ssc-367 - Ship Structure Committee

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TOP[C U.K.DEPARTMENTOF ENERGY(OEn) AMERICANPETROLEUMINSTITUTE GENERALCONSIDERATIONS o Fatiguelife Life*~Servlce Life Life> 2x Serv~ceLife o FatigueLoading o FatigueAnalyslsjDes~gn All cyclicloads(Ref.21.2.1OC) (Ref.5.2.5) - SimplifiedMethod No Yes,allowablestressmethod appl~cableto Gulfof~exlco (GOM) (Ref.5.1.1) - DetailedAnalysis Recommended Recommendedfor: waterdepth~400 ~t (122m),or * lifeshouldnotbe 620years - platformperiod> 3 see,or andan additionalfactoron - environmentharsherthanGOM Ilfeis recommendedwhen (Ref.5.1.2) structuralredundancyis ln~dequate(Ref.21.2.10f) DETERMINATIONOF STRESSES o Ob.ject~ve To determinecycl~cstressranges To determineCYCIICstresses (j.e.,meanstressesare neglected- properlyaccountingactualj Ref.21.2.11) distributionof waveenergyover entirefrequencyrange,spectral analysistechniquesare recommended. o Modeling No spectficreference Spaceframeanalysistoobtaln structuralresponseandstress distribution(Includlngdynnmlc effects) o Analysis A detailedfatigueanalyslsallowln9 Typically,spectralanalysisto eachcrltlcalareato be considered. determinestressresponsefor each sea state. J Page1 of 5 . Figure4-7 Comparisonof Recommendations U.K.GuidanceNotesandAPI RP 2A
~ AMERICAN ETPOLEUMlNSTITUTE )tiotSpotStress RangeIs theproductof the nom~na~ RangeIsohtalnedby multiplyingthe stressrangeIn the braceandthe nominalstressrangeat’tubular SCF. ItIncorporatesthe effectsof jointby SCF. overalljointgeometrybut.omitsthe stre<strong>ssc</strong>oncentratingInfluenceof theweld itself. iTRESSCONCENTRATION ‘ACTORS(SCFs~ } Scf ho referencesgiven SCFSdefinedarebaseduponmodl~led Kelloggformulas forchord and Marshallformula[ forbrace 1 (Ref. C5.1,Table5.1.1-1) ISimpleJoints- Nodal JEmpiricalEquations OtherJoints iTRESSHISTORY Nonedefined Noned~flned SCFSdefinehot spotstresses Immediatelyadjacentto the olnt intersection(0.25”toO.1d from weldtoe,Ref.C 5.4) K, T, Y andX jointsdefinedfor axial,In-planeandout~ofplane loading Recommendsa braceSCF~6 (Ref.5.5) )WaveClimate Page2 of 5 i Figure4-7 Comparisonof Recommendations U.K.GuidanceNotesandAP1fW 2A Waveclimatesmay be derivedfrom bothrecordeddataandhlndcasts. Aggregateof allsea statesto be expectedoverthe longterm condensedIntorepresentativesea states. A sea state,characterized by wave energyspectrumandprobabilityof occurrence,may be definedby: o Twoparameterscatterdiagrams o Directionalscatterdiagrams o i)lrectlonalscatterdiagramswith spreading
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SSC-367 - FATIGUE TECHNOLOGY ASSESS
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SHIP STRUCTURF COMMllTFF The SHIP S
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—.--— 1. Report No. 2. Gowotnmr
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FATIGUE TECHNOLOGY Assessment AND D
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6. FATIGUE STRESS HISTORY MODELS 6,
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APPENDICES A. REVIEW OF OCEAN ENVIR
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D. VORTEX SHEDDING AVOIDANCE AND FA
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LIST OF FIGURES (cent.) FIGURE TITL
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HOT-SPOT STRESS . The hot-spot stre
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QA/Qc : Quality Assurance/QualityCo
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1. INTRODUCTION 1.1 BACKGROUND The
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general assessmentof fatiguewhile t
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2. OVERVIEW OF FATIGUE 2.1 FATIGUE
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2.2 FATIGUE ANALYSIS 2.2.1 Anal.vsi
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● Loads generated as affected by
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A deterministic method is sometimes
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1 APPLICATION OF NUMEROUS CYCLIC ST
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I MOBiLEANDSTATIONARY MARWE STRUCTU
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3. FATIGUE DESIGN AND ANALYSIS PARA
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and in-plane/out-of-planeangles,and
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the general quality of fabrication,
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3.2 REVIEW OF FATIGUE ANALYSIS PARA
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frequencies of interest, requiring
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● Reqular Waves in FrecjuencvDoma
Page 50 and 51: The finite element models of increa
Page 52 and 53: The stressmodel parametersdiscussed
Page 54 and 55: While API S-N curves are applicable
Page 56 and 57: DESIGN Osn40H rAnNsirsR8 FAMcA~ M P
Page 58 and 59: Primarily Affect .--------+’ & In
Page 60 and 61: MOTIONS MODEL — .—. ● ;LOADS
Page 62 and 63: loa 1 10 -— — — -t-i-nT 1[ -t
Page 64 and 65: 4. GLOBAL REVIEW OF FATIGUE 4.1 APP
Page 66 and 67: An allowable stress method, also co
Page 68 and 69: esults of work covering assessment
Page 70 and 71: location. Thus, the method should b
Page 72 and 73: 1. SDectral FaticlueAnalvsis Althou
Page 74 and 75: 2. Weibull AtIDroach The Weibull sh
Page 76 and 77: energy about the central direction
Page 78 and 79: Although considered to be an emergi
