IGC Code IMO's "International Gas Carrier Code" is a common basis for calculations for the classification societies Implemented in DNV Rules Yield and

IGC Code

• IMO's "International Gas Carrier Code" is a common basis for calculations for the classification societies

• Implemented in DNV Rules• Yield and fatigue requirements for the LNG tank

structure:– ”… the operating life is normally taken to

correspond to 108 wave encounters on the North Atlantic".

– This corresponds to 20 years of operation in the North Atlantic.

– For membrane type tanks the Code has no specific requirement for fatigue assessment of hull structures.

• Geometry of Cargo Tanks

• Material Selection

• Acceleration ellipse and C/tank pressures, Pt. 5 Ch. 5

• Strength of inner hull - plates and stiffeners

• Cargo hold FEM model- typical results

• Cases

• Fatigue

• Additional Notation - PLUS-1 / PLUS-2

• Critical Areas with respect to Fatigue

LNG Carriers with Membrane Tanks

Rev. 030611

Typical Midship Section

• No CL Bulkhead

• Complete double hull

ì.e. “clean” tanks

• Rigid double bottom

grid structure

• High grade steel in

inner hull

Trunk Deck

Upper Deck

Passage Way

Hull Structure

C2

C1

Double side width : min 760 mm

Double bottom height : min 2 m or B/15

H1

Relationship between parameters as follows:

- C1 0.3 x H1

- C2 2.5 m

Double hull:

Height and width limited by the IGC Code

Appr. 135°

Membrane Tanks - Tank Shapes

Hull Structure

Plan viewCross section

Tank nos.

2, 3 & 4

Min 2.2 m

Tank no 1

Membrane Tanks - Tank Shapes

• For a typical 4 tank / 140000 m3 ship:

- Tank 1 13% LBP

- Tank 2 & 3 17% LBP

- Tank 4 15% LBP

Typical Tank ArrangementHull Structure

Reinforced AreasHull Structure

Reinforced Area

Transverse corners

Oblique Dihedron

Long. Dihedron

Trihedron

Selection of Steel Grades

-23ºC

-22ºC

-2 ºC-3ºC

-15ºC

-7ºC-5ºC

-19ºC

-27ºC

-27ºC

Cofferdam:

withoutheating:

with heating:

- 61ºC- 64ºC

+ 5ºC0ºC

Membrane, GTT NO96

Assumptions:

• LNG on secondary membrane• Air temp.: - 18°C (USCG)• Sea temp.: 0°C• LNG temp.: - 163°C• USCG Alaska is not included• Separate analysis for outer hull, IGC: air 5°C & sea 0°C

Insulation thickness:

Primary : 230 mmSecondary : 300 mm

Blue: Inner hull steel temperatureRed: Compartment temperature

DNV Rules:


Several material grades,NVA, B, D, E & SUS

NVE

NVD

NVD

NVD

NVB


Hull Strength

FAILURE MODES IN HULL STRUCTURES

•Yield, e.g. permanent plastic deformations/rupture of a bulkhead stiffener after a ballast tank has been subjected to overpressure.

•Buckling, e.g. a plate, a stiffener or a pillar subjected to compression may fail.

•Fatigue, e.g. a crack in way of a bracket toe due to wave loads or vibration.

•Brittle fracture, e.g. carbon steel will become brittle if the temperature becomes too low; hull material grade selection

IGC Code

• IMO's "International Gas Carrier Code" is a common basis for calculations for the classification societies

• Implemented in DNV Rules, Pt.5 Ch.5

• Yield and fatigue requirements for the LNG tank structure, i.e. the inner hull:

- ”… the operating life is normally taken to correspond to 108 wave encounters on the North Atlantic".

- This corresponds to 20 years of operation in the North Atlantic.

Local Strength of Inner Hull

All parts of the vessel should be checked against the Rule requirements for main class as given in Pt.3 Ch.1, inclusive the inner hull members supporting the membrane tanks.

The pressures and allowable stresses for plates and stiffeners are given in the Rules Pt.3 Ch.1, Sec. 6 for inner bottom, Sec. 8 for inner deck and Sec. 9 for inner side and transverse bulkheads.

Cargo tank pressures given in the Rules Pt.5 Ch.5 Sec.5A should be applied for the local scantlings for inner hull (plates and stiffeners). The local scantlings of plates and stiffeners should satisfy the allowable stresses given in Pt.5 Ch.5 Sec.5 H.

