Adopted by IACS Council on 14 December 2005 Summary of CSR – Tanker Rules – Bulk Carrier Rules...

Adopted by IACS Council on 14 December 2005

• Summary of CSR

– Tanker Rules

– Bulk Carrier Rules

• Harmonization

• Maintenance

Common Structural Rules for Tankers and Bulk Carriers

IACS Common Structural Rules 2

Summary of CSRsSummary of CSRs

“Common Structural Rules for Double Hull Oil Tankers”

“IACS Common Structural Rules for Bulk Carriers”


Summary of CSRsSummary of CSRs

Jun 2004 1 Jan 2005

1st Draft available to Public

2nd Draft available to Public

30 Sep 2005Apr 2005

Publish15 Jan 2006

CSR Effective

1 Apr 2006

CSR Adopted

1 Jan 2006

Industry comments6 months

Industry comments5 months


CSR TankersCSR Tankers



Section Topic

1

2

3

4

5

6

7

8

Introduction

Underlying Principles

Rules Applications

Basic Information

Structural Arrangement

Material and Welding

Loads

Scantling Requirements

Section Topic

9

10

11

12

A

B

C

D

Design Verification

Buckling and Ultimate-

Strength

General Requirements

Renewal Criteria (SiO) Hull Girder Ultimate Strength

Structural Strength Assessment

Fatigue Strength Assessment

Buckling Strength Assessment



1st hearing (Jun ~ Dec 2004)– 2834 comments received during hearing

period– 988 (35%) of which resulted in either editorial

or rule changes– 197 of which are noted for future

development

2nd hearing (Apr ~ Sep 2005)– 228 comments received during hearing period– 76 (33%) of which resulted in either editorial

or rule changes– 12 of which are noted for future development

2005 feedback from industry meetings with designers, shipyards and shipowner groups– Japan (3 visits in 2005)– Korea (2 visits in 2005)– China (1 visit in 2005)– Shipowner groups (5 visits in 2005)


CSR Tankers CSR Tankers – Summary of Industry Feedback– Summary of Industry Feedback

a) General scantling increase - Feedback received that the general scantling increase needs justification and is not supported by damage records

Rule change: Criteria reviewed and increase of some of the allowable stresses for plate and stiffener requirements by 5-7% found justified.

b) Large localised increases from FE buckling - 2nd draft JTP Rules require some areas where net scantlings are significantly above the as-built scantlings of present fleet. Typically buckling assessment for FE caused the increase.

Rule change: FE procedure revised to take into account combined probability of cargo density, loading pattern and dynamic load level by introducing a correction factor applied on the cargo pressure for the extreme dynamic load combination.

c) Too many load cases - the number of FE load cases to be assessed makes assessment very labour intensive

Rule change: almost halved the number of load cases by removing cases which do not govern scantlings.


CSR TankersCSR Tankers – Summary of Industry Feedback– Summary of Industry Feedback

d) Corrosion margins - corrosion margins are too small for a design life of 25 years and will lead to a significant amount of steel replacement.

Rule change: upward adjustments made to the average and local (pitting, edge and groove) corrosion.

e) Coating performance standard - lack of a minimum performance standard for coating leads to large variation in application and actual coating life. The coating of some ships is so poor that compete renewal by sandblasting and re-coating is needed after a few years.

Rule change: IACS agreed to include a requirement for a minimum performance standard in the common structural Rules by reference to SOLAS upcoming regulation.

f) Grinding - allowance for grinding as a measure for increasing the fatigue life was questioned.

Rule change: Rules modified to be more specific on where credit may be given for grinding. Detailed requirements introduced on what is required for the grinding procedure.



g) Fatigue – the fatigue design standard of 25 year operation in North Atlantic wave environment is too severe taking into account the typical operation of the majority of tankers. The criteria in principle disallows designs with material of HT36 in deck.

