classification notes no. 34.1 csa - direct analysis of

CLASSIFICATION NOTES

No 341

CSA - DIRECT ANALYSIS OF SHIP STRUCTURES

JANUARY 2011

DET NORSKE VERITAS

Veritasveien 1 NO-1322 Hoslashvik Norway Tel +47 67 57 99 00 Fax +47 67 57 99 11

FOREWORD

DET NORSKE VERITAS (DNV) is an autonomous and independent foundation with the objectives of safeguarding lifeproperty and the environment at sea and onshore DNV undertakes classification certification and other verification andconsultancy services relating to quality of ships offshore units and installations and onshore industries worldwide andcarries out research in relation to these functions

Classification NotesClassification Notes are publications that give practical information on classification of ships and other objects Examplesof design solutions calculation methods specifications of test procedures as well as acceptable repair methods for somecomponents are given as interpretations of the more general rule requirements

All publications may be downloaded from the Societyrsquos Web site httpwwwdnvcom

The Society reserves the exclusive right to interpret decide equivalence or make exemptions to this Classification Note

Main changesThe main changes are

mdash New class notation CSA-1 and CSA-FLS1 includedmdash CSA-FLS1 has reduced fatigue scope compared to existing class notation CSA-FLSmdash CSA-1 includes requirements for ULS and CSA-FLS1mdash Existing notations CSA-FLS and CSA-2 are kept but CSA-FLS is renamed CSA-FLS2mdash Include experience from recent project on ore carrier

The electronic pdf version of this document found through httpwwwdnvcom is the officially binding versioncopy Det Norske Veritas

Any comments may be sent by e-mail to rulesdnvcomFor subscription orders or information about subscription terms please use distributiondnvcomComputer Typesetting (Adobe Frame Maker) by Det Norske Veritas

If any person suffers loss or damage which is proved to have been caused by any negligent act or omission of Det Norske Veritas then Det Norske Veritas shall pay compensation tosuch person for his proved direct loss or damage However the compensation shall not exceed an amount equal to ten times the fee charged for the service in question provided thatthe maximum compensation shall never exceed USD 2 millionIn this provision Det Norske Veritas shall mean the Foundation Det Norske Veritas as well as all its subsidiaries directors officers employees agents and any other acting on behalfof Det Norske Veritas

Classification Notes - No 341 January 2011

Page 3

CONTENTS

1 Introduction 411 Objective 412 General413 Definitions414 Programs 5

2 Overview of CSA Analysis 621 General622 Scope and acceptance criteria 623 Procedures and analysis 624 Documentation and verification overview8

3 Hydrodynamic Analysis 831 Introduction832 Hydrodynamic model933 Roll damping1134 Hydrodynamic analysis1135 Design waves for ULS1236 Load Transfer13

4 Fatigue Limit State Assessment 1541 General principles 1542 Locations for fatigue analysis 1643 Corrosion model2044 Loads2045 Component stochastic fatigue analysis 2146 Full stochastic fatigue analysis 2447 Damage calculation27

5 Ultimate Limit State Assessment 2951 Principle overview 2952 Global FE analyses ndash local ULS 2953 Hull girder collapse - global ULS37

6 Structural Modelling Principles 4061 Overview4062 General 4263 Global structural FE-model4364 Sub models4565 Mass modelling and load application 46

7 Documentation and Verification 4871 General4872 Documentation4873 Verification 49

8 References 55

Appendix ARelative Deflection Analysis 56

Appendix BDNV Program Specific Items 59

Appendix CSimplified Hull Girder Capacity Model - MU 62

Appendix DHull Girder Capacity Assessment Using Non-linear FE Analysis 65

Appendix EPULS Buckling Code ndash Design Principles ndash Stiffened Panels 66

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1 Introduction

11 ObjectiveThis Classification Note for Computational Ship Analysis CSA provides guidance on how to perform anddocument analyses required for compliance with the classification notations CSA-FLS1 CSA-FLS2 CSA-1and CSA-2 as described in the DNV Rules for Classification of Ships Pt3 Ch1 The aim of the class notationsis to ensure that all critical structural details are adequately designed to meet specified fatigue and strengthrequirements

12 GeneralCSA-FLS1 CSA-FLS2 CSA-1 and CSA-2 are optional class notations for enhanced structural calculations ofships All calculations are based on direct calculation of load and response CSA-FLS1 and CSA-FLS2 coverfatigue analyses while CSA-1 and CSA-2 additionally covers fatigue and ultimate strength analyses

The CSA notations have requirements for the structural parts and details of the ship hull Tank systems andtheir supports are not a part of the scope for CSA Likewise structural details connected to moorings or offshoreloading systems are outside the scope of CSA

Loads caused by slamming sloshing and vibration are not included in the CSA notations

This Classification Note describes the following steps of the CSA analyses

mdash scope of analysis (areasdetails to be considered)mdash procedures for

- modelling- hydrodynamic analyses- structural analysis- ULS post processing- FLS post processing

mdash acceptance criteriamdash documentation and verification of the analyses

The CSA notations are applicable to all ship types Details to be analysed is specified for the following shiptypes

mdash Tankersmdash LNG carriers (Moss type and membrane type)mdash LPG carriersmdash Container shipsmdash Ore carrier

For other ship types the details are selected on case by case basis

The notations are especially relevant for vessels fulfilling one or more of the following criteria

mdash novel vessel designmdash increased size compared to existing vessel designmdash operating in harsh environmentmdash operational challenges different from similar shipsmdash high requirements for minimizing off-hire

13 Definitions

131 AbbreviationsThe following abbreviations and definitions are used in this Classification Note

FLS Fatigue Limit StateULS Ultimate Limit StateDNV Det Norske VeritasCSA Computational Ship AnalysisCSA-FLS1 Computational Ship Analysis - Fatigue Limit State with limited scopeCSA-FLS2 Computational Ship Analysis ndash Fatigue Limit State with full scopeCSA-1 Computational Ship Analysis - Fatigue Limit State with limited scope and Ultimate Limit StateCSA-2 Computational Ship Analysis ndash Fatigue Limit State with full scope and Ultimate Limit State

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132 SymbolsThe following symbols are used in this Classification Note

14 ProgramsThe CSA procedure requires programs with possibility for direct application of pressures and inertia from a 3Dnon-linear hydrodynamic program to a finite element (FE) analysis program with suitable applications and

CSR Common Structural RulesPLUS Class Notation covering additional fatigue requirements based on rule loadsCN Classification NoteSCF Stress concentration factor

D Moulded depthB Moulded breadthTact Actual draughtK Stress concentration factorσhot spot Stress at hotspotσnominal Nominal stress in structureθ Roll-angleζ Wave amplituderp Correction factor for external pressure in waterline regionpd Dynamic pressure amplitudezwl Water head due to external wave pressure at waterlineN Number of cyclesa constant related to mean S-N curvem S-N fatigue parameterΔσ Stress rangefm Factor taking into account mean stress ratioσf Yield stress of materialf1 Material factorσe Nominal Von Mises stressσ Nominal stressσg Nominal stress from global bendingaxial forceσ2 Nominal stress from secondary bending (eg double bottom bending)τ Nominal shear stressη Usage factorAW Effective shear area AWmod Modelled shear areat thicknessp Pressureρ Densityav Vertical accelerationpn Fraction of time at sea in the different loading conditionsg Gravitational constantMS is the still water vertical bending momentMW is the wave vertical bending momentMUI is the ultimate moment capacity of the intact hull girderMUD is the ultimate moment capacity of the damaged hull girderγ S Partial safety factors reflecting uncertainties and ensuring the overall required target safety margin

with respect to the still water vertical bending momentγ D Partial safety factors reflecting uncertainties and ensuring the overall required target safety margin

with respect to the wave vertical bending momentγ M Partial safety factors reflecting uncertainties and ensuring the overall required target safety margin

with respect to the ultimate moment capacityV maximum service speed in knots defined as the greatest speed which the ship is designed to main-

tain in service at her deepest seagoing draught

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post-processing tools to ensure good documentation and verification possibilities for a third party to review

The Nauticus programs provided by DNV are well suited for these analyses Relevant Nauticus applicationsare described in Section 8 Other programs may also be accepted

2 Overview of CSA Analysis

21 GeneralThe requirements for the CSA notations are given in the Rules for Classification of Ships Pt3 Ch1

CSA notations require compliance with NAUTICUS (Newbuilding) or CSR whichever is applicable

For class notation CSR this implies that all CSR requirements are to be complied with and documented

For NAUTICUS (Newbuilding) the ULS analysis are to be complied with independent of CSA Howeverrequirements for FLS need not be performed if compliance with CSA is documented and confirmed

All details except the stiffener-frame connections as defined by the PLUS notation shall also be included inCSA-FLS2 but only the details in 22 are to be included in the scope of CSA-FLS1

In case PLUS notation in addition to CSA is specified calculations for stiffener frame connections have to beperformed according to the procedure specified by the PLUS notation including low cycle fatiguerequirements while other requirements are documented and confirmed as part of CSA

22 Scope and acceptance criteriaThe CSA procedure includes the following analysis and checks

CSA-FLS1

mdash Fatigue of critical details in cargo hold area

- knuckles- discontinuities- deck openings and penetrations

CSA-FLS2

mdash Fatigue of longitudinal end connections and frame connection in cargo hold areamdash Fatigue of bottom and side-shell plating connection to framestiffener in the cargo hold areamdash Fatigue of critical details in cargo hold area


CSA-1

mdash FLS - Fatigue requirements as for CSA-FLS1mdash Local ULS - Yield and buckling strength of structure in the cargo hold areamdash Global ULS - Hull girder capacity of the midship section in intact and two damaged conditions

CSA-2


Each project should together with the Society define the total scope of the calculations Note that fatigue andstrength analyses may also be required outside the cargo hold area if deemed necessary by the Society Somedetails outside the cargo hold area are already specified in the Rules

The design life basis for CSA-analysis is the minimum design life as defined by class notation NAUTICUS(Newbuilding) or CSR whichever is relevant as defined in the Rules for Classification of Ships Pt3 Ch1 Theacceptance criteria for fatigue is stated in Section 471 while the acceptance criteria for Local-ULS andGlobal-ULS is given in Section 525 and Section 534 respectively

23 Procedures and analysisThe flowchart in Figure 2-2 shows the typical analysis procedure for a typical CSA

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Figure 2-1CSA calculation procedure

All calculations shall be based on direct calculated wave loads using a 3D hydrodynamic program includingeffect of forward speed The pressures and inertia loads from the hydrodynamic analysis shall be transferred tothe FE-models maintaining the phasing definitions

For FLS two principal fatigue calculation methodologies are used to comply with CSA requirements

mdash full stochastic (spectral) fatigue analysis (Section 46)mdash DNV component stochastic method (Section 47)

CSA-FLS1 require analysis with full stochastic analysis while for CSA-FLS2 both analysis procedures areneeded

Two types of ULS analyses are to be carried out ie

1) Global FE analyses ndash local ULS (Section 53)Is required for all structural members in the cargo hold area Linear FE stress analyses are performed for verification of plating stiffeners girders etc against bucklingand material yield The buckling and ultimate strength limits are evaluated using PULS buckling code Thisis required for all structural members in the cargo hold area however buckling is in general only performedfor longitudinal members

2) Hull girder collapse ndash global ULS (Section 54)This ULS assessment is based on separate hull girder strength models accounting for buckling and non-linear structural behaviour of plating stiffeners girders etc in the cross-section The purpose is to controland ensure sufficient overall hull girder strength preventing global collapse and loss of vessel Simplifiedstructural models (HULS) or advanced non-linear FE analyses may be used Both intact and damaged hullsections are to be assessed

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The CSA analysis is based on a set of different structural FE-models (Section 6) A global FE-model isrequired for the analyses in addition to models with element definition applicable for evaluation of yieldbuckling strength and fatigue strength respectively

24 Documentation and verification overviewThe analysis shall be verified in order to ensure accuracy of the results Verification shall be documented andenclosed with the analysis report

The documentation shall be adequate to enable third parties to follow each step of the calculations For thispurpose the following should as a minimum be documented or referenced

mdash basic input (drawings loading manual weather conditions etc)mdash assumptions and simplifications made in modellinganalysismdash modelsmdash loads and load transfermdash analysismdash results (including quality control) mdash discussion andmdash conclusion

Checklists for quality assurance shall also be developed before the analysis work commences It is suggestedthat project-specific checklists be defined before the start of the project and to be included in the project qualityplan These checklists will depend on the engineering practices of the party carrying out the analysis andassociated software

3 Hydrodynamic Analysis

31 IntroductionSea keeping and hydrodynamic load analysis for CSA-FLS1 CSA-FLS2 CSA-1 and CSA-2 shall be carriedout using 3-D potential theory with possibility of forward speed with a recognized computer program Non-linear theory needs to be used for design waves for ULS assessment where non-linear effects are consideredimportant The program shall calculate response amplitude operators (RAOs transfer functions) and timehistories for motions and loads in regular waves The inertia loads and external and internal pressures calculatedin the hydrodynamic analysis are directly transferred to the structural model

For FLS the reference loads shall represent the stresses that contribute the most to the fatigue damage egtypical loading conditions with forward speed in typical trading routes It is assumed that the loads contributingmost to fatigue damage have short return periods and are therefore small but frequent waves It is thereforesufficient to use linear analysis for fatigue assessments since the linear wave loads give sufficientapproximation of the loads for waves with small amplitudes or when ship sides are vertical For linearizationand documentation purposes a reference load level of 10-4 is to be used representing a daily load level

For ULS the loads representing the condition that leads to the most critical response of the vessel shall be foundNormally a design wave representing the most critical response (load or stress) is applied and thesimultaneous acting loads (inertia and pressures) at the moment when maximum response is achieved istransferred to the structural model Several design waves are defined representing different structuralresponses In general the hydrodynamic loads should be represented by non-linear theory for design waveswhere the response is dominated by vertical bending moment and shear force Other design waves may bebased on linear theory since the non-linear effects are negligible or difficult to capture

Figure 3-1 shows a schematic overview of the work flow for the hydrodynamic analysis as part of the CSA-FLS1 CSA-FLS2 CSA-1 and CSA-2 calculations

Section 44 and Section 522 defines loading conditions environment conditions etc applicable for FLS andULS hydrodynamic analysis respectively

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Figure 3-1Flow chart of a hydrodynamic analysis for CSA

This section describes the procedure for the hydrodynamic analysis

32 Hydrodynamic model

321 GeneralThere should be adequate correlation between hydrodynamic and structural models ie both models shouldhave

mdash equal buoyancy and geometrymdash equal mass balance and centre of gravity

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0

The hydrodynamic model and the mass model should be in proper balance giving still water shear forcedistribution with zero value at FP and AP Any imbalance between the mass model and hydrodynamic modelshould be corrected by modification of the mass model

322 Hydrodynamic panel modelThe element size of the panels for the 3-D hydrodynamic analysis shall be sufficiently small to avoid numericalinaccuracies The mesh should provide a good representation of areas with large transitions in shape hence thebow and aft areas are normally modelled with a higher element density than the parallel midship area Thehydrodynamic model should not include skewed panels The number of elements near the surface needs to besufficient in order to represent the change of pressure amplitude and phasing since the dynamic wave loadsincreases exponentially towards the surface This is particularly important when the loads are to be used forfatigue assessment In order to verify that the number of elements is sufficient it is recommended to double thenumber of elements and run a head sea analysis for comparison of pressure time series The number of panelsneeded to converge differs from code to code

Figure 3-2 shows an example of a panel model for the hydrodynamic code WASIM

Figure 3-2Example of a panel model

The panels should as far as possible be vertical oriented as indicated to the right in Figure 3-3 This is to easethe load transfer For component stochastic fatigue analysis transverse sections with pressures are input to theassessment which is easier with the model to the right

Figure 3-3Schematic mesh model

323 Mass modelThe mass of the FE-model and hydrodynamic model has to be identical in order to obtain balance in thestructural analysis Therefore the hydrodynamic analysis shall use a mass-model based on the global FEstructural model In many cases however the hydrodynamic analysis will be performed prior to the completionof the structural model A simplified mass model may then be used in the initial phase of the hydrodynamicanalysis The structural mass model shall be used in the hydrodynamic analysis that establishes the pressureloads and inertia loads for the load transfer

3231 Simplified Mass modelIf the structural model is not available a simplified mass model shall be made The mass model shall ensure aproper description of local and global moments of inertia around the longitudinal transverse and vertical globalship axes The determination of sectional loads can be particularly sensitive to the accuracy and refinement ofthe mass model Mass points at every meter should be sufficient

3232 FE-based Mass modelThe FE-based mass model is described in Section 65

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33 Roll dampingThe roll damping computed by 3-D linear potential theory includes moments acting on the vessel hull as a resultof the waves created when the vessel rolls At roll resonance however the 3-D potential theory will under-predict the total roll damping The roll motion will consequently be grossly over-predicted To adequatelypredict total roll damping at roll resonance the effect from damping mechanisms not related to wave-makingsuch as vortex-induced damping (eddy-making) near sharp bilges drag of the hull (skin friction) skegs andbilge keels (normal forces and flow separation) should be included Such non-linear roll damping models havetypically been developed based on empirical methods using numerical fitting to model test data Example ofnon-linear roll damping methods for ship hulls includes those published by Tanaka 6 and Kato 910

Results from experiments indicate that non-linear roll damping on a ship hull is a function of roll angle wavefrequency and forward speed As the roll angle is generally unknown and depends on the scatter diagramconsidered an iteration process is required to derive the non-linear roll damping

The following 4-step iteration procedure may be used for guidance

a) Input a roll angle θxinput to compute non-linear roll damping

b) Perform vessel motion analysis including damping from a)c) Calculate long-term roll motion θx

update with probability level 10-4 for FLS or 10-8 for ULS using designwave scatter diagram

d) If θxupdate from c) is close to θx

input in step a) stop the iteration Otherwise set θxinput as the mean value

of θxupdate and θx

input and go back to a)

Viscous effects due to roll are to be included in cases where it influences the result Roll motion can affectresponses such as acceleration pressure and torsion Viscous damping should be evaluated for beam andquartering seas The viscous roll damping has little influence in cases where the natural period of the roll modeis far away from the exciting frequencies For fatigue it is sufficient to calibrate the viscous damping for beamsea and use the same damping for all headings

34 Hydrodynamic analysis

341 Wave headingsA spacing of 30 degree or less should be used for the analysis ie at least twelve headings

342 Wave periodsThe hydrodynamic load analysis shall consider a sufficient range of regular wave periods (frequencies) so asto provide an accurate representation of wave energies and structural response

The following general requirements apply with respect to wave periods

mdash The range of wave periods shall be selected in order to ensure a proper representation of all relevantresponse transfer functions (motions sectional loads pressures drift forces) for the wave period range ofthe applicable scatter diagram Typically wave periods in the range of 5-40 seconds can be used

mdash A proper wave period density should be selected to ensure a good representation of all relevant responsetransfer functions (motions sectional loads pressures drift forces) including peak values Typically 25-30 wave periods are used for a smooth description of transfer functions

Figure 3-4 shows an example of a poor and a good representation of a transfer function For the transferfunction with a poor representation the range of periods does not cover the high frequency part of the transferfunction and the period density is not high enough to capture the peak

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Figure 3-4Poor representation of a transfer function on the left and on the right a transfer function where peak and shorterwave periods are well represented

35 Design waves for ULS

351 GeneralA design wave is a wave which results in a design load at a given reference value (eg return period) Using adesign wave the phasing between motions and loads will be maintained giving a realistic load picture

Normally it is assumed that maximising the load will result in also the maximised stress response

However some responses are correlated and the combined effect may give higher stresses than if each load ismaximised In such cases it is recommended to transfer the load RAOrsquos and perform a full stochastic analysis Thestress RAOrsquos of the most critical regions can then be used as basis for design waves

In case of linear design waves the response of the response variable shall be the same as the long term responsedescribed in Section 352

For non-linear design waves eg for vertical bending moment the non-linear maximum response is notnecessarily at the same location as the maximum linear response Several locations need to be evaluated inorder to locate the non-linear maximum response The linear and non-linear dynamic response shall becompared including the non-linear factor defined as the ratio between the maximum non-linear and lineardynamic response

Water on deck also called green water might occur during ULS design conditions If the software does nothandle water on deck in a physical way it is conservative to remove the elements and pressures from the deckIn a sagging wave the bow will be planted into a wave crest Applying deck pressures in such case will reducethe sagging moment

There are several ways of generating design waves The following presents two acceptable ways

mdash regular design wavemdash conditioned irregular extreme wave

352 Regular design waveA regular design wave can be made such that a linear simulation results in a dynamic response equal to the longterm response The wave period for the regular wave shall be chosen as the period corresponding to the maximumvalue of the transfer function see Figure 3-5 The wave amplitude shall be chosen as

Transfer Function for Vertical Bending Moment

000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50 60Wave Period

VB

M

Wav

e A

mp

litu

de


000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50Wave Period

VB

M

Wav

e A

mp

litu

de

[ ] [ ]

⎥⎦⎤

⎢⎣⎡

=

m

Nm

Nm

peakfunctionTransfer

responseermtLongmζ

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Figure 3-5Example of transfer function

The wave steepness shall be less than the steepness criterion given in DNV-RP-205 3 If the steepness is toolarge a different wave period combined with the corresponding wave amplitude should be chosen The regularresponse shall converge before results can be used

353 Conditioned irregular extreme wavesDifferent methods exist to make a conditioned irregular extreme wave (ref 11 12 13) In principle anirregular wave train which in linear simulations returns the long term response after short time is created Thesame wave train can be used for non linear simulations in order to study the non-linear effects

36 Load Transfer

361 GeneralThe hydrodynamic loads are to be taken from the hydrodynamic load analysis To ensure that phasing of allloads is included in a proper way for further post processing direct load transfer from the hydrodynamic loadanalysis to the structural analysis is the only practical option The following loads should be transferred to thestructural model

mdash inertia loads for both structural and non-structural members mdash external hydro pressure loads mdash internal pressure loads from liquid cargo ballast 1)

mdash viscous damping forces (see below)

1) The internal pressure loads may be exchanged with mass of the liquid (with correct center of gravity)provided that this exchange does not significantly change stresses in areas of interest (the mass must beconnected to the structural model)

Inertia loads will normally be applied as acceleration or gravity components The roll and pitch induced fluctuatinggravity component (gsdot sin(θ) asymp gsdot θ) in sway and surge shall be included

Pressure loads are normally applied as normal pressure loads to the structural model If stresses influenced bythe pressure in the waterline region are calculated pressure correction according to the procedure described inSection 3622 need to be performed for each wave period and heading

Viscous damping forces can be important for some vessels particularly those vessels where roll resonance isin an area with substantial wave energy ie roll resonance periods of 6-15 seconds The roll damping maydepending on Metocean criteria be neglected when the roll resonance period is above 20-25 seconds If torsionis an important load component for the ship the effect of neglecting the viscous damping force should beinvestigated


000E+ 00

100E+ 05

200E+ 05

300E+ 05

400E+ 05

500E+ 05

600E+ 05

700E+ 05

800E+ 05

900E+ 05

0 10 20 30 40 50 60Wa ve Period

VB

M

Wa

ve

Am

pli

tud

e

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362 Load transfer FLSThe loads from the hydrodynamic analysis are used in the fatigue analysis

For the full stochastic analysis the inertia is applied to the FE model and the inertia pressure of tank liquids andwave-pressures are transferred to the global FE model for all frequencies and headings of the hydrodynamicanalysis

For the component stochastic analysis the load transfer functions at the applicable sections and locations arecombined with nominal stress per unit load giving nominal stress transfer functions The loads of interest arethe inertia pressures in the tanks the sea-pressures and the global hull girder loads ie vertical and horizontalbending moment and axial elongation

3621 Inertia tank pressuresThe transfer functions for internal cargo and ballast pressures due to acceleration in x- y- and z-direction arederived from the vessel motions The acceleration transfer functions are to be determined at the tank centre ofgravity and include the gravity component due to pitch and roll motions

Based on the free surface and filling level in the tank the pressure heads to the load point in question isestablished and the total internal transfer function is found by linear summation of pressure due to accelerationin x y and z-direction for the load point in question (FE pressure panel for full stochastic and load point forcomponent stochastic)

3622 Effect of intermittent wet surfaces in waterline regionThe wave pressure in the waterline region is corrected due to intermittent wet and dry surfaces see Figure 3-6 This is mainly applicable for details where the local pressure in this region is important for the fatigue lifeeg longitudinal end connections and plate connections at the ship side

Figure 3-6Correction due to intermittent wetting in the waterline region

Since panel pressures refer to the midpoint of the panel the value at waterline is found from extrapolating thevalues for the two panels closest to the waterline Above the waterline the pressure should be stretched usingthe pressure transfer function for the panel pressure at the waterline combined with the rp-factor

