ShipRight Notice 1 Design and Construction

Structural Design Assessment

Primary Hull and Cargo Tank Supporting Structure of Type C Liquefied Gas Carriers, January 2017 The status of this Rule set is amended as shown and is now to be read in conjunction with this and prior

Notices. Any corrigenda included in the Notice are effective immediately.

Issue date: June 2018

Amendments to Approved date

Chapter 1, Section 2 June 2018

Chapter 2, Section 4 June 2018

Chapter 2, Section 5 June 2018

Chapter 2, Section 6 June 2018

Working together for a safer world

LLOYD’S REGISTER 1

Document History

Document Date: Notes:

September 2015 Preliminary release

March 2016 Final release

January 2017 Consolidated version to revise buckling acceptance criteria in Table 2.6.1 and Corrigenda for March 2016 version.

June 2018 Notice 1

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CHAPTER 1 INTRODUCTION Section 2 Symbols (Part only shown) 2.1 Definition P0 = design vapour pressure, see Ch 4, Cargo Containment 4.1.2 of the Rules for Ships for Liquefied Gases. P0 is not to be

taken as less than 0,25 bar. Phold+ = Cargo hold overpressure to be taken as the maximum positive pressure (above atmospheric) setting of the cargo hold

pressure relief device. Phold- = Cargo hold underpressure (suction) to be taken as the minimum pressure (below atmospheric) setting of the cargo hold

pressure relief device if fitted, or the lowest operating pressure of the dry-air/inert-gas circulation system for the hold. CHAPTER 2 ANALYSIS OF PRIMARY STRUCTURES OF TYPE C LIQUIFIED GAS

CARRIERS Section 4 Loading conditions 4.9 Hold flooded load cases 4.9.1 The objective of the load cases is to examine the yield and buckling capability of the transverse watertight bulkhead and double bottom structures to withstand the load in the event that the cargo hold is flooded as a result of collision or other accidental occurrence. 4.9.2 Each cargo hold is to be considered flooded separately. The hold flooded load cases to be analysed are specified in Table 2.4.6 Special load cases. 4.9.3 All cargo tanks are to be fully loaded and the ship is to be at its deepest draught. The damaged loading condition is summarised in Table 2.4.7 Summary of loading condition with one cargo hold flooded. 4.9.4 External and internal hydrostatic pressure due to flooded waterline in damaged heel condition is to be applied. The pressure described in Table 2.4.7 Summary of loading condition with one cargo hold flooded is to be applied to the transverse bulkheads of the flooded cargo hold. Static load due to all deadweight and lightweight items is to be applied. The ship is to be balanced vertically on a trimmed waterline. 4.9.5 No additional vertical bending moment is required to be applied to the FE model, i.e., the vertical bending moment in the model is equal to the still water bending moment generated by the loads. Existing sub-Sections 4.9 to 4.14 are to be renumbered 4.10 to 4.15.

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(Part only shown) 4.1415 Support and chock design loads Table 2.4.1 Wave load cases

Load case Still water bending moment

Rule vertical wave bending

moment

External pressure

Internal pressure

Additional sub-load

cases

Tank loading pattern

Boundary conditions

Alternate 1 S2.1, see Notes 5 and 7

MSW Hog

MW Hog

Balanced waterline

g, P0

(Phold+, Phold-) see Note 9

- (e)

See Ch 2, 3.2 Symmetrical boundary conditions for global loads and Figure 2.3.1 Boundary conditions for the application of symmetric global loads

- - - - Wave crest (f)

See Ch 2, 3.3 Symmetrical boundary conditions for local loads and Figure 2.3.2 Boundary conditions for the application of symmetric local loads and Figure 2.3.3 Alternative boundary conditions for the application of symmetric local loads

Tank loading pattern images

(e)

(f)

Alternate 2 S3.1, see Notes 6 and 7

MSW Hog

MW Hog

Balanced waterline

g, P0

(Phold+, Phold-) see Note 9

- (g)

See Ch 2, 3.2 Symmetrical boundary conditions for global loads and Figure 2.3.1 Boundary conditions for the application of symmetric global loads

- - - - Wave crest (h)

See Ch 2, 3.3 Symmetrical boundary conditions for local loads and Figure 2.3.2 Boundary conditions for the application of symmetric local loads and Figure 2.3.3 Alternative

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boundary conditions for the application of symmetric local loads

Tank loading pattern images

(g)

(h)

Note 1. The Rule design vertical wave bending moment and the permissible vertical still water bending moment envelope, Msw, is to be

applied to bending moment sub-load cases, see Ch 1, 2.1 Definition 2.1.1 and Ch 2, 4.1 Introduction 4.1.5 for definition of Msw.

Note 2. All lightweight and deadweight items are to be applied in bending moment sub-load cases.