Reply: As the 25 NA design standard is given in the draft IMO Goal Based Standard the project has decided not to make any amendments to the fatigue target.

h) Hull girder ultimate strength – the hull girder ULS requirement in the second draft is too severe and some existing vessels will not pass even in the as-built condition. Use of material of HT36 is needed for compliance but contradicts the fatigue criteria.

Reply: Studies performed during the Rule development did not support changes to the requirement.

i) IACS recommendation 47 Shipbuilding and Repair Quality Standard - the IACS recommendation is not up to date and may cause conflicts with commonly used national standards.

Reply: The comment has been forwarded to IACS Survey Panel. The Rules have been updated to make it clear that acceptable national standards are allowed. Rec. 47 is used as common reference document for strength assessment.



j) Delete primary support member prescriptive rules – the prescriptive requirements for PSM are not needed since the members are checked with FEM.

Reply: PMS requirements have been retained to have a consistent application of requirements, a solid baseline minimum strength level, and to “catch” limitations in the FE analysis such as limited quantity of loading cases/conditions and assumptions for boundary conditions. To account for differences between the two methods, the Rules permit scantlings to be reduced to 85% of the prescriptive requirements where the FE results demonstrate that reduction is acceptable.

k) Demonstrate link between damages and scantling increases – there is no need for the scantling increase if there is no damage.

Reply: CSR was not developed as a response to damages on existing vessels. Scantling increases will result from increasing the design basis.



l) Rolling tolerances - the under tolerances are eating into the wastage allowance and should not be accepted. UGS also commented on lack of specified procedures/locations for performing thickness measurements.

Reply: Question/issue is under review by IACS.

m) Approval of national fabrication standards - UGS raised concern over approval of national fabrication standards on a class by class basis without common procedures for the approval of such

Reply: The request is under review by IACS.


CSR Bulk CarriersCSR Bulk Carriers


CSR Bulk Carriers : Table of ContentsCSR Bulk Carriers : Table of Contents

Ch 1. General principles

Ch 2. General arrangement design

Ch 3. Structural design principles

Ch 4. Design loads

Ch 5. Hull girder strength

Ch 6. Hull scantlings

Ch 7. Direct strength analysis

Ch 8. Fatigue check of structural details

Ch 9. Other structures

Ch 10. Hull outfitting

Ch 11. Construction and testing

Ch 12. GRAB additional notation

Ch 13. Maintenance of Class & Thickness measurements


CSR Bulk CarriersCSR Bulk Carriers

1st hearing (Jun ~ Dec 2004)– About 3000 comments received

during hearing period– 17 major modifications in the Rules

and re-writing of Chapters 7(Direct Strength Analysis), 8 (Fatigue), 11 (Construction) and 12 (Ships in Service)

– Modifications issued in 2nd Draft

2nd hearing (Apr ~ Sep 2005)– About 1000 comments received

during hearing period– 16 major modifications in the Rules– Modifications issued in Final Draft


MAJOR MODIFICATIONS OF BULK CARRIERS MAJOR MODIFICATIONS OF BULK CARRIERS RULES AFTER THE FIRST DRAFTRULES AFTER THE FIRST DRAFT

– Larger uniform corrosion wastage allowances for transverse bulkheads, side shell in line with 95% probability of non-exceedance (instead of 90%)

– Thickness rounding procedure is modified, due to harmonisation between JTP and JBP

– Harmonisation of ships in service requirements between JTP and JBP

– Rewritten FEM procedure: Finite element models are now only three holds models, with modified boundary conditions to provide same results between direct and superposition methods

– Reduction of the number of loading cases to be considered in Direct strength analysis

– Compliance with new SOLAS requirements for flooding of DSS bulk carriers

– Quartering sea loading for cross-deck structure, further to harmonisation between JTP and JBP