Using the wave-pressure at waterline with corresponding water-head at 10-4 probability level as basis thewave-pressure in the region limited by the water-head below the waterline is given linear correction see Figure3-6 The dynamic external pressure amplitude (half pressure range) pe for each loading condition may betaken as

where

pd is dynamic pressure amplitude below the waterlinerp is reduction of pressure amplitude in the surface zone

Pressures at 10-

4 probability

Extrapolated t

Water head f

Water head f Corrected

p r pe p d =

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In the area of side shell above z = Tact + zwl it is assumed that the external sea pressure will not contribute tofatigue damage

Above waterline the wave-pressure is linearly reduced from the waterline to the water-head from the wave-pressure

363 Load transfer ULSIn case of load transfer for ULS the pressure and inertia forces are transferred at a snapshot in time Everywetted pressure panel on the structural FE model shall have one corresponding pressure value while inertiaforces in six degrees of freedoms are transferred to the complete model

4 Fatigue Limit State Assessment

41 General principles

411 Methodology overviewThe following defines fatigue strength analysis based on spectral fatigue calculations Spectral fatiguecalculations are based on complex stress transfer functions established through direct wave load calculationscombined with subsequent stress response analyses Stress transfer functions then express the relation betweenthe wave heading and frequency and the stress response at a specific location and may be determined by either

mdash component stochastic analysismdash full stochastic analysis

Component stochastic calculations may in general be employed for stiffeners and plating and other details witha well defined principal stress direction mainly subjected to axial loading due to hull girder bending and localbending due to lateral pressures Full stochastic calculations can be applied to any kind of structural details

Spectral fatigue calculations imply that the simultaneous occurrence of the different load effects are preservedthrough the calculations and the uncertainties are significantly reduced compared to simplified calculationsThe calculation procedure includes the following assumptions for calculation of fatigue damage

mdash wave climate is represented by a scatter diagrammdash Rayleigh distribution applies for the response within each short term condition (sea state)mdash cycle count is according to zero crossing period of short term stress responsemdash linear cumulative summation of damage contributions from each sea state in the wave scatter diagram as

well as for each heading and load condition

The spectral calculation method assumes linear load effects and responses Non-linear effects due to largeamplitude motions and large waves are neglected assuming that the stress ranges at lower load levels(intermediate wave amplitudes) contribute relatively more to the cumulative fatigue damage Wherelinearization is required eg in order to determine the roll damping or intermittent wet and dry surfaces in thesplash zone the linearization should be performed at the load level representing stress ranges giving the largestcontribution to the fatigue damage In general a reference load or stress range at 10-4 probability of exceedanceshould be used

Low cycle fatigue and vibrations are not included in the fatigue calculations described in this ClassificationNote

412 Classification Note No 307Fatigue calculations for the CSA notations are based on the calculation procedures as described inClassification Note No 307 4 This Classification Note describes details and procedures relevant for the

= 10 for z lt Tact ndash zwl

= for Tact ndash zwl lt z lt Tact+ zwl

= 00 for Tact+ zwl lt zzwl is distance in m measured from actual water line to the level of zero pressure taken equal to water-head

from pressure at waterline =

pdT is dynamic pressure at waterline Tact

T z z

zact wl

wl

+ minus2

g

pdT

ρ4

3

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CSA-notation For further details reference is made to CN 307 In case of conflicting procedure the procedureas given in CN 307 has precedence

42 Locations for fatigue analysis

421 GeneralFatigue calculations should in general be performed for all locations that are fatigue sensitive and that may haveconsequences for the structural integrity of the ship The locations defined by NAUTICUS (Newbuilding) orCSR whichever is relevant and PLUS shall be documented by CSA fatigue calculations The generallocations are shown in Table 4-1 with some typical examples given in Figure 4-1 to Figure 4-7

For the stiffener end connections and shell plate connection to stiffeners and frames it is normally sufficient toperform component stochastic fatigue analysis using predefined loadstress factors and stress concentrationfactors All other details including those required by ship type need full-stochastic analysis with use of stressconcentration models with txt mesh (element size equal to plate thickness)

Figure 4-1Longitudinal end connection

Table 4-1 General overview of fatigue critical detailsDetail Location Selection criteria

Stiffener end connection mdash one frame amidshipsmdash one bulkhead amidshipsmdash one frame in fwd tankmdash one frame in aft tank)

All stiffeners included

Bottom and side shell plating connection to stiffener and frames

mdash one frame amidshipsmdash one frame in fwd tankmdash one frame in aft tank)

All plating to be included

Stringer heels and toes mdash one location amidshipsmdash one location in fwd hold)

mdash other locations)

Based on global screening analysis and evaluation of details

Panel knuckles mdash one lower hopper knuckle amidshipsmdash other locations identified)


Discontinuous plating structure mdash between hold no 1 and 2)

mdash between Machinery space and cargo region)


Deck plating including stress concentrations from openings scallops pipe penetrations and attachments


) Global screening and evaluation of design in discussion with the Society to be basis for selection

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Figure 4-2Plate connection to stiffener and frame

Figure 4-3Stringer heel and toe

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Figure 4-4Example of panel knuckles

Figure 4-5Example of discontinuous plating structure

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Figure 4-7Hotspots in deck-plating

422 Details for fine mesh analysisIn addition to the general positions as described in Section 421 fine mesh full stochastic fatigue analysis fordefined ship specific details also need to be performed see the Rules for Classification of Ships Pt3 Ch1 Theship specific details are details either found to be specially fatigue sensitive andor where fatigue cracks mayhave an especially large impact on the structural integrity

Typical vessel specific locations that require fine mesh full stochastic analysis are specified in the followingIn the following the mandatory locations in need of fine mesh full stochastic analysis are listed for differentvessel types For vessel-types not listed details to be checked need to be evaluated for each design

Tankers

mdash lower hopper knucklemdash upper hopper knucklemdash stringer heels and toesmdash one additional critical location found on transverse web-frame from global screening of midship area

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Membrane type LNG carriers

mdash lower hopper knucklemdash upper hopper knucklemdash stringer heels and toesmdash dome opening and coamingmdash lower and upper chamfer knuckles mdash longitudinal girders at transverse bulkheadmdash trunk deck at transverse bulkheadmdash termination of tank no 1 longitudinal bulkheadmdash aft trunk deck scarfing

Moss type LNG carriers

mdash lower hopper knucklemdash stringer heels and toesmdash tank cover to deck connectionmdash tank skirt connection to foundation deckmdash inner side connection to foundation deck in the middle of the tank web framemdash longitudinal girder at transverse bulkhead

LPG carriers

mdash dome opening and coamingmdash lower and upper side bracketmdash longitudinal girder at transverse bulkhead

Container vessel

mdash top of hatch coaming corner (amidships in way of ER front bulkhead and fore-ship)mdash upper deck hatch corner (amidships in way of ER front bulkhead and fore-shipmdash hatch side coaming bracket in way of ER front bulkheadmdash scarfing brackets on longitudinal bulkhead in way of ERmdash critical stringer heels in fore-shipmdash stringer heel in way of HFO deep tank structure (where applicable)

Ore carrier

mdash inner bottom and longitudinal bulkhead connection mdash horizontal stringer toe and heel in ballast tankmdash cross-tie connection in ballast tankmdash hatch cornermdash hatch coaming bracketsmdash upper stool connection to transverse bulkheadmdash additional critical locations found from screening of midship frame

43 Corrosion model

431 ScantlingsAll structural calculations are to be carried out based on the net-scantlings methodology as described by therelevant class notation This yields for both global and local stresses Eg for oil tankers with class notationCSR 50 of the corrosion addition is to be deducted for local stress and 25 of the corrosion addition is to bededucted for global stress For other class notations the full corrosion addition is to be deducted

44 Loads

441 Loading conditionsVessel response may differ significantly between loading conditions Therefore the basis of the calculationsshould include the response for actual and realistic seagoing loading conditions Only the most frequent loadingconditions should be included in the fatigue analysis normally the ballast and full load condition which shouldbe taken as specified in the loading manual Under certain circumstances other loading conditions may beconsidered

442 Time at seaFor vessels intended for normal world wide trading the fraction of the total design life spent at sea should notbe taken less than 085 The fraction of design life in the fully loaded and ballast conditions pn may be taken

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according to the Rules for Classification of Ships Pt3 Ch1 summarised in Table 4-2

Other fractions may be considered for individual projects or on ownersrsquo request

443 Wave environmentThe wave data should not be less severe than world wide or North Atlantic for vessels with NAUTICUS(Newbuilding) notation or CSR notation respectively The scatter-diagrams for World Wide and NorthAtlantic are defined in CN 307 Other wave data may also be considered in addition if requested by ownerThis could typically be a sailing route typical for the specific ship

Fatigue is governed by the daily loads experienced by the vessel hence the reference probability level forfatigue loads and responses shall be based on 10-4 probability level Weibull fitting parameters are normallytaken as 1 2 3 and 4

A Pierson-Moskowitz wave spectrum with a cos2 wave spreading shall be used

If a different wave data is specified it is recommended to perform a comparative analysis to advice which ofthe scatter diagram gives worse fatigue life If one yields worse results this scatter diagram may be used for allanalysis If the results are comparative fatigue life from both wave environments may need to be established

444 Hydrodynamic analysisA vessel speed equal to 23 of design speed should be used as an approximation of average ship speed over thelifetime of the vessel

All wave headings (0deg to 360deg) should be assumed to have an equal probability of occurrence and maximum30deg spacing between headings should be applied

Linear wave load theory is sufficient for hydrodynamic loads for FLS since the daily loads contribute most tothe fatigue damage

Reference is made to Section 3 for hydrodynamic analysis procedure

445 Load applicationThe loads from the hydrodynamic analysis are used in the fatigue analysis

For the full stochastic analysis the following hydrodynamic loads are applied to the global structural model forall headings and frequencies

mdash external panel pressures mdash internal tank pressuresmdash inertia loads due to rigid body accelerations

For the component stochastic analysis the loads at the applicable sections and locations are combined withstress transfer functions representing the stress per unit load The loads to be considered are

mdash inertial loads (eg liquid pressure in the tanks) mdash sea-pressure mdash global hull girder loads

- vertical bending moment - horizontal bending moment and - axial elongation

Details are described in Section 3

45 Component stochastic fatigue analysisComponent stochastic fatigue analysis is used for stiffener end connections and plate connection to stiffenersand frames see Section 421

The component stochastic fatigue calculation procedure is based on linear combination of load transferfunctions calculated in the hydrodynamic analysis and stress response factors representing the stress per unitload The nominal stress transfer functions for each load component is combined with stress concentrationfactors before being added together to one hot spot transfer function for the given detail

The flowchart shown in Figure 4-8 gives an overview of the component stochastic calculation procedure givinga hot-spot stress transfer function used in subsequent fatigue calculations If the geometry and dimensions of

Table 4-2 Fraction of time at sea in loaded and ballast conditionVessel type Tanker Gas carrier Bulk carrier Container vessel Ore carrierLoaded condition 0425 045 050 065 050Ballast condition 0425 040 035 020 035

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the given detail does not have predefined SCFs the stress concentration factor need to be found through a stressanalysis using a stress concentration model for the detail see CN 307 4 In such cases the procedure andresults shall be documented together with the results from the fatigue analysis

A short overview of the procedure for stiffener end connections and plate connections is given in Section 452and Section 453 respectively

Figure 4-8DNV component stochastic fatigue analysis procedure

451 Considered loadsThe loads considered normally include

mdash vertical hull girder bending momentmdash horizontal hull girder bending momentmdash hull girder axial forcemdash internal tank pressuremdash external (panel) pressures

In the surface region the transfer function for external pressures should be corrected by the rp factor asexplained in Section 3622 and as given in CN 307 4 to account for intermittent wet and dry surfaces Thetank pressures are based on the procedure given in Section 3621

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452 Stiffener end connectionsFatigue calculations for stiffener end connections are to be carried out for end connections at ordinary framesand at transverse bulkheads

Note that the web-connection of longitudinals (cracks of web-plating) is not covered by the CSA-notationsThis is covered by PLUS notation only and shall follow the PLUS procedure

4521 Nominal stress per unit loadThe stresses considered are stress due to

mdash global bending and elongation mdash local bending due to internal and external pressuremdash relative deflections due to internal and external pressure

Stress from double side or double bottom bending may be neglected in the CSA analyses since these stresses arerelative small and varies for each frame The stress due to relative deflection is only assessed for the bulkheadconnections where the stress due to relative deflection will add on to the stress due to local bending and hencereduce the fatigue life A description of the relative deflection procedure is given in Appendix A

Formulas for nominal stress per unit load are given in CN 307 They may alternatively be found from FE-analysis

4522 Hotspot stressThe nominal stress transfer function is further multiplied with stress concentration factors as defined in CN 307For end connections of longitudinals they are typically defined for axial elongation and local bending

The total hotspot stress transfer function is determined by linear complex summation of the stresses due to eachload component

453 PlatingFatigue calculations for plating are carried out for the plate welds towards stiffenerslongitudinals and framesas illustrated in Figure 4-3

The stress in the weld for a plateframe connections consist of the following responses

mdash local plate bending due to externalinternal pressuremdash global bending and elongation

For a platelongitudinal connection the global effects may be disregarded and only the contributions fromstresses in transverse directions are included The total stress in the welds for a platelongitudinal connectionis mainly caused by the following responses

mdash local plate bendingmdash relative deflection between a stringergirder and the nearby stiffenermdash rotation of asymmetrical stiffeners due to local bending of stiffener

These three effects are illustrated in Figure 4-9

Figure 4-9Nominal stress components due to local bending (left) relative deflection between stiffener and stringersgirders(middle) and rotation of asymmetrical stiffeners (right)

The local plate bending is the dominating effect but relative deflection and skew bending may increase thestresses with up to 20 This effect should be considered and investigated case by case As guidance thefollowing factors can be used to correct the stress calculations for a platelongitudinal connection

plate weld towards stringergirder 115plate weld towards L-stiffener 11

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The combined nominal stress transfer function is determined by linear complex summation of the stresses dueto each load component

4531 Hotspot stress The nominal stress transfer function is further multiplied with stress concentration factors as defined in CN307 The total hotspot stress transfer function is determined by linear complex summation of the stresses dueto applicable load components

46 Full stochastic fatigue analysis

461 GeneralA full stochastic fatigue analysis is performed using a global structural model and local fine-mesh sub-modelsThis method requires that the wave loads are transferred directly from the hydrodynamic analysis to thestructural model The hydrodynamic loads include panel pressures internal tank pressures and inertia loads dueto rigid body accelerations By direct load transfer the stress response transfer functions are implicitly describedby the FE analysis results and the load transfer ensures that the loads are applied consistently maintainingload-equilibrium

Quality assurance is important when executing the full stochastic method The structural and hydrodynamicanalysis results should have equal shape and magnitude for the bending moment and shear force diagramsAlso the reaction forces due to unbalanced loads in the structural analysis should be minimal

Figure 4-10 shows a flow chart for the full stochastic fatigue analysis using a global model References torelevant sections in this CN are given for each step

Figure 4-10Full stochastic fatigue analysis procedure

The analysis is based on a global finite element model including the entire vessel in addition to local modelsof specified critical details in the hull Local models are treated as sub models to the global model and the

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Page 25

displacements from the analysis are transferred to the local model as boundary displacements From local stressconcentration models the geometric stress transfer functions at the hot spots are determined by the t x t elementsthat pick up the stress increase towards the hotspot

The hotspot transfer functions are combined with the wave scatter diagram and S-N data and the fatiguedamage is summarised from each heading for all sea states in the scatter diagram (wave period and waveheight)

462 Global screening analysisThe global screening analysis is a full stochastic fatigue analysis performed on the global model or parts of theglobal model using a SCF typical for the details investigated The global screening analysis generally has fourdifferent purposes

mdash calculate allowable stress concentrations in deckmdash find the most fatigue critical detail from a number of similar or equal detailsmdash establish a fatigue ratio between identical detailsmdash evaluate if there are fatigue critical details that are not covered in the specification

Note that the global screening analysis only includes global effects as global bending and double bottombending Local effects from stiffener bending etc are not included

4621 Allowable stress concentration in deckA significant part of the total fatigue cracks occur in the deck region This is mainly due to the large nominalstresses in parts of this area and the fact that there are many cut-outs attachments etc leading to local stressincreases

A crack in the deck is considered critical since a crack propagating in the deck will reduce the effective hullgirder cross section Even if a crack in the deck will be discovered at an early stage due to easy inspection andhigh personnel activity it is important to control the fatigue of the deck area

The nominal stress level in the deck varies along the ship normally with a maximum close to amidships Largeropenings structural discontinuities change in scantlings or additional structure will change the stress flow andlead to a variation of stress flow both longitudinally and transversely

The information from the fatigue screening analysis may be used together with drawing information aboutdetails in the deck Typical details that need to be taken into consideration are

mdash deck openingsmdash butt weld in the deck (including effect of eccentricity and misalignment)mdash scallopsmdash cut outs pipe-penetrations and doubling plates

The stress concentrations for each of these details need to be compared to the results from the global screeninganalysis in order to show that the required fatigue life is obtained for all parts of the deck area

4622 Finding the most critical location for a detailA ship will have many identical or similar details It is not always evident which ones are more critical sincethey are subject to the same loads but with different amplitudes and combinations Through a global screeninganalysis the most critical location might be identified by comparing the global effects

Local effects which may be of major importance for the fatigue damage are not captured in the globalscreening analysis Element mesh must be identical for the positions that are compared otherwise the effect ofchanging the mesh may override the actual changes in loads

An example of the result from a global screening for one detail type is shown in Figure 4-11 where relativedamage between different positions in a ship is shown for three different tanks

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Figure 4-11Fatigue screening example ndash relative damage between different positions

4623 Fatigue ratio between different positionsThe fatigue calculations used for relative damage between different positions for identical details helpsevaluate where reinforcements are necessary Eg if local reinforcements are necessary in the middle of thecargo hold for the example shown in Figure 4-11 it may not be needed towards the ends of the cargo hold

New detailed fatigue calculations should be performed in order to verify fatigue lives if different reinforcementmethods are selected

4624 Finding critical locations not specified for the vessel

By specifying a critical level for relative damage the model can be scanned for elements that exceed the givenlimit indicating that it may be a fatigue critical region Since not all effects are included the results are notreliable but will give an overview of potential problem areas This exercise will also help confirm assumedcritical areas from the specifications stage of the project in addition to point at new critical areas

463 Local fatigue analysis The full stochastic detailed analysis is used to calculate fatigue damages for given details The analysis isnormally performed either for details where the stress concentration is unknown or where it is not possible toestablish a ratio between the load and stress Full stochastic calculations may also be used for stiffener endconnections and bottomside shell plating and will in that case overrule the calculations from the componentstochastic analysis

Several types of models can be used for this purpose

mdash local model as a part of the global modelmdash local shell element sub-modelmdash local solid element model

If sub-models are used the solution (displacements) of the global analysis is transferred to the local modelsThe idea of sub-modelling is in general that a particular portion of a global model is separated from the rest ofthe structure re-meshed and analysed in greater detail The calculated deformations from the global analysisare applied as boundary conditions on the borders of the sub-models represented by cuts through the globalmodel Wave loads corresponding to the global results are directly transferred from the wave load analysis tothe local FE models as for the global analysis

It is not always easy to predefine the exact location of the hotspot or the worst combination of stress

Lower Chamfer Knuckle

0

025

05

075

1

125

15

175

2

100425 120425 140425 160425 180425 200425 220425

Distance from AP [mm]

Fat

igue

Dam

age

[-]

Screening Results

TBHD Pos

Local Model Result

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Page 27

concentration factor and load level and therefore the fine-mesh model frequently does not include fine meshin all necessary locations The local model shall be screened outside the already specified hotspot to evaluateif other locations in close proximity may be prone to fatigue damage requiring evaluation with mesh size inthe order of t times t This can be performed according to the procedure shown in Section 462

464 Determination of hotspot stress

4641 GeneralFrom the results of the local structural analysis principal stress transfer functions at the notch are calculatedfor each wave heading In general quadratic shaped elements with length equal to the plate thickness areapplied at the investigated details and the geometry of the weld is not represented in the model Since thestresses are derived in the element gauss points it is necessary to extrapolate the stresses to the consideredpoint The extrapolation procedure is given in CN307 4

Alternatively to the extrapolation procedure the stress at t2 multiplied with 112 is also appropriate for thestress evaluation at the hotspot

4642 Cruciform connectionsAt web stiffened cruciform connections the following fatigue crack growth is not linear across the plate andthe stresses need to be specially considered The procedures for the cruciform joints and extrapolation to theweld toe are described in CN 307 4

4643 Stress concentration factorThe total stress concentration K is defined as

Also other effects like eccentricity of plate connections need to be considered together with the stress-resultsfrom the fine-mesh analysis

This needs to be included in the post-processing

47 Damage calculation

471 Acceptance criteriaCalculated fatigue damage shall not be above 10 for the design life of the vessel Owner may require loweracceptable damage for parts of the vessel

The fatigue strength evaluation shall be carried out based on the target fatigue life and service area specifiedfor the vessel but minimum 20 years world wide for vessels with Nauticus (Newbuilding) or 25 years NorthAtlantic for vessels with CSR notation The owner may require increased fatigue life compared to theminimum requirement

472 Cumulative damageFatigue damage is calculated on basis of the Palmgrens-Miner rule assuming linear cumulative damage Thedamage from each short term sea state in the scatter diagram is added together as well as the damage fromheading and load condition

473 S-N curvesThe fatigue accumulation is based on use of S-N curves that are obtained from fatigue tests The design S-Ncurves are based on the mean-minus-two-standard-deviation curves for relevant experimental data The S-Ncurves are thus associated with a 976 probability of survival

Relevant S-N curves according to CN 307 4 should be used

It is important that consistency between S-N curves and calculated stresses is ensured

4731 Effect of corrosive environmentCorrosion has a negative effect on the fatigue life For details located in corrosive environment (as water ballastor corrosive cargo) this has to be taken into account in the calculations

For details located in water ballast tanks with protection against corrosion or where the corrosive effect is smallthe total fatigue damage can be calculated using S-N curve for non-corrosive environment for parts of the designlife and S-N curve for corrosive environment for the remaining part of the design life Guidelines on which S-Ncurve to use and the fraction in corrosive and non-corrosive environment are specified by CN 307 4

alno

spothotK

minσσ

=

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Page 28

For details without corrosion protection a S-N curve for corrosive environment has to be used in thecalculations for the entire lifetime

4732 Thickness effectThe fatigue strength of welded joints is to some extent dependent on plate thickness and on the stress gradientover the thickness Thus for thickness larger than 25 mm the S-N curve in air reads

where t is thickness (mm) through which the potential fatigue crack will grow This S-N curve in generalapplies to all types of welds except butt-welds with the weld surface dressed flush and with small local bendingstress across the plate thickness The thickness effect is less for butt welds that are dressed flush by grinding ormachining

The above expression is equivalent with an increase of the response with

474 Mean stress effectThe procedure for the fatigue analysis is based on the assumption that it is only necessary to consider the rangesof cyclic principal stresses in determining the fatigue endurance However some reduction in the fatiguedamage accumulation can be credited when parts of the stress cycle are in compression

A factor fm accounting for the mean stress effect can be calculated based on a comparison of static hotspotstresses and dynamic hotspot stresses at a 10-4 probability level

4741 Base materialFor base material fm varies linearly between 06 when stresses are in compression through the entire load cycleto 10 when stresses are in tension through the entire load cycle

4742 Welded materialFor welded material fm varies between 07 and 10

475 Improvement of fatigue life by fabricationIt should be noted that improvement of the toe will not improve the fatigue life if fatigue cracking from the rootis the most likely failure mode The considerations made in the following are for conditions where the root isnot considered to be a critical initiation point for fatigue cracks

Experience indicates that it may be a good design practice to exclude this factor at the design stage Thedesigner is advised to improve the details locally by other means or to reduce the stress range through designand keep the possibility of fatigue life improvement as a reserve to allow for possible increase in fatigue loadingduring the design and fabrication process

It should also be noted that if grinding is required to achieve a specified fatigue life the hot spot stress is ratherhigh Due to grinding a larger fraction of the fatigue life is spent during the initiation of fatigue cracks and thecrack grows faster after initiation This implies use of shorter inspection intervals during service life in orderto detect the cracks before they become dangerous for the integrity of the structure

The benefit of weld improvement may be claimed only for welded joints which are adequately protected fromcorrosion

The following methods for fatigue improvement are considered

mdash weld toe grinding (and profiling)mdash TIG dressingmdash hammer peening

Among these three weld toe grinding is regarded as the most appropriate method due to uncertaintiesregarding quality assurance of the other processes