Note 3. External pressure is applied to the wave crest and wave trough sub-load cases. No lightweight, deadweight and other load items

are to be applied. See Ch 2, 4.2 Wave load cases 4.2.3 and Ch 2, 4.13 Procedure to apply local wave crest or trough for the application of

wave crest and wave trough. See Ch 2, 3.3 Symmetrical boundary conditions for local loads for the application of vertical ground springs and

vertical balance forces.

Note 4. Bending moment sub-load case and wave crest/trough sub-load case are run separately. The resultant stresses are to be

combined by superposition.

Note 5. Alternately loaded condition with odd number tanks full and odd number tanks empty. For illustration, figure shown is a ship with

three cargo tanks.

Note 6. Alternately loaded condition with even number tanks full and odd number tanks empty. For illustration, figure shown is a ship with

three cargo tanks.

Note 7. Full ballast tanks are shown in way of empty cargo tanks. If the ship’s Loading Manual contains conditions in which ballast tanks in

way of empty cargo tanks are empty or have reduced filling level, then these conditions are to be analysed.

Note 8. A deep draught loading condition with most water ballast tanks filled.

Note 9. Cargo hold overpressure (Phold+) is to be applied to the boundary of the holds with loaded cargo tanks. Cargo hold underpressure

(Phold-) is to be applied to boundary of the holds with empty cargo tanks. These loads are applied for the assessment of the strength of the

transverse bulkheads against build-up of pressure and suction in cargo holds. Cargo hold overpressure and underpressure are not to be

applied to the cargo tank surface.

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(Part only shown) Table 2.4.6 Special load cases

Load case Still water bending moment

Rule vertical wave bending

moment

External pressure

Internal pressure

Additional sub-load cases to

apply

Tank loading pattern

Boundary conditions

Flotation case

Flotation case O5, see Notes 4, 5, 6 and 7

- - - - - (b)

See Ch 2, 3.3 Symmetrical boundary conditions for local loads and Figure 2.3.2 Boundary conditions for the application of symmetric local loads and Figure 2.3.3 Alternative boundary conditions for the application of symmetric local loads

Tank loading pattern image

(b) Deleted

Revised

Reference plot (sample) of all holds flooded

Hold flooded cases

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Hold flooded cases O6, see Notes 2, 8 and 9

Actual due to flooded

waterline in heel

condition

-

Hydrostatic pressure due to flooded and

heeled waterline

Tank pressure

Hydrostatic pressure due to

flooded and heeled

waterline

- (c)

An Inertia Relief solution is recommended. If the FE package being used does not provide this facility, then alternative boundary conditions given in Figure 2.3.1 Boundary conditions for the application of symmetric global loads may be used. See Ch 2, 3.4 Asymmetric boundary conditions for transverse loads.

Tank loading pattern image

(c)

Case 1:

Case 2:

Case 3:

Case 4:

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Note 1. The tank test case(s) are to consider the ship in the actual loading conditions when the tank test procedures are undertaken. It

may be necessary to analyse load cases for the testing of each cargo tank separately. The actual ship conditions proposed for the tests of

cargo tanks 1 and 2 must be used together with the lightest draughts chosen for each condition as described in Ch 2, 4.7 Tank test

condition 4.7.1.

Note 2. All still water load items are to be applied.

Note 3. External hydrostatic pressures due to the still waterline are to be applied.

Note 4. Cargo tanks are to be empty. External buoyancy, deadweight and lightweight items and all other loads are not to be applied.

Note 5. This load case is not based on an actual loading condition.

Note 6. Only the void space between the inside of the hold and the outside of the cargo tank boundaries is assumed to be flooded up to

the scantling draught.

Note 7. If damage stability calculations are available, then the depth of flooding from the damage stability calculations may be used in

lieu of the scantling draught as described in Ch 2, 4.8 Flotation load cases 4.8.4.

Note 8. All cargo tanks are to be fully loaded. Each cargo hold is to be considered flooded in a separate load case. The heeled flooding

condition is to be determined in accordance with Table 2.4.7 Summary of loading condition with one cargo hold flooded. Damage stability

calculation may be used to determine the flooded waterline and heel angle. See Ch 2, 4.9 Application of loads.

Note 9. External and internal hydrostatic pressure due to flooded waterline in damaged heel condition is to be applied. The pressure

described in Table 2.4.7 Summary of loading condition with one cargo hold flooded is to be applied to the transverse bulkheads of the

flooded cargo hold.

Note 810. For illustration, figures shown are ships with four cargo tanks.