The cargo pressure for a full tank is given by:

peq = p0 + (pgd)max. ( bar)

pgd = aβ·Z·ρ/(1.02·10 4) ( bar)

where

p0 = design vapour pressure is the maximum gauge pressure at the top of thetank, not to be taken less than 0.25 bar

(pgd)max.= maximum combined internal liquid pressure, resulting from combinedeffects of gravity and dynamic acceleration

aβ = the dimensionless acceleration (relative to the acceleration of gravity)resulting from gravitational and dynamic loads, in an arbitrarydirection β (a more detailed description is given below)

ρ = the maximum density of the cargo in kg/m3 at the design temperatureZ = largest liquid height (m) above the point where the pressure is to be

determined measured from the tank shell in the a direction

Liquid Pressure in Cargo Tanks - Pt. 5 Ch. 5

Acceleration Ellipse - Pt. 5 Ch. 5

DYNAMIC LIQUID PRESSURE IN CARGO TANKS

Pgd(Pgd)max.

Z pgd

0°

5°

peq = p0 + (pgd)max. ( bar)

pgd = aβ·Z·ρ/(1.02·10 4) ( bar)

Z

Accelerations for Liquified Gas Carriers

The Rule values of ax, ay and az may be replaced by accelerations calculated from direct wave load analysis

Liquid Pressure in Cargo Tanks

Liquid Pressure in Cargo Tanks

The required plate thickness for inner hull is:

t = 15.8 s (peq/)½ + tk (mm)

Where:

= 0.80·Y allowable stress

Y = yield stress (N/mm2)s = stiffener spacing (m)tk = corrosion addition (mm)

Local Strength of Inner Hull - Plates

Local Strength of Inner Hull - Stiffeners

Inner Hull - Allowable Stresses

stat + dyn all [N/mm2]

where

stat = bending stress due to the maximum still water moment calculated for the severest loaded condition or ballast condition which ever are the most severest

dyn = bending stress due to maximum wave corresponding to the 10-8 probability for winter north Atlantic Conditions

all = allowable hull girder bending stress for inner hull,120 N/mm2 for GTT NO96 and175 N/mm2 for GTT Mark III

Allowable stresses given for GTT NO96 and GTT Mark III:

• Hull structure shall generally to be designed according to Pt. 3 Ch. 1, similar to a conventional tanker

• Maximum hull girder stresses at inner hull to be within allowable stresses for the containment system

• Inner hull supporting the cargo containment system shall be designed based on dynamic loads at 10-8 level, ref. Pt. 5 Ch. 5

• Material selection for hull to be according to Pt. 5 Ch. 5 based on temperature analysis

Strength Analysis of Membrane LNG Carrier

Midship Section - Section Scantlings

At hand verification of:•Hull girder strength•Local strength and buckling ( plates/stiffeners )

NAUTICUS-Hull MODELLING

Concept Model

Cargo Hold Analysis - FEM

FEM Results

FEM Model

Concept Model

Cargo Hold Analysis - Load Cases

Table 4.1 Rule loading conditions for membrane tankers for LNGLCNo

Draught ConditionExternalpressure

Internalpressure

Figure

L1 T Sea Dynamic Static 1)

L2 TA Sea Static Dynamic 2)

L3 0.5T Harbour Static Static 1)

L4 TA Sea Dynamic 3) Dynamic 3)

Comments:1) Pressure should include overpressure, p0; p = ρg0h s + p0

2) Pressure should include vertical acceleration and overpressure, p0; p = ρ(g 0 + 0.5av)hs + p0

3) External pressure in accordance with Rules Pt.3 Ch.1 Sec.134) Internal pressure in accordance with Rules Pt.3 Ch.1 Sec.13, including overpressure, p0

• Scantling draught: T

• Minimum draught with one C/tank full: TA

• The cargo tanks should not be operated in sea going condition with filling between 10% of tank length and 80% of tank height (sloshing).