The different fatigue improvements by welding are described in CN 307 4

σΔminus⎟⎠⎞⎜

⎝⎛minus= log

25log

4loglog m

tmN a

4

1

25⎟⎠⎞⎜

⎝⎛=Δ t

respσ

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Page 29

5 Ultimate Limit State Assessment

51 Principle overview

511 GeneralThe Ultimate Limit State (ULS) analyses shall cover necessary assessments for dimensioning against materialyield buckling and ultimate capacity limits of the hull structural elements like plating stiffeners girdersstringers brackets etc in the cargo region

ULS assessments shall also ensure sufficient global strength in order to prevent hull girder collapse ductile hullskin fracture and compartment flooding

Two levels of ULS assessments are to be carried out ie

mdash global FE analyses - local ULS mdash hull girder collapse - global ULS

The basic principles behind the two types of assessments are described in more detail in the following

512 Global FE analyses ndash local ULSThe local ULS design assessment is based on a linear global FE model with automatic load transfer fromhydrodynamic wave load programs The design of the structural elements in different areas of the ship arecovered by different design conditions Each design condition is defined by a loading condition and a governingsea statewave condition which together are dimensioning for the structural element

For each design condition the calculation procedure follows the flow chart in Figure 5-1 ie the static andhydrodynamic wave loads for the loading condition are transferred to the structural FE model for a linearnominal stress assessment The nominal stresses are to be measured against material yield buckling andultimate capacity criteria of individual stiffened panels girders etc

The material yield checks cover von Mises stress control using a cargo hold model and for high peak stressedareas using local fine-mesh models

The local ULS buckling control follow two different principles allowing and not allowing elastic bucklingdepending on the elements main function in the global structure using PULS 8

The procedure for local ULS assessment is further described in Section 52

513 Hull girder collapse - global ULS The hull girder collapse criteria are used to check the total hull section capacity against the correspondingextreme global loads This is to be carried out for the mid-ship area for one intact and two damaged hullconditions Specially developed hull girder capacity models based on simplified non-linear theory or full-blown FE analyses are to be used for assessing the hull capacity The extreme loads are to be based on directcalculations and the static + dynamic load combination giving the highest total hull girder moment shall beused including both the extreme sagging and hogging condition

For some ship types other sections than the mid-ship area may be relevant to be checked if deemed necessaryby the Society This applies in particular to hull sections which are transversely stiffened eg engine room ofcontainer ships etc

The procedure for the global ULS assessment is further described in Section 53

514 Scantlingscorrosion modelAll FE calculations shall be based on the net scantlings methodology as defined by the relevant class notationsNAUTICUS (Newbuilding) or CSR

The buckling calculations are to be carried out on net scantlings

52 Global FE analyses ndash local ULS

521 GeneralThe local ULS design assessment is based on a linear global FE analysis with automatic load transfer fromhydrodynamic programs as schematically illustrated in Figure 5-1

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Figure 5-1Flowchart for ULS analysis Load transfer Hydro rarr Global FE model

Selection of design loads and procedures for selection of stress and application of the yield and bucklingcriteria is described in the following

522 Designloads

5221 GeneralThis section is closely linked to Section 3 which explains how hydrodynamic analyses are to be performed

5222 Design condition and selection of critical loading conditionsThe design loading conditions are to be based on the vessels loading manual and shall include ballast full loadand part load conditions as relevant for the specific ship type The loading conditions and dynamic loads areselected such that they together define the most critical structural response Depending on the purpose of thedesign condition eg the region to be analysed and failure mode (yieldbuckling) for the structural elementsdifferent loading conditions and design waves are required to ensure that the relevant response is at itsmaximum Any loading condition in the loading manual that combined with its hydrodynamic extreme loadsmay result in the design loads should be evaluated

For each loading condition hydrodynamic analysis shall be performed forming the basis for selection ofdesign waves and stress assessment For areas where non-linear effects are not necessary to consider (eg fortransverse structural members) a design wave need not be defined The design stress is then based on long-termstress where the stress at 10-8 probability level for the loading condition is found A design wave is requiredif non-linear effects need to be considered The design wave may be defined based on structural response orwave load depending on the purpose of the design condition

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Page 31

Table 5-1 gives an overview of the design conditions that need to be evaluated and should at a minimum becovered Additional design conditions need to be evaluated case by case depending on the ships structuralconfiguration tradingoperational conditions etc which may require several design conditions to ensure thatall the structures critical failure modes are covered

5223 Hydrodynamic analysisThe hydrodynamic analyses are to be performed for the selected critical loading conditions A vessel speed of5 knots is to be used for application of loads that are dominated by head seas For design conditions where thedriving response is dominated by beam or quartering seas the speed is to be taken as 23 of design speed

5224 Design life and wave environmentWave environment is minimum to be the North Atlantic wave environment as defined in the CN 307 4 Ifother wave environment is required by design it should not be less severe than the North Atlantic waveenvironment

The hydrodynamic loads are to be taken as 10-8 probability of exceedance according to Pt3 Ch1 Sec3 B300and Pt8 Ch1 Sec2 for Nauticus (Newbuilding) and CSR respectively using a cos2 wave spreading functionand equal probability of all headings

5225 Design wavesThe design waves used in the hydrodynamic analysis should basically cover the entire cargo hold areaDifferent design waves are used to check the capacity of different parts of the ship It is important that thedesign waves are not used outside the area for which the design wave is valid ie a design wave made for tankno1 must not be used amidships

An overview of the relation between the design loads and areas they are applicable for should be checkedagainst the different design loads is given in Table 5-1 The design conditions together with its applicableloading condition and design load need to be reviewed on project basis It can be agreed with ClassificationSociety that some design conditions can be removed based on review of design together with loadingconditions and operational profile

It is considered that only design waves which represents vertical bending moment and vertical shear force needto be performed with non-linear hydrodynamic analysis

5226 Load transferA load transfer (snap-shot) from the hydrodynamic analysis to the structural analysis shall be performed whenthe total loadresponse from the hydrodynamic time-series is at its maximumminimum The load transfer shallinclude both gravitational and inertial loads and the still water and wave pressures see Section 36

Table 5-1 Guidance on loading condition selectionDesign Condition Loading condition amp design loads

ID

Reference loadresponse

(Dominant or max loadresponse)

Design area Loading condition Typical loading pattern

Design wave(maximised re-sponseload)

1A hogging bending moment Midship (global hull) Maxlarge hogging

bending momentMax hogging wave moment

1B Sagging bending moment Midship (global hull) Maxlarge sagging

bending momentMax sagging wave moment

2A Hogging + doublebottom bending

Midship double bot-tomTransverse bulk-heads

Large hogging com-bined with deep draft

Tankshold empty across with adjacent tankshold full

Max hogging wave moment

2B Sagging + double bottom bending

Midship double bot-tom

Large sagging com-bined with shallow draft

Tankshold full across with adjacent tankshold empty

Max sagging wave moment

3A Shear force at aft quarter length

Aft hold shear ele-ments Max shear force aft

Max wave shear force at aft quarter-length

3B Shear force at fwd quarter length

Fwd hold shear ele-ments Max shear force fwd

Max wave shear force at fwd quarter length

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Page 32

523 Design stress

5231 GeneralBased on the global FE analysis a nominal stress flow in the hull structure is available This nominal stress flowshall be checked against material yield and acceptable buckling criteria (PULS)

The nominal stresses produced from the FE analysis will be a combination of the stress components fromseveral response effects which in a simplistic manner can be categorized as follows

mdash hull girder bending momentmdash hull girder shear forcemdash hull girder axial loads (small)mdash hull girder torsion and warping effects (if relevant)mdash double sidebottom bendingmdash local bending of stiffenermdash local bending of platesmdash transverse stresses from cargo and sea pressuremdash transverse and shear stresses from double hull bendingmdash other stress effects due to local design issues knuckles cut-outs etc

Guidelines for determining design stresses are given in the following

5232 Material yield assessmentIn the material yield control all effects are to be included apart from local bending stress across the thicknessof the plating This means that the yield check involves the von Mises stress based on membrane stresses andshear stresses in the structure evaluated in the middle plane of plating stiffener webs and stiffener flanges

For cases where large openings are not modelled in the FE-analysis either as cut-outs or by reduced thicknesssee Section 6322 the von Mises stress should be corrected to account for this

In areas with high peaked stress where the von Mises stress exceeds the acceptance criteria the structureshould be evaluated using a stress concentration model (t x t mesh) Frame and girder models (stiffener spacingmesh or equivalent) that reflect nominal stresses should not be used for evaluation of strain response in yieldareas Areas above yield from the linear element analysis may give an indication of the actual area ofplastification Non-linear FE analysis may be used to trace the full extent of plastic zones large deformationslow cycle fatigue etc but such analyses are normally not required

For evaluation of large brackets the stress calculated at the middle of a bracketrsquos free edge is of the samemagnitude for models with stiffener spacing mesh size as for models with a finer mesh Evaluation of bracketsof well-documented designs may be limited to a check of the stress at the free edge When 4-node elementsare used fictitious bar elements are to be applied at the free edge to give a straightforward read-out of thecritical edge stress For brackets where the design needs to be verified a fine mesh model needs to be used

4A Internal pressureload in no1 tankhold

Tank no 1 double bottom

Loaded at shallow draft fwd

No1 tankshold full across with no2 tankshold empty

Maximum vertical accelerations at no1 tankshold in head sea

4B External pressure at no1 tankshold

Tank no1 double bottom

Loaded at deep draft fwd

No1 tankshold emp-ty across with no2 tankshold full

Maximum bottom wave pressure at no1 tankshold in head seas

5Combined vertical horizontal and tor-sional bending

Entire cargo region

Loaded condition with large GM com-bined with large hog-ging for hogging vessels or large sag-ging for sagging ves-sels

Design wave(s) in quarteringbeam sea conditionmdash maximised torsionmdash maximised

horizontal bendingmdash maximised stress

at hatch cornerslarge openings

6 Maximum transverse loading Entire cargo region Loaded with maxi-

mum GMMaximum transverse acceleration

Table 5-1 Guidance on loading condition selection (Continued)Design Condition Loading condition amp design loads

ID





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Page 33

Figure 5-2Bracket stress to be used

5233 Buckling assessmentIn order to be consistent with available buckling codes the nominal stress pattern has to be simplified ie stressgradients has to be averaged and the local bending stress due to lateral pressure effects has to be eliminatedThe membrane stress components used for buckling control shall include all effects listed in Section 5231except for the stresses due to local stiffener and plate bending since these effects are included in the bucklingcode itself

When carrying out the local ULS-buckling checks the nominal FE stress flow has to be simplified to a formconsistent with the local co-ordinate system of the standard buckling codes In the PULS buckling code the bi-axial and shear stress input reads (see Figure 5-3)

σ1 axial nominal stress in primary stiffener and plating (normally uniform) (sign convention in bucklingcode (PULS) positive stress in compression negative stress in tension)

σ2 transverse nominal stress in plating Normally uniform stress distribution but it can vary linearly acrossthe plate length in the PULS code also into the tension range σ 21 σ 22 at plate ends)

τ 12 nominal in-plane shear stress in plating (uniform and as assessed by Section 5333p net uniform (average) lateral pressure from sea or cargo (positive pressure acting on flat plate side)

Figure 5-3PULS nominal stress input for uni-axially or orthogonally stiffened panels (bi-axial + shear stresses)

σ =

Primary stiffeners direction1ndash x -

Secondary stiffeners ndash any) x2- direction (if

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Page 34

Note Varying stress along the plate edge can be considered by checking each stiffener for the stress acting at thatposition Since the PULS buckling model only consider uniform stresses a fictive PULS model have to beused with the actual number of stiffener between rigid lateral supports (girders etc) or limited by maximum5 stiffeners)

The local plate bending stress is easily excluded by using membrane stresses in the plating The stiffenerbending stress can not directly be excluded from the stress results unless stresses are visualised in the combinedpanel neutral axis This is for most program systems not feasible

Figure 5-4Stiffener bending stress - mesh variations

The magnitude of the stiffener bending stress included in the stress results depends on the mesh division andthe element type that is used This is shown in Figure 5-4 where the stiffener bending stress as calculated bythe FE-model is shown dependent on the mesh size for 4-node shell elements One element between floorsresults in zero stiffener bending Two elements between floors result in a linear distribution with approximatelyzero bending in the middle of the elements

When a relatively fine mesh is used in the longitudinal direction the effect of stiffener bending stresses shouldbe isolated from the girder bending stresses for buckling assessment

For the buckling capacity check of a plate the mean shear stress τ mean is to be used This may be defined asthe shear force divided on the effective shear area The mean shear stress may be taken as the average shearstress in elements located within the actual plate field and corrected with a factor describing the actual sheararea compared to the modelled shear area when this is relevant For a plate field with n elements the followingapply

where

AW = effective shear area according to the Rules for Classification of Ships Pt3 Ch1 Sec3 C503AWmod = shear area as represented in the FE model

524 Local buckling assessment - plates stiffeners girders etc

5241 GeneralBuckling control of plating stiffeners and girdersfloors shall be carried out according to acceptable designprinciples All relevant failure modes and effects are to be considered such as

mdash plate buckling mdash local buckling of stiffener and girder web plating mdash torsionalsideways buckling and global (overall) buckling of both stiffeners and girdersmdash interactions between buckling modes boundary effects and rotational restraints between plating and

stiffenersgirdersmdash free plate edge buckling to be excluded by fitting edge stiffeners unless detailed assessments are carried out

The buckling design of stiffened panels follows two main principles namely

( )W

Wmodn21mean A

A

n

ττττ sdot+++=

DET NORSKE VERITAS


Page 35

mdash Method 1 ndash Ultimate Capacity (UC)The stiffened panels are designed against their ultimate capacity limit thus accepting elastic buckling ofplating between stiffeners and load redistributions from plating to stiffenersgirders No major von Misesyielding and development of permanent setsbuckles should take place

mdash Method 2 ndash Buckling Strength (BS) The stiffened panels are designed against the buckling strength limit This means that elastic buckling ofneither the plating nor the stiffeners are accepted and thus redistribution of loads due to buckling areavoided The buckling strength (BS) is the minimum of the Ultimate Capacity (UC) and the elastic bucklingstrength (minimum Eigenvalue)

The load bearing limits using Method 1 and Method 2 will be coincident for moderate to slender designs whilethey will diverge for slender structures with the Method 1 giving the highest load bearing capacity This is dueto the fact that Method 1 accept elastic plate buckling between stiffeners and utilize the extra post-bucklingcapacity of flat plating (ldquoovercritical strengthrdquo) while Method 2 cuts the load bearing capacity at the elasticbuckling load level

From a design point of view Method 1 principle imply that thinner plating can be accepted than using Method2 principle

These principles are implemented in PULS buckling code 8 which is the preferred tool for bucklingassessment see Appendix E

5242 ApplicationMethod 1 design principles are in general used for stiffened panels relevant for the longitudinal strength or themain elements that contribute to the hull girder while Method 2 design principles are used for the primarysupport members of the hull girder eg panels that form the web-plating of girders stringers and floors Table5-2 summarises which method to use for different structural elements

For Method 1 the panel can be uni-axially stiffened or orthogonally stiffened The latter arrangement isillustrated in Figure 5-5

In general the application of Method 1 versus Method 2 follows the same principles as IACS-CSR TankerRules see the Rules for Classification of Ships Pt8 Ch1 App D52

Table 5-2 Application of Method 1 and Method 2Method 1 Method 2 1)

mdash bottom-shellmdash side-shellsmdash deckmdash inner bottommdash longitudinal bulkheadsmdash transverse bulkheads

mdash girdersmdash stringersmdash floors

1) Webs that may be considered to have fixed in-plane boundary-conditions eg girders below longitudinal bulkheads can utilize Method 1

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Page 36

Figure 5-5Schematic illustration of elastic plate buckling (load in x2-direction) load shedding from plating towards the stiff-eners takes place when designing according to Method 1 principle (ie reduced effective plate widthstiffness dueto buckling)

5243 Other structures ndash Pillars brackets etcFor designs where the buckling strength of structural members apart from the longitudinal material in cargoregion the following guidelines may be used as reference for assessment

mdash Pillars IACSCSR Sec10 Part 241mdash Brackets IACSCSR Sec10 Part 242mdash Cut-outs openings IACSCSR Sec10 Part 243 and Part 341mdash Reinforcements of free edges ie in way of openings brackets stringers pillars etc IACSCSR Sec10

Part 243mdash The buckling and ultimate strength control of unstiffened and stiffened curved panels (eg bilge) may be

performed according to the method as given in DNV-RP-C202 Ref 2

525 Acceptance criteria

5251 GeneralAcceptance requirements are given separately for material yield control and buckling control even though thelatter also includes yield checks locally in plate and stiffeners

The yield check is related to the nominal stress flow in the structure ie the local bending across the platethickness is not included

The buckling check is also based on the nominal stress flow idealized as described in Section 5233 to beconsistent with input to the PULS buckling code The check includes ldquosecondary stress effectsrdquo due toimperfections and elastic buckling effects thus preventing major permanent sets

5252 Material yield checkThe longitudinal hull girder and main girder system nominal and local stresses derived from the direct strengthcalculations are to be checked according to the criteria specified listed below

Allowable equivalent nominal von Mises stresses (combined with relevant still water loading) are given inTable 5-3

Table 5-3 Allowable stress levels ndash von Mises membrane stressSeagoing condition

General σe = 095 σf Nmm2

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Page 37

For areas with pronounced geometrical changes local linear peak stresses (von-Mises membrane) of up to 400f1 may be accepted provided plastic mechanisms are not developed in the associated structural parts

5253 Buckling checkThe ULS local buckling check for stiffened panels follows the guidelines as given in Section 5242 using thePULS buckling code For other structures the guidelines in Section 5243 apply

The acceptance level is as follows

mdash the PULS usage factor shall not exceed 090 for stiffened panels girder web plates etc This applies forMethod 1 and Method 2 principle

526 Alternative methods ndash non-linear FE etcAlternative non-linear capacity assessment of local panels girders etc using recognised non-linear FEprograms are acceptable on a case by case evaluation by the Society In such cases inclusion of geometricalimperfections residual stresses and boundary conditions needs careful evaluation The models should becapable of capturing all relevant buckling modes and interactions between them The accept levels are to bespecially considered

53 Hull girder collapse - global ULS

531 GeneralThe hull girder collapse criteria shall ensure sufficient safety margins against global hull failure under extremeload conditions and the vessel shall stay afloat and be intact after the ldquoincidentrdquo Buckling yielding anddevelopment of permanent setsbuckles locally in the hull section are accepted as long as the hull girder doesnot collapse and break with hull skin cracking and compartment flooding

The hull girder collapse criteria involve the vertical global bending moments in the considered critical sectionand have the general format

γ S MS + γ W MW le MU γ M

where

Ms = the still water vertical bending momentMw = the wave vertical bending moment MU = the ultimate moment capacity of the hull girderγ = a set of partial safety factors reflecting uncertainties and ensuring the overall required target safety

margin

The actual loads Ms and Mw giving the most severe combination in sagging and hogging respectively are tobe considered

The hull girder capacity MU shall be assessed using acceptable methods recognized by the Society Acceptablesimplified hull capacity models are given in Appendix C Appendix D describes alternative methods based onadvanced non-linear FE analyses

The hull girder collapse criteria shall be checked for both sagging and hogging and for the intact and twodamaged conditions see Section 582 The ultimate sagging and hogging bending capacities of the hull girderis to be determined for both intact and damaged conditions and checked according to criteria in Table 5-4

Global ULS shear capacity is to be specially considered if relevant for actual ship type and operating loadingconditions

532 Damage conditionsThere are two different damaged conditions to be considered collision and grounding The damage extents areshown in Figure 5-6 and further described in Table 5-4

DET NORSKE VERITAS


Page 38

Figure 5-6Damage extent collision (left) and grounding (right)

All structure within a breath of B16 is regarded as damaged for the collision case while structure within aheight of B15 is regarded as damaged for the grounding case Structure within the boxes shown in Figure 5-6should have no structural contribution when hull girder capacity is calculated for the collision or groundingdamage case

When assessing the ultimate strength (MU) of the damaged hull sections the following principles apply

mdash damaged area as defined in Table 5-4 carry no loads and is to be removed in the capacity model mdash the intact hull parts and their strength depend on the boundary supports towards the damaged area ie loss

of support for transverse frames at shipside etc The modelling of such effects need special considerationsreflecting the actual ship design

The changes in still-water and wave loads due to the damages are implicitly considered in the load factors γ Sand γ W see Table 5-5 No further considerations of such effects are needed

533 Hull girder capacity assessment (MU) - simplified approachAssuming quasi-static response the hull girder response is conveniently represented as a moment-curvaturecurve (M - κ) as schematically illustrated in Figure 5-6 The curve is non-linear due to local buckling andmaterial yielding effects in the hull section The moment peak value MU along the curve is defined as theultimate capacity moment of the total hull girder section

For ships with varying scantlings in the longitudinal direction changing stiffener spans etc the moment-curvature relation of the critical hull section should be analysed

Critical sections are normally found within the mid-ship area but for some ship designs like container vesselscritical sections can be outside 04 L eg in the engine room area

Table 5-4 Damage parametersDamage extent

Single sidebottom Double sidebottom

Collision in ship sideHeight hD 075 060Length lL 010 010

Grounding in ship bottomBreath bB 075 055Length lL 050 030

L - ship length l - damage length

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Page 39

Figure 5-7Moment-curvature (M-κ) curve for hull sections schematic illustration in sagging (quasi ndashstatic loads)

534 Accept criteria ndash intact and damagedThe ultimate hull girder capacity is calculated according to the accept criteria and limits shown in Table 5-5

Table 5-5 Hull girder strength check accept criteria ndash required safety factorsIntact strength Damaged strength

MS + γ W1 MW le MUIγ M γ S MS + γ W2 MW le MUDγ Mwhere

MS = Still water momentMW = Design wave moment

(20 year return period ndash North Atlantic)MUI = Ultimate intact hull girder capacityγ W1 = 11 (partial safety factor for environmental loads)γ M = 115 (material factor) in generalγ M = 130 (material factor) to be considered for hogging

checks and designs with bi-axialshear stresses conditions in bottom area eg double bottoms etc

where


(20 year return periodndash North Atlantic)MUD = Damaged hull girder capacityγ S = 11 (factor on MS allowing for moment increase with

accidental flooding of holds)γ W2 = 067 (hydrodynamic load reduction factor corresponding

to 3 month exposure in world-wide climate)γ M = 10 in generalγ M = 110 (material factor) to be considered for hogging checks

and designs with bi-axialshear stresses conditions in bottom area eg double bottoms etc

DET NORSKE VERITAS


Page 40

6 Structural Modelling Principles

61 Overview

611 Model typesThe CSA analysis is based on a set of different structural FE-models This section gives an overview of thestructural (and mass) modelling required for a CSA analysis

The structural models as shown in Table 6-1 are normally included in a CSA analyses

Figure 6-1 Figure 6-2 and Figure 6-3 show typical structural models used in a CSA analysis

Figure 6-1Global model example with cargo hold model included (port side shown)

Table 6-1 Structural models used in CSA analysesModel type Characteristics Used for

Global structural model

mdash The whole structure of the vesselmdash S times S mesh (girder spacing mesh)mdash May include cargo hold model (stiffener

spacing mesh)mdash May include fine mesh (t times t type mesh)mdash Includes mass-model

Global analysis (FLS and ULS)Cargo systemsBuckling stresses

Cargo hold model

mdash Part of vessel (typical cargo-hold model)mdash s x s mesh (stiffener spacing mesh)mdash May include fine mesh (t times t type mesh)mdash Includes mass-model particularly when used

as sub-model

Global fatigue screeningYield stressesBuckling stressesRelative deflection analysis

Stress concentration modelmdash Fine mesh (t times t type mesh)mdash Sub-modelmdash Size such that boundary effects are avoidedmdash Mass-model normally not included

Detailed fatigue analysisYield evaluation

DET NORSKE VERITAS


Page 41

Figure 6-2Stiffener spacing mesh (structural model of No1 hold on left and Midship cargo hold model on right)

Figure 6-3Stress concentration model

6111 Global structural modelThe global structural model is intended to provide a reliable description of the overall stiffness and global stressdistribution in the primary members in the hull The following effects shall be taken into account

mdash vertical hull girder bending including shear lag effectsmdash vertical shear distribution between ship side and bulkheadsmdash horizontal hull girder bending including shear lag effects mdash torsion of the hull girder (if open hull type)mdash transverse bending and shear