Table 2.4.7 Summary of loading condition with one cargo hold flooded

Item Loading condition

Damage flooded condition

All cargo tanks are to be fully loaded and the ship is at its deepest draught. Two separate flooding conditions resulting in the following scenarios are to be considered: • Maximum draught at centreline of the forward and aft bulkheads of the flooded hold (𝑻𝟏) • Maximum draught at the outboard boundary of the forward and aft bulkheads of the flooded hold (𝑻𝟐)

The damaged heel waterline is to be determined based on the damage stability calculation. Where damage stability calculation is not available, 𝑻𝟏 and 𝑻𝟐 may be obtained as follows:

𝑻𝟏 = 𝑻𝐬𝐬 + 𝟏,𝟐 × 𝟏,𝟎𝟐𝟎× � 𝑽𝐡 +𝑽𝒃𝟏𝟎𝟎 𝐓𝐓𝐓

� (in m) 𝑻𝟐 = 𝑻𝟏 + 𝟎,𝟐𝟐 𝒃 where 𝑽𝐡 is the volume of the void space in the flooded cargo hold corresponding to the level of scantling draught (in m3) 𝑽𝐛 is the volume of the double bottom and hopper tanks, on one side of the centre line, in way of the flooded cargo hold (in m3) 𝒃 is the width of the cargo hold TPC is the displacement (tonnes) immersion per centimetre as given in the ship’s Loading Manual

Transverse bulkheads in flooded hold

Hydrostatic pressure due to the flooded waterline and pressure head due to the ship’s pitch motion. The pressure head due to the ship’s pitch motion, 𝒉𝐩𝐩𝐩𝐬𝐡, is given by:

𝒉𝐩𝐩𝐩𝐬𝐡 = 𝟎,𝟑𝟎 𝒍𝐇 𝐩𝐭𝐭(𝛙)

𝒍𝐇 𝐩𝐬 𝐩𝐡𝐭 𝐥𝐭𝐭𝐥𝐩𝐡 𝐨𝐨 𝐩𝐡𝐭 𝐨𝐥𝐨𝐨𝐟𝐭𝐟 𝐡𝐨𝐥𝐟 𝛙 is the pitch angle calculated in accordance with Pt 3, Ch 14, 1.6 Symbols and definitions of the Rules for Ships

Cargo hold boundary, side and bottom shell Pressure based on heeled waterline defined by 𝑻𝟏 and 𝑻𝟐

Cargo tanks All cargo tanks fully loaded. Pressure differential due to cargo and flooded heeled waterline is to be applied to the tank boundary in the flooded hold.

Note 1. The pressure head to be applied to the external shell plating and longitudinal internal plating is different to that specified for the bulkhead. The purpose of these load cases is to impose flood water loads, including the effect of ship motions, onto the bulkhead structure; hence the increased pressure head applied to the bulkhead.

Table 2.4.78 Friction coefficient (reference values)

CHAPTER 2 ANALYSIS OF PRIMARY STRUCTURES OF TYPE C LIQUIFIED

GAS CARRIERS Section 5 Permissible stresses 5.1 Permissible stresses Table 2.5.2 Maximum permissible membrane stresses for collision (O1, O2 and O3) and flotation load cases (O5),

flotation (O5) and hold flooded (O6) load cases

Structural item Load cases

Permissible stresses

Combined stress, σe

Direct stress, σ

Shear stress τ

Tank support systems and structure in way of

Cradle support (bracket) O1, O2 and O3 σ0 - 0,55 σ0 (see Note 3)

Anti-flotation chock seating O5 σ0 - 0,55 σ0 (see Note 3)

Topside transverse webs and flange O5 0,75σ0 - 0,35 σ0 (see Note 4)

Transverse bulkhead structure and immediate integration areas

Transverse watertight bulkhead:

Plating σ0 0,95 σ0 0,55 σ0 (see Note 3)

Vertical webs and horizontal stringers: (a) Web plating (b) Face plates

O6

σ0

_

0,95 σ0

σ0

0,55 σ0 (see Note 3)

_

Double bottom girders, side shell, inner bottom, hopper, topside and deck integration with transverse bulkhead

σ0 0,95 σ0 0,55 σ0 (see Note 3)

Note 1. Stress criteria are based on the coarse mesh described in Ch 2, 2.1 FE modelling 2.1.5. Note 2. If a finer mesh size is used, then stresses may be averaged over an area equal to the size of the coarse mesh element in way of the structure being considered. The averaging is to be based only on elements with their boundary located within the desired area. Stress average is not to be carried out across structural discontinuity or abutting structure. Note 3. Criteria relate to single FE element. Note 4. Criteria relate to mean stress over the depth of the member.

CHAPTER 2 ANALYSIS OF PRIMARY STRUCTURES OF TYPE C LIQUIFIED

GAS CARRIERS Section 6 Buckling acceptance criteria 6.1 Buckling criteria Table 2.6.2 Local plate panel required factor against buckling (collision and flotation, flotation and hold flooded load

cases)

Structural item Factor against buckling λ

Tank support systems and structure in way of

Cradle support (bracket) Anti-flotation chock seating Topside transverse web

1,0

Bulkhead structure and immediate areas of integration

Plating, vertical webs, stringers and girders 1,0

Note 1. Immediate areas of integration are to include side, bottom and deck structure from one web frame aft of the bulkhead to one web frame forward of the bulkhead.