• Allowable stresses and buckling control for double hull structure and cofferdam bulkheads according to main class as given in Pt.3 Ch.1

Cargo Hold Analysis - Strength Analysis

Cargo Hold Analysis - FEM Results

FEM Results - Outer Shell

Buckling, in the middle of empty hold

FEM Results - Inner Hull

Buckling, in the middle of empty hold

Buckling, in way of full hold, compression both

horizontally and vertically

FEM Results - Transverse Bulkhead

High shear stress

FEM Results - Girders

Edit in Veiw > Header and footer Edit in Veiw > Header and footerSlide 33

LNG Carriers with Spherical Tanks

• Design for spherical tanks and hull tanks• Wave load analysis• Hull structural design

- Temperature analysis

- Selection of material

- Cargo hold analysis

- Fatigue analysis

MOSS Type Containment System

Design for Spherical Cargo Tanks

•BACKGROUND–DNV developed the first set of design criteria in connection with the introduction of the Spherical LNG Containment system in the early 1970’ies

•Keywords: Leak-before-Failure, fracture mechanics, direct load and strength analysis, buckling and fatigue

• DEVELOPMENTS– Based on extensive experimental and analytical research

on the buckling strength criteria of the• cylindrical skirt foundation and

• the spherical tanks

DNV introduced improved buckling design criteria in the late 1970’ies (CN30.3)

– 1979 : A design acceptance programme for the spherical shell part was made in based on the current set of criteria (NVKULE).

– 1987 : The criteria were issued as Class Note 30.3 covering spherical shells only


• NEW CRITERIA– 1995: An updated PC version of NVKULE with new

spherical tank criteria and extended membrane stress combinations

– 1996: A new PC design acceptance programme NVSKIRT for the cylindrical skirt foundation available

– 1997: Class Note 30.3 with new design criteria issued

Design for Spherical Cargo Tanks, cont.

• NEW DEVELOPMENTS– The structural reliability and

the buckling criteria were in the period 1989-1996 re-examined through a series of projects

– A new set of buckling criteria for both the spheres and skirts were developed and formulated in a modern Limit State format


Structural Analysis Spherical Tank LNG Carrier

Spherical Tank - frame and girder models

1234

FEM MODEL REQUIRED FOR CLASS APPROVAL

• Include hull, skirt, cargo tanks and covers• Interaction forces in tank shell and covers• Tank foundation flexibility• Coarse overall stress flow

FEM Analysis of Hull and Tank Structure

In this case a global FEM model from bow to end of tank 3 shall has a sufficiently fine mesh to analyse deformation and stresses in:

• Skirt• Cargo tanks• Hull girder/framing system• Tank foundation deck


No filling restrictions due to sloshing.

Aftship FE-model

Foreship FE-model

Midship FE-model


Structural Analysis -1

• Structural Analyses of Hull and Cargo Tank

• DNV uses the SESAM suite of analysis programs, which includes

– Wave load analysis programs

– Automatic load transfer to structural analysis part

– Structural response (FEM)

– Post-processing & plotting

– Strength checks (yield, buckling, fatigue)

• Special tank shell analyses with (BOSOR4/5) or NISA for spherical tank systems

Wave Load Analysis

• Environmental conditions– North Atlantic (Extreme loads - ULS)– Word-wide operation (Fatigue - FLS)

• Six loading condition have been considered– full load, ballast plus 4 part load conditions

• Calculation of transfer functions– Linear strip theory program (WAVESHIP), alternatively 3D-

sink source program (WADAM) and SWAN– responses in irregular short crested seas– 2 forward speeds have been calculated to allow for speed

reduction in heavy weather (WAVESHIP, 0, 12 & 20 knots), SWAN (0 & 16 knots), WADAM (0 knots)

– Statistical processing for long term (extreme) loads

• Automatic load transfer to structural FEM model



Fem Models - 1

A global model (full width) extending over the total hull. – to analyze the hull girder stress response and

the overall deformation response of main hull structural members

– The wave loads derived from the wave load analysis will be automatically transferred to the model thus ensuring equilibrium.

Fem Models - 2

Two frame and girder models - one for tank no. 1 and one for tank 2 & 3

OBJECTIVE: To analyze deformations as well as stresses in the framing/girder system including the tank foundation deck.

– the model were used as a stand-alone models for a rule based midship area analysis

– The frame and girder models were included in the global model

Structural Analysis - 4

Fem Models - 3

Local finite element Models

• Calculation of local stresses for determination of Stress Concentration Factors (SCF) in fatigue sensitive areas

• These models were inserted into the global model or analysed separately using the sub-modeller technique available in SESAM.


Ship Hull Analysis (cont..)

