement

C 100 Location and separation of spaces101 The cargo pump rooms are to be separated from the car-go area by cofferdam or insulation, preferably an open, venti-lated cofferdam.

C 200 Equipment within the cargo area

201 Equipment fitted on cargo tank deck or inside the cargotanks is to be fastened to the main structure with due consider-ation to the thermal expansion and stresses that will occur.

C 300 Surface metal temperature301 See Pt.5 Ch.3 Sec.3 J100.

C 400 Cargo heating media

401 See Pt.5 Ch.3 Sec.4 D.

D. Load Conditions

D 100 Full and partial cargo conditions101 See Sec.5 or Pt.5 Ch.3 or Ch.4, whichever is relevant.


DET NORSKE VERITAS

102 All partial cargo conditions where cargo temperature ex-ceeds 80°C are to be arranged with symmetric loading in thetransverse direction. During charging and discharging themaximum difference between two adjacent liquid levelsshould be limited to abt. 3 meters or 1/4 h whichever is the less,where h is the depth of the longitudinal bulkhead or the tankdepth. Alternate tank filling in longitudinal direction should bebasis for the thermal stresses.

D 200 Water ballast conditions

201 Water ballast is at no time to be carried adjacent to thetanks with hot cargo. A defined safe zone must be specified.

E. Scantlings of the Cargo area

E 100 Construction considerations

101 Hot cargo directly on the outer side shell plating is to beavoided.

102 With a cargo temperature of up to about 140°C, an inte-gral cargo stiffening system consisting of single bottom, deckand double boundary at sides, transverse/longitudinal girdersand stiffeners may be feasible. Longitudinal and transversecargo separation bulkheads may be of non-corrugated type,preferably without deep girders/stringers. The dimensions anddetails to be calculated and considered with due respect to thetemperature stresses.

With a cargo temperature of up to about 200°C, an integral car-go system consisting of double skin may be feasible. The innercontainment to be transverse stiffened while outer systemshould be longitudinal stiffened. Single deck may be accepted.Longitudinal and transverse cargo separation bulkheads to beof vertically corrugated type without girders/stringers. Whenlongitudinal strength is calculated the transverse stiffened skinmay be allowed to buckle and thus disregarded when subject tocompressive longitudinal forces.

With a cargo containment temperature above about 200°C in-dependent cargo system will normally be required.

103 The termination of structure at forward or aft end of thecargo area is to be designed to transfer axial forces (longitudi-nal forces) due to temperature decrease.

104 Where the temperatures as well as temperature gradientsare high, all transitions in the main structures are to be careful-ly designed with respect to high shear forces.

105 Weld dimensions in structures where high shear forcesare involved are to be specially calculated.

E 200 Thermal stress analysis

201 It will generally be accepted that the temperature stress-es are established within the parallel midship portion of thecargo area and then used generally for the whole cargo area.

Guidance note:For a ship with class notation Tanker for Asphalt the follow-ing coefficients may be used in the heat balance calculations.

The air in the double bottom is assumed stationary layered withthe same temperature as the structure. Hence no heat transferfrom air to the structure will exist.The air in side tanks is not stationary.For the deck beams:

— asphalt to deck beam: 50

The following material data for mild steel may be used:

— density: 7860 kg/m3

— specific heat: 0,114 kcal/kg/°C— coefficient for heat conduction: 0,3 t + 59,l96 kcal/h m °C.

The effect from various scantlings is negligible.


202 The calculated temperature loadings are to represent fullload and partial load conditions, seagoing as well as harbourconditions.

203 The ambient temperature in the sea water and in the airis to be 0°C when heat flow is calculated.

204 The temperature stresses are to be combined with stillwater and wave bending stresses as well as static and dynamicstresses from cargo and seawater.

205 The total results are to be checked against allowablestresses, see below, and the global and local buckling strength.

Local elastic buckling is acceptable, see also Appendix A. Re-duced stiffness of plating is to be used in the calculations. Thefinal results are to include correct stiffnesses.

Guidance note:The 3-dimensional finite element method model, or an equiva-lent means for establishing the temperature stresses, may extendfrom middle of one cargo hold to the middle of an adjacent hold.Symmetric condition may be assumed at the centre line.


E 300 Acceptable stress level301 The stress level is not to exceed the values given in thischapter, where actual loading conditions are calculated with-out taking temperature into account.

302 For independent cargo tank systems, reference is madeto Pt.5 Ch.5 Sec.5.

303 When the temperature stresses are included the follow-ing stresses are acceptable (all values are given at 180°C):

a) Transverse and longitudinal girders

When the thermal stresses are the dominant part of thestress level, higher stresses than above may be accepted lo-cally

b) Hull section modulus

Stresses from cargo conditions are to be as given by Sec.5C303 when D102 is taken account of. The same effect ap-plies to the minimum requirement.

kcal/hour/m2/°CAsphalt to inner bottom: 50Asphalt to inner ship side: 50Seawater to outer ship side: 7400 (with ship moving)Air to outer ship side: 20Air to deck (outside): in be-tween inner and outer shell

10

Air to outer ship side: 10Air to inner ship side: 10Air to web in the trans. web-frame:

5

- nominal stress for NV-NS σmax = 190 N/mm2

- nominal stress for NV32 σmax = 260 N/mm2

- nominal stress for NV36 σmax = 300 N/mm2

- shear stress for NV-NS τmax = 110 N/mm2

- shear stress for NV32 τmax = 155 N/mm2

- shear stress for NV36 τmax = 175 N/mm2

- equivalent stress for NV-NS σe max = 205 N/mm2

- equivalent stress for NV32 σe max = 280 N/mm2

- equivalent stress for NV36 σe max = 315 N/mm2

up to σmax σF and τmax

σF

3-------= =

� �� .


DET NORSKE VERITAS

c) Longitudinals

The stresses are to be as given in this chapter increased by30 N/mm2 for NV-NS or 80 N/mm2 for NV36 steel whenthe temperature in elements is 180°C.

d) Beams, frames

The stresses are to be as given in this chapter increased by30 N/mm2 for NV-NS or 80 N/mm2 for NV36 steel whenthe temperature in elements is 180°C.

e) Plating

Minimum thicknesses to be as for an ordinary ship withouthigh temperatures.