The mesh density of the model shall be sufficient to describe deformations and nominal stresses due to theeffects listed above Stiffened panels may be modelled by a combination of plate and beam elementsAlternatively layered (sandwich) elements or anisotropic elements may be used

Since it is required to use a regular mesh density for yield evaluation and for global fatigue screening it isrecommended to model a region of the global model with stiffener spacing type mesh by means of suitableelement transitions to the coarse mesh model see Figure 6-1 Since a full-stochastic fatigue analysis mayinclude as much as 200 to 300 complex load cases the region of regular mesh density might need to be restrictedto reduce computation time If it is unpractical to include all desired areas with a regular mesh density the

DET NORSKE VERITAS


Page 42

remaining parts should be modelled as sub-models see Section 64

The fatigue analysis and high stress yield areas require even denser mesh than that provided by regular meshtype Including these meshes in the global model will increase the number of degrees of freedom andcomputational time even more resulting in a database that is not easy to navigate It is therefore normal to haveseparate sub-models with finer mesh regions complementing the global model

Figure 6-4Global model with stiffener spacing mesh in Midshipcargo region

6112 Cargo hold model The cargo hold model is used to analyse the deformation response and nominal stress in primary structuralmembers It shall include stresses caused by bending shear and torsion

The model may be included in the global model as mentioned in Section 6111 or run separately withprescribed boundary deformations or boundary forces from the global model

The element size for cargo hold models is described in ship specific Classification Notes and in CN 307 4

Vessels with CSR notation may follow the net-scantlings methodology of CSR and the FE-model used forCSR assessment may also be used during CSA analysis It should however be noted that stiffeners modelledco-centric for CSR shall be modelled eccentric for CSA

6113 Stress concentration modelThe element size for stress concentration models is well described in ship specific Classification Notes and inClassification Note No 307 It is therefore not described here even if it is a part of the global structural model

62 General

621 PropertiesAll structural elements are to be modelled with net scantlings ie deducting a corrosion margin as defined bythe actual notation

622 Unit systemThe unit system as given in Table 6-2 is recommended as this is consistent and easy to use in the DNVprograms

DET NORSKE VERITAS


Page 43

623 Co-ordinate systemThe following co-ordinate system is proposed right hand co-ordinate system with the x-axis positive forwardy-axis positive to port and z-axis positive vertically from baseline to deck The origin should be located at theintersection between aft perpendicular baseline and centreline The co-ordinate system is illustrated in Figure6-5

Figure 6-5Co-ordinate system

63 Global structural FE-model

631 Model extentThe entire ship shall be modelled including all structural elements Both port and starboard side need to beincluded in the global model

All main longitudinal and transverse structure of the hull shall be modelled Structure not contributing to theglobal strength of the vessel may be disregarded The mass of disregarded elements shall be included in themodel

The superstructure is generally not a part of the CSA scope and may be omitted However for some ships itwill also be required to model the superstructure as the stresses in the termination of the cargo area areinfluenced by the superstructure It is recommended to include the superstructure in order to easily include themass

632 Model idealisation

6321 Elements and mesh size of plates and stiffenersWhere possible a square mesh (length to breadth of 1 to 2 or better) should be adopted A triangular mesh is

Table 6-2 Unit SystemMeasure Unit

Length Millimetre [mm]Mass Metric tonne [Te]Time Second [s]Force Newton [N]Pressure and stress 106middotPascal [MPa or Nmm2]Gravitation constant 981middot103 [mms2]Density of steel 785middot10-9 [Temm3]Youngrsquos modulus 210middot105 [Nmm2]Poissonrsquos ratio 03 [-]Thermal expansion coefficient 00 [-]

baseline

x fwd

z up

y port

AP

centreline

DET NORSKE VERITAS


Page 44

acceptable to avoid out of plane elements but not necessary since this can be handled by the analysis system

Plate elements should be modelled with linear (4- and 3-node) or quadratic (8- and 6-node) elements Stiffenersmay be modelled with two or three node elements (according to shell element type)

The use of higher level elements such as 8-node or 6-node shell or membrane elements will not normally leadto reduced mesh fineness 8-node elements are however less sensitive to element skewness than 4-nodeelements and have no ldquoout of planerdquo restrictions In addition 6-node elements provide significantly betterstiffness representation than that of 3-node elements Use of 6-node and 8-node elements is preferred but canbe restricted by computer capacity

The following rules can be used as a guideline for the minimum element sizes to be used in a globalstiffnessstructural model using 4-node andor 8ndashnode shell elements (finer mesh divisions may be used)

General One element between transverse framesgirders Girders One element over the height

Beam elements may be used for stiffness representationGirder brackets One elementStringers One element over the widthStringer brackets One elementHopper plate One to two elements over the height depending on plate sizeBilge Two elements over curved areaStiffener brackets May be disregardedAll areas not mentioned above should have equal element sizes One example of suitable element mesh withsuitable element sizes is illustrated by the fore and aft-parts of Figure 6-1

The eccentricity of beam elements should be included The beams can be modelled eccentric or the eccentricitymay be included by including the stiffness directly in the beam section modulus

6322 Modelling of girdersGirder webs shall be modelled by means of shell elements in areas where stresses are to be derived Howeverflanges may be modelled using beam and truss elements Web and flange properties shall be according to theactual geometry The axial stiffness of the girder is important for the global model and hence reduced efficiencyof girder flanges should not be taken into account Web stiffeners in direction of the girder should be includedsuch that axial shear and bending stiffness of the girder are according to the girder dimensions

The mean girder web thickness in way of cut-outs may generally be taken as follows for rco values larger than12 (rco gt 12)

Figure 6-6Mean girder web thickness

where

tw = web thickness

lco = length of cut-outhco = height of cut-out

Wco

comean t

rh

hht sdot

sdotminus=

( )2co

2co

cohh26

l1r

minus+=

DET NORSKE VERITAS


Page 45

For large values of rco (gt 20) geometric modelling of the cut-out is advisable

633 Boundary conditionsThe boundary conditions for the global structural model should reflect simple supports that will avoid built-instresses A three-two-one fixation as shown in Figure 6-7 can be applied Other boundary conditions may beused if desirable The fixation points should be located away from areas of interest as the loads transferredfrom the hydrodynamic load analysis may lead to imbalance in the model Fixation points are often applied atthe centreline close to the aft and the forward ends of the vessel

Figure 6-7Example of boundary conditions

634 Ship specific modelling

6341 Membrane type LNG carrierThe stiffness of the tank system is normally not included in the structural FE-model Pressure loads are directlytransferred to the inner hull

6342 Spherical LNG carriersThe spherical tanks shall be modelled sufficiently accurate to represent the stiffness A mesh density in theorder of 40 elements around the circumference of a tank will normally be sufficient However the transitiontowards the hull will normally have a substantially finer mesh

The mesh density of the cover has to be consistent with the hull mesh Special attention should be given to thedeckcover interaction as this is a fatigue critical area

6343 LPGLNG carrier with independent tanksThe tank supports will normally only transfer compressive loads (and friction loads) This effect need to beaccounted for in the modelling A linearization around the static equilibrium will normally be sufficient

64 Sub models

641 GeneralThe advantage of a sub-model (or an independent local model) as illustrated in Figure 6-2 is that the analysisis carried out separately on the local model requiring less computer resources and enabling a controlled stepby step analysis procedure to be carried out For this sub model the mass data must be as for the global modelin order to ensure correct inertia loads

The various mesh models must be ldquocompatiblerdquo ie the coarse mesh models shall produce deformations andor forces applicable as boundary conditions for the finer mesh models (referred to as sub-models)

Sub-models (eg finer mesh models) may be solved separately by use of the boundary deformations boundaryforces and local internal loads transferred from the coarse model This can be done either manually or if sub-modelling facilities are available automatically by the computer program

The sub-models shall be checked to ensure that the deformations andor boundary forces are similar to thoseobtained from the coarse mesh model Furthermore the sub-model shall be sufficiently large that its boundariesare positioned at areas where the deformation stresses in the coarse mesh model are regarded as accurateWithin the coarse model deformations at web frames and bulkheads are usually accurate whereas

h = height of girder web

DET NORSKE VERITAS


Page 46

deformations in the middle of a stiffener span (with fewer elements) are not sufficiently accurate

The sub-model mesh shall be finer than that of the coarse model eg a small bracket is normally included in alocal model but not in global model

642 PrincipleSub-models using boundary deformationsforces from a coarse model may be used subject to the followingrules The rules aim to ensure that the sub-model provides correct results These rules can however vary fordifferent program systems

The sub-model shall be compatible with the global (parent) model This means that the boundaries of the sub-modelshould coincide with those elements in the parent model from which the sub-model boundary conditions areextracted The boundaries should preferably coincide with mesh lines as this ensures the best transfer ofdisplacements forces to the sub-model

Special attention shall be given to

1) Curved areasIdentical geometry definitions do not necessarily lead to matching meshes Displacements to be used at theboundaries of the sub-model will have to be extrapolated from the parent model However only radialdisplacements can be correctly extrapolated in this case and hence the displacements on sub-model canconsequently be wrong

2) The boundaries of the sub-model shall coincide with areas of the parent model where the displacementsforces are correct For example the boundaries of the sub-model should not be midway between two frames if the mesh sizeof the parent model is such that the displacements in this area cannot be accurately determined

3) Linear or quadratic interpolation (depending on the deformation shape) between the nodes in the globalmodel should be considered Linear interpolation is usually suitable if coinciding meshes (see above) are used

4) The sub-model shall be sufficiently large that boundary effects due to inaccurately specified boundarydeformations do not influence the stress response in areas of interest A relatively large mesh in theldquoparentrdquo model is normally not capable of describing the deformations correctly

5) If a large part of the model is substituted by a sub model (eg cargo hold model) then mass properties mustbe consistent between this sub-model and the ldquoparentrdquo model Inconsistent mass properties will influencethe inertia forces leading to imbalance and erroneous stresses in the model

6) Transfer of beam element displacements and rotations from the parent model to the sub-model should beespecially considered

7) Transitions between shell elements and solid elements should be carefully considered Mid-thickness nodesdo not exist in the shell element and hence special ldquotransition elementsrdquo may be required

The model shall be sufficiently large to ensure that the calculated results are not significantly affected byassumptions made for boundary conditions and application of loads If the local stress model is to be subject toforced deformations from a coarse model then both models shall be compatible as described above Forceddeformations may not be applied between incompatible models in which case forces and simplified boundaryconditions shall be modelled

643 Boundary conditionsThe boundary conditions for the sub-model are extracted from the ldquoparentrdquo model as displacements applied tothe edges of the model and pressures are applied to the outer shell and tank boundaries

Sub-model nodes are to be applied to the border of the models which are given displacements as found in parentmodel

65 Mass modelling and load application

651 GeneralThe inertia loads and external pressures need to be in equilibrium in the global FE-analysis keeping thereaction forces at a minimum The sum of local loads along the hull needs to give the correct global responseas well as local response for further stress evaluation Since the inertia and wave pressures are obtained andtransferred from the hydrodynamic analysis using the same mass-model for both structural analysis andhydrodynamic analysis ensure consistent load and response between structural and hydrodynamic analysisThis means that the mass-model used need to ensure that the motion characteristics and load application isproperly represented

In the hydrodynamic analysis the mass needs to be correctly described to produce correct motions and sectional

DET NORSKE VERITAS


Page 47

forces while globallocal stress patterns are affected by the mass description in the structural analysis Themass modelling therefore needs to be according to the loading manual ie have the same

mdash total weightmdash longitudinal centre of gravitymdash vertical centre of gravitymdash transverse centre of gravitymdash rotational mass in roll and pitch

Experience shows that the hydrodynamic analysis will give some small modification to the total mass andcentre of gravity where the buoyancy is decided by the draft and trim of the loading condition in question

Each loading condition analysed needs an individual mass-model The lightship weight is consistent for all themodels but the draft and cargo loadballast distribution is different from one loading condition to another

To obtain the correct mass-distribution in the FE model an iteration process for tuning the mass distributionhas to be carried out in the initial phase of the global analysis

652 Light weightLight weight is defined as the weight that is fixed for all relevant loading conditions eg steel weightequipment machinery tank fillings (if any) etc

The steel weight should be represented by material density Missing steel weight and distributed deadweightcan be represented by nodal masses applied to shell and beam elements

The remaining lightweight should be represented by concentrated mass points at the centre of gravity of eachcomponent or by nodal masses whichever is more appropriate for the mass in question

The point mass representation should be sufficiently distributed to give a correct representation of rotationalmass and to avoid unintended results Point masses should be located in structural intersections such that localresponse is minimised

653 Dead weightDead weight is defined as removable weight ie weight that varies between loading conditions The mostcommon are

mdash liquid cargo and ballastmdash containersmdash bulk cargo

Different ship-types and tankcargo types may need special consideration to ensure that the mass is modelledin a way that both represent the motion characteristics of the vessel at the same time as the inertia load isproperly applied

The following contains some guidelinesbest practice for some ship-typesmass-types Other methods may alsobe applicable

6531 Ballast and liquid cargoIn most cases liquid should be represented by distributed pressure in the FE-analysis at least within the areasof interest In the hydrodynamic analysis the pressure is represented as mass-points distributed within the tank-boundaries of the tank

6532 Container cargoThe weight of containers need to give the correct vertical forces at the container supports but also forcesoccurring in the cell guides due to rolling and pitching need to be included

6533 Bulk ore cargoFor bulk cargo the correct centre of gravity and the roll radii of gyration need to be ensured The forces needto be applied such that the lateral forces but also friction forces of the bulk cargo are correctly applied

This can be achieved by modelling part of the load as mass-points and part of the load as pressure-loads wherethe pressure loads will ensure some lateral pressure on the transverse and longitudinal bulkheads and the mass-points will ensure that most of the load is taken by the bottom structure

The ratio between cargo modelled by mass-points and by pressure load depends on the inclination of thesupporting transverselongitudinal structure

6534 Spherical tanks For spherical tanks there are two important effects that need to be considered ie

DET NORSKE VERITAS


Page 48

mdash the rotational mass of the cargomdash cargo distribution has a correct representation of how the load from the cargo is transferred into the hull

For spherical tanks the inner side of the tank is without any stiffening arrangement and only the frictionbetween the tank surface and the liquid (in addition to the drag effect of the tower) will make the liquid rotateHence the rotational mass from this effect can normally be neglected and only the Steiner contribution (mr2)of the rotational mass should be included

By neglecting the rotational mass the roll Eigen period will be slightly under estimated from this procedureThis is conservative since a lower Eigen period normally will give higher roll acceleration of the vessel

Normally the weight of the cargo can be assumed to be uniformly distributed along the skirt of the tank

7 Documentation and Verification

71 GeneralCompliance with CSA class notations shall be documented and submitted for approval The documentationshall be adequate to enable third parties to follow each step of the calculations For this purpose the followingshould as a minimum be documented or referenced

mdash basic inputmdash assumptions and simplifications made in modellinganalysismdash modelsmdash loads and load transfermdash analysismdash resultsmdash discussion andmdash conclusion

The analysis shall be verified in order to ensure accuracy of the results Verification shall be documented andenclosed with the analysis report

Checklists for quality assurance shall also be developed before the analysis work commences It is suggestedthat project-specific checklists are defined before the start of the project and are included in the project qualityplan These checklists will depend on the shipyardrsquos or designerrsquos engineering practices and associatedsoftware

The following contains the documentation requirements to each step (Section 72) and some typical verificationsteps (Section 73) that compiles the total delivery Input files and result files may be accepted as part of theverification

72 Documentation

721 Basic inputThe following basis for the analysis need to be included in the documentation

mdash basic ship information including revision number- drawings- loading manuals- hull-lines

mdash deviations simplifications from ship informationmdash assumptionsmdash scope overview

- analysis basis- loading conditions- wave data- design waves (including purpose)- time at sea

mdash requirementsacceptance criteria

722 ModelsAll models used should be documented where the use and purpose of the model is stated In addition thefollowing to be included

mdash unitsmdash boundary conditions

DET NORSKE VERITAS


Page 49

mdash coordinate system

723 Loads and hydrodynamic analysisTypical properties to be documented are listed below and should be based on the selected probability level forlong-term analysis

mdash viscous damping levelmdash mass properties (radii of gyration)mdash motion reference pointmdash long term responses with corresponding Weibull shape parameter and zero-crossing period for

- motions- sectional loads within cargo region- accelerations within cargo region- sea pressures

mdash design waves parameters with corresponding basis and non-linear results (if relevant)

It is recommended that the documentation of the hydrodynamic parameters is initiated in the start of the projectin order to have comparable numbers throughout the project

724 Load transferThe following to be documented confirming that the individual and total applied loads are correct

mdash pressures transfermdash global loads (vertical bending moment and shear force) between hydro-model and structural model the

same

725 Structural analysisOverview of which structural analysis are performed

726 Fatigue damage assessmentFollowing to be documented

mdash reference to or methodology usedmdash welding effects includedmdash factors accounting for effects not present in structural analysis (correction of stress)mdash SN curves usedmdash damage including mean stress effect if anymdash stress patternsmdash global screening

727 Ultimate limit state assessment ndash local yield and bucklingFollowing to be documented

mdash results showing compliance based on yielding criteriamdash results showing compliance based on buckling criteriamdash results from fine mesh evaluationmdash special considerations corrections and assumptions made need to be summarizedmdash amendments needed to achieve compliance

728 Ultimate limit state assessment - hull girder collapseFollowing to be documented

mdash reference to evaluation methodmdash reference to special considerationsmdash results showing compliance for intact conditions including loads and capacitymdash results showing compliance for damaged conditions including loads and capacity

73 Verification

731 GeneralEach step of the procedure should be verified before next step begins As major verification milestones thefollowing should at a minimum be documented before the work is continued

FE model

mdash scantlings geometry etcmdash load cases and boundary conditionsmdash test-run to ensure that FE-model is OK to be performed

DET NORSKE VERITAS


Page 50

Mass-model

mdash total mass and centre of gravitymdash still water vertical bending moment and shear force (of structural and hydro model)

Hydro-analysis

mdash hydro-modelmdash transfer-functionsmdash long-term responsesmdash design waves (if relevant)

Load transfer

mdash vertical bending moments and shear forces mdash equilibriummdash load patterns

FE analysis

mdash responsesmdash global displacement patternsmagnitudesmdash local displacement patternsmdash global sectional forcesmdash stress level and distributionmdash sub-model boundary displacementsforces and stressmdash reaction forces and moments

Verification steps should be included as Appendix or Enclosed together with main reportdocumentation

732 Verification of Structural ModelsFor proper documentation of the model requirements given in the Rules for Classification of Ships Pt3 Ch1Sec13 should be followed Some practical guidance is given in the following

Assumptions and simplifications are required for most structural models and should be listed such that theirinfluence on the results can be evaluated Deviations in the model compared with the actual geometry accordingto drawings shall be documented

The set of drawings on which the model is based should be referenced (drawing numbers and revisions) Themodelled geometry shall be documented preferably as an extract directly from the generated model Thefollowing input shall be reflected

mdash plate thicknessmdash beam section propertiesmdash material parameters (especially when several materials are used)mdash boundary conditionsmdash out of plane elements (4-node elements see Section 6)mdash mass distributionbalance

733 Verification of Hydrodynamic Analysis

7331 ModelThe mass model should have the same properties as described in the loading manual ie total mass centre ofgravity and mass distribution

The linking of the hydrodynamic and structural models shall be verified by calculating the still water bendingmoments and shear forces These shall be in accordance with the loading manual Note that the loading manualsdo not include moments generated by pressures with components acting in the longitudinal direction Thesepressures are illustrated by the two triangular shapes in Figure 7-1

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Page 51

Figure 7-1End pressures contributing to vertical bending moment

Two ways of including the longitudinal forces are presented One way is to add the moment given by

where

ρ = sea-water densityg = acceleration of gravityd = draughtB = breadthZNA = distance from the keel to the neutral axis

The correction is not correct towards the ends since the vessel is not shaped like a box Figure 7-2 shows anexample of the procedure above The loading manual corresponds with the potential theory as long as thetransverse section has a rectangular shape

Figure 7-2Example of verification of still water loads

Another option is to apply pressures acting only in longitudinal direction to the structural model and integratethe resulting stresses to bending moments In this way the potential theory shall match the corrected loading

)3

d-(Z

2

B dNA5 gdM ρ=Δ

Still water bending moment

-2500000

-2000000

-1500000

-1000000

-500000

0

500000

1000000

0 50 100 150 200 250 300 350

Longitudinal position of the vessel

Sti

ll w

ater

ben

din

g m

om

ent

Loding Manual

Loading Man Corr

Potential theory

DET NORSKE VERITAS


Page 52

manual all over the vessel

When the internal tanks have large free surfaces the metacentric height might change significantly This willaffect the roll natural frequency If there is wave energy present for this frequency range these free surfaceeffects should be included in the model The viscous and potential code should use the same physics andthereby give the same natural frequency for roll Correction of metacentric height in the potential code Wasimcan be included by modifying the stiffness matrix

where

C = the stiffness matrix ρ = the water density g = the acceleration of gravity

7332 Roll dampingIf the method in Section 33 is used the roll angle given as input to the damping module should be the same asthe long term roll angle which is based on the final transfer functions In general increased motion will resultin increased damping It is therefore normally more viscous damping for ULS than for FLS

7333 Transfer functionsThe transfer functions shall be reviewed and verified For short waves all motion responses (6 degrees offreedom) shall be zero For long waves transfer function for heave shall be equal to one When the roll andpitch transfer functions are normalized with the wave amplitude it shall be zero for long waves and normalizedwith wave steepness they shall be constant for long waves Transfer functions for surge in head and followingsea should be equal to one for long periods while transfer functions for sway should be one in beam sea

All global wave load components shall be equal to zero for long and short waves

7334 Design waves for ULSFor linear design waves the dynamic response of the maximized response shall be the same as the long termresponse described in Section 35

For non-linear design waves the comparisons of linear and non-linear results shall be presented It is importantthat if the non-linear simulation is repeated in linear mode the result would be the linear long term response

734 Verification of loadsInaccuracy in the load transfer from the hydrodynamic analysis to the structural model is among the main errorsources for this type of analysis The load transfer can be checked on basis of the structural response and onbasis on the load transfer itself

It is possible to ensure the correct transfer in loads by integrating the stress in the structural model and theresulting moments and shear forces should be compared with the results from the hydrodynamic analysisFigure 7-3 and Figure 7-4 compares the global loads from the hydrodynamic model with that resulting fromthe loads applied to the structural model

correctionGMntDisplacemeVolumegC timestimes=Δ ρ44

DET NORSKE VERITAS


Page 53

Figure 7-3Example of QA for section loads ndash Vertical Shear Force

Figure 7-4Example of QA for sectional loads ndash Vertical Bending Moment

10 sections are usually sufficient in order to establish a proper description of the bending moment and shearforce distribution along the hull However this may depend on the shape of the load curves The first and lastsections should correspond with the ends of the finite element model

In case of problems with the load transfer it is recommended to transfer the still water pressures to the structural

-200E+05

-150E+05

-100E+05

-500E+04

000E+00

500E+04

100E+05

150E+05

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ver

tical

she

ar f o

rce

[kN

]

-200E+06

000E+00

200E+06

400E+06

600E+06

800E+06

100E+07

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ve

rtic

a l b

end i

ng m

o men

t [kN

m]

DET NORSKE VERITAS


Page 54

FE model in order to verify the models and tools

Pressures applied to the model can be verified against transfer-functions of shell pressure in the hydrodynamicanalysis For use of sub-models it shall be verified that the pressure on the sub-model is the same as that fromthe parent model

735 Verification of structural analysis

7351 Verification of ResponseThe response should be verified at several levels to ensure that the analysis is correct The following aspectsshould be verified as applicable for each load considered

mdash global displacement patternsmagnitudemdash local displacement patternsmagnitudemdash global sectional forcesmdash stress levels and distributionmdash sub model boundary displacementsforcesmdash reaction forces and moments

7352 Global displacement patternsmagnitudeIn order to identify any serious errors in the modelling or load transfer the global action of the vessel shouldbe verified against expected behaviourmagnitude

7353 Local displacement patternsDiscontinuities in the model such as missing connections of nodes incorrect boundary conditions errors inYoungrsquos modulus etc should be investigated on basis of the local displacement patternsmagnitude

7354 Global sectional forcesGlobal bending moments and shear force distributions for still water loads and hydrodynamic loads should beaccording to the loading manual and hydrodynamic load analysis respectively Small differences will occur andcan be tolerated Larger differences (gt5 in wave bending moment) can be tolerated provided that the sourceis known and compensated for in the results Different shapes of section force diagrams between hydrodynamicload analysis and structural analysis indicate erroneous load transfer or mass distribution and hence should notnormally be allowed