Structural strength evaluation

– Yield and buckling checks

– Fatigue life evaluation

– Hull girder strength



Cargo Containment System

• Detailed stress analyses of tanks and skirts (NISA)• Detailed stress concentration analyses of tanks and skirts (FEM)

– equator profile and tower connections to upper and lower hemisphere

• Strength evaluation of tanks and skirts– Strength margins of spheres and skirts (buckling, allow. stress)– fatigue and fracture/crack analyses - ”leak-before-failure”

• Temperature distributions in cargo tanks, skirts and void spaces – Steady-State temperature distributions (design) – transient temperature distributions (optimisation of loading

procedure)

WAVE LOAD ANALYSIS

A utomatic transfer of dynamic internal/external pressures and inertia loads

D irect wave load and response analysis

Wave load analysis

Pressure distribution

Wave Load Analysis - Spectral Fatigue Analysis

Loading Conditions

The following six loading conditions will normally be applied:

— LC06: Normal ballast condition– LC11: Departure - full load– LC13: Departure - tank no. 1 full – LC14: Departure - tank no. 2 full– LC15: Departure - tank no. 3 full– LC18: Departure - tanks no. 2 + 4

full

Loading Conditions

Normal ballast condition (LC06)

Loading Conditions

Departure - full load (LC11)

Loading Conditions

Departure - tank no. 1 full (LC013)

Loading Conditions


Loading Conditions


Loading Conditions

Departure - tanks no. 2 + 4 full (LC18)

Load Components - LNG Carriers

• Hull girder bending and torsion

• external and internal pressure loads

• inertia loads from hull, equipment and cargo

Wave Load Analysis

Calculation Procedure

• Hydrodynamic modeling and calculation of transfer functions for 6 d.o.f. at selected sections

• Prediction of long term values for ULS (20 year) and FLS (probability 10-4)

• Determine design waves (heading, height and period)

• Calculate pressure distribution and accelerations for design waves and transfer to structural model

• Determine non-linear correction factors (if any)

Wave Load Analysis

Hydrodynamic Analysis Options

DNV ENVIRONMENTALLOAD PROGRAMMES

WADAM

FASTSEA

STRIP THEORY

3-D

2-D

ZERO LOW MODERATE HIGH

SPEED

SWAN

WAVESHIP:Linear strip theory, frequency domainNV1418: Non-linear strip theory, time domainWADAM: 3-D linear diffraction theory, zero forward speed FASTSEA: 2.5-D high speed theory, valid for Fn above 0.4SWAN: Linear and non-linear, frequency domain with forward speed, time domain with zero and forward speed

Wave Load Analysis

Wave Climate Description• Traditional

– Scatter diagram for sea area - conditional Weibull Distribution of Hs and Tz

– Long term distribution derived from short term responses

• Present approach– Uses actual scatter diagram of Hs and Tz for the sea area

considered

– Actual contribution from each Hs and Tz taken into account

– Result can be used for both Ultimate Strength (ULS) and Fatigue (FLS) evaluations

Wave Load Analysis

• Mesh size in the order of the plate thickness• All local and global load effects included• 8 headings times 22 wave periods per

heading => 176 load cases for each loading condition

Stochastic Fatigue AnalysisFull stochastic analysis

Midship sectionMidship section

TankTank Weather coverWeather cover

Pipe TowerPipe Tower

Midship sectionMidship section

Cylindrical skirtCylindrical skirt

Supporting girderSupporting girder

Steady - state temperature distribution in tanks

Temperatures:

LNG = - 162 oCBelow tank inside skirt = 20 oCOutside tank skirt = 28 oC


0

1 0 0 0

2 0 0 0

3 0 0 0

4 0 0 0

5 0 0 0

Equator

Temperatures:

Sea = 32 0CAir = 45 0CLNG = -162 0C


0

1 0 0 0

2 0 0 0

3 0 0 0

4 0 0 0

5 0 0 0

The Equator Profile

Hull Structures

Generally hull structural analysis according to Pt.3 Ch.1:

• Local Scantlings of Plates and Stiffeners• Longitudinal Strength• Fatigue, NAUTICUS(Newbuilding), PLUS-1/2

USCG material grade for deck corner and bilge strake:

• USCG: Deck corner to be of grade NVE, NV32E or NV36E and bilge plate to be of grade NVD, NV32D or NV36D.