E 400 Girders401 The forces introduced to the girder system due to thetemperature rise (i.e. the temperature gradients) make it impor-tant to control the girders with respect to axial-bending andshear stresses, tripping strength, welding (type and size), con-tinuity, transfer of forces when flanges change direction, cut-outs (shape, situation, local strengthenings) etc.

F. Type of Cargoes

F 100 List of cargoes101 Examples of cargoes which may be covered by theserules:

Cargo Specific gravity

t/m3

Temperature °C

Asphalt (bitumen) 1,025 130-250Coal tar (solvents) 1,20 130-250Creosote 1,10 90-105Coal tar (pitch molten) 1,20 230-280 1)

Carbon Black feedstock about 1,2 about 100Sulphur (molten) 1,80 155 1)

1) Independent tanks required according to Pt.5 Ch.4.


DET NORSKE VERITAS

SECTION 16SPECIAL REQUIREMENTS - ADDITIONAL CLASS

A. General

A 100 Objectives101 The principal objective of the requirements specified inthis section is to provide a framework for the evaluation of thehull structure against defined acceptance criteria based on anextended calculation procedure covering load and structuralresponse analysis. The requirements are ensuring that thestructures comply with the general load and strength criteria asoutlined in Sec.3 B.

102 The class notations described in this section are in gen-eral voluntary notations, supplementary to the main class re-quirements and possible additional class requirements. Thenotation NAUTICUS(Newbuilding) is, however, mademandatory for certain ship types and sizes.

A 200 Application201 The rules in this section are applicable for vessels withthe class notations NAUTICUS(Newbuilding), PLUS-1,PLUS-2, COAT-1, COAT-2, and CSA2 .

The requirements specified for class notation CSA-2 are ap-plicable to all types of ships. The notation covers conventionalships as well as special design configurations as related to maindimensions, hull form, structural arrangement and/or mass(steel, equipment and cargo) distribution.

202 The calculations specified in the requirements are to becarried out by computer programmes supplied by or recog-nised by the Society. As recognised programmes are consid-ered all programmes applied by shipyards where reliableresults have been demonstrated to the satisfaction of the Soci-ety.

Wave load analysis programmes and their application are to bespecially approved.

B. Class Notation NAUTICUS(Newbuilding)

B 100 General101 The notation NAUTICUS(Newbuilding) describes anextended calculation procedure for the verification of hullstructures. The procedure includes use of finite element analy-sis for determination of scantlings in the midship area, and ex-tended requirements to fatigue calculations for end structuresof longitudinals in bottom, inner bottom, side, inner side, lon-gitudinal bulkheads and upper deck.

102 The notation is mandatory for certain vessels. When ap-plicable, this is stated in Pt.5 for the type of vessel in question.

103 The direct strength calculation is in general to be basedon the principles given in Sec.13, with scope of the analysis asdefined in B200.

B 200 Finite element analysis201 A finite element analysis is to be performed for the mid-ship region to document results as listed below:

— relative deflections of supporting members as bulkheads,floors, web frames and girders

— stresses in transverse bulkheads— stresses in longitudinal girders in bottom, side, bulkhead

and deck— stresses in transverse girders in bottom, side, bulkhead and

deck— stresses in girders and stringers on transverse bulkheads

— stresses in brackets of longitudinal, transverse or verticalgirder structures located on bottom, side, deck or bulkhead

— stresses in selected stiffeners and associated bracketswhere the stiffeners' supports are subjected to relative de-flections.

The stresses are not to exceed the acceptance criteria given inSec.13 B400.


For ships where this class notation is mandatory, details re-garding areas to be evaluated by finite element analysis aregiven in Pt.5.

The above mentioned results can be obtained by using a cargohold or tank analysis and frame and girder analysis, togetherwith local structure analyses for stiffeners, subject to relativedeformations and other critical details, when relevant.

Further description of such calculations are given in Sec.13,subsections D, E and F. Acceptable procedures are given inclassification notes for the respective types of vessels.

B 300 Fatigue strength assessment

301 The fatigue strength assessment is in general to be car-ried out for end structures of longitudinals in the cargo area lo-cated in bottom, inner bottom, side, inner side, longitudinalbulkheads and strength deck. The assessment is to be carriedout in accordance with Sec.17

302 The effect of relative deformation is to be taken into ac-count in the fatigue evaluation of longitudinals. The deforma-tions are to be based on results from the finite element analysisrequired in 200, applying fatigue loads as described in Sec.17.

C. Class Notation PLUS-1 and PLUS-2

C 100 General

101 The PLUS-1 and PLUS-2 notations are intended forvessels operating in harsh areas and for vessels with increasedtarget design life. The notations include additional require-ments for the fatigue life of hull structural details.

C 200 Application

201 The PLUS-1 and PLUS-2 notations are primarily in-tended for tankers, bulk carriers and container carriers of con-ventional design, but can also be applied to other types ofvessel. Generally the vessels shall comply with:

— Class notation NAUTICUS(Newbuilding)and

— The criteria related to fatigue requirements described in400.

Guidance note:The PLUS-2 notation is recommended for vessels intended foroperation mainly in harsh areas.


C 300 Documentation

301 Calculations documenting the fatigue life are to be sub-mitted for information.


DET NORSKE VERITAS

C 400 Requirements for fatigue life

401 Fatigue calculations shall in general be performed as de-scribed in Sec.17 with the following modifications:

— Fatigue calculations, including those required for NAUTI-CUS(Newbuilding), are to be carried out with thenumber of wave encounters related to a design life of 30years for the PLUS-1 notation and 40 years for thePLUS-2 notation.

— Fatigue strength assessment of details according to 402 to404 depending on the vessel type are to be carried out bysimplified fatigue calculation procedure described inSec.17 and in Classification Note No. 30.7. When a stressconcentration factor is not available for the structure inquestion this may be found by the finite element analysisas described in Classification Note No. 30.7.

402 For tankers, fatigue strength assessment of the follow-ing details shall be carried out in addition to those required forclass notation NAUTICUS(Newbuilding):

a) Representative longitudinal stiffener connections in themidship area, in the bottom and inner bottom, includingthe stiffener on top, cut out and collar plate. See Guidancenote.

b) Representative longitudinal stiffener connections in themidship area, in the side and inner side, including the stiff-ener on top, cut out and collar plate. See Guidance note.

c) Representative deck openings.

The results from the investigation of the details in the midshiparea, mentioned in a), b) and c) above, are to be utilised withinthe cargo area. A detailed procedure is described in Classifica-tion Note No. 30.7.