When transferring loads for FLS at least two sections along the vessel should be chosen and transfer functionsfor sectional loads from hydrodynamic and structural FE model shall be compared eg one section amidshipsand one section in the forward or aft part of the vessel as a minimum When ULS is considered the sectionalloads from the hydrodynamic model at time of load transfer shall be compared with the integrated stresses inthe structural FE model

7355 Stress levels and distributionThe stress pattern should be according to global sectional forces and sectional properties of the vessel takinginto account shear lag effects More local stress patterns should be checked against probable physicaldistribution according to location of detail Peak stress areas in particular should be checked for discontinuitiesbad element shapes or unintended fixations (4-node shell elements where one node is out of plane with the otherthree nodes)

Where possible the stress results should be checked against simple beam theory checks based on a dominantload condition eg deck stress due to wave bending moment (head sea) or longitudinal stiffener stresses dueto lateral pressure (beam sea)

7356 Sub-model boundary displacementsforcesThe displacement pattern and stress distribution of a sub-model should be carefully evaluated in order to verifythat the forced displacementsforces are correctly transferred to the boundaries of the sub-model Peak stressesat the boundaries of the model indicate problems with the transferred forcesdisplacements

7357 Reaction forces and momentsReacting forces and moments should be close to zero for a direct structural analysis Large forces and momentsare normally caused by errors in the load transfer The magnitude of the forces and moments should becompared to the global excitation forces on the vessel for each load case

DET NORSKE VERITAS


Page 55

8 References

1 DNV Rules for Classification of Ships Pt3 Ch1 Hull Structural Design Ships with Length 100 metresand above July 2008

2 DNV Recommended Practice DNV-RP-C202 Buckling Strength of Shells April 20053 DNV Recommended Practice DNV-RP-C205 Environmental Conditions and Environmental Loads

October 20084 DNV Classification Note 307 Fatigue assessment of ship structures October 20085 DNV Classification Note 342 PLUS - Extended fatigue analysis of ship details April 20096 Tanaka ldquoA study of Bilge Keels Part 4 on the Eddy-making Resistance to the Rolling of a Ship Hullrdquo

Japan Soc of Naval Arch Vol 109 19607 DNV Rules for Classification of Ships Pt8 Ch2 Common Structural Rules for Double Hull Oil

Tankers above 150 metres of length October 20088 DNV Recommended Practice DNV-RP-C201 Part 2 Buckling strength of plated structures PULS

buckling code Oct 20029 Kato ldquoOn the frictional Resistance to the Rolling of Shipsrdquo Journal of Zosen Kiokai Vol 102 195810 Kato ldquoOn the Bilge Keels on the Rolling of Shipsrdquo Memories of the Defence Academy Japan Vol IV

No3 pp 339-384 196611 Friis-Hansen P Nielsen LP ldquoOn the New Wave model for kinematics of large ocean wavesrdquo Proc

OMAE Vol I-A pp 17-24 199512 Pastoor LW ldquoOn the assessment of nonlinear ship motions and loadsrdquo PhD thesis Delft University

of Technology 200213 Tromans PS Anaturk AR Hagemeijer P ldquoA new model for the kinematics of large ocean waves

- application as a design waverdquo Proc ISOPE conf Vol III pp 64-71 1991

DET NORSKE VERITAS


Page 56

Appendix ARelative Deflection Analysis

A1 GeneralThe following gives the procedure for finding the relative deflection to be used in component stochasticanalysis for bulkhead connections A FE analysis using a cargo-hold model is performed to calculate relativedeflections at the midship bulkhead

A2 Structural modellingA cargo-hold model representing the midship region is used with frac12 + 1 + frac12 cargo holds or 3 cargo holds Seevessel types individual class notation for modelling principles and boundary conditions

Plating is represented by 6- and 8-node shell elements and stiffeners are represented by 3-node beam elementsAn image of the model is shown in Figure A-1

The model is to be based on net scantlings unless other is stated by class notation

Figure A-13-D Cargo Hold Model

DET NORSKE VERITAS


Page 57

A3 Load casesThe applied load cases are described in Table A-1

A4 LoadsThe loads are to be based on the hydrodynamic analysis for FLS for each loading condition respectively Theloads are to be taken at 10-4 probability level and are to be based on the defined scatter-diagram with cos2

spreading

A41 Sea pressure

The panel pressures from hydrodynamic analysis at midship section are subtracted and the long-term valuesare found The pressure is applied to the cargo-hold model with same value along the model If panels do notmatch the pressures they are to be interpolated according to coordinates

The pressure in the intermittent wetdry region on the side-shell is to be corrected according to the procedurespecified in Section 3622 (see also CN 307)

A42 Cargo loadtank pressure

The cargo loadpressure due to vessel accelerations applied is to be based on accelerations at 10-4 probabilitylevel Loads from accelerations in vertical transverse and longitudinal direction are to be considered on projectbasis For most vessels it is sufficient to apply the loads due to vertical acceleration only but some designs mayneed to consider transverse and longitudinal acceleration also

The acceleration is to be taken at the centre of gravity of the tank(s)hold in the midship region and thereference point for the pressure distribution is to be taken at the centre of free surface The density is to be takenas 1025 tonnesm3 for ballast water in ballast tanks and as cargo densityload as specified in the loading manualfor full load condition

Table A-1 Midship model fatigue load cases LC no Loading condition Load component Figure

LC1 Full load condition Dynamic sea pressure

LC2 Full load condition Dynamic cargo pressure (vertical acceleration)

LC4 Ballast condition Dynamic sea pressure

LC5 Ballast condition Dynamic ballast pressure(vertical acceleration)

DET NORSKE VERITAS


Page 58

The long term acceleration is to be used for the pressures calculation The pressure distribution due to positiveacceleration shall apply

It is sufficient to use the same acceleration for the tank(s) forward and aft of the tank(s)hold in question withouttaking into account the phasing or difference in long term value between adjacent tanks forward and aft

A5 Boundary conditionsThe boundary conditions are to be taken according to vessels applicable CN for strength assessment

A6 Post-processing

A61 Subtracting resultsThe relative deflection between the bulkhead and the closest frame is found from the FE-analysis

Based on the relative deflection the stress due to the deflection can be calculated based on beam theory see CN307 4

The deflection of each detail is further normalised based on the load it is caused by (eg the wave pressure oracceleration at 10-4 probability level) giving the nominal stress per unit load By combining it with the transferfunction of the response the nominal stress due to relative deflection is found The stress concentration factoris added and the transfer-function can be added to the total stress transfer function

DET NORSKE VERITAS


Page 59

Appendix BDNV Program Specific Items

B1 GeneralThere are several steps and different programs that are necessary for an analysis that involve direct calculationof loads and stress including a load transfer

Typical programs are given in the following

B2 Modelling

B21 General mass modelling

In order to tune the position of the centre of gravity and verify the weight distribution it is recommended todivide the vessel in longitudinal and transverse blocks This allows easy specification of individual mass andmaterial properties for each block

B22 External loads

To be able to transfer the hydrodynamic loads a dummy hydro pressure must be applied to the hull This mustbe load case no 1 (SESAM) The pressure shall be defined by applying hydro pressure (PROPERTY LOAD xHYDRO-PRESSURE) acting on the shell (all parts of the hull may be wetted by the wave) The pressure shallpoint from the water onto the shell A constant pressure may be applied since the real pressure distribution willbe calculated in WASIM and directly transferred to the structural model The model must also have a mesh lineat or close to the respective waterlines for each of the draft loading conditions (full load and ballast) to beconsidered

HydroD is an interactive application for computation of hydrostatics and stability wave loads and motion response for ships and offshore structures The wave loads and motions are computed by Wadam or Wasim in the SESAM suite of programs

WASIM linear and non-linear 3D time domain program WASIM in its linear mode calculates transfer functions for motions sea pressure and sectional forces of the vessel In its non-linear mode time series of the specified responses are generated and additional Froude-Krylov and hydrostatic forces from wave action above still-water level are included Vessel speed effects are accounted for in WASIM and the vessel is kept directional and positional stable by springs or auto-pilot

WAVESHIP is a linear 2D frequency domain program WAVESHIP can be applied for calculation of viscous roll damping

PATRAN_PRE is a general pre-processor for graphical geometry modelling of structures and genera-tion of Finite Element Models

SESTRA is a program for linear static and dynamic structural analysis within the SESAM pro-gram system

SUBMOD Program for retrieval of displacements on a local part (sub-model) of a structure from a global (complete) model for refined or detailed analysis

PRESEL is a program for assembling super-elements (part models) to form the complete model to be analysed It also has functions for changing coordinate system to easily allow part models to be moved

STOFAT is an interactive postprocessor performing stochastic fatigue calculation of welded shell and plate structures The fatigue calculations are based on responses given as stress transfer functions STOFAT also has an application for calculation of statistical long term post-processing of stresses

XTRACT is the model and results visualization program of SESAM It offers general-purpose fea-tures for selecting further processing displaying tabulating and animating results from static and dynamic structural analysis as well as results from various types of hydrody-namic analysis

POSTRESP is a wave statistical post-processor for determination of short and long term responses of motions and loads

CUTRES is a post-processing tool for sectional results calculating the force distribution through-out the cross section and integrate the force to form total axial force shear forces bend-ing moments and torsional moment for the cross section

NAUTICUS HULL has an application for component stochastic fatigue analysis the program (Component) Stochastic Fatigue in Section Scantlings is a tool for performing stochastic fatigue anal-ysis of longitudinal stiffeners with corresponding plates according to Classification Note 307 The program uses all the structural input specified in Section Scantlings to-gether with result and specified data from the wave analysis to calculate stochastic fa-tigue life

DET NORSKE VERITAS


Page 60

B23 Ballast and liquid cargoUsing SESAM tools require that the tanks are predefined in the FE-model as separate load cases Each loadcase consists of dummy-pressures applied to the tank-boundaries of the tank In the interface between thehydro-analysis and structural analysis each tank is given a density and a filling level producing a surfacecentre of gravity and weight of the liquid in the tank Based on these properties the mass points for the tank canbe generated for the hydrodynamic analysis and a tank-pressure distribution based on the inertia for thestructural analysis

If above procedure cannot be applied the following is an alternative procedure

General

mdash One separate super element covering all tanks (ballast and cargo) is mademdash Each tank is defined with a set name identical to the one used for the structural modelmdash Each tank is specified with one specific density ie one material to be defined for each tank

Ballast tanks

mdash The frames for each ballast tank (excluding ends of tank) are meshed see Figure B-1 The same mesh asused in the globalmid-ship model may be used

mdash Alternatively a new mesh may be created Shell or solid elements may be used This mesh only needs tobe fine enough to capture global geometry changes Typical mesh size

- one mesh between each frame (for solid elements)- one mesh between each stringergirder

Cargo tanks

mdash The tank is modelled with solid elements The mesh only needs to be fine enough to capture globalgeometry changes Typical mesh size

mdash One mesh between each framemdash One mesh between each stringergirder

Figure B-1Mass model ballast tanks

B24 Container cargoContainers may be modelled as boxes by using 8 QUAD shell elements The changing the thickness will givea total weight of the containers in the holds By connecting the containers to the bulkheads with springs theforce from roll and pitch are transferred

End frames

DET NORSKE VERITAS


Page 61

B25 Spherical tanks The mass can be represented by longitudinal strings of mass through the centre of the tank ensuring the correcttotal mass and centre of gravity In addition it is important that the mass represents the longitudinal distributionof how the weight is transferred to the structure which may be assumed to be uniformly distributed along thetank skirt This to ensure that the sectional loads calculated in the hydrodynamic analysis are correct

B3 Structural analysisInertia relief shall not be utilized during the structural analysis

DET NORSKE VERITAS


Page 62

Appendix CSimplified Hull Girder Capacity Model - MU

C1 Multi step methods (incremental ndash iterative procedures HULS-N)The general way to find the MU value will be to solve the non-linear physical problem (equilibrium equations)by stepping along the M ndash k curve using an incremental-iterative numerical approach This means that theultimate capacity can be found by summing up the incremental moments along the curve until the peak valueis reached ie

Here the Δ Mi is an incremental moment corresponding to an incremental curvature Δki and N is the numberof steps used in order to reach the peak value MU beyond which the incremental moments become negative(post-collapse region)

The incremental moment ΔMi is related to the incremental curvature Δki through the tangent stiffness relation

Here (EI)red-i represent the incremental bending stiffness of the hull girder The (EI)red-i stiffness is state (load)dependent and will be gradually lower along the M-k curve and zero at global hull collapse level (MU) The(EI)red-i parameter shall include all important effects such as

a) geometrical and material non-linear effects

b) buckling post-buckling and yielding of individual hull section members

c) geometrical imperfectionstolerances - size and shape trigger of critical modes

d) interaction between buckling modes

e) bi-axial compressiontension andor shear stresses acting simultaneously with the longitudinal stresses

f) double bottom bending effects (hogging)

g) shift in neutral axis due to bucklingcollapse and consequent load shedding between elements in the cross-section

h) boundary conditions and interactionsrestraints between elements

i) global shear loads (vertical bending)

j) lateral pressure effects

k) local patch loads (crane loads equipment etc)

l) for damaged hull cases (Sec542) special consideration are to be given to flooding effects non-symmetricdeformations warping horizontal bending residual stresses from the collision grounding

One version of the multi-step method is the Smith method which is based on integrating simplified semi-empirical load-shortening (P - ε load-strain) curves across the hull section to give the total moment M - κrelation The maximum value MU along the M - κ curve is found by incrementing the curvature κ of the hullsection between two frames in steps and then calculated the corresponding moment at each step When themoment starts to drop the maximum moment MU is identified

The critical issue in the Smith method and similar approaches is the construction of the P - ε curves for thecompressed and collapsing elements and how the listed effects a) to l) above are embedded into these relations

The Hull girder check can be based on the multi-step method (Smith method) according to the Societiesapproval on a case by case basis All the effects as listed in a) to l) above should be included and documentedto be consistent with results from more advanced non-linear FE analyses see Sec545

C2 Single step method (HULS-1)A single step method for finding the MU value is acceptable as long as the listed effects are consistentlyincluded This gives the following formula for MU

where

= Effective section modulus in deck (centreline or average deck height) accounting for local buckling and collapse of individual elements on the compressive side of the neutral axis Each compressed element has an effective area defined as AeffAnom = σUσF The effective area to be modelled as reduced thickness tefftnom = AeffAnom or using effective plate widths for cal-culating the effective section modulus Weff

NiU MMMMM Δ++++Δ+Δ= 21 (C1)

iiredi EIM κΔ=Δ minus)( (C2)

)( min bottomF

bottomeff

deckF

deckeffU WWM σσ= (C3)

deckeffW

DET NORSKE VERITAS


Page 63

The minimum test on the MU value in the formula eq (C3) is included in order to check whether the final hullgirder failure is initiated by compression or tension failure in the deck or bottom respectively

Typically for a hogging case the final collapse may be triggered due to tension yield in the deck even thoughcompression yield the bottom (ldquohard cornersrdquo) is the most normal failure mechanism (depends on neutral axisposition)

The same type of argument apply for a sagging condition even though tension yielding in the bottom is not solikely for normal ship design due to the location of the neutral axis well below D2

The Society accept the HULS-1 model approach for the intact and damaged sections with partial load and safetyfactors as given in Table 5-5

The hogging case require a stricter material factor γ M than in sagging for ship designs in which double bottombending and bi-axial stressshear stress effects are important for the ultimate capacity assessment The factorsare given in Table 5-5

C3 Background to single step method (HULS-1)The basis for the single step method is to summarize the moments carried by each individual element acrossthe hull section at the point of hull girder collapse ie

where

Pi = Axial load in element no i at hull girder collapse (Pi = (EA)eff-i ε i g-collapse)

zi = Distance from hull-section neutral axis to centre of area of element no i at hull girder collapseThe neutral axis position is to be shifted due to local buckling and collapse of individual elementsin the hull-section

(EA)eff-i = Axial stiffness of element no i accounting for buckling of plating and stiffeners (pre-collapsestiffness)

K = Total number of assumed elements in hull section (typical stiffened panels girders etc)ε i = Axial strain of centre of area of element no i at hull girder collapse (ε i = ε i

g-collapse the collapsestrain for each element follows the displacement hypothesis assumed for the hull section

σ = Axial stress in hull-sectionz = Vertical co-ordinate in hull-section measured from neutral axis

It is generally accepted for intact vessels that the hull sections rotate under the assumption of Navierrsquoshypothesis ie plane sections remain plane and normal to neutral axis ie

where

ε i = axial strain of centre of area of element no i (relative end-shortening) κ = curvature of the hull section between two transverse frames (across hull section length L)LS = length of considered hull sectionθ = relative rotation angle of hull section end planes (across hull section length L)

This gives the following formula for the Ultimate moment (eq(C5) into eq(C4))

= Effective section modulus in bottom accounting for local buckling and collapse of individual elements on the compressive side of the neutral axis Each compressed element has an effec-tive area defined as AeffAnom = σUσF The effective area to be modelled as reduced thickness tefftnom = AeffAnom or effective plate widths for calculating the effective section modulus Weff

= Weighted yield stress of deck elements if material class differences (Rule values)= Weighted yield stress of the bottom elements if material class differences (Rule values) (cor-

rections to be considered if inner bottom has lower yield stress than bottom) = Ultimate nominal capacity of individual stiffened panels using PULS = Ultimate moment capacity of hull section A separate MU value for sagging and hogging is to

be calculated and checked in the overall strength criteria eq (C3)

bottomeffW

deckFσbottomFσ

UσUM

sumint sum minusminus =

=== iiieff

tionhull

K

iiiU zEAzPdAzM εσ )(

sec 1

(C4)

κε ii z= sL θκ = (C5)

UeffU EIM κ)(= (C6)

DET NORSKE VERITAS


Page 64

where

The curvature expression eq(C7) subjected into eq(C6) gives

with the following definitions

) An assumption in this approach is that the ultimate capacity moment is reached when the longitudinal strainover the considered section with length LS reaches the yield strain εF This is normally an acceptedassumption (von Karman effective width concept) However it may be that some very slender stiffenedpanel design has an ldquounstablerdquo response (mode snapping etc) for which the yield strain-collapsehypothesis is violated on the non-conservative side This has then to be corrected for and implemented intothe axial stiffness value (EA)eff-I using input from non-linear FE analyses or similar considerations

) Such a correction of the element strength is only needed if the major moment carrying elements such asdeck or bottom structures are suffering ldquounstablerdquo response If only some local elements in the hull sectionshows ldquounstablerdquo response this has marginal impact on the overall strength and can be neglected Fornormal steel ship proportions and designs ldquounstablerdquo buckling responses are not an issue

Effective bending stiffness of the hull section accounting for reduced axial stiffness (EA)eff-i of individual elements due to local buckling and collapse of stiffeners plates etc

Effective axial stiffness of individual elementsstiffened panels ac-counting for local buckling of plates and stiffeners and interactions be-tween them Effects from geometrical imperfections and out-of flatness to be included

Hull curvature at global collapse (C7)

Average axial strain in deck at global collapse εUdeck = εF

deck = σFE is accepted see comment ) below

Average axial strain in bottom at global collapse εUbottom = εF

bottom = σFE is accepted see com-ment ) below

Weighted yield strain of deck elements if material class differences (uni-axial linear material law ε

F = σFE)

Weighted yield strain of the bottom elements if material class differences (uni-axial linear material law εF = σFE) (corrections to be considered if inner bottom has lower yield stress than bottom)

Effective section modulus of the hull section in the deck

Effective section modulus of the hull section in the bottom

sum=

minus=K

iiieffeff zEAEI

1

2)()()(

ieffEA minus)(

)( minbottom

bottomU

deck

deckU

U zz

εεκ =

deckUε

bottomUε

deckFε

bottomFε

)( min bottomF

bottomeff

deckF


deck

effdeckeff z

IW =

bottom

effbottomeff z

IW =

DET NORSKE VERITAS


Page 65

Appendix DHull Girder Capacity Assessment Using Non-linear FE Analysis

D1 GeneralAdvanced non-linear finite element analyses models may be used for the assessment of the hull girder ultimatecapacity Such models are to consider the relevant effects important to the non-linear responses with dueconsiderations of the items listed in Section 583

Particular attention is to be given to modelling the shape and size of geometrical imperfections such as out-of-flatness from productionswelding etc It is to be ensured that the shape and size of imperfections trigger themost critical failure modes

For damaged hull sections with large holes in ship side andor bottom it is important to ensure the developmentof asymmetric deformations such as torsion horizontal bending warping local shear deformations etcBoundary conditions need special considerations in this respect in order not to constrain the model fromdeforming into the natural and most critical deformation pattern

The model extent is to be large enough to cover all effects as listed in Section 532

D2 Non-linear FE modelling featuresThe FE mesh density is to be fine enough to capture all relevant types of local buckling deformations andlocalized plastic collapse behaviour in plating stiffeners girders bulkheads bottom deck etc

The following requirements apply when using 4 node plate element (thin-shell element is sufficient)

i) Minimum 5 elements across the plating between stiffenersgirdersii) Minimum 3 elements across stiffener web height iii) One element across stiffener flange is acceptableiv) Longitudinal girders minimum 5 elements between local secondary stiffenersv) Element aspect ratio 2 or less in critical areas susceptible to buckling vi) For transverse girders a coarser meshing is acceptable The girder modelling should represent a realistic

stiffness and restraint for the longitudinal stiffeners ship hull plating tank top plating etc vii) Man holes and large cut-outs in girder web frames and stringers shall be modelledviii)Secondary stiffener on web frames prone to buckling shall be modelled One plate elements across the

stiffener web height is OK (ABAQUS need minimum 2 to represent the correct bending stiffness)ix) Plated and shell elements shall be used in all structural elements and areas susceptible to buckling and

localized collapsex) Stiffeners can be modelled as beam-elements in areas not critical from a local buckling and collapse point

of view

When using non-linear FE analyses the accept criteria and partial safety factors in strength format need specialconsideration The Society will accept non-linear FE methods based on a case by case evaluation

DET NORSKE VERITAS


Page 66

Appendix EPULS Buckling Code ndash Design Principles ndash Stiffened PanelsDNVrsquos PULS buckling code is an acceptable method for assessing the strength of stiffened panels and fulfilsall the design requirements implemented as part of Method 1 (UC) and Method 2 (BS) In addition the code isbased on the following principles

mdash The stiffeners are designed such that overall (global) buckling is not dominant ie the plating is hangingon solid stiffenersgirders with a reduced plate efficiency (effective plate widths accounting for bucklingeffects) Figure 5-5

mdash The stiffened panel shall be designed to resist the combination of simultaneously acting in-plane bi-axialand shear loads (and lateral pressure) without suffering main permanent structural damage All possiblecombinations of compression tension and shear giving the most critical buckling condition is to beconsidered

mdash Orthogonally stiffened panels are preferably checked as a single unit with primary and secondary stiffenersmodelled in orthogonal directions (Figure 5-5 S3 element ndash primary + secondary stiffeners)

mdash Uni-axially stiffened panels are typical between transverse and longitudinal girders in deck ship side etc(S3 element ndash primary stiffeners)

mdash For stiffened panels with more than 5 stiffeners application of 5 stiffeners in the PULS model is acceptedmdash Flanges (free flange outstands) on stiffeners and girders are to be proportioned such that they can carry the

yield stress without buckling fftf le 15 (ff is the free flange outstand tf is the flange thickness) mdash Maximum slenderness limits for plate and stiffeners implemented in the PULS code are (code validity

limits)

Plate between stiffeners stp le 200Flat bar stiffeners htw le 35Angle and T profiles htw le 90 fftf lt 15 bfhw gt 22Global (overall) strength λg lt 4 (limits stiffener span in relation to stiffener height λg = sqrt (σFσEg) global

slenderness σEg ndash global minimum Eigenvalue)

DET NORSKE VERITAS

CSA - Direct Analysis of Ship Structures

1 Introduction

11 Objective

12 General

13 Definitions

14 Programs


21 General

22 Scope and acceptance criteria

23 Procedures and analysis

24 Documentation and verification overview


31 Introduction


33 Roll damping



36 Load Transfer




43 Corrosion model

44 Loads

45 Component stochastic fatigue analysis








61 Overview

62 General


64 Sub models



71 General

72 Documentation

73 Verification

8 References

Appendix A Relative Deflection Analysis

Appendix B DNV Program Specific Items

Appendix C Simplified Hull Girder Capacity Model - MU

Appendix D Hull Girder Capacity Assessment Using Non-linear FE Analysis

Appendix E PULS Buckling Code ndash Design Principles ndash Stiffened Panels

FOREWORD

DET NORSKE VERITAS (DNV) is an autonomous and independent foundation with the objectives of safeguarding lifeproperty and the environment at sea and onshore DNV undertakes classification certification and other verification andconsultancy services relating to quality of ships offshore units and installations and onshore industries worldwide andcarries out research in relation to these functions