Midship Section - Section Scantlings

Typical hull girder section i.w.o. centre of cargo tank

A t hand verification of:•Hull girder strength•Local strength and buckling capacity of plates/stiffeners

Selection of Materials - Temperature Analysis

• IGC: Air temperature 5°C and sea temperature 0°C, applicable for all hull structure in cargo area

• USCG: Air temperature -18°C and sea temperature 0°C, applicable for inner hull and members connected to inner hull

• USCG Alaska: Air temperature -29°C and sea temperature -2°C, applicable for inner hull and members connected to inner hull

Temperature analysis for selection of material grade to be based on a hypothetical outflow of gas (leak before failure). Steel grade according to Pt.5 Ch.5 Sec. 2 for the following conditions:

Temperature Analysis Results

-8ºC

-10ºC

-3ºC

1ºC

-6ºC

-3ºC

-25ºC

IGC temperature:

Air: 5ºC

Sea: 0ºC

Temperature Analysis Results

-8ºC

-10ºC

-27ºC

-15ºC

-31ºC

-19ºC

-26ºC

USCG temperature:

Air: -18ºC

Sea: 0ºC

Selection of Materials - Temperature Analysis

DNV Rules:

Tank category or boundary betweendifferent category tanks/spaces

Within 1,5 m belowweather deck

Elsewhere

Cargo oil tank only 2.0 1.0Ballast tank 3.0 1.5Cargo oil /ballast tank 2.5 1.5Cargo tank/hull exterior 1.0 0.5Ballast tank/hull exterior 2.0 1.0

Corrosion additions, tk, in DNV Rules:

Local Stresses applying net Scantling

Cargo Hold Model to be based on net Scantlings, t - tk:

3DGM - Inner 3DGM - Inner StructureStructure

Double BottomDouble Bottom

Foundation deckFoundation deck

Double sideDouble side

Passage wayPassage way

Transverse bulkheadTransverse bulkhead

Single skin trv. bhdSingle skin trv. bhd

Upper stoolUpper stool

3D Global Model3D Global Model

Midship block - Plate thickness Midship block - Plate thickness mapmap

Double sideDouble side

Trv. BhdTrv. Bhd

Double bottomDouble bottom

NV-NSNV-NS

NV-36NV-36

NV-32NV-32

Midship block - Material class Midship block - Material class mapmap

Cargo Hold Analysis - Long. Stresses

Empty HoldBi/axial buckling of bottom plate,Shear stress in DB floors/gir.

Fatigue Strength

Why focus on fatigue?

• Most common hull damage

• May cause water ingress to

insulation spaces

• High cost and time consuming

repairs

• LNG vessels often designed

for extended life time

Hull Structure

Fatigue

Fatigue Crack

Fatigue Crack

Fatigue Crack

Fatigue Requirements

Area North-Atlantic World WideBallast tanks 20 years 31 yearsCargo tanks 20 years 39 years

Class Notation Rules Scope Method Requirement 1A1 Pt. 3 Ch. 1.

Sec. 17Implicit in the rules, e.g. f1 factor.Side longitudinals, dynamic stress

20 years WW

Tanker forLiquefied Gas

Pt. 5 Ch. 5.Sec. 5

Cargo tank structure Wave load analysis 20 years N-A

NAUTICUS(Newbuilding)

Pt. 3 Ch. 1.Sec. 16 B

Longitudinals in cargoarea

CN 30.7Nauticus Hull

20 years WW

PLUS-1 /PLUS-2

Pt. 3 Ch. 1.Sec. 16 C

Longitudinalconnections and deckopenings in cargo area

CN 30.7Addendum of ditto

30 years WW /40 years WW

Fatigue - Higher Tensile Steel

Fatigue in General

• In a simplified way the fatigue life can be expressed:

• wereN = fatigue life in years

C = constant including the environment

= nominal stress

k = stress concentration factor (notch factor)

31

kCN

10% uncertainty in stresses gives

30% uncertainty in fatigue life

Hull Structure

• Fatigue damages are caused by dynamic loading

Fatigue

Fatigue and Corrosion

Thinning Effect

Fatigue Level

Fully protected

5 10 15 20 25 30 Years

Bare Stee

l, Cor

rodin

g

Unacceptable Damage Zone

5 yr.

Paint S

pec.

10 yr

. Pain

t Spe

c.

15 yr

. Pain

t Spe

c.