Page 80 and 81: many design rules implement this ap
Page 82 and 83: Detailed Anal.vsisMethods The detai
Page 84 and 85: The DnV X-curve and the DEn Guidanc
Page 86 and 87: ending restrictions. Cruciform and
Page 88 and 89: period, are also designed tomeet th
Page 90 and 91: incorporates inspection-strategy(Re
Page 92 and 93: ‘Thereare numerous finite element
Page 94 and 95: LOCATIONs oF FATIGUE CMCKS Figure 4
Page 96 and 97: TW=’T ——— ———___ __ r
Page 98 and 99: 1 —. — — — — -.. - .. - .
Page 102 and 103: :1 U.K.DEPARTMENTOF ENERGY(DEn) AME
Page 104 and 105: TOPIC U.K.DEPARTMENJOFEIWRGV(oEn) O
Page 106 and 107: 5. FATIGUE STRESS MODELS 5.1 REVIEW
Page 108 and 109: ● The water particle kinematicsar
Page 110 and 111: “radiation pressure” of waves,
Page 112 and 113: influence on the applied loading. H
Page 114 and 115: their function, selecting appropria
Page 116 and 117: hydrostatic stiffness is introduced
Page 118 and 119: structure is unique and an allowabl
Page 120 and 121: loads directly. Since the diffracti
Page 122 and 123: typically from 0.6 to 0.8 and 1.5 t
Page 124 and 125: therefore be defined uniformly alon
Page 126 and 127: load analysisof adetailed three-dim
Page 128 and 129: esponsesare required , or where con
Page 130 and 131: either multiple stick elements (for
Page 132 and 133: Braces may have stubs or cones, whi
Page 134 and 135: Whatever the basis for an empirical
Page 136 and 137: The SCF equations currently in use
Page 138 and 139: life. During the comprehensive desi
Page 140 and 141: ?.s I z - ]LEvE~ ~ 1,5 \ i i+ 11 Is
Page 142 and 143: -. Figure 5-5 Comparison of Detaile
Page 144 and 145: ( -t ) ( T-JOINT Y-JOINT ( \ I / K-
Page 146 and 147: SMEDLEY-WORDSWORTH 0 d =— = D 600
Page 148 and 149: Wave Records Older wave and wind in
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In many cases wind informationmay b
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q = 3.3 s = 0.07, for f< fm s = 0.0
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Seasonal Variation The annual wave
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4. ~arpkaya spreading. (Reference 6
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~. \“ life of a structure,cannot
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6.3 TIME-DOMAIN ANALYSES Nonlinear
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The wave environmentdefinitionsbase
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.,..,, ....- ., ;., .. .... .- .. .
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● Fatiguetest data should be care
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assessmentis typically identifiedas
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damage accumulation similar to that
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“FabricationRestrictions Fabricat
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Fatigue strength of a tubular joint
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Current recommendations,rules and s
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n NB=T 1 [p=+pi Ei . ‘c where: NB
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(2) Damage computation does not acc
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DNB = (f. T/K) (2/2 U)m r (f+ 1) wh
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interactionof multiple fatigue crac
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amplitude loading and loading seque
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n“ CAP PASSES ROOT = * { A A 4 I
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It should be pointed out that the e
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v= flow velocity normal to the cyli
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8.4 METHODS OF MINIMIZING VORTEX SH
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Ra < S REGIME OF UNSE?ARATE~ FLOW 5
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ages. The designer has no control o
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failure data on various structures,
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connections, knife edge crossings,
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9.3.1 Fabrication Effects The fatig
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● Controlled Erosion An alternate
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after a given number of stress cycl
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A second pass with polishingdisc is
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others. Extensive analytical and ex
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d) Stress SDectrum Hot-spot stresse
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Cumulativefatiguedamagecomputations
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as a parametric study intended to i
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Additional areas requiring further
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GROUP Modification of Weld Profile
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400 ‘,, . . 350 - I I 300r [ ~ ,0
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TOPIC SUBJECT INVESTIGATOR COMPLETI
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3.1 Soyak, J. F., Caldwell, J. W.,
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4.12 Daidola, J.C., and Basar, N.S.