Guidance note:The following criteria may be used for the determination of rep-resentative longitudinals:

— longitudinal stiffener where the minimum fatigue life is ob-tained from Nauticus Hull Fatigue calculations

— longitudinal stiffener showing representative behaviour ofthe adjacent longitudinals

— longitudinal stiffener in areas where the maximum webframe shear stress is anticipated

— longitudinal stiffener where the maximum dynamic pressureis applied.


403 For bulk carriers, fatigue strength assessment of the fol-lowing details shall be carried out in addition to those requiredfor class notation NAUTICUS(Newbuilding):

a) Representative longitudinal stiffener connections in themidship bilge area, in the bottom and inner bottom, includ-ing the stiffener on top, cut out and collar plate. See Guid-ance note to 402.

b) Representative lower and upper bracket ends of the sideframe, located in the middle of an ore hold, within the mid-ship area.

c) Hatch coaming bracket amidships for ships with largedeck openings (total width of hatch openings in one trans-verse section exceeding 65% of the ship’s breadth orlength of hatch opening exceeding 75% of hold length)

The results from the investigation of the details in the midshiparea mentioned in a), b) and c) above, are to be utilised withinthe cargo area. A detailed procedure is described in Classifica-tion Note No. 30.7.

404 For container carriers, fatigue strength assessment ofthe following details shall be carried out in addition to those re-quired for class notation NAUTICUS(Newbuilding):

a) Representative longitudinal stiffener connections in thebilge area of midship, including the stiffener on top, cutout and collar plate. See Guidance note to 402.

b) Fatigue strength assessment of the following hatch cornersand coamings shall normally be carried out:

- typical hatch corner and coaming, amidships- the after hatch corners and coamings in the after cargo

hold (the hatch corner located in front of engine roomforward bulkhead)

- one hatch corner and coaming selected as the most crit-ical hatch corner with respect to fatigue within the for-ward part of the cargo area.

Such fatigue assessment will normally have to be based ona global finite element analysis.

The results from investigation of the details in the midship areamentioned in a) above, are to be utilised within the cargo area.A detailed procedure is described in Classification Note No.30.7.

405 If the PLUS-1 or PLUS-2 notation is applied in combi-nation with the CSA-2 notation, all fatigue calculations are tobe based on the design life specified for the PLUS-1 orPLUS-2 notations

D. Class Notation COAT-1 and COAT-2

D 100 General

101 The COAT-1 and COAT-2 notations include additionalrequirements for corrosion prevention of tanks and holds fornewbuildings.

D 200 Application

201 The COAT-1 and COAT-2 notations are primarily in-tended for tankers, bulk carriers and container vessels of con-ventional design, but may also be applied to other types ofvessel. The vessels shall comply with the requirements for cor-rosion prevention of tanks and spaces as described in D.

D 300 Documentation

301 A coating specification shall be submitted for approval.The coating specification is to be based on the principles de-scribed in Sec.18 Table A1.

D 400 Requirements for corrosion prevention

401 A corrosion prevention system is to be specified and ap-plied to the ballast water tanks and cargo area as described in402 to 404 for different types of ships. The coating systems re-ferred in the following are described in Classification Note No.33.1.

402 For crude oil tankers the following corrosion preventionsystem shall be specified and applied:

— All ballast water tanks shall be protected by a corrosionprevention system, equal to, or better than, coating systemII for the COAT-1 notation and system III for the COAT-2 notation.

— Inner bottom of all cargo tanks and 0.5 m up, shall be pro-tected by a corrosion prevention system, equal to, or betterthan, coating system II for both the COAT-1 and COAT-2 notation.

— Upper part1 of horizontal stringers in cargo tanks shall beprotected by a corrosion prevention system, equal to, orbetter than, coating system I for the COAT-1 notation andsystem II for the COAT-2 notation.

— Deckhead and 2 m down shall be protected by a corrosionprevention system, equal to, or better than, coating systemI for the COAT-1 notation and system II for the COAT-2notation.


DET NORSKE VERITAS

1) Upper part of horizontal stringers means:

— The stringer’s horizontal side facing upwards and ad-jacent vertical surfaces (above the stringer web) up tominimum 10 cm above the stringer.

— The vertical edge of cut-outs in the same horizontalsurface (lugs etc., to be covered by stripe coats)

— The parts of the stringer face plate, accessible whenstanding on the top of the stringer, see Figure 1.

Fig. 1Area of stringer to be coated

403 For bulk carriers the following corrosion prevention

system shall be specified and applied:

— All ballast water tanks shall be protected by a corrosionprevention system, equal to, or better than, coating systemII for the COAT-1 notation and system III for the COAT-2 notation.

— Cargo holds: All internal and external surfaces of hatchcoamings and hatch covers and all internal surfaces of thecargo holds, excluding the flat tank top areas and the hop-per tanks sloping plating and transverse bulkheads bottomstool approximately 300 mm below the side shell frameand brackets, shall be protected by a corrosion preventionsystem, equal to, or better than, coating system I for theCOAT-1 notation and system II for the COAT-2 notation.

404 For other ships the following corrosion prevention sys-tem shall be specified and applied:

— All ballast water tanks shall be protected by a corrosionprevention system equal to, or better than, coating systemII for the COAT-1 notation and coating system III for theCOAT-2 notation.

D 500 Survey and testing

501 A report from the yard documenting the obtained qual-ity of steel surface preparation and applied coating is to be sub-mitted for information. The report shall, as a minimum,contain detected deviations from the approved specification.

Guidance note:

The Society will not be involved in inspections related to appli-cation of the corrosion protection system.


E. Class Notation CSA-2

E 100 General101 The calculation procedure in this subsection is an exten-sion of the finite element method calculations described for thenotation NAUTICUS(Newbuilding).The hull structural scantlings are however not to be less thandetermined by the main class requirements.

102 All structural calculations are to be carried out on re-duced scantlings, i.e. corrosion addition tk, as defined in Sec.2D200, is to be deducted from the proposed scantlings.

103 The procedure for CSA-2 described in this subsection isbased on the results from the NAUTICUS(Newbuilding)analysis in which an envelope set of quasistatic loads havebeen applied to cater for most loading situations in general.The procedure for CSA-2 is using a selected set of loadingconditions defined in the vessels loading manual as basis fordirect hydrodynamic analysis and finite element response anal-ysis. The strength analysis is then to be carried out for the mostextreme loading situation checking local structural areas aswell as the complete hull girder capacity. Fatigue analysis ofboth longitudinal and transverse structural elements are to becarried out.