World Wide Trading

• Standard Rule Requirement is Assuming World Wide Trading

• 20 years world wide corresponds to 10 years North Atlantic

• Wave environment for fatigue needs to be specified by owner if increased fatigue strength is requested

Operation Route Reduction Factor, fe

fe = 1,0 for North Atlantic operation

= 0,8 for world-wide operation

Trading Route

Fatigue Level

5 10 15 20 25 30 Years


Years of Operation

Fully protected, World Wide

Fully Protec

ted, N

orth Atla

ntic

10 yr

. Pain

t Spe

c.

Fully protected, PG-

Japan


Part Time at Sea, Assumptions

Vessel type Bulk carrierslarger thanPanamax (*)

Panamaxbulkcarriers andsmaller (*)

Vesselsintend tocarry orecargoesmostly

Alternatecondition

0.25 0 0.5

Homogenouscondition

0.25 0.5 0

Ballastcondition

0.35 0.35 0.35

Vessel type Tankers

Loaded conditions 0.45

Ballast conditions 0.40

Vessel type Container vessels

Loaded conditions 0.65

Ballast conditions 0.20

• Satisfactory Fatigue Life Depends on:

Design / Approval:

Intended trade area Paint Specification Workmanship Appropriate Class Notations

Hull Structure

Fatigue

End connections

F atigue life assessment based on SN-curves

R ule dynamic loads for identification of posproblem areas

CLASSIFICATION NOTE 30.7

NAUTICUS(Newbuilding) - Fatigue Analysis

NAUTICUS(Newbuilding)

Most critical area w.r.t. fatigue of longitudinals

Hopper Knuckle

High Stress Concentration

Critical Areas - Lower Hopper KnuckleHull Structure

Inner Bottom

Fatigue Calculations L/Gir. Local FEM

Additional Notation - PLUS-1 / PLUS-2Additional Fatigue requirements compared to 1A1 and NAUTICUS(Newbuilding):

•Increased design lifetime, 20years 30 years / 40 years•Additional details, e.g. stiffener on top, cut out and collar plate

PLUS - Location of hotspots

Hotspots forlug type

Hotspots forslit type

PLUS - Local FEM models

Local models in D/B

PLUS - Local FEM models

Standard lug New lug No lug

Hull Structure

Fatigue: PLUS-2

High stress concentration

Fatigue: PLUS-2 Hull Structure

Deck Opening

Critical Areas against fatigueHull Structure

3

2

1

4

Details to pay particular attention to:

1. Hopper tank, lower knuckle2. Hopper tank, upper knuckle3. Side longitudinals4. Alignment, bulkhead - bottom structure5. Deck opening

5

Critical Areas - Typical Web Frame

Fatigue

PLUS-1/ PLUS-2

PLUS-1 / PLUS 2

Shear Stress

Shear Stress

Critical Areas – Tank boundary

Weld joint in tank boundary

Lower hopper, lower joint:

- Full penetration- 100% MPI- 100% UT

Lower hopper, upper joint:

- Full penetration- 100% MPI- 100% UT

Upper hopper, lower joint:

- Deep penetration- 100% MPI

Material & Welding Control

Ensuring weld quality and tightness

Weld profiling and weld toe grinding

SCF (Kw) =1,09

SCF (Kw) =1,19

Weld Toe Grinding

Weld profiling (dressed weld)

Fatigue

Transverse bulkhead

Longitudinal bulkhead

Critical Areas - TBHD & LBHD

Critical Areas – Lower Hopper Corner

Important: alignment & grinding

Critical Areas – Upper Hopper Corner

Important: alignment & grindingImportant: alignment & grinding

Yield & Fatigue

Shear

Critical Areas – Vertical girder in TBHD

Critical Areas – deck opening

Opening edge grinding

Critical Areas - Trans. BHD

• Fatigue

• Weld toe grinding

Material grade of hull structuresHull Structure

DB

B

B

D

E

E

EE

A

WAVE LOAD ANALYSIS

A utomatic transfer of dynamic internal/external pressures and inertia loads

D irect wave load and response analysis

Wave load analysis

Pressure distribution


Hotspot positions for lower hopper knuckle

Critical areas with respect to transverse stresses


Hotspot positions for upper hopper knuckle

Fatigue analysis of anchoring bar to becarried out in case ofinvar membrane

Documents

IGC Code IMO's "International Gas Carrier Code" is a common basis for calculations for the classification societies Implemented in DNV Rules Yield and