Classification NotesClassification Notes are publications that give practical information on classification of ships and other objects Examplesof design solutions calculation methods specifications of test procedures as well as acceptable repair methods for somecomponents are given as interpretations of the more general rule requirements

All publications may be downloaded from the Societyrsquos Web site httpwwwdnvcom

The Society reserves the exclusive right to interpret decide equivalence or make exemptions to this Classification Note

Main changesThe main changes are

mdash New class notation CSA-1 and CSA-FLS1 includedmdash CSA-FLS1 has reduced fatigue scope compared to existing class notation CSA-FLSmdash CSA-1 includes requirements for ULS and CSA-FLS1mdash Existing notations CSA-FLS and CSA-2 are kept but CSA-FLS is renamed CSA-FLS2mdash Include experience from recent project on ore carrier

The electronic pdf version of this document found through httpwwwdnvcom is the officially binding versioncopy Det Norske Veritas

Any comments may be sent by e-mail to rulesdnvcomFor subscription orders or information about subscription terms please use distributiondnvcomComputer Typesetting (Adobe Frame Maker) by Det Norske Veritas

If any person suffers loss or damage which is proved to have been caused by any negligent act or omission of Det Norske Veritas then Det Norske Veritas shall pay compensation tosuch person for his proved direct loss or damage However the compensation shall not exceed an amount equal to ten times the fee charged for the service in question provided thatthe maximum compensation shall never exceed USD 2 millionIn this provision Det Norske Veritas shall mean the Foundation Det Norske Veritas as well as all its subsidiaries directors officers employees agents and any other acting on behalfof Det Norske Veritas


Page 3

CONTENTS








8 References 55






DET NORSKE VERITAS


Page 4

1 Introduction














13 Definitions



DET NORSKE VERITAS


Page 5









DET NORSKE VERITAS


Page 6











CSA-FLS1



CSA-FLS2



CSA-1


CSA-2





DET NORSKE VERITAS


Page 7









DET NORSKE VERITAS


Page 8












DET NORSKE VERITAS


Page 9






DET NORSKE VERITAS


Page 10










DET NORSKE VERITAS


Page 11



















DET NORSKE VERITAS


Page 12













000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50 60Wave Period

VB

M

Wav

e A

mp

litu

de


000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50Wave Period

VB

M

Wav

e A

mp

litu

de

[ ] [ ]

⎥⎦⎤

⎢⎣⎡

=

m

Nm

Nm


responseermtLongmζ

DET NORSKE VERITAS


Page 13




36 Load Transfer









000E+ 00

100E+ 05

200E+ 05

300E+ 05

400E+ 05

500E+ 05

600E+ 05

700E+ 05

800E+ 05

900E+ 05

0 10 20 30 40 50 60Wa ve Period

VB

M

Wa

ve

Am

pli

tud

e

DET NORSKE VERITAS


Page 14










where


Pressures at 10-

4 probability

Extrapolated t

Water head f


p r pe p d =

DET NORSKE VERITAS


Page 15




















T z z

zact wl

wl

+ minus2

g

pdT

ρ4

3

DET NORSKE VERITAS


Page 16























DET NORSKE VERITAS


Page 17



DET NORSKE VERITAS


Page 18



DET NORSKE VERITAS


Page 19





Tankers


DET NORSKE VERITAS


0





LPG carriers


Container vessel


Ore carrier


43 Corrosion model


44 Loads



DET NORSKE VERITAS


Page 21






















DET NORSKE VERITAS


Page 22







DET NORSKE VERITAS


Page 23


















DET NORSKE VERITAS


Page 24









DET NORSKE VERITAS


Page 25















DET NORSKE VERITAS


Page 26












0

025

05

075

1

125

15

175

2

100425 120425 140425 160425 180425 200425 220425


Fat

igue

Dam

age

[-]

Screening Results

TBHD Pos

Local Model Result

DET NORSKE VERITAS


Page 27


















alno

spothotK

minσσ

=

DET NORSKE VERITAS


Page 28


















⎝⎛minus= log

25log

4loglog m

tmN a

4

1

25⎟⎠⎞⎜

⎝⎛=Δ t

respσ

DET NORSKE VERITAS


Page 29




















DET NORSKE VERITAS


Page 30



522 Designloads




DET NORSKE VERITAS


Page 31










ID

























DET NORSKE VERITAS


Page 32

523 Design stress




















Entire cargo region








ID





DET NORSKE VERITAS


Page 33








σ =



DET NORSKE VERITAS


Page 34







where







( )W

Wmodn21mean A

A

n

ττττ sdot+++=

DET NORSKE VERITAS


Page 35













DET NORSKE VERITAS


Page 36














DET NORSKE VERITAS


Page 37










where


margin






DET NORSKE VERITAS


Page 38















DET NORSKE VERITAS


Page 39








where






DET NORSKE VERITAS


Page 40


61 Overview










Cargo hold model


as sub-model




DET NORSKE VERITAS


Page 41







DET NORSKE VERITAS


Page 42









62 General



DET NORSKE VERITAS


Page 43











baseline

x fwd

z up

y port

AP

centreline

DET NORSKE VERITAS


Page 44











where

tw = web thickness


Wco

comean t

rh

hht sdot

sdotminus=

( )2co

2co

cohh26

l1r

minus+=

DET NORSKE VERITAS


Page 45









64 Sub models






DET NORSKE VERITAS


Page 46



















DET NORSKE VERITAS


Page 47




















DET NORSKE VERITAS


Page 48











72 Documentation








DET NORSKE VERITAS


Page 49









same








73 Verification


FE model


DET NORSKE VERITAS


Page 50

Mass-model


Hydro-analysis


Load transfer


FE analysis










DET NORSKE VERITAS


Page 51



where





)3

d-(Z

2

B dNA5 gdM ρ=Δ


-2500000

-2000000

-1500000

-1000000

-500000

0

500000

1000000

0 50 100 150 200 250 300 350


Sti

ll w

ater

ben

din

g m

om

ent

Loding Manual

Loading Man Corr

Potential theory

DET NORSKE VERITAS


Page 52



where










DET NORSKE VERITAS


Page 53





-200E+05

-150E+05

-100E+05

-500E+04

000E+00

500E+04

100E+05

150E+05

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ver

tical

she

ar f o

rce

[kN

]

-200E+06

000E+00

200E+06

400E+06

600E+06

800E+06

100E+07

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ve

rtic

a l b

end i

ng m

o men

t [kN

m]

DET NORSKE VERITAS


Page 54














DET NORSKE VERITAS


Page 55

8 References











DET NORSKE VERITAS


Page 56







DET NORSKE VERITAS


Page 57



spreading

A41 Sea pressure











DET NORSKE VERITAS


Page 58




A6 Post-processing




DET NORSKE VERITAS


Page 59




B2 Modelling



B22 External loads














DET NORSKE VERITAS


Page 60



General


Ballast tanks




Cargo tanks





End frames

DET NORSKE VERITAS


Page 61



DET NORSKE VERITAS


Page 62






















where




)( min bottomF

bottomeff

deckF


deckeffW

DET NORSKE VERITAS


Page 63







where








where







bottomeffW

deckFσbottomFσ

UσUM


=== iiieff

tionhull

K


sec 1

(C4)



DET NORSKE VERITAS


Page 64

where













F = σFE)




sum=

minus=K

iiieffeff zEAEI

1

2)()()(

ieffEA minus)(

)( minbottom

bottomU

deck

deckU

U zz

εεκ =

deckUε

bottomUε

deckFε

bottomFε

)( min bottomF

bottomeff

deckF


deck

effdeckeff z

IW =

bottom

effbottomeff z

IW =

DET NORSKE VERITAS


Page 65












of view


DET NORSKE VERITAS


Page 66








limits)



DET NORSKE VERITAS


1 Introduction

11 Objective

12 General

13 Definitions

14 Programs


21 General





31 Introduction


33 Roll damping



36 Load Transfer




43 Corrosion model

44 Loads









61 Overview

62 General


64 Sub models



71 General

72 Documentation

73 Verification

8 References







CONTENTS








8 References 55






DET NORSKE VERITAS


Page 4

1 Introduction














13 Definitions



DET NORSKE VERITAS


Page 5









DET NORSKE VERITAS


Page 6











CSA-FLS1



CSA-FLS2



CSA-1


CSA-2





DET NORSKE VERITAS


Page 7









DET NORSKE VERITAS


Page 8












DET NORSKE VERITAS


Page 9






DET NORSKE VERITAS


Page 10










DET NORSKE VERITAS


Page 11



















DET NORSKE VERITAS


Page 12













000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50 60Wave Period

VB

M

Wav

e A

mp

litu

de


000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50Wave Period

VB

M

Wav

e A

mp

litu

de

[ ] [ ]

⎥⎦⎤

⎢⎣⎡

=

m

Nm

Nm


responseermtLongmζ

DET NORSKE VERITAS


Page 13




36 Load Transfer









000E+ 00

100E+ 05

200E+ 05

300E+ 05

400E+ 05

500E+ 05

600E+ 05

700E+ 05

800E+ 05

900E+ 05

0 10 20 30 40 50 60Wa ve Period

VB

M

Wa

ve

Am

pli

tud

e

DET NORSKE VERITAS


Page 14










where


Pressures at 10-

4 probability

Extrapolated t

Water head f


p r pe p d =

DET NORSKE VERITAS


Page 15




















T z z

zact wl

wl

+ minus2

g

pdT

ρ4

3

DET NORSKE VERITAS


Page 16























DET NORSKE VERITAS


Page 17



DET NORSKE VERITAS


Page 18



DET NORSKE VERITAS


Page 19





Tankers


DET NORSKE VERITAS


Page 20





LPG carriers


Container vessel


Ore carrier


43 Corrosion model


44 Loads



DET NORSKE VERITAS


Page 21






















DET NORSKE VERITAS


Page 22







DET NORSKE VERITAS


Page 23


















DET NORSKE VERITAS


Page 24









DET NORSKE VERITAS


Page 25















DET NORSKE VERITAS


Page 26












0

025

05

075

1

125

15

175

2

100425 120425 140425 160425 180425 200425 220425


Fat

igue

Dam

age

[-]

Screening Results

TBHD Pos

Local Model Result

DET NORSKE VERITAS


Page 27


















alno

spothotK

minσσ

=

DET NORSKE VERITAS


Page 28


















⎝⎛minus= log

25log

4loglog m

tmN a

4

1

25⎟⎠⎞⎜

⎝⎛=Δ t

respσ

DET NORSKE VERITAS


Page 29




















DET NORSKE VERITAS


Page 30



522 Designloads




DET NORSKE VERITAS


Page 31










ID

























DET NORSKE VERITAS


Page 32

523 Design stress




















Entire cargo region








ID





DET NORSKE VERITAS


Page 33








σ =



DET NORSKE VERITAS


Page 34







where







( )W

Wmodn21mean A

A

n

ττττ sdot+++=

DET NORSKE VERITAS


Page 35













DET NORSKE VERITAS


Page 36














DET NORSKE VERITAS


Page 37










where


margin






DET NORSKE VERITAS


Page 38















DET NORSKE VERITAS


Page 39








where






DET NORSKE VERITAS


Page 40


61 Overview










Cargo hold model


as sub-model




DET NORSKE VERITAS


Page 41







DET NORSKE VERITAS


Page 42









62 General



DET NORSKE VERITAS


Page 43











baseline

x fwd

z up

y port

AP

centreline

DET NORSKE VERITAS


Page 44











where

tw = web thickness


Wco

comean t

rh

hht sdot

sdotminus=

( )2co

2co

cohh26

l1r

minus+=

DET NORSKE VERITAS


Page 45









64 Sub models






DET NORSKE VERITAS


Page 46



















DET NORSKE VERITAS


Page 47




















DET NORSKE VERITAS


Page 48











72 Documentation








DET NORSKE VERITAS


Page 49









same








73 Verification


FE model


DET NORSKE VERITAS


Page 50

Mass-model


Hydro-analysis


Load transfer


FE analysis










DET NORSKE VERITAS


Page 51



where





)3

d-(Z

2

B dNA5 gdM ρ=Δ


-2500000

-2000000

-1500000

-1000000

-500000

0

500000

1000000

0 50 100 150 200 250 300 350


Sti

ll w

ater

ben

din

g m

om

ent

Loding Manual

Loading Man Corr

Potential theory

DET NORSKE VERITAS


Page 52



where










DET NORSKE VERITAS


Page 53





-200E+05

-150E+05

-100E+05

-500E+04

000E+00

500E+04

100E+05

150E+05

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ver

tical

she

ar f o

rce

[kN

]

-200E+06

000E+00

200E+06

400E+06

600E+06

800E+06

100E+07

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ve

rtic

a l b

end i

ng m

o men

t [kN

m]

DET NORSKE VERITAS


Page 54














DET NORSKE VERITAS


Page 55

8 References











DET NORSKE VERITAS


Page 56







DET NORSKE VERITAS


Page 57



spreading

A41 Sea pressure











DET NORSKE VERITAS


Page 58




A6 Post-processing




DET NORSKE VERITAS


Page 59




B2 Modelling



B22 External loads














DET NORSKE VERITAS


Page 60



General


Ballast tanks




Cargo tanks





End frames

DET NORSKE VERITAS


Page 61



DET NORSKE VERITAS


Page 62






















where




)( min bottomF

bottomeff

deckF


deckeffW

DET NORSKE VERITAS


Page 63







where








where







bottomeffW

deckFσbottomFσ

UσUM


=== iiieff

tionhull

K


sec 1

(C4)



DET NORSKE VERITAS


Page 64

where













F = σFE)




sum=

minus=K

iiieffeff zEAEI

1

2)()()(

ieffEA minus)(

)( minbottom

bottomU

deck

deckU

U zz

εεκ =

deckUε

bottomUε

deckFε

bottomFε

)( min bottomF

bottomeff

deckF


deck

effdeckeff z

IW =

bottom

effbottomeff z

IW =

DET NORSKE VERITAS


Page 65












of view


DET NORSKE VERITAS


Page 66








limits)



DET NORSKE VERITAS


1 Introduction

11 Objective

12 General

13 Definitions

14 Programs


21 General





31 Introduction


33 Roll damping



36 Load Transfer




43 Corrosion model

44 Loads









61 Overview

62 General


64 Sub models



71 General

72 Documentation

73 Verification

8 References







1 Introduction














13 Definitions



DET NORSKE VERITAS


Page 5









DET NORSKE VERITAS


Page 6











CSA-FLS1



CSA-FLS2



CSA-1


CSA-2





DET NORSKE VERITAS


Page 7









DET NORSKE VERITAS


Page 8












DET NORSKE VERITAS


Page 9






DET NORSKE VERITAS


Page 10










DET NORSKE VERITAS


Page 11



















DET NORSKE VERITAS


Page 12













000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50 60Wave Period

VB

M

Wav

e A

mp

litu

de


000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50Wave Period

VB

M

Wav

e A

mp

litu

de

[ ] [ ]

⎥⎦⎤

⎢⎣⎡

=

m

Nm

Nm


responseermtLongmζ

DET NORSKE VERITAS


Page 13




36 Load Transfer









000E+ 00

100E+ 05

200E+ 05

300E+ 05

400E+ 05

500E+ 05

600E+ 05

700E+ 05

800E+ 05

900E+ 05

0 10 20 30 40 50 60Wa ve Period

VB

M

Wa

ve

Am

pli

tud

e

DET NORSKE VERITAS


Page 14










where


Pressures at 10-

4 probability

Extrapolated t

Water head f


p r pe p d =

DET NORSKE VERITAS


Page 15




















T z z

zact wl

wl

+ minus2

g

pdT

ρ4

3

DET NORSKE VERITAS


Page 16























DET NORSKE VERITAS


Page 17



DET NORSKE VERITAS


Page 18



DET NORSKE VERITAS


Page 19





Tankers


DET NORSKE VERITAS


Page 20





LPG carriers


Container vessel


Ore carrier


43 Corrosion model


44 Loads



DET NORSKE VERITAS


Page 21






















DET NORSKE VERITAS


Page 22







DET NORSKE VERITAS


Page 23


















DET NORSKE VERITAS


Page 24









DET NORSKE VERITAS


Page 25















DET NORSKE VERITAS


Page 26












0

025

05

075

1

125

15

175

2

100425 120425 140425 160425 180425 200425 220425


Fat

igue

Dam

age

[-]

Screening Results

TBHD Pos

Local Model Result

DET NORSKE VERITAS


Page 27


















alno

spothotK

minσσ

=

DET NORSKE VERITAS


Page 28


















⎝⎛minus= log

25log

4loglog m

tmN a

4

1

25⎟⎠⎞⎜

⎝⎛=Δ t

respσ

DET NORSKE VERITAS


Page 29




















DET NORSKE VERITAS


Page 30



522 Designloads




DET NORSKE VERITAS


Page 31










ID

























DET NORSKE VERITAS


Page 32

523 Design stress




















Entire cargo region








ID





DET NORSKE VERITAS


Page 33








σ =



DET NORSKE VERITAS


Page 34







where







( )W

Wmodn21mean A

A

n

ττττ sdot+++=

DET NORSKE VERITAS


Page 35













DET NORSKE VERITAS


Page 36














DET NORSKE VERITAS


Page 37










where


margin






DET NORSKE VERITAS


Page 38















DET NORSKE VERITAS


Page 39








where






DET NORSKE VERITAS


Page 40


61 Overview










Cargo hold model


as sub-model




DET NORSKE VERITAS


Page 41







DET NORSKE VERITAS


Page 42









62 General



DET NORSKE VERITAS


Page 43











baseline

x fwd

z up

y port

AP

centreline

DET NORSKE VERITAS


Page 44











where

tw = web thickness


Wco

comean t

rh

hht sdot

sdotminus=

( )2co

2co

cohh26

l1r

minus+=

DET NORSKE VERITAS


Page 45









64 Sub models






DET NORSKE VERITAS


Page 46



















DET NORSKE VERITAS


Page 47




















DET NORSKE VERITAS


Page 48











72 Documentation








DET NORSKE VERITAS


Page 49









same








73 Verification


FE model


DET NORSKE VERITAS


Page 50

Mass-model


Hydro-analysis


Load transfer


FE analysis










DET NORSKE VERITAS


Page 51



where





)3

d-(Z

2

B dNA5 gdM ρ=Δ


-2500000

-2000000

-1500000

-1000000

-500000

0

500000

1000000

0 50 100 150 200 250 300 350


Sti

ll w

ater

ben

din

g m

om

ent

Loding Manual

Loading Man Corr

Potential theory

DET NORSKE VERITAS


Page 52



where










DET NORSKE VERITAS


Page 53





-200E+05

-150E+05

-100E+05

-500E+04

000E+00

500E+04

100E+05

150E+05

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ver

tical

she

ar f o

rce

[kN

]

-200E+06

000E+00

200E+06

400E+06

600E+06

800E+06

100E+07

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ve

rtic

a l b

end i

ng m

o men

t [kN

m]

DET NORSKE VERITAS


Page 54














DET NORSKE VERITAS


Page 55

8 References











DET NORSKE VERITAS


Page 56







DET NORSKE VERITAS


Page 57



spreading

A41 Sea pressure











DET NORSKE VERITAS


Page 58




A6 Post-processing




DET NORSKE VERITAS


Page 59




B2 Modelling



B22 External loads














DET NORSKE VERITAS


Page 60



General


Ballast tanks




Cargo tanks





End frames

DET NORSKE VERITAS


Page 61



DET NORSKE VERITAS


Page 62






















where




)( min bottomF

bottomeff

deckF


deckeffW

DET NORSKE VERITAS


Page 63







where








where







bottomeffW

deckFσbottomFσ

UσUM


=== iiieff

tionhull

K


sec 1

(C4)



DET NORSKE VERITAS


Page 64

where













F = σFE)




sum=

minus=K

iiieffeff zEAEI

1

2)()()(

ieffEA minus)(

)( minbottom

bottomU

deck

deckU

U zz

εεκ =

deckUε

bottomUε

deckFε

bottomFε

)( min bottomF

bottomeff

deckF


deck

effdeckeff z

IW =

bottom

effbottomeff z

IW =

DET NORSKE VERITAS


Page 65












of view


DET NORSKE VERITAS


Page 66








limits)



DET NORSKE VERITAS


1 Introduction

11 Objective

12 General

13 Definitions

14 Programs


21 General





31 Introduction


33 Roll damping



36 Load Transfer




43 Corrosion model

44 Loads









61 Overview

62 General


64 Sub models



71 General

72 Documentation

73 Verification

8 References















DET NORSKE VERITAS


Page 6











CSA-FLS1



CSA-FLS2



CSA-1


CSA-2





DET NORSKE VERITAS


Page 7









DET NORSKE VERITAS


Page 8












DET NORSKE VERITAS


Page 9






DET NORSKE VERITAS


Page 10










DET NORSKE VERITAS


Page 11



















DET NORSKE VERITAS


Page 12













000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50 60Wave Period

VB

M

Wav

e A

mp

litu

de


000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50Wave Period

VB

M

Wav

e A

mp

litu

de

[ ] [ ]

⎥⎦⎤

⎢⎣⎡

=

m

Nm

Nm


responseermtLongmζ

DET NORSKE VERITAS


Page 13




36 Load Transfer









000E+ 00

100E+ 05

200E+ 05

300E+ 05

400E+ 05

500E+ 05

600E+ 05

700E+ 05

800E+ 05

900E+ 05

0 10 20 30 40 50 60Wa ve Period

VB

M

Wa

ve

Am

pli

tud

e

DET NORSKE VERITAS


Page 14










where


Pressures at 10-

4 probability

Extrapolated t

Water head f


p r pe p d =

DET NORSKE VERITAS


Page 15




















T z z

zact wl

wl

+ minus2

g

pdT

ρ4

3

DET NORSKE VERITAS


Page 16























DET NORSKE VERITAS


Page 17



DET NORSKE VERITAS


Page 18



DET NORSKE VERITAS


Page 19





Tankers


DET NORSKE VERITAS


Page 20





LPG carriers


Container vessel


Ore carrier


43 Corrosion model


44 Loads



DET NORSKE VERITAS


Page 21






















DET NORSKE VERITAS


Page 22







DET NORSKE VERITAS


Page 23


















DET NORSKE VERITAS


Page 24









DET NORSKE VERITAS


Page 25















DET NORSKE VERITAS


Page 26












0

025

05

075

1

125

15

175

2

100425 120425 140425 160425 180425 200425 220425


Fat

igue

Dam

age

[-]

Screening Results

TBHD Pos

Local Model Result

DET NORSKE VERITAS


Page 27


















alno

spothotK

minσσ

=

DET NORSKE VERITAS


Page 28


















⎝⎛minus= log

25log

4loglog m

tmN a

4

1

25⎟⎠⎞⎜

⎝⎛=Δ t

respσ

DET NORSKE VERITAS


Page 29




















DET NORSKE VERITAS


Page 30



522 Designloads




DET NORSKE VERITAS


Page 31










ID

























DET NORSKE VERITAS


Page 32

523 Design stress




















Entire cargo region








ID





DET NORSKE VERITAS


Page 33








σ =



DET NORSKE VERITAS


Page 34







where







( )W

Wmodn21mean A

A

n

ττττ sdot+++=

DET NORSKE VERITAS


Page 35













DET NORSKE VERITAS


Page 36














DET NORSKE VERITAS


Page 37










where


margin






DET NORSKE VERITAS


Page 38















DET NORSKE VERITAS


Page 39








where






DET NORSKE VERITAS


Page 40


61 Overview










Cargo hold model


as sub-model




DET NORSKE VERITAS


Page 41







DET NORSKE VERITAS


Page 42









62 General



DET NORSKE VERITAS


Page 43











baseline

x fwd

z up

y port

AP

centreline

DET NORSKE VERITAS


Page 44











where

tw = web thickness


Wco

comean t

rh

hht sdot

sdotminus=

( )2co

2co

cohh26

l1r

minus+=

DET NORSKE VERITAS


Page 45









64 Sub models






DET NORSKE VERITAS


Page 46



















DET NORSKE VERITAS


Page 47




















DET NORSKE VERITAS


Page 48











72 Documentation








DET NORSKE VERITAS


Page 49









same








73 Verification


FE model


DET NORSKE VERITAS


Page 50

Mass-model


Hydro-analysis


Load transfer


FE analysis










DET NORSKE VERITAS


Page 51



where





)3

d-(Z

2

B dNA5 gdM ρ=Δ


-2500000

-2000000

-1500000

-1000000

-500000

0

500000

1000000

0 50 100 150 200 250 300 350


Sti

ll w

ater

ben

din

g m

om

ent

Loding Manual

Loading Man Corr

Potential theory

DET NORSKE VERITAS


Page 52



where










DET NORSKE VERITAS


Page 53





-200E+05

-150E+05

-100E+05

-500E+04

000E+00

500E+04

100E+05

150E+05

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ver

tical

she

ar f o

rce

[kN

]