– Mandatory GRAB notation for grab loading and steel coil requirements


CSR Bulk Carriers CSR Bulk Carriers – Summary of Industry Feedback– Summary of Industry Feedback

a) Mandatory grab notation – In order to protect the inner bottom against cargo damages, grab notation has been made mandatory (Ship owners comment)

b) Increase in values of corrosion additions – Wastage allowances have been increased by 1 mm to 2 mm compared to first draft. Higher increases concern heated HFO tanks, transverse bulkheads and Side shell wind & water strake (Ship owners comment)

c) Modifications of prescriptive requirements in Ch 3 Sec 6 & Ch 9 Sec 1 & 2 – Continuity of strength within primary members (from cargo area to engine room and fore/aft parts) has been put to the top level and the text modified to avoid vague expressions (UGS comment). Prescriptive requirements concerning spacing of primary members have been modified to suit successful recent designs (Shipyards comments)

d) Prescriptive requirements for bulkheads - Prescriptive requirements for transverse bulkheads in way of ballast holds of ships smaller than 150 m in length have been added (Ship owners comments)

e) Number of loading conditions for Direct Strength Analyses – the number of cases to be computed has been divided by a factor 2 to consider only the cases having practical influence on the design (Shipyards comments)

f) Buckling procedure – the buckling requirements have been rewritten to be more explicit and easy to apply ( Shipyards comments)



g) Relative deflection criteria – Relative deflection criteria between the double bottom and the transverse bulkheads has been added to cope with UGS concerns about flexible D/B structure (Ship owners comment)

h) Permissible misalignments – Values of IACS Rec. 47 for permissible misalignments of some important structural details have been included in the rules as minimum requirements (Ship owners comment)

i) Minimum thickness– Minimum thickness of weather deck has been found too conservative and aligned on Oil Tankers CSR and inner side of DSS bulk carriers has been reduced to be not greater than side shell (Shipyards comments)

j) Requirements for pillars - Prescriptive requirements for pillars have been added and fillet weld accepted in compression only (Shipyards comments)

k) Deep penetration welding – The number of details where deep penetration welding is requested has been increased (Class comments)

l) Scantling pressure for hatch covers in ballast holds – the pressure has been reduced to take into account ullage effect ( Manufacturers comments)

m) Prescriptive coating performance standard – Lack of requirements in this case may lead to poor standards applied in practice therefore this new item has been introduced in the Rules (Shipowners comment)



n) Provide mandatory prescriptive requirements for the spacing/scantlings of all primary members– Direct strength analysis ( stresses + buckling + deflections) is fundamentally trusted for scantlings of primary members in line with modern practices (Ship owners comment)

o) Request complete ship extent FEM model - results of 3 holds models in the cargo area may be extrapolated to fore/aft regions (Ship owners comments)

p) Increases of corrosion allowances not connected to IACS statistics – partially accepted for areas where some damages could be omitted from the statistics (voluntary grounding, contact damages on side shell) but not in general, as corrosion allowances are based on IACS statistics ( Ship owners comments)

q) Reduce mini thickness of longitudinals – reducing mini thickness of longitudinals to fit present practices was refused due to increase of corrosion allowances (Shipyards comments)

r) FEM analyses and fatigue procedure lead to unreasonable increases of scantlings – These increases are justified by excessive spacing of primary members. FEM analysis is effective to detect this problem. Fatigue results are backed by real damage cases (Shipyards comments)


Modifications between the third and final draftsModifications between the third and final drafts

Corrosion allowance change limit length is returned back to 150 m

– IACS statistics show a difference of corrosion between Handymax and Handysize on one side, Panamax and Capesize of the other side. The limit is 50,000 dwt, corresponding approximately to 190 m in length

– While the limit of 190 m is technically justified, an additional wastage margin was provided in 1st and 2nd drafts for vessels greater or equal to 150 m in length. The length limit of 150 m was maintained in the Rules.