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5.4 Papanikolaou,A. and Zaraphoniti
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5.21 -”’ ” ”---”---”
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“7.2 Jordan, C.R., and Cochran, C
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7.19 Niemi, E.J., “FatigueTests o
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9.1 Skaar, K.T., “ContributingFac
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COMMllTEE ON MARINE STRUCTURES Comm
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U.S.Department of Transportation Un
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Member Agencies: United States Coas
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‘ METRIC CONVERSION FACTORS Appro
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APPENDIX A REVIEW OF OCEAN ENVIRONM
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The most distinctive feature-of a r
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s(w) = 2*(4*112) - For a “height
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common probability distributions, t
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T: v. Visually Observed Period, or
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The characteristic wave heights of
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H~ is the significantwave height, a
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a = 0.09, for UJ>wm The U value of
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H~ is the significant height, ‘m
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If the wind duration is less than t
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Sample Wave scatter Diagram s 12 +.
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Nm is the total number of waves in
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turbulence largely a function of te
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Applied Wind Speed Vz(t) ft/s (m/s)
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A.1O REFERENCES A*I Mechanics of Wa
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APPENDIX B REVIEW OF LINEAR SYSTEM
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Awhite noise function-may be used t
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Multiplication of the wave spectrum
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B.2.2.2 Response Amplitude Operator
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0.2.3 Wave Spectra The wave spectru
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9 is the acceleration of gravity in
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The following is..a. sample...of..a
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is the damping ratio,..the ratio of
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the set of extreme conditions, and
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A response scatter diagram could be
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2.4 2.2 2 1 ‘Sen &-”Swull$p~ctr
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L ‘2
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o Kuang (ReferenceCl) “ o Wordswo
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C.2 STRESS CONCENTRATION FACTOR EQU
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C.3 PARAMETRIC STUDY RESULTS . C.3.
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30. 2s , 20. 15. 10. 5. & wORDSWORT
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ChordSide Brace Side K-Joints SCFU
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Definition of Parameters, Validitv
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-, l— I + ?1 -— I . 4> a ,- I I
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Kuang SCF Computdion 1 L u UI \ f-
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., I , 1- out— FIano SCF m tg n I
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— 6 Smedley-Wordswoti SCF Computa
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T ln— Plan- SCF CrOwn POsltlon o
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C.3.l(C) Kuang Chord SCF’S for T-
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5 Kuang SCF Computation 4 IL u M 3
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C.3.l(d) Smedley-WordsworthChord SC
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. ,i 5 Smedley-Wordsworth SCF Compu
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I I K Out— Plan= SCF —— Saddl
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- 10 Smedley-Wordsworth SCFComputat
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‘\, ?v x out— Plan- SCF ——
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C.3.2(a) Kuang Chord SCF’S for T-
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KuwqSE _im T-joint In%neW UrrdSicko
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C.3.2(b) Smedley-HordsworthChord SC
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T-joint Axial SF Saddle Posiiim
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-— T-joint CtkuHlane ELFSaddlePci
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I 1 1 1 1 ~. l~o ~ ha= 1s0 : ~. ~J
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1 ! ! O.fi ;0.762 %841 0,769 O,= !0
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Ikrdwth-kdlw SF l%quiaiifm K-joint
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hdsmthqwdhy W Camputatim l-joint Ax
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Ejrnnt flkf+lane SF SaddlePmitim ~,
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MAXIMUM PRINCIPAL STRESS SCF = ----
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‘-W, .\ I Ill I : II m -,, !) .
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’ \./ ““’ w~”mm m ““-
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. . I Column L’ Longitudinal Gird
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C.8 Underwater Engineering Group,
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APPENDIX D VORTEX SHEDDING AVOIDANC
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a an b d f“ f ar f~ ‘bmax f~ fn
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D. VORTEX SHEDDING 0.1. INTRODUCTIO
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Vortex Shedding Frequency (f”) fv
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waves. When only isolated members u
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member’s nominal diameter and thi
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\Lf-! of cycles. Thus, the reduced
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s ; J steady current, by substituti
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Step 3: Obtain a new valueof 1/10 b
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vortex shedding will occur, i.e., V
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h. The fatigue