E 200 Selection of loading conditions201 The design load conditions for CSA-2 are to be based onthe vessels loading manual and are to include ballast, full loadand part load conditions as relevant for the specific type ofship.

For selection of still water load conditions to be used as basisfor extreme wave load determination, (return period of 20years), the most demanding loading conditions defined in theloading manual are to be used.

Loading conditions for fatigue are to be selected to representtypical loading situations, which will be used during most ofthe operational lifetime of the vessel while at sea. For harbourconditions only static loads need to be considered.

The loading conditions are in addition to be defined to coverthe full range of still water bending moments and shear forcesfrom maximum sagging to maximum hogging conditions.

E 300 Wave load analysis301 Direct wave load calculations are to be performed in ac-cordance with the general principles stated in ClassificationNote No. 30.7. The transfer functions are to be calculatedbased on a linear strip theory method or better. Non-linear ef-fects are to be accounted for in the determination of verticalshear forces and bending moments.

302 Design loads are to be determined for loading conditionsgiving maximum vertical wave bending moment amidships,maximum horizontal and torsional moment (if relevant) andvertical maximum acceleration at forward perpendicular.

Partial loading conditions resulting in large hull girder loadsand local pressures are to be considered if relevant.

The stillwater bending moment and shear forces are to be com-bined with the corresponding extreme wave loads such thatsets of simultaneously acting loads are obtained.

Guidance note:The stresses in the hull from the selected still water loading con-ditions should be added to the dynamic parts. The dynamic stresscombinations should be constructed taking due consideration ofsimultaneously acting loads with proper phasing or time lag asdetermined from the hydrodynamic calculations.


303 Reference loads for extreme loads are to be calculatedfor a 20-year return period using wave scatter diagrams for theNorth Atlantic. This will serve as basis for the wave load anal-

Table D1 Coating system to be applied for different shipsShip Location COAT-1 COAT-2Crude oil tankers Ballast water tanks II III

Inner bottom in CT II IIUpper part of string-ers in CT

I II

Deckhead in CT I IIBulk carriers Ballast water tanks II III

Cargo hold, upper part

I II

Other ships Ballast water tanks II IIIDetails are given in the rule text. The coating systems refers to Classifica-tion Note No. 33.1.


DET NORSKE VERITAS

ysis with respect to the calculation of hull girder and main gird-er system stress response (400 and 500) as well as hull girdercapacity analysis (600).

Fatigue loads are to be based on 10-4 probability of exceed-ance. However, other probability levels may be accepted pro-vided a consistent direct analysis procedure has been used.Wave scatter diagrams for a world-wide trading pattern, willserve as basis for the fatigue analysis (700), unless a more se-vere fatigue environment has been specified.

E 400 Finite element analysis

401 The finite element analysis of the hull structure is to becarried out in accordance with the principles given in 402 to406. The analysis described in 403 to 405 may be included inhigher level analyses.

402 Global stiffness model (Model level 1)In this model, a relatively coarse mesh extending over the totalhull length is to be used to represent the overall stiffness andglobal stress distribution of the primary members of the hull.

Wave loads derived from the wave load analysis as given in300 are to be applied. The following effects are to be taken intoaccount:

— vertical hull girder bending including shear lag effects— vertical shear distribution between ship side and bulk-

heads— horisontal hull girder bending including shear lag effects— torsion of the hull girder (if open hull type)— transverse bending and shear.

The analysis may be carried out with a relatively coarse mesh.Stiffened panels may be modelled by means of anisotropic el-ements. Alternatively, a combination of plate elements andbeam elements, may be used. It is important to have a goodrepresentation of the overall membrane panel stiffness in thelongitudinal and transverse directions and for shear.

The global model provides boundary conditions for the cargohold model in 403.

403 Cargo hold model (Model level 2)The model is used for the midship area and aims to analyse thedeformation response and nominal stresses in primary structur-al members. See Sec.13 and relevant classification notes forapplicable requirements and guidelines for such models.

The cargo hold model may be included in the global stiffnessmodel.

The cargo hold model may provide boundary conditions forthe frame and girder model in 404.

404 Frame and girder model (Model level 3)The frame and girder analysis is to be used to analyse stressesand deformations in the main framing or girder system. SeeSec.13 and relevant classification notes for applicable require-ments and guidelines for such analyses.

The calculations are to include results as membrane stressescaused by bending, shear and torsion. The minimum require-ments for the areas to be considered are given in:

— for tankers: see Pt.5 Ch.3 Sec.2 D103— for bulk carriers: see Pt.5 Ch.2 Sec.5 C403— for container carriers: see Pt.5 Ch.2 Sec.6 C402 and 403.

In addition to the above, at least one transverse web frame inthe forward cargo hold or tank is to be analysed.

The model may be included in the cargo tank or hold analysismodel, or run separately with prescribed boundary deforma-tions or boundary forces from the cargo hold model.

405 Local structure models (Model level 4)The local structure analyses are used to analyse stresses in lo-cal areas. Stresses in laterally loaded local plates and stiffeners

may need to be investigated. Further, stiffeners subjected tolarge relative deformations between girders or frames andbulkheads are to be investigated along with stress increase incritical areas such as brackets with continuous flanges. Localstructure models may also be used to determine the edge stressin way of critical hatch corner openings in, e.g. container car-riers and bulk carriers.

In general, such analysis shall be performed in areas as definedin Pt.5 for the various ship types.

Local structure models may be included in the cargo hold mod-el or the frame and girder model or run separately with pre-scribed boundary deformations or boundary forces from theframe and girder model.

406 Stress concentration models (Model level 5)Fine mesh finite element models are to be applied at criticalstress concentration details as required for fatigue assessmentaccording to 702. The model extent is to be such that the cal-culated results are not significantly affected by assumptionsmade for boundary conditions and application of loads.

Elements size for stress concentration analysis is to be in theorder of the plate thickness. Normally, shell elements are to beused for the analysis while solid elements may be used on acomparative basis to investigate stress concentration factors inspecial areas. If solid modelling is used, the element size inway of the hot spot may have to be reduced to half the platethickness in case the overall geometry of the weld is includedin the model representation. For further details, see Classifica-tion Note No. 30.7.

E 500 Acceptance criteria501 The longitudinal hull girder and main girder systemnominal and local stresses derived from the direct strength cal-culations in B and C are to be checked according to the criteriaspecified below.

Allowable equivalent nominal stresses referred to 20 yearNorth Atlantic conditions are:

Seagoing conditions:

σe = 0,95σf (N/mm2)

In transverse girders the flange stress is not to exceed 0,85 σf.

Harbour conditions:

σe = 0,85σf (N/mm2)

In transverse girders the flange stress is not to exceed 0,75 σf.

σf = minimum upper yield stress of the materialσe = equivalent stress

— buckling control, see 503— hull girder capacity, see 600— fatigue control, see 700.

502 Local linear peak stresses in areas with pronounced ge-ometrical changes, such as in hatch corners, frame corners etc.,may need special consideration. Local peak stresses in thiscontext are stresses calculated with Stress concentration mod-els (Model level 5) that have a finer finite element mesh repre-sentation than used for nominal stress determination.

For extreme 20 year North Atlantic loads, linear peak stresscorresponding to an acceptable equivalent plastic strain is:

σe = 400 f1 (N/mm2)

Local peak stresses as given above may be accepted providedplastic mechanisms are not approached (developed) in the as-sociated structural parts.

Guidance note:Areas above yield determined by a linear finite element methodanalysis may give an indication of the actual area of plastifica-tion. Otherwise, a non-linear finite element method analysis may


DET NORSKE VERITAS

need to be carried out in order to trace the full extent of the plasticzone.


503 The buckling control of panels (plate and stiffener com-binations) is to be performed as given in Classification NoteNo. 30.1. The usage factor for stiffened panels is not to exceed0,90.

E 600 Hull girder capacity

601 For vessels with notation CSA-2, the ultimate saggingand hogging bending capacity of the hull girder is to be deter-mined, for both intact and damaged conditions.

602 The following damage conditions are to be consideredindependently, using the worst possible position in each case:

1. Collision

with penetration of one ship side, single or double side withina breadth of B/16.

The damage extents are given by:

Guidance note:Calculations utilising symmetrical characteristics, i.e. the capac-ities of the damaged parts of the cross section are reduced with50% on both sides of the ship, will be accepted.


2. Grounding

with penetration of bottom, single or double bottom within aheight of B/15. The damage extents are given by:

603 The ultimate hull girder bending capacity is to complywith the following limits:

Intact design

Damaged condition

γS MS + γW2 MW ≤ MUD

MS = maximum design sagging or hogging still water mo-ment according to the loading conditions from theloading manual used in the wave load analysis

MW = design wave bending moment according to thewave load analysis in 300

M UI = hull girder bending moment capacity in intact con-dition, determined as given below

M UD = hull girder bending moment capacity in damagedcondition, determined as given below

γM = 1,15 (material factor)γ'W1 = 1,1 (partial safety factor on MW for environmental

loads)

γS = 1,1 (factor on MS allowing for moment increasewith accidental flooding of holds)

γ W2 = 0,67 (wave load reduction factor corresponding to 3month exposure in world-wide climate).

The hull girder strength capacity may be calculated for the in-tact midship section as well as for the remaining intact parts ofthe damaged midship section by summing up the buckling andthe yield capacities of the intact structural elements of thewhole section:

A = area of panelz = distance from panel to plastic neutral axis using the ac-

tual yield/buckling capacities in the tension/ compres-sion side respectively

σ cr = critical buckling stress of panels on the compressionside, according to Classification Note No. 30.1

σf = yield stress of panels on the tension sidej = includes all panels on compression sidek = includes all panels on tension side.

The MU is to be calculated both for sagging and hogging con-ditions.

E 700 Fatigue strength assessment

701 The fatigue strength assessment is to be performed ac-cording to Sec.17. The dynamic stresses based on the global fi-nite element calculations for wave loads derived from thedirect load calculations, as given in B and C, are to be utilised.

Fatigue stress evaluation based on nominal calculated stressesand application of relevant stress concentration factors maynormally be accepted. When stress concentration factors forthe geometrical details are not available, a fine mesh finite el-ement calculation is to be performed, see 406. The weld in-duced stress concentration factor (due to the weld geometry)may be based on standard values.

702 The fatigue strength assessment is in general to be car-ried out for longitudinal and transverse structural elements(longitudinals and plates) in bottom, inner bottom, side, innerside, longitudinal and transverse bulkheads and the strengthdeck in the midship region and the forebody.

Fatigue assessment is also to be carried out for highly stressedstructural details in the midship region and in the forebody, asfollows:

In general:

In way of welded details at high stress areas, such as:

— weld attachments of bulkhead corrugations to supportingstructures

— panel knuckles.

For tankers:

— one transverse bulkhead in the midship area— one transverse web frame in the middle of a tank amid-

ships and one frame in tank No. 1 in the forebody— end structures of stiffeners— bracket and flange terminations of main girder systems.

For bulk carriers:

— main frame attachments to hopper and/or top wing tanks— hatch corners in open type bulk carriers, amidships and at

the ends of the cargo area.

For container carriers:

— hatch corners amidships and at the ends of the cargo area.

Damage parameterDamage extent

Single side Double sideheight: h/D 0,75 0,60Length: l/L 0,10 0,10h= penetration height

l= penetration length

Damage parameterDamage extent

Single side Double sideheight: b/B 0,75 0,55Length: l/L 0,50 0,30b= penetration breadth

MS γW1MW

MUI

γM-----------≤+

MU σcrj Aj zj

j� σfk Ak zk

k�+=


DET NORSKE VERITAS

SECTION 17FATIGUE CONTROL

A. General

A 100 Introduction

101 The background and assumptions for carrying out fa-tigue calculations in addition to or as a substitute to the specificrule requirements in Sec.5 to Sec.12 are given in this section.Load conditions, design criteria and applicable calculationmethods are specified.

For some ship types, such direct fatigue calculations are spec-ified in the rules for the class notation in question.

A 200 Application

201 The application of direct fatigue calculations is gov-erned by the following cases:

1) The calculations are required as part of rule scantling de-termination when simplified formulations do not representthe dynamic stress distribution and a direct stress analysishas been required with a reference to this section.

2) Serving as an alternative basis for the scantlings, directstress calculations may give reduced scantlings comparedto the explicit fatigue requirements.

A 300 Loads

301 The vessel is to be evaluated for fatigue due to globaland local dynamic loads. For the local loads, stresses due to in-ternal and external pressures may be calculated separately andcombined using a correlation factor between the sea pressureloads and internal pressure loads. Simplified formulas for dy-namic loads are given in Classification Note No. 30.7, Ch.4.The simplified loads may be substituted by directly computeddynamic loads.

Guidance note:

In case the values of roll radius Kr and the metacentric height GMhave not been calculated for the relevant loading conditions, thefollowing approximate values may be used:


302 The fatigue strength evaluation is to be based on themost frequently used design load conditions. The fraction ofthe lifetime operating under each considered loading conditionis to reflect the intended operational trading pattern of the ship.If nothing else is specified, the values in Table A1 are to beused.

A 400 Design criteria

401 The fatigue analysis is to be based on a period equal tothe planned life of the vessel. The period is, however, normally

not to be taken less than 20 years. Unless otherwise specified,the fatigue calculation is to be based on the North Atlanticwave scatter diagram, reduced by 80% as described in Classi-fication Note No. 30.7.

402 The cumulative effect of the stress history may be ex-pressed by linear cumulative damage usage factor (Miner-Palmgren), which is not to exceed the value η = 1,0 using S-Ndata for mean value minus 2 times the standard deviation.

A 500 Calculation methods

501 Acceptable calculation methods are given in Classifica-tion Note No. 30.7.

502 The influence of the corrosive environments in tanks isnormally to be taken into account by considering that coatedstructures are protected against corrosion for a coating life of10 years plus 5 years, assuming effective coating maintenanceshall be used as a basis for the selection of S-N curves. This isto be regarded as a part of the fatigue calculation method..

The effects of a corrosive environment on the fatigue life areto be taken into account through appropriate S-N curves.

For coated tanks, an S-N curve for a welded joint in air may beused for the protective time of the coating and an S-N curve fora welded joint in corrosive environment is to be used for the re-maining time of the target lifetime.

For uncoated cargo oil tanks, an S-N curve for a welded jointin air may be used for half the target life time and an S-N curvefor corrosive environment is to be used for the remaining timeof the target life time.

In void spaces and dry cargo holds an S-N curve for a weldedjoint in air may be used for the whole target life time.

B. Basic Requirements

B 100 Longitudinals

101 For longitudinals the fatigue evaluation may be carriedout based on direct calculation of the stresses. The stresses tobe taken into account are:

1) Nominal hull girder longitudinal stresses.

2) Stresses due to bending of longitudinal girders due to lat-eral loading.

3) Local bending stresses of longitudinals for lateral loading.

4) Bending stresses due to support deflection of longitudi-nals.

Global stress components may be calculated based on grossscantlings.

Local stress components should be calculated based on re-duced scantlings, i.e. gross scantlings minus corrosion additiontk.

The calculated stress may be reduced due to the mean stress ef-fect. The correction is to be based on a calculated value of themean stress. The stress concentration factors are to be includedwhen calculating the mean stress.

Tanker Bulk carrier Container carrierKr GM Kr GM Kr GM

Loaded 0,39B 0,12B 0,39B 0,17B 0,39B 0,04BBallast 0,39B 0,33B 0,39B 0,25B 0,39B 0,04B

Table A1 Distribution of design load conditionsVessel type Tankers Bulk carriers Container carrierLoaded condition 0,45 0,5 0,65Ballast condition 0,4 0,35 0,2


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SECTION 18CORROSION PREVENTION

A. General

A 100 Definitions

101 The following definitions are used in this section:

Anode: An electrode through which direct current enters anelectrolyte.

Cathodic protection: A way of protecting a steel surface fromcorrosion by installing sacrificial anodes, in contact with thesteel in the electrochemical seawater corrosion cell.

Hard coating: A coating which chemically converts during itscuring process, normally used for new constructions, or non-convertible air drying coating which may be used for mainte-nance purposes. Hard coating can be either inorganic or organ-ic.

Guidance note:Commonly used organic "hard coatings" are epoxy based, suchas pure epoxies and coal tar epoxies. Zinc silicate primers are ex-amples of inorganic hard coatings.


Primer coat: The first coating applied in the shipyard (to dif-ferentiate it from shop-primer).

(IMO Res. A.798(19))

A 200 Documentation201 Specifications for corrosion prevention systems for wa-ter ballast tanks, comprising selection, application and mainte-nance, are to be submitted for information.

Guidance note:The Society’s involvement concerns the contents of the specifi-cation only and does not imply any approval of the surface prep-aration or coating as applied.


202 The purpose of the coating specification is to describethe scheme for selection, application and maintenance of thecorrosion prevention system. It is recommended that the sys-tem comprises of those items described in Table A1.

203 Ballast tanks’ anode distribution drawings are to be sub-mitted for approval. Such drawings shall include details of theconnections to the hull, e.g. welding details.


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B. Corrosion prevention systems

B 100 General

101 All steel surfaces except in tanks other than ballast tanksare to be protected against corrosion by paint of suitable com-position or other effective coating. Holds for dry bulk cargoeswill be specially considered. See also Sec.2 D203.

102 Corrosion prevention of seawater ballast tanks

This regulation applies to oil tankers and bulk carriers con-structed on or after 1 July 1998.

All dedicated seawater ballast tanks shall have an efficient cor-rosion prevention system, such as hard protective coatings orequivalent. The coatings should preferably be of a light colour.The scheme for the selection, application and maintenance ofthe system shall be approved by the Administration, based onthe Guidelines adopted by the Organization*. Where appropri-ate, sacrificial anodes shall also be used.

* Refer to the Guidelines for the selection, application andmaintenance of corrosion prevention systems of dedicatedseawater ballast tanks, adopted by the Organization by res-olution A.798(19).

(SOLAS Reg. II-1/3-2)

Guidance note:The Organization in this context is to be understood as IMO.


B 200 Coatings

201 Shop primers applied over areas which will subsequent-ly be welded, are to be of a quality accepted by the Society ashaving no detrimental effect on the finished weld. See «Regis-ter of Type Approved Products No.1 Non-Metallic Materials».

202 The use of aluminium paint is generally not accepted intanks for liquid cargo with flash point below 60°C, in adjacent

Table A1 Contents of coating specificationScheme for (see SOLAS Reg. II-1/3-2)

Items to be described in specification

General The yard’s owner’s and coating manufacturer’s agreement on the specification.Selection of coating 1) Coating type, material and manufacturer's data sheets concerning items 2) to 5) listed below.

2) Definition of coating system, including number of coats and minimum/maximum variation in dry film thickness.

Application of coating 3) Surface preparation, including preparation of edges and welds, and surface cleanliness standard (e.g. blast cleaning to Sa 2,5).

4) Coating manufacturer's safety data sheets.5) Maximum allowable air humidity in relation to air and steel temperatures during surface preparation

and coating application.6) Yard's control and inspection procedures *) including:

- acceptance criteria- tests/checks (e.g. surface cleanliness, film thickness, air humidity, temperature controls)- handling of deviations from specified quality.

7) Details of anodes, if used.8) Evidence of yard's experience in coating application **).

Maintenance of coating 9) Coating manufacturer's recommended procedure, preferably alternative procedures, for future maintenance of coating on the ship in operation.

Notes:

* The items listed in a) to q) should be described in the control and inspection procedures (and thus included in the coating specification) for the ship new-building.

a) Organisation of operators, inspectors, facilities, equipment and procedures.

b) Working conditions, e.g. access, stageing, illumination.

c) Conditioning of steel temperatures and relative humidity.

d) Methods of conditioning of steel temperatures and relative humidity, e.g. indoor facilities for blast cleaning and coating, heating/drying equipment, etc.

e) Storing of coating materials and abrasives.

f) Preparation of sharp edges.

g) Blast cleaning and any other surface preparation

h) Cleaning, including removal of abrasives after blast cleaning.

i) Cleanliness with respect to chloride content on surfaces to be coated, oil, weld smoke, dirt, etc.

j) Shielding off painted surfaces from blasting operations.

k) Blast cleaning equipment and type of abrasive.

l) Coating application equipment and methods.

m) Curing times for individual coats in relation to temperatures.

n) Dry film thickness of individual coats.

o) Total dry film thickness.

p) Coating repairs in case of damage, and handling of coated surfaces.

q) Installation of anodes, if specified. See B300.

** Minimum evidence will be a reference list stating (some or all) ships coated by the Yard. Other relevant evidence may be for example technical reportson the performance of coatings applied by the Yard, e.g. inspection reports on coating condition in ballast tanks after a number of years, or a qualitysystem certificate for the Yard's coating application division or subcontractor. It is essential that the evidence is acceptable to the Owner.


DET NORSKE VERITAS

ballast tanks, in cofferdams, in pump rooms or on deck abovethe mentioned spaces, nor in any other area where cargo gasmay accumulate. Paint containing aluminium may, however,be accepted in places as mentioned above, provided it has beenshown by tests that the paint will not increase the sparking haz-ard.

Guidance note:Coating containing aluminium in gas hazardous areas limited toAl maximum 10% by weight in the dry film is acceptable. Areas containing "liquid cargo with flash point below 60°C" areconsidered as "gas-dangerous" areas.


203 Regarding coating of ballast tanks, see Sec.2 D203.

B 300 Cathodic protection

301 The Society is to approve the fitting arrangement for ca-thodic protection of steel structures in tanks used for liquid car-go, with flash point below 60 °C, with regard to safety againstfire and explosion. This approval also applies to adjacenttanks.

Guidance note:Approval of sacrificial anodes and their fastening devices is nor-mally given as a type approval. See "Register of Type ApprovedProducts No.3: Containers, Cargo Handling, Lifting Appliancesand Miscellaneous Equipment".


302 All anodes are to be attached to the structure in such away that they will remain securely fastened both initially and

during service. Fillet welds are to be continuous and have ade-quate cross section. Attachment by clamps fixed by setscrewswill normally not be accepted. Attachments by properly se-cured through-bolts or other positive locking devices mayhowever be accepted.

Anode steel cores bent and directly welded to the steel struc-ture are to be of a material complying with the requirements forgrade NV A or equivalent.

303 Tanks in which anodes are installed, are to have suffi-cient holes for the circulation of air to prevent gas from collect-ing in pockets.

304 In tanks, permanent anodes made of, or alloyed with,magnesium are not accepted. Impressed current systems arenot to be used in tanks due to development of chlorine and hy-drogen that can result in an explosion hazard. Aluminium an-odes are accepted in general. However, with regard to tanks forliquid cargo with flash point below 60°C and in adjacent bal-last tanks, aluminium anodes are to be so located that a kineticenergy of not more than 275 J is developed in event of theirloosening and becoming detached.

Guidance note:Aluminium anodes in gas-dangerous areas will be accepted whenattached to tank bottoms, on stringer decks and up to a certainheight above the tank bottom or stringer deck. The height abovethe tank bottom or stringer deck will be dependent upon anodeweight, whose maximum acceptable height in m is 28 divided bythe weight of the anode in kg. The attachment is to be arrangedso that the anodes cannot eventually become detached and fallthrough holes or scallops in stringer decks.


Rules for Ships, January 2001Pt.3 Ch.1 App.A –

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APPENDIX AELASTIC BUCKLING AND ULTIMATE STRENGTH

A. Introduction

A 100 Scope and description101 Average in-plane compressive stresses above the elasticbuckling stress σel may be allowed for plate elements subjectto extreme loading conditions (probability level of 10-8 orless), as long as functional requirements do not prohibit largeand off-plane elastic deflections.

An accepted procedure for evaluating the ultimate compres-sive strength is given in the following.

The ultimate stress limit and effective width of local plate pan-els are given in B100 and B200. The ultimate strength of stiff-ened panels, simple girders and ship hull girders is given inB300 to B500.

B. Calculation Procedure

B 100 Estimation of ultimate stress

101 For each local panel where elastic buckling is expected(σa > ησel), the maximum allowable compressive stress σu isgiven by:

σu = ψu σel

σel = elastic buckling stress as calculated from Sec.14 B201ψu = excess factor given as a function of σf / σel

For longitudinally stiffened plating:

For transversely stiffened plating (compressive stressperpendicular to longest side l of plate panel):

B 200 Calculation of effective width201 Due to the elastic buckling the effective width of platingtaking part in the compression area will be reduced.

The effective width for stresses induced above the elasticbuckling level is given by:

σu = ultimate stress given in 100σf = minimum upper yield stress of material.

b and be is always to be taken perpendicular to the direction ofthe compressive stress.