CSR notation is introduced for vessels complying with new Rules

– This will allow easy identification of ships built according to the new Common Structural Rules for Oil Tankers and Bulk Carriers


Harmonization and MaintenanceHarmonization and Maintenance


Short-term harmonizationShort-term harmonization

Short-term harmonization issues identified as barriers

to adoption have been concluded.

– Corrosion additions

– Rounding

– Wave loads (quartering sea, H.G. shear)

– Hull Girder Ultimate Strength

– Buckling (prescriptive buckling)

– Finite element analysis (two methods in JBP)


Long-term harmonizationLong-term harmonization

Full harmonization required for

– Wave loads

– Fatigue

– Finite element analysis

– Buckling

– Prescriptive requirements


Long-term harmonizationLong-term harmonization

Full Harmonization Plan

• One year application and feedback period before long term

harmonization

• Detail plan for full harmonization will be developed by the Hull

Panel by the end of the one-year feedback period

• Three years of harmonization work

• One year for implementation (industry review)

• Full harmonization in five years from implementation


Maintenance of the RulesMaintenance of the Rules

• Common interpretations

• Feedback from Members and Industry

• Future amendments to CSR



Groups involved in the rule maintenance

– Permanent Secretariat

– GPG

– Hull Panel

– Tanker and Bulk Carrier Project Teams

– Project Teams for Cross-checking FE and Prescriptive Requirements



Permanent Secretariat

• Coordinates the feedback, interpretation and amendment processes

and maintains master copy of the rules

GPG

• Provides oversight for the feedback, interpretation and amendment

processes and deals with policy matters

Hull Panel

• Is responsible for consistent implementation through common

interpretations, consistent replies, and future amendments

Tanker and Bulk Carrier Teams

• Provide technical expertise and prepare replies and interpretations for

Members



Additional Project Teams to prepare for consistent

implementation of CSR

• FEA team cross-checking FE requirements

• Prescriptive Rule team for cross-checking prescriptive

requirements

• Teams will provide benchmark data for software

testing to ensure common application and

implementation


Features of the Common Structural Features of the Common Structural RulesRules

Some of the new features in the CSRs

include:

• Rounding

• Net thickness

• Hull girder ultimate strength

• Coating performance standard


Feature – RoundingFeature – Rounding

Round UP to next 0.5mm on wastage allowance

Example:

twas = 2.5mm from rounding up 2.2

2.2 = 1.0(side1)+1.2(side2)

Round TO nearest 0.5 mm on net thickness

Example:

tnet = 15.5mm from rounding 15.65

Add the two rounded numbers and the reserve addition to

give the gross thickness:

tgross = 15.5 + 2.5 + 0.5 = 18.5 mm


Feature – Net Scantling ApproachFeature – Net Scantling Approach

Predicted corrosion

in 2.5 years (0.5 mm)

RequiredNet

Thickness

CorrosionAddition

Design

RequiredRenewalThickness

WastageAllowance

In Service

Annual ThicknessMeasurements


Feature – Tanker Sample Wastage Allowance ValuesFeature – Tanker Sample Wastage Allowance Values


Inner bottom: 5.5mm

Internal member: 3.0mm

Bulkhead : 6.5mm

Slant of Lower Stool: 6.5mm (void)

Inner skin :4.0mm

Hopper Slant:5.5mm

Side shell:S/H:3.5mm4.0 mm (wind&water)

D/H:3.0mm3.5mm (wind&water)

Within 3.0m below the top of tank

Upper Deck: 4.0mm

Sheer strake: 3.5mm

Feature – Sample Wastage Allowance Values for BC-A Feature – Sample Wastage Allowance Values for BC-A and BC-B Bulk Carriers with L > 150 mand BC-B Bulk Carriers with L > 150 m

Slant : 3.5mm

Deck iwo Tr. upper stool (Void) : 3.0mm

Bilge strake: 3.0mm

Bottom: 3.0mm Keel: 3.0mm


Slant : 4.0mm

Internal member:

4.0mm

Face of PSM: 4.5mm

Hatch coaming: 3.5mm

Face of PSM: 3.5mm

Slant of stool: 4.0 mm

Upper bracket: 4.5 mmSide frames: 4.5 mm Lower bracket: 5.0 mm

Bulkhead (Upper): 5.5mm

Wat

er B

alla

st

Water Ballast


Inner bottom: 4.5mm


Bulkhead : 3.5 mm

Slant of Lower Stool: 4.0mm (void)

Inner skin :3.0mm

Hopper Slant:4.5mm

Side shell:SH:3.0mm3.5mm (wind&water)

DH:3.0mm3.5mm (wind&water)

Within 3.0m below the top of tank

Upper Deck: 4.0mm

Sheer strake: 3.5mm

Feature – Sample Wastage Allowance Values for BC-C Feature – Sample Wastage Allowance Values for BC-C or Bulk Carriers with L < 150 mor Bulk Carriers with L < 150 m

Slant : 3.0mm

Deck iwo Tr. upper stool (Void) : 3.0mm

Bilge strake: 3.0mm

Bottom: 3.0mm Keel: 3.0mm


Slant : 3.5mm

Internal member:

4.0mm

Face of PSM: 4.5mm

Hatch coaming: 2.5mm

Face of PSM: 3.5mm

Slant of stool: 3.0 mm

Upper bracket: 2.5 mmSide frames: 3.0 mm Lower bracket: 3.0 mm

Bulkhead (Upper): 2.5mm

Wat

er B

alla

st

Water Ballast


Feature – Feature – Hull girder ultimate strengthHull girder ultimate strength

• Harmonised design criteria

• JBP ultimate capacity method is included in

the JTP Rules

1.1/2.10.1

1.1/3.10.1

UWSEAPERMSW

UWFULLSW

MMM

MMM

With full load homogeneous still water moment:

With permissible still water moment:


Feature – Coating performance standardFeature – Coating performance standard

• For ships contracted for construction on or after the date of IMO adoption of the amended SOLAS Regulation II-1/3-2, by which an IMO “Performance standard for protective coatings for ballast tanks and void spaces” will be made mandatory, the coatings of internal spaces subject to the amended SOLAS Regulation are to satisfy the requirements of the IMO performance standard.

• Consistent with IMO Resolution A.798(19) and IACS UI SC 122, the selection of the coating system, including coating selection, specification, and inspection plan, are to be agreed between the shipbuilder, coating system supplier and the owner, in consultation with the Classification Society, prior to commencement of construction . The specification for the coating system for these spaces is to be documented and this documentation is to be verified by the Classification Society and is to be in full compliance with the coating performance standard.

• The shipbuilder is to demonstrate that the selected coating system with associated surface preparation and application methods is compatible with the manufacturing processes and methods.

• The shipbuilder is to demonstrate that the coating inspectors have proper qualification as required by the IMO standard.

• The attending surveyor of the Classification Society will not verify the application of the coatings but will review the reports of the coating inspectors to verify that the specified shipyard coating procedures have been followed.


IMO Coating Performance Standards (CPS)Earliest Implementation Schedule for SOLAS and IACS CSR

RevisedSOLAS II-1/3-2 entry into force mandating CPSfor shipswith keel laidon/after 01 Jul 08

Draft CPS(DE 49)

SOLAS XII/6.3 enters into force recommending CPS for Bulk Carriers

Approval of CPS and SOLAS II-1/3-2(MSC 81)

Adoption of CPS and Revised SOLAS II-1/3-2 (MSC 82)

IACS CSR requires CPS for shipscontracted for construction on/after the adoption date of the Revised SOLAS II-1/3-2

2007(Jan)

2006(Jan)

2008(Jan)

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Adopted by IACS Council on 14 December 2005 Summary of CSR – Tanker Rules – Bulk Carrier Rules...

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