-200E+06

000E+00

200E+06

400E+06

600E+06

800E+06

100E+07

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ve

rtic

a l b

end i

ng m

o men

t [kN

m]

DET NORSKE VERITAS


Page 54














DET NORSKE VERITAS


Page 55

8 References











DET NORSKE VERITAS


Page 56







DET NORSKE VERITAS


Page 57



spreading

A41 Sea pressure











DET NORSKE VERITAS


Page 58




A6 Post-processing




DET NORSKE VERITAS


Page 59




B2 Modelling



B22 External loads














DET NORSKE VERITAS


Page 60



General


Ballast tanks




Cargo tanks





End frames

DET NORSKE VERITAS


Page 61



DET NORSKE VERITAS


Page 62






















where




)( min bottomF

bottomeff

deckF


deckeffW

DET NORSKE VERITAS


Page 63







where








where







bottomeffW

deckFσbottomFσ

UσUM


=== iiieff

tionhull

K


sec 1

(C4)



DET NORSKE VERITAS


Page 64

where













F = σFE)




sum=

minus=K

iiieffeff zEAEI

1

2)()()(

ieffEA minus)(

)( minbottom

bottomU

deck

deckU

U zz

εεκ =

deckUε

bottomUε

deckFε

bottomFε

)( min bottomF

bottomeff

deckF


deck

effdeckeff z

IW =

bottom

effbottomeff z

IW =

DET NORSKE VERITAS


Page 65












of view


DET NORSKE VERITAS


Page 66








limits)



DET NORSKE VERITAS


1 Introduction

11 Objective

12 General

13 Definitions

14 Programs


21 General





31 Introduction


33 Roll damping



36 Load Transfer




43 Corrosion model

44 Loads









61 Overview

62 General


64 Sub models



71 General

72 Documentation

73 Verification

8 References

















CSA-FLS1



CSA-FLS2



CSA-1


CSA-2





DET NORSKE VERITAS


Page 7









DET NORSKE VERITAS


Page 8












DET NORSKE VERITAS


Page 9






DET NORSKE VERITAS


Page 10










DET NORSKE VERITAS


Page 11



















DET NORSKE VERITAS


Page 12













000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50 60Wave Period

VB

M

Wav

e A

mp

litu

de


000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50Wave Period

VB

M

Wav

e A

mp

litu

de

[ ] [ ]

⎥⎦⎤

⎢⎣⎡

=

m

Nm

Nm


responseermtLongmζ

DET NORSKE VERITAS


Page 13




36 Load Transfer









000E+ 00

100E+ 05

200E+ 05

300E+ 05

400E+ 05

500E+ 05

600E+ 05

700E+ 05

800E+ 05

900E+ 05

0 10 20 30 40 50 60Wa ve Period

VB

M

Wa

ve

Am

pli

tud

e

DET NORSKE VERITAS


Page 14










where


Pressures at 10-

4 probability

Extrapolated t

Water head f


p r pe p d =

DET NORSKE VERITAS


Page 15




















T z z

zact wl

wl

+ minus2

g

pdT

ρ4

3

DET NORSKE VERITAS


Page 16























DET NORSKE VERITAS


Page 17



DET NORSKE VERITAS


Page 18



DET NORSKE VERITAS


Page 19





Tankers


DET NORSKE VERITAS


Page 20





LPG carriers


Container vessel


Ore carrier


43 Corrosion model


44 Loads



DET NORSKE VERITAS


Page 21






















DET NORSKE VERITAS


Page 22







DET NORSKE VERITAS


Page 23


















DET NORSKE VERITAS


Page 24









DET NORSKE VERITAS


Page 25















DET NORSKE VERITAS


Page 26












0

025

05

075

1

125

15

175

2

100425 120425 140425 160425 180425 200425 220425


Fat

igue

Dam

age

[-]

Screening Results

TBHD Pos

Local Model Result

DET NORSKE VERITAS


Page 27


















alno

spothotK

minσσ

=

DET NORSKE VERITAS


Page 28


















⎝⎛minus= log

25log

4loglog m

tmN a

4

1

25⎟⎠⎞⎜

⎝⎛=Δ t

respσ

DET NORSKE VERITAS


Page 29




















DET NORSKE VERITAS


Page 30



522 Designloads




DET NORSKE VERITAS


Page 31










ID

























DET NORSKE VERITAS


Page 32

523 Design stress




















Entire cargo region








ID





DET NORSKE VERITAS


Page 33








σ =



DET NORSKE VERITAS


Page 34







where







( )W

Wmodn21mean A

A

n

ττττ sdot+++=

DET NORSKE VERITAS


Page 35













DET NORSKE VERITAS


Page 36














DET NORSKE VERITAS


Page 37










where


margin






DET NORSKE VERITAS


Page 38















DET NORSKE VERITAS


Page 39








where






DET NORSKE VERITAS


Page 40


61 Overview










Cargo hold model


as sub-model




DET NORSKE VERITAS


Page 41







DET NORSKE VERITAS


Page 42









62 General



DET NORSKE VERITAS


Page 43











baseline

x fwd

z up

y port

AP

centreline

DET NORSKE VERITAS


Page 44











where

tw = web thickness


Wco

comean t

rh

hht sdot

sdotminus=

( )2co

2co

cohh26

l1r

minus+=

DET NORSKE VERITAS


Page 45









64 Sub models






DET NORSKE VERITAS


Page 46



















DET NORSKE VERITAS


Page 47




















DET NORSKE VERITAS


Page 48











72 Documentation








DET NORSKE VERITAS


Page 49









same








73 Verification


FE model


DET NORSKE VERITAS


Page 50

Mass-model


Hydro-analysis


Load transfer


FE analysis










DET NORSKE VERITAS


Page 51



where





)3

d-(Z

2

B dNA5 gdM ρ=Δ


-2500000

-2000000

-1500000

-1000000

-500000

0

500000

1000000

0 50 100 150 200 250 300 350


Sti

ll w

ater

ben

din

g m

om

ent

Loding Manual

Loading Man Corr

Potential theory

DET NORSKE VERITAS


Page 52



where










DET NORSKE VERITAS


Page 53





-200E+05

-150E+05

-100E+05

-500E+04

000E+00

500E+04

100E+05

150E+05

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ver

tical

she

ar f o

rce

[kN

]

-200E+06

000E+00

200E+06

400E+06

600E+06

800E+06

100E+07

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ve

rtic

a l b

end i

ng m

o men

t [kN

m]

DET NORSKE VERITAS


Page 54














DET NORSKE VERITAS


Page 55

8 References











DET NORSKE VERITAS


Page 56







DET NORSKE VERITAS


Page 57



spreading

A41 Sea pressure











DET NORSKE VERITAS


Page 58




A6 Post-processing




DET NORSKE VERITAS


Page 59




B2 Modelling



B22 External loads














DET NORSKE VERITAS


Page 60



General


Ballast tanks




Cargo tanks





End frames

DET NORSKE VERITAS


Page 61



DET NORSKE VERITAS


Page 62






















where




)( min bottomF

bottomeff

deckF


deckeffW

DET NORSKE VERITAS


Page 63







where








where







bottomeffW

deckFσbottomFσ

UσUM


=== iiieff

tionhull

K


sec 1

(C4)



DET NORSKE VERITAS


Page 64

where













F = σFE)




sum=

minus=K

iiieffeff zEAEI

1

2)()()(

ieffEA minus)(

)( minbottom

bottomU

deck

deckU

U zz

εεκ =

deckUε

bottomUε

deckFε

bottomFε

)( min bottomF

bottomeff

deckF


deck

effdeckeff z

IW =

bottom

effbottomeff z

IW =

DET NORSKE VERITAS


Page 65












of view


DET NORSKE VERITAS


Page 66








limits)



DET NORSKE VERITAS


1 Introduction

11 Objective

12 General

13 Definitions

14 Programs


21 General





31 Introduction


33 Roll damping



36 Load Transfer




43 Corrosion model

44 Loads









61 Overview

62 General


64 Sub models



71 General

72 Documentation

73 Verification

8 References















DET NORSKE VERITAS


Page 8












DET NORSKE VERITAS


Page 9






DET NORSKE VERITAS


Page 10










DET NORSKE VERITAS


Page 11



















DET NORSKE VERITAS


Page 12













000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50 60Wave Period

VB

M

Wav

e A

mp

litu

de


000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50Wave Period

VB

M

Wav

e A

mp

litu

de

[ ] [ ]

⎥⎦⎤

⎢⎣⎡

=

m

Nm

Nm


responseermtLongmζ

DET NORSKE VERITAS


Page 13




36 Load Transfer









000E+ 00

100E+ 05

200E+ 05

300E+ 05

400E+ 05

500E+ 05

600E+ 05

700E+ 05

800E+ 05

900E+ 05

0 10 20 30 40 50 60Wa ve Period

VB

M

Wa

ve

Am

pli

tud

e

DET NORSKE VERITAS


Page 14










where


Pressures at 10-

4 probability

Extrapolated t

Water head f


p r pe p d =

DET NORSKE VERITAS


Page 15




















T z z

zact wl

wl

+ minus2

g

pdT

ρ4

3

DET NORSKE VERITAS


Page 16























DET NORSKE VERITAS


Page 17



DET NORSKE VERITAS


Page 18



DET NORSKE VERITAS


Page 19





Tankers


DET NORSKE VERITAS


Page 20





LPG carriers


Container vessel


Ore carrier


43 Corrosion model


44 Loads



DET NORSKE VERITAS


Page 21






















DET NORSKE VERITAS


Page 22







DET NORSKE VERITAS


Page 23


















DET NORSKE VERITAS


Page 24









DET NORSKE VERITAS


Page 25















DET NORSKE VERITAS


Page 26












0

025

05

075

1

125

15

175

2

100425 120425 140425 160425 180425 200425 220425


Fat

igue

Dam

age

[-]

Screening Results

TBHD Pos

Local Model Result

DET NORSKE VERITAS


Page 27


















alno

spothotK

minσσ

=

DET NORSKE VERITAS


Page 28


















⎝⎛minus= log

25log

4loglog m

tmN a

4

1

25⎟⎠⎞⎜

⎝⎛=Δ t

respσ

DET NORSKE VERITAS


Page 29




















DET NORSKE VERITAS


Page 30



522 Designloads




DET NORSKE VERITAS


Page 31










ID

























DET NORSKE VERITAS


Page 32

523 Design stress




















Entire cargo region








ID





DET NORSKE VERITAS


Page 33








σ =



DET NORSKE VERITAS


Page 34







where







( )W

Wmodn21mean A

A

n

ττττ sdot+++=

DET NORSKE VERITAS


Page 35













DET NORSKE VERITAS


Page 36














DET NORSKE VERITAS


Page 37










where


margin






DET NORSKE VERITAS


Page 38















DET NORSKE VERITAS


Page 39








where






DET NORSKE VERITAS


Page 40


61 Overview










Cargo hold model


as sub-model




DET NORSKE VERITAS


Page 41







DET NORSKE VERITAS


Page 42









62 General



DET NORSKE VERITAS


Page 43











baseline

x fwd

z up

y port

AP

centreline

DET NORSKE VERITAS


Page 44











where

tw = web thickness


Wco

comean t

rh

hht sdot

sdotminus=

( )2co

2co

cohh26

l1r

minus+=

DET NORSKE VERITAS


Page 45









64 Sub models






DET NORSKE VERITAS


Page 46



















DET NORSKE VERITAS


Page 47




















DET NORSKE VERITAS


Page 48











72 Documentation








DET NORSKE VERITAS


Page 49









same








73 Verification


FE model


DET NORSKE VERITAS


Page 50

Mass-model


Hydro-analysis


Load transfer


FE analysis










DET NORSKE VERITAS


Page 51



where





)3

d-(Z

2

B dNA5 gdM ρ=Δ


-2500000

-2000000

-1500000

-1000000

-500000

0

500000

1000000

0 50 100 150 200 250 300 350


Sti

ll w

ater

ben

din

g m

om

ent

Loding Manual

Loading Man Corr

Potential theory

DET NORSKE VERITAS


Page 52



where










DET NORSKE VERITAS


Page 53





-200E+05

-150E+05

-100E+05

-500E+04

000E+00

500E+04

100E+05

150E+05

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ver

tical

she

ar f o

rce

[kN

]

-200E+06

000E+00

200E+06

400E+06

600E+06

800E+06

100E+07

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ve

rtic

a l b

end i

ng m

o men

t [kN

m]

DET NORSKE VERITAS


Page 54














DET NORSKE VERITAS


Page 55

8 References











DET NORSKE VERITAS


Page 56







DET NORSKE VERITAS


Page 57



spreading

A41 Sea pressure











DET NORSKE VERITAS


Page 58




A6 Post-processing




DET NORSKE VERITAS


Page 59




B2 Modelling



B22 External loads














DET NORSKE VERITAS


Page 60



General


Ballast tanks




Cargo tanks





End frames

DET NORSKE VERITAS


Page 61



DET NORSKE VERITAS


Page 62






















where




)( min bottomF

bottomeff

deckF


deckeffW

DET NORSKE VERITAS


Page 63







where








where







bottomeffW

deckFσbottomFσ

UσUM


=== iiieff

tionhull

K


sec 1

(C4)



DET NORSKE VERITAS


Page 64

where













F = σFE)




sum=

minus=K

iiieffeff zEAEI

1

2)()()(

ieffEA minus)(

)( minbottom

bottomU

deck

deckU

U zz

εεκ =

deckUε

bottomUε

deckFε

bottomFε

)( min bottomF

bottomeff

deckF


deck

effdeckeff z

IW =

bottom

effbottomeff z

IW =

DET NORSKE VERITAS


Page 65












of view


DET NORSKE VERITAS


Page 66








limits)



DET NORSKE VERITAS


1 Introduction

11 Objective

12 General

13 Definitions

14 Programs


21 General





31 Introduction


33 Roll damping



36 Load Transfer




43 Corrosion model

44 Loads









61 Overview

62 General


64 Sub models



71 General

72 Documentation

73 Verification

8 References


















DET NORSKE VERITAS


Page 9






DET NORSKE VERITAS


Page 10










DET NORSKE VERITAS


Page 11



















DET NORSKE VERITAS


Page 12













000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50 60Wave Period

VB

M

Wav

e A

mp

litu

de


000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50Wave Period

VB

M

Wav

e A

mp

litu

de

[ ] [ ]

⎥⎦⎤

⎢⎣⎡

=

m

Nm

Nm


responseermtLongmζ

DET NORSKE VERITAS


Page 13




36 Load Transfer









000E+ 00

100E+ 05

200E+ 05

300E+ 05

400E+ 05

500E+ 05

600E+ 05

700E+ 05

800E+ 05

900E+ 05

0 10 20 30 40 50 60Wa ve Period

VB

M

Wa

ve

Am

pli

tud

e

DET NORSKE VERITAS


Page 14










where


Pressures at 10-

4 probability

Extrapolated t

Water head f


p r pe p d =

DET NORSKE VERITAS


Page 15




















T z z

zact wl

wl

+ minus2

g

pdT

ρ4

3

DET NORSKE VERITAS


Page 16























DET NORSKE VERITAS


Page 17



DET NORSKE VERITAS


Page 18



DET NORSKE VERITAS


Page 19





Tankers


DET NORSKE VERITAS


Page 20





LPG carriers


Container vessel


Ore carrier


43 Corrosion model


44 Loads



DET NORSKE VERITAS


Page 21






















DET NORSKE VERITAS


Page 22







DET NORSKE VERITAS


Page 23


















DET NORSKE VERITAS


Page 24









DET NORSKE VERITAS


Page 25















DET NORSKE VERITAS


Page 26












0

025

05

075

1

125

15

175

2

100425 120425 140425 160425 180425 200425 220425


Fat

igue

Dam

age

[-]

Screening Results

TBHD Pos

Local Model Result

DET NORSKE VERITAS


Page 27


















alno

spothotK

minσσ

=

DET NORSKE VERITAS


Page 28


















⎝⎛minus= log

25log

4loglog m

tmN a

4

1

25⎟⎠⎞⎜

⎝⎛=Δ t

respσ

DET NORSKE VERITAS


Page 29




















DET NORSKE VERITAS


Page 30



522 Designloads




DET NORSKE VERITAS


Page 31










ID

























DET NORSKE VERITAS


Page 32

523 Design stress




















Entire cargo region








ID





DET NORSKE VERITAS


Page 33








σ =



DET NORSKE VERITAS


Page 34







where







( )W

Wmodn21mean A

A

n

ττττ sdot+++=

DET NORSKE VERITAS


Page 35













DET NORSKE VERITAS


Page 36














DET NORSKE VERITAS


Page 37










where


margin






DET NORSKE VERITAS


Page 38















DET NORSKE VERITAS


Page 39








where






DET NORSKE VERITAS


Page 40


61 Overview










Cargo hold model


as sub-model




DET NORSKE VERITAS


Page 41







DET NORSKE VERITAS


Page 42









62 General



DET NORSKE VERITAS


Page 43











baseline

x fwd

z up

y port

AP

centreline

DET NORSKE VERITAS


Page 44











where

tw = web thickness


Wco

comean t

rh

hht sdot

sdotminus=

( )2co

2co

cohh26

l1r

minus+=

DET NORSKE VERITAS


Page 45









64 Sub models






DET NORSKE VERITAS


Page 46



















DET NORSKE VERITAS


Page 47




















DET NORSKE VERITAS


Page 48











72 Documentation








DET NORSKE VERITAS


Page 49









same








73 Verification


FE model


DET NORSKE VERITAS


Page 50

Mass-model


Hydro-analysis


Load transfer


FE analysis










DET NORSKE VERITAS


Page 51



where





)3

d-(Z

2

B dNA5 gdM ρ=Δ


-2500000

-2000000

-1500000

-1000000

-500000

0

500000

1000000

0 50 100 150 200 250 300 350


Sti

ll w

ater

ben

din

g m

om

ent

Loding Manual

Loading Man Corr

Potential theory

DET NORSKE VERITAS


Page 52



where










DET NORSKE VERITAS


Page 53





-200E+05

-150E+05

-100E+05

-500E+04

000E+00

500E+04

100E+05

150E+05

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ver

tical

she

ar f o

rce

[kN

]

-200E+06

000E+00

200E+06

400E+06

600E+06

800E+06

100E+07

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ve

rtic

a l b

end i

ng m

o men

t [kN

m]

DET NORSKE VERITAS


Page 54














DET NORSKE VERITAS


Page 55

8 References











DET NORSKE VERITAS


Page 56







DET NORSKE VERITAS


Page 57



spreading

A41 Sea pressure











DET NORSKE VERITAS


Page 58




A6 Post-processing




DET NORSKE VERITAS


Page 59




B2 Modelling



B22 External loads














DET NORSKE VERITAS


Page 60



General


Ballast tanks




Cargo tanks





End frames

DET NORSKE VERITAS


Page 61



DET NORSKE VERITAS


Page 62






















where




)( min bottomF

bottomeff

deckF


deckeffW

DET NORSKE VERITAS


Page 63







where








where







bottomeffW

deckFσbottomFσ

UσUM


=== iiieff

tionhull

K


sec 1

(C4)



DET NORSKE VERITAS


Page 64

where













F = σFE)




sum=

minus=K

iiieffeff zEAEI

1

2)()()(

ieffEA minus)(

)( minbottom

bottomU

deck

deckU

U zz

εεκ =

deckUε

bottomUε

deckFε

bottomFε

)( min bottomF

bottomeff

deckF


deck

effdeckeff z

IW =

bottom

effbottomeff z

IW =

DET NORSKE VERITAS


Page 65












of view


DET NORSKE VERITAS


Page 66








limits)



DET NORSKE VERITAS


1 Introduction

11 Objective

12 General

13 Definitions

14 Programs


21 General





31 Introduction


33 Roll damping



36 Load Transfer




43 Corrosion model

44 Loads









61 Overview

62 General


64 Sub models



71 General

72 Documentation

73 Verification

8 References












DET NORSKE VERITAS


Page 10










DET NORSKE VERITAS


Page 11



















DET NORSKE VERITAS


Page 12













000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50 60Wave Period

VB

M

Wav

e A

mp

litu

de


000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50Wave Period

VB

M

Wav

e A

mp

litu

de

[ ] [ ]

⎥⎦⎤

⎢⎣⎡

=

m

Nm

Nm


responseermtLongmζ

DET NORSKE VERITAS


Page 13




36 Load Transfer









000E+ 00

100E+ 05

200E+ 05

300E+ 05

400E+ 05

500E+ 05

600E+ 05

700E+ 05

800E+ 05

900E+ 05

0 10 20 30 40 50 60Wa ve Period

VB

M

Wa

ve

Am

pli

tud

e

DET NORSKE VERITAS


Page 14










where


Pressures at 10-

4 probability

Extrapolated t

Water head f


p r pe p d =

DET NORSKE VERITAS


Page 15




















T z z

zact wl

wl

+ minus2

g

pdT

ρ4

3

DET NORSKE VERITAS


Page 16























DET NORSKE VERITAS


Page 17



DET NORSKE VERITAS


Page 18



DET NORSKE VERITAS


Page 19





Tankers


DET NORSKE VERITAS


Page 20





LPG carriers


Container vessel


Ore carrier


43 Corrosion model


44 Loads



DET NORSKE VERITAS


Page 21






















DET NORSKE VERITAS


Page 22







DET NORSKE VERITAS


Page 23


















DET NORSKE VERITAS


Page 24









DET NORSKE VERITAS


Page 25















DET NORSKE VERITAS


Page 26












0

025

05

075

1

125

15

175

2

100425 120425 140425 160425 180425 200425 220425


Fat

igue

Dam

age

[-]

Screening Results

TBHD Pos

Local Model Result

DET NORSKE VERITAS


Page 27


















alno

spothotK

minσσ

=

DET NORSKE VERITAS


Page 28


















⎝⎛minus= log

25log

4loglog m

tmN a

4

1

25⎟⎠⎞⎜

⎝⎛=Δ t

respσ

DET NORSKE VERITAS


Page 29




















DET NORSKE VERITAS


Page 30



522 Designloads




DET NORSKE VERITAS


Page 31










ID

























DET NORSKE VERITAS


Page 32

523 Design stress




















Entire cargo region








ID





DET NORSKE VERITAS


Page 33








σ =



DET NORSKE VERITAS


Page 34







where







( )W

Wmodn21mean A

A

n

ττττ sdot+++=

DET NORSKE VERITAS


Page 35













DET NORSKE VERITAS


Page 36














DET NORSKE VERITAS


Page 37










where


margin






DET NORSKE VERITAS


Page 38















DET NORSKE VERITAS


Page 39








where






DET NORSKE VERITAS


Page 40


61 Overview










Cargo hold model


as sub-model




DET NORSKE VERITAS


Page 41







DET NORSKE VERITAS


Page 42









62 General



DET NORSKE VERITAS


Page 43











baseline

x fwd

z up

y port

AP

centreline

DET NORSKE VERITAS


Page 44











where

tw = web thickness


Wco

comean t

rh

hht sdot

sdotminus=

( )2co

2co

cohh26

l1r

minus+=

DET NORSKE VERITAS


Page 45









64 Sub models






DET NORSKE VERITAS


Page 46



















DET NORSKE VERITAS


Page 47




















DET NORSKE VERITAS


Page 48











72 Documentation








DET NORSKE VERITAS


Page 49









same








73 Verification


FE model


DET NORSKE VERITAS


Page 50

Mass-model


Hydro-analysis


Load transfer


FE analysis










DET NORSKE VERITAS


Page 51



where





)3

d-(Z

2

B dNA5 gdM ρ=Δ


-2500000

-2000000

-1500000

-1000000

-500000

0

500000

1000000

0 50 100 150 200 250 300 350


Sti

ll w

ater

ben

din

g m

om

ent

Loding Manual

Loading Man Corr

Potential theory

DET NORSKE VERITAS


Page 52



where










DET NORSKE VERITAS


Page 53





-200E+05

-150E+05

-100E+05

-500E+04

000E+00

500E+04

100E+05

150E+05

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ver

tical

she

ar f o

rce

[kN

]

-200E+06

000E+00

200E+06

400E+06

600E+06

800E+06

100E+07

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ve

rtic

a l b

end i

ng m

o men

t [kN

m]