B 300 Ultimate load of stiffened panels

301 The ultimate load capacity of a stiffened plate panel incompression is given by:

PU = 0,1 [ σ el A + (σm – σel ) AR ] (kN)

A = total area (cm2) of panel

= 10 b (t – tk) + Σ asAR = reduced area of panel = 10 be (t – tk) + Σ asb = total width (m) of panelbe = reduced width (m) as given in 201t = thickness (mm) of platingas = area (cm2) of stiffener/girder in direction of compres-

sive stressσel = elastic buckling stress (N/mm2) of platingσm = σc lσf or 0,9 , whichever is the smaller, when stiffeners

in direction of stress = 0,9 σf when stiffeners perpendicular to stressσc l = critical buckling stress of stiffeners in direction of

compressive stresses, as calculated in Sec.14 C200 andC300.

The design condition is given by:

PU ≥ PA / ηu

PA = actual compressive load in panel, based on extreme dy-namic load

= 0,1 σa Aηu = 0,85.

B 400 Ultimate strength of simple girders with stiffened panel flange

401 The ultimate bending moment capacity of girders with astiffened plate flange in compression is given by:

MU = ME + ∆ MU (kNm)

ME = moment capacity corresponding to the elastic buck-ling limit

=

σel = elastic buckling stress (N/mm2) of plating in com-pression flange calculated with 100% effectiveplate

I = moment of inertia of girder (cm4) with intact plateflange b (100% effective)

zp = distance (cm) from neutral axis to compressionflange, see Fig. 1

Fig. 1Simple girder with panel flange

∆ MU = additional moment due to increase in allowablestress above elastic buckling limit

= ∆ MUP or ∆ MUF whichever is the smaller:

ψu 1 0 375σf

σel------- 2–

� �� ,+=

ψu 1 cσf

σe l------- 2–

� �� +=

c0 75,ls-- 1+------------=

be

b-----

σu σel–

σf σel–-------------------=

σe l I

1000 zp------------------ (kNm)


DET NORSKE VERITAS

zf = distance (cm) from neutral axis to tension flange ofintact section

zpb = distance (cm) from neutral axis to compressionflange of buckled section

zfb = distance (cm) from neutral axis to tension flange ofbuckled section

IB = moment of inertia (cm4) of girder with buckledplate flange be.

σm as given in 300.

The area of the buckled plate flange (AR) is estimated as out-lined in 300. The design condition is given by:

MU ≥ MA / ηu

MA = actual moment in girder, based on extreme dynamicload

ηu = 0,85.

B 500 Ultimate strength of complex girders

501 The ultimate bending moment capacity of a ship hullgirder with stiffened plate panels at various levels is given by:

MU = ME + ∆ MU (kNm)

ME = moment capacity corresponding to the elasticbuckling limit of the local plate panel subject toelastic buckling (see Guidance note)

=

σel = elastic buckling stress (N/mm2) of local platepanel

I = moment of inertia of hull girder (cm4) with in-tact plating (100% effective plating)

ze = vertical distance (cm) from neutral axis of intactsection to middle of buckled plate panel, see Fig.2

Fig. 2Hull girder

∆ MU = additional moment above elastic buckling limit,to be taken as the smaller of:∆ MUP1, ∆ MUP2, ∆ MUP3 and ∆ MUF

∆ MUP1 =

σcp = critical buckling stress of the intact plate panel(on compression side) with the smallest buck-ling safety (σc / σa) as calculated in Sec.14 B200

σep = σel zp / zezp = vertical distance (cm) from neutral axis of intact

section to middle of intact plate panelzpb = vertical distance (cm) from neutral axis of buck-

led section to middle of intact plate panel.IB = moment of inertia (cm4) of hull section with

buckled plate panel, which is inserted with ef-fective width as given in 201

∆ MUP2 =

σcl = critical buckling stress of the longitudinal (onthe compression side) with the smallest bucklingsafety (σc / σa) as calculated in Sec.14 C200 orC300

σe n = σel zl / zezl = vertical distance (cm) from neutral axis of intact

section to longitudinal in questionzl b = vertical distance (cm) from neutral axis of buck-

led section to longitudinal

∆ MUP3 =

σem = σel zm / zezm = vertical distance (cm) from neutral axis of intact

section to deck or bottom, whichever is in com-pression

zmb = vertical distance (cm) from neutral axis of buck-led section to deck or bottom (in compression)

∆ MUF =

σef = σel zf / zezf = vertical distance (cm) from neutral axis of intact

section to deck or bottom, whichever is in ten-sion

zfb = vertical distance (cm) from neutral axis of buck-led section to deck or bottom (in tension).

The design condition is given by:

MU ≥ MA / ηu

MA = actual moment in hull girderηu = 0,85.

Guidance note:In cases where several plate panels with different values of elas-tic buckling stress are involved, a stepwise calculation of ME hasto be made according to the general formula:

∆MUP

σm σel–

1000 zpb---------------------- IB (kNm)=

∆MUF

0 9σ, f σe l zf zp⁄–

1000 zfb-------------------------------------------- IB (kNm)=

σe l I

1000 ze------------------ (kNm)

1 18 σcp, σep–

1000 zpb------------------------------------ IB (kNm)

σcl σen–

1000 zlb---------------------- IB (kNm)

0 9σ, f σem–

1000 zmb------------------------------ IB (kNm)

0 9σ, f σef–

1000 zfb---------------------------- IB (kNm)

ME ∆MEI

i 1=

n

�=

∆MEI

σei σe i 1–( )zei

ze i 1–( )---------------------–

1000 zei----------------------------------------------------------------= IE i 1–( )


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In the first step IE(i – 1) = I (intact moment of inertia). σE1 willbe the lowest elastic buckling stress in relation to the actual stressin the considered plate, and σE(i – 1) = 0.When last step in the elastic buckling calculation (∆ MENME) hasbeen performed and the total found, the highest elastic bucklingstress σen is to be used as σe in the further calculation of ∆ MU.


σei = elastic buckling stress (N/mm2) of local panel considered in step i

σE(i – 1) = elastic buckling stress of local panel considered in previous step

IE(i – 1) = moment of inertia of hull girder with effective width of elastically buckled panels in earlier steps inserted

zei = vertical distance (cm) from neutral axis in above section to middle of the plate panel i

zE(i – 1) = vertical distance from neutral axis in above sec-tion to the plate panel i – 1.


DET NORSKE VERITAS

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