DET NORSKE VERITAS


Page 54














DET NORSKE VERITAS


Page 55

8 References











DET NORSKE VERITAS


Page 56







DET NORSKE VERITAS


Page 57



spreading

A41 Sea pressure











DET NORSKE VERITAS


Page 58




A6 Post-processing




DET NORSKE VERITAS


Page 59




B2 Modelling



B22 External loads














DET NORSKE VERITAS


Page 60



General


Ballast tanks




Cargo tanks





End frames

DET NORSKE VERITAS


Page 61



DET NORSKE VERITAS


Page 62






















where




)( min bottomF

bottomeff

deckF


deckeffW

DET NORSKE VERITAS


Page 63







where








where







bottomeffW

deckFσbottomFσ

UσUM


=== iiieff

tionhull

K


sec 1

(C4)



DET NORSKE VERITAS


Page 64

where













F = σFE)




sum=

minus=K

iiieffeff zEAEI

1

2)()()(

ieffEA minus)(

)( minbottom

bottomU

deck

deckU

U zz

εεκ =

deckUε

bottomUε

deckFε

bottomFε

)( min bottomF

bottomeff

deckF


deck

effdeckeff z

IW =

bottom

effbottomeff z

IW =

DET NORSKE VERITAS


Page 65












of view


DET NORSKE VERITAS


Page 66








limits)



DET NORSKE VERITAS


1 Introduction

11 Objective

12 General

13 Definitions

14 Programs


21 General





31 Introduction


33 Roll damping



36 Load Transfer




43 Corrosion model

44 Loads









61 Overview

62 General


64 Sub models



71 General

72 Documentation

73 Verification

8 References
















DET NORSKE VERITAS


Page 11



















DET NORSKE VERITAS


Page 12













000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50 60Wave Period

VB

M

Wav

e A

mp

litu

de


000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50Wave Period

VB

M

Wav

e A

mp

litu

de

[ ] [ ]

⎥⎦⎤

⎢⎣⎡

=

m

Nm

Nm


responseermtLongmζ

DET NORSKE VERITAS


Page 13




36 Load Transfer









000E+ 00

100E+ 05

200E+ 05

300E+ 05

400E+ 05

500E+ 05

600E+ 05

700E+ 05

800E+ 05

900E+ 05

0 10 20 30 40 50 60Wa ve Period

VB

M

Wa

ve

Am

pli

tud

e

DET NORSKE VERITAS


Page 14










where


Pressures at 10-

4 probability

Extrapolated t

Water head f


p r pe p d =

DET NORSKE VERITAS


Page 15




















T z z

zact wl

wl

+ minus2

g

pdT

ρ4

3

DET NORSKE VERITAS


Page 16























DET NORSKE VERITAS


Page 17



DET NORSKE VERITAS


Page 18



DET NORSKE VERITAS


Page 19





Tankers


DET NORSKE VERITAS


Page 20





LPG carriers


Container vessel


Ore carrier


43 Corrosion model


44 Loads



DET NORSKE VERITAS


Page 21






















DET NORSKE VERITAS


Page 22







DET NORSKE VERITAS


Page 23


















DET NORSKE VERITAS


Page 24









DET NORSKE VERITAS


Page 25















DET NORSKE VERITAS


Page 26












0

025

05

075

1

125

15

175

2

100425 120425 140425 160425 180425 200425 220425


Fat

igue

Dam

age

[-]

Screening Results

TBHD Pos

Local Model Result

DET NORSKE VERITAS


Page 27


















alno

spothotK

minσσ

=

DET NORSKE VERITAS


Page 28


















⎝⎛minus= log

25log

4loglog m

tmN a

4

1

25⎟⎠⎞⎜

⎝⎛=Δ t

respσ

DET NORSKE VERITAS


Page 29




















DET NORSKE VERITAS


Page 30



522 Designloads




DET NORSKE VERITAS


Page 31










ID

























DET NORSKE VERITAS


Page 32

523 Design stress




















Entire cargo region








ID





DET NORSKE VERITAS


Page 33








σ =



DET NORSKE VERITAS


Page 34







where







( )W

Wmodn21mean A

A

n

ττττ sdot+++=

DET NORSKE VERITAS


Page 35













DET NORSKE VERITAS


Page 36














DET NORSKE VERITAS


Page 37










where


margin






DET NORSKE VERITAS


Page 38















DET NORSKE VERITAS


Page 39








where






DET NORSKE VERITAS


Page 40


61 Overview










Cargo hold model


as sub-model




DET NORSKE VERITAS


Page 41







DET NORSKE VERITAS


Page 42









62 General



DET NORSKE VERITAS


Page 43











baseline

x fwd

z up

y port

AP

centreline

DET NORSKE VERITAS


Page 44











where

tw = web thickness


Wco

comean t

rh

hht sdot

sdotminus=

( )2co

2co

cohh26

l1r

minus+=

DET NORSKE VERITAS


Page 45









64 Sub models






DET NORSKE VERITAS


Page 46



















DET NORSKE VERITAS


Page 47




















DET NORSKE VERITAS


Page 48











72 Documentation








DET NORSKE VERITAS


Page 49









same








73 Verification


FE model


DET NORSKE VERITAS


Page 50

Mass-model


Hydro-analysis


Load transfer


FE analysis










DET NORSKE VERITAS


Page 51



where





)3

d-(Z

2

B dNA5 gdM ρ=Δ


-2500000

-2000000

-1500000

-1000000

-500000

0

500000

1000000

0 50 100 150 200 250 300 350


Sti

ll w

ater

ben

din

g m

om

ent

Loding Manual

Loading Man Corr

Potential theory

DET NORSKE VERITAS


Page 52



where










DET NORSKE VERITAS


Page 53





-200E+05

-150E+05

-100E+05

-500E+04

000E+00

500E+04

100E+05

150E+05

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ver

tical

she

ar f o

rce

[kN

]

-200E+06

000E+00

200E+06

400E+06

600E+06

800E+06

100E+07

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ve

rtic

a l b

end i

ng m

o men

t [kN

m]

DET NORSKE VERITAS


Page 54














DET NORSKE VERITAS


Page 55

8 References











DET NORSKE VERITAS


Page 56







DET NORSKE VERITAS


Page 57



spreading

A41 Sea pressure











DET NORSKE VERITAS


Page 58




A6 Post-processing




DET NORSKE VERITAS


Page 59




B2 Modelling



B22 External loads














DET NORSKE VERITAS


Page 60



General


Ballast tanks




Cargo tanks





End frames

DET NORSKE VERITAS


Page 61



DET NORSKE VERITAS


Page 62






















where




)( min bottomF

bottomeff

deckF


deckeffW

DET NORSKE VERITAS


Page 63







where








where







bottomeffW

deckFσbottomFσ

UσUM


=== iiieff

tionhull

K


sec 1

(C4)



DET NORSKE VERITAS


Page 64

where













F = σFE)




sum=

minus=K

iiieffeff zEAEI

1

2)()()(

ieffEA minus)(

)( minbottom

bottomU

deck

deckU

U zz

εεκ =

deckUε

bottomUε

deckFε

bottomFε

)( min bottomF

bottomeff

deckF


deck

effdeckeff z

IW =

bottom

effbottomeff z

IW =

DET NORSKE VERITAS


Page 65












of view


DET NORSKE VERITAS


Page 66








limits)



DET NORSKE VERITAS


1 Introduction

11 Objective

12 General

13 Definitions

14 Programs


21 General





31 Introduction


33 Roll damping



36 Load Transfer




43 Corrosion model

44 Loads









61 Overview

62 General


64 Sub models



71 General

72 Documentation

73 Verification

8 References

























DET NORSKE VERITAS


Page 12













000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50 60Wave Period

VB

M

Wav

e A

mp

litu

de


000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50Wave Period

VB

M

Wav

e A

mp

litu

de

[ ] [ ]

⎥⎦⎤

⎢⎣⎡

=

m

Nm

Nm


responseermtLongmζ

DET NORSKE VERITAS


Page 13




36 Load Transfer









000E+ 00

100E+ 05

200E+ 05

300E+ 05

400E+ 05

500E+ 05

600E+ 05

700E+ 05

800E+ 05

900E+ 05

0 10 20 30 40 50 60Wa ve Period

VB

M

Wa

ve

Am

pli

tud

e

DET NORSKE VERITAS


Page 14










where


Pressures at 10-

4 probability

Extrapolated t

Water head f


p r pe p d =

DET NORSKE VERITAS


Page 15




















T z z

zact wl

wl

+ minus2

g

pdT

ρ4

3

DET NORSKE VERITAS


Page 16























DET NORSKE VERITAS


Page 17



DET NORSKE VERITAS


Page 18



DET NORSKE VERITAS


Page 19





Tankers


DET NORSKE VERITAS


Page 20





LPG carriers


Container vessel


Ore carrier


43 Corrosion model


44 Loads



DET NORSKE VERITAS


Page 21






















DET NORSKE VERITAS


Page 22







DET NORSKE VERITAS


Page 23


















DET NORSKE VERITAS


Page 24









DET NORSKE VERITAS


Page 25















DET NORSKE VERITAS


Page 26












0

025

05

075

1

125

15

175

2

100425 120425 140425 160425 180425 200425 220425


Fat

igue

Dam

age

[-]

Screening Results

TBHD Pos

Local Model Result

DET NORSKE VERITAS


Page 27


















alno

spothotK

minσσ

=

DET NORSKE VERITAS


Page 28


















⎝⎛minus= log

25log

4loglog m

tmN a

4

1

25⎟⎠⎞⎜

⎝⎛=Δ t

respσ

DET NORSKE VERITAS


Page 29




















DET NORSKE VERITAS


Page 30



522 Designloads




DET NORSKE VERITAS


Page 31










ID

























DET NORSKE VERITAS


Page 32

523 Design stress




















Entire cargo region








ID





DET NORSKE VERITAS


Page 33








σ =



DET NORSKE VERITAS


Page 34







where







( )W

Wmodn21mean A

A

n

ττττ sdot+++=

DET NORSKE VERITAS


Page 35













DET NORSKE VERITAS


Page 36














DET NORSKE VERITAS


Page 37










where


margin






DET NORSKE VERITAS


Page 38















DET NORSKE VERITAS


Page 39








where






DET NORSKE VERITAS


Page 40


61 Overview










Cargo hold model


as sub-model




DET NORSKE VERITAS


Page 41







DET NORSKE VERITAS


Page 42









62 General



DET NORSKE VERITAS


Page 43











baseline

x fwd

z up

y port

AP

centreline

DET NORSKE VERITAS


Page 44











where

tw = web thickness


Wco

comean t

rh

hht sdot

sdotminus=

( )2co

2co

cohh26

l1r

minus+=

DET NORSKE VERITAS


Page 45









64 Sub models






DET NORSKE VERITAS


Page 46



















DET NORSKE VERITAS


Page 47




















DET NORSKE VERITAS


Page 48











72 Documentation








DET NORSKE VERITAS


Page 49









same








73 Verification


FE model


DET NORSKE VERITAS


Page 50

Mass-model


Hydro-analysis


Load transfer


FE analysis










DET NORSKE VERITAS


Page 51



where





)3

d-(Z

2

B dNA5 gdM ρ=Δ


-2500000

-2000000

-1500000

-1000000

-500000

0

500000

1000000

0 50 100 150 200 250 300 350


Sti

ll w

ater

ben

din

g m

om

ent

Loding Manual

Loading Man Corr

Potential theory

DET NORSKE VERITAS


Page 52



where










DET NORSKE VERITAS


Page 53





-200E+05

-150E+05

-100E+05

-500E+04

000E+00

500E+04

100E+05

150E+05

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ver

tical

she

ar f o

rce

[kN

]

-200E+06

000E+00

200E+06

400E+06

600E+06

800E+06

100E+07

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ve

rtic

a l b

end i

ng m

o men

t [kN

m]

DET NORSKE VERITAS


Page 54














DET NORSKE VERITAS


Page 55

8 References











DET NORSKE VERITAS


Page 56







DET NORSKE VERITAS


Page 57



spreading

A41 Sea pressure











DET NORSKE VERITAS


Page 58




A6 Post-processing




DET NORSKE VERITAS


Page 59




B2 Modelling



B22 External loads














DET NORSKE VERITAS


Page 60



General


Ballast tanks




Cargo tanks





End frames

DET NORSKE VERITAS


Page 61



DET NORSKE VERITAS


Page 62






















where




)( min bottomF

bottomeff

deckF


deckeffW

DET NORSKE VERITAS


Page 63







where








where







bottomeffW

deckFσbottomFσ

UσUM


=== iiieff

tionhull

K


sec 1

(C4)



DET NORSKE VERITAS


Page 64

where













F = σFE)




sum=

minus=K

iiieffeff zEAEI

1

2)()()(

ieffEA minus)(

)( minbottom

bottomU

deck

deckU

U zz

εεκ =

deckUε

bottomUε

deckFε

bottomFε

)( min bottomF

bottomeff

deckF


deck

effdeckeff z

IW =

bottom

effbottomeff z

IW =

DET NORSKE VERITAS


Page 65












of view


DET NORSKE VERITAS


Page 66








limits)



DET NORSKE VERITAS


1 Introduction

11 Objective

12 General

13 Definitions

14 Programs


21 General





31 Introduction


33 Roll damping



36 Load Transfer




43 Corrosion model

44 Loads









61 Overview

62 General


64 Sub models



71 General

72 Documentation

73 Verification

8 References



















000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50 60Wave Period

VB

M

Wav

e A

mp

litu

de


000E+00

100E+05

200E+05

300E+05

400E+05

500E+05

600E+05

700E+05

800E+05

900E+05

0 10 20 30 40 50Wave Period

VB

M

Wav

e A

mp

litu

de

[ ] [ ]

⎥⎦⎤

⎢⎣⎡

=

m

Nm

Nm


responseermtLongmζ

DET NORSKE VERITAS


Page 13




36 Load Transfer









000E+ 00

100E+ 05

200E+ 05

300E+ 05

400E+ 05

500E+ 05

600E+ 05

700E+ 05

800E+ 05

900E+ 05

0 10 20 30 40 50 60Wa ve Period

VB

M

Wa

ve

Am

pli

tud

e

DET NORSKE VERITAS


Page 14










where


Pressures at 10-

4 probability

Extrapolated t

Water head f


p r pe p d =

DET NORSKE VERITAS


Page 15




















T z z

zact wl

wl

+ minus2

g

pdT

ρ4

3

DET NORSKE VERITAS


Page 16























DET NORSKE VERITAS


Page 17



DET NORSKE VERITAS


Page 18



DET NORSKE VERITAS


Page 19





Tankers


DET NORSKE VERITAS


Page 20





LPG carriers


Container vessel


Ore carrier


43 Corrosion model


44 Loads



DET NORSKE VERITAS


Page 21






















DET NORSKE VERITAS


Page 22







DET NORSKE VERITAS


Page 23


















DET NORSKE VERITAS


Page 24









DET NORSKE VERITAS


Page 25















DET NORSKE VERITAS


Page 26












0

025

05

075

1

125

15

175

2

100425 120425 140425 160425 180425 200425 220425


Fat

igue

Dam

age

[-]

Screening Results

TBHD Pos

Local Model Result

DET NORSKE VERITAS


Page 27


















alno

spothotK

minσσ

=

DET NORSKE VERITAS


Page 28


















⎝⎛minus= log

25log

4loglog m

tmN a

4

1

25⎟⎠⎞⎜

⎝⎛=Δ t

respσ

DET NORSKE VERITAS


Page 29




















DET NORSKE VERITAS


Page 30



522 Designloads




DET NORSKE VERITAS


Page 31










ID

























DET NORSKE VERITAS


Page 32

523 Design stress




















Entire cargo region








ID





DET NORSKE VERITAS


Page 33








σ =



DET NORSKE VERITAS


Page 34







where







( )W

Wmodn21mean A

A

n

ττττ sdot+++=

DET NORSKE VERITAS


Page 35













DET NORSKE VERITAS


Page 36














DET NORSKE VERITAS


Page 37










where


margin






DET NORSKE VERITAS


Page 38















DET NORSKE VERITAS


Page 39








where






DET NORSKE VERITAS


Page 40


61 Overview










Cargo hold model


as sub-model




DET NORSKE VERITAS


Page 41







DET NORSKE VERITAS


Page 42









62 General



DET NORSKE VERITAS


Page 43











baseline

x fwd

z up

y port

AP

centreline

DET NORSKE VERITAS


Page 44











where

tw = web thickness


Wco

comean t

rh

hht sdot

sdotminus=

( )2co

2co

cohh26

l1r

minus+=

DET NORSKE VERITAS


Page 45









64 Sub models






DET NORSKE VERITAS


Page 46



















DET NORSKE VERITAS


Page 47




















DET NORSKE VERITAS


Page 48











72 Documentation








DET NORSKE VERITAS


Page 49









same








73 Verification


FE model


DET NORSKE VERITAS


Page 50

Mass-model


Hydro-analysis


Load transfer


FE analysis










DET NORSKE VERITAS


Page 51



where





)3

d-(Z

2

B dNA5 gdM ρ=Δ


-2500000

-2000000

-1500000

-1000000

-500000

0

500000

1000000

0 50 100 150 200 250 300 350


Sti

ll w

ater

ben

din

g m

om

ent

Loding Manual

Loading Man Corr

Potential theory

DET NORSKE VERITAS


Page 52



where










DET NORSKE VERITAS


Page 53





-200E+05

-150E+05

-100E+05

-500E+04

000E+00

500E+04

100E+05

150E+05

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ver

tical

she

ar f o

rce

[kN

]

-200E+06

000E+00

200E+06

400E+06

600E+06

800E+06

100E+07

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ve

rtic

a l b

end i

ng m

o men

t [kN

m]

DET NORSKE VERITAS


Page 54














DET NORSKE VERITAS


Page 55

8 References











DET NORSKE VERITAS


Page 56







DET NORSKE VERITAS


Page 57



spreading

A41 Sea pressure











DET NORSKE VERITAS


Page 58




A6 Post-processing




DET NORSKE VERITAS


Page 59




B2 Modelling



B22 External loads














DET NORSKE VERITAS


Page 60



General


Ballast tanks




Cargo tanks





End frames

DET NORSKE VERITAS


Page 61



DET NORSKE VERITAS


Page 62






















where




)( min bottomF

bottomeff

deckF


deckeffW

DET NORSKE VERITAS


Page 63







where








where







bottomeffW

deckFσbottomFσ

UσUM


=== iiieff

tionhull

K


sec 1

(C4)



DET NORSKE VERITAS


Page 64

where













F = σFE)




sum=

minus=K

iiieffeff zEAEI

1

2)()()(

ieffEA minus)(

)( minbottom

bottomU

deck

deckU

U zz

εεκ =

deckUε

bottomUε

deckFε

bottomFε

)( min bottomF

bottomeff

deckF


deck

effdeckeff z

IW =

bottom

effbottomeff z

IW =

DET NORSKE VERITAS


Page 65












of view


DET NORSKE VERITAS


Page 66








limits)



DET NORSKE VERITAS


1 Introduction

11 Objective

12 General

13 Definitions

14 Programs


21 General





31 Introduction


33 Roll damping



36 Load Transfer




43 Corrosion model

44 Loads









61 Overview

62 General


64 Sub models



71 General

72 Documentation

73 Verification

8 References










36 Load Transfer









000E+ 00

100E+ 05

200E+ 05

300E+ 05

400E+ 05

500E+ 05

600E+ 05

700E+ 05

800E+ 05

900E+ 05

0 10 20 30 40 50 60Wa ve Period

VB

M

Wa

ve

Am

pli

tud

e

DET NORSKE VERITAS


Page 14










where


Pressures at 10-

4 probability

Extrapolated t

Water head f


p r pe p d =

DET NORSKE VERITAS


Page 15




















T z z

zact wl

wl

+ minus2

g

pdT

ρ4

3

DET NORSKE VERITAS


Page 16























DET NORSKE VERITAS


Page 17



DET NORSKE VERITAS


Page 18



DET NORSKE VERITAS


Page 19





Tankers


DET NORSKE VERITAS


Page 20





LPG carriers


Container vessel


Ore carrier


43 Corrosion model


44 Loads



DET NORSKE VERITAS


Page 21






















DET NORSKE VERITAS


Page 22







DET NORSKE VERITAS


Page 23


















DET NORSKE VERITAS


Page 24









DET NORSKE VERITAS


Page 25















DET NORSKE VERITAS


Page 26












0

025

05

075

1

125

15

175

2

100425 120425 140425 160425 180425 200425 220425


Fat

igue

Dam

age

[-]

Screening Results

TBHD Pos

Local Model Result

DET NORSKE VERITAS


Page 27


















alno

spothotK

minσσ

=

DET NORSKE VERITAS


Page 28


















⎝⎛minus= log

25log

4loglog m

tmN a

4

1

25⎟⎠⎞⎜

⎝⎛=Δ t

respσ

DET NORSKE VERITAS


Page 29




















DET NORSKE VERITAS


Page 30



522 Designloads




DET NORSKE VERITAS


Page 31










ID

























DET NORSKE VERITAS


Page 32

523 Design stress




















Entire cargo region








ID





DET NORSKE VERITAS


Page 33








σ =



DET NORSKE VERITAS


Page 34







where







( )W

Wmodn21mean A

A

n

ττττ sdot+++=

DET NORSKE VERITAS


Page 35













DET NORSKE VERITAS


Page 36














DET NORSKE VERITAS


Page 37










where


margin






DET NORSKE VERITAS


Page 38















DET NORSKE VERITAS


Page 39








where






DET NORSKE VERITAS


Page 40


61 Overview










Cargo hold model


as sub-model




DET NORSKE VERITAS


Page 41







DET NORSKE VERITAS


Page 42









62 General



DET NORSKE VERITAS


Page 43











baseline

x fwd

z up

y port

AP

centreline

DET NORSKE VERITAS


Page 44











where

tw = web thickness


Wco

comean t

rh

hht sdot

sdotminus=

( )2co

2co

cohh26

l1r

minus+=

DET NORSKE VERITAS


Page 45









64 Sub models






DET NORSKE VERITAS


Page 46



















DET NORSKE VERITAS


Page 47




















DET NORSKE VERITAS


Page 48











72 Documentation








DET NORSKE VERITAS


Page 49









same








73 Verification


FE model


DET NORSKE VERITAS


Page 50

Mass-model


Hydro-analysis


Load transfer


FE analysis










DET NORSKE VERITAS


Page 51



where





)3

d-(Z

2

B dNA5 gdM ρ=Δ


-2500000

-2000000

-1500000

-1000000

-500000

0

500000

1000000

0 50 100 150 200 250 300 350


Sti

ll w

ater

ben

din

g m

om

ent

Loding Manual

Loading Man Corr

Potential theory

DET NORSKE VERITAS


Page 52



where










DET NORSKE VERITAS


Page 53





-200E+05

-150E+05

-100E+05

-500E+04

000E+00

500E+04

100E+05

150E+05

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ver

tical

she

ar f o

rce

[kN

]

-200E+06

000E+00

200E+06

400E+06

600E+06

800E+06

100E+07

0 50 100 150 200 250 300 350

Length [m]

WASIM

CUTRES

Ve

rtic

a l b

end i

ng m

o men

t [kN

m]

DET NORSKE VERITAS


Page 54














DET NORSKE VERITAS


Page 55

8 References











DET NORSKE VERITAS


Page 56







DET NORSKE VERITAS


Page 57



spreading

A41 Sea pressure











DET NORSKE VERITAS


Page 58




A6 Post-processing




DET NORSKE VERITAS


Page 59




B2 Modelling



B22 External loads














DET NORSKE VERITAS


Page 60



General


Ballast tanks




Cargo tanks





End frames

DET NORSKE VERITAS


Page 61



DET NORSKE VERITAS


Page 62






















where




)( min bottomF

bottomeff

deckF


deckeffW

DET NORSKE VERITAS


Page 63







where








where







bottomeffW

deckFσbottomFσ

UσUM


=== iiieff

tionhull

K


sec 1

(C4)



DET NORSKE VERITAS


Page 64

where













F = σFE)




sum=

minus=K

iiieffeff zEAEI

1

2)()()(

ieffEA minus)(

)( minbottom

bottomU

deck

deckU

U zz

εεκ =

deckUε

bottomUε

deckFε

bottomFε

)( min bottomF

bottomeff

deckF


deck

effdeckeff z

IW =

bottom

effbottomeff z

IW =

DET NORSKE VERITAS


Page 65












of view


DET NORSKE VERITAS


Page 66








limits)



DET NORSKE VERITAS


1 Introduction

11 Objective

12 General

13 Definitions

14 Programs


21 General





31 Introduction


33 Roll damping



36 Load Transfer




43 Corrosion model

44 Loads









61 Overview

62 General


64 Sub models



71 General

72 Documentation

73 Verification

8 References






classification notes no. 34.1 csa - direct analysis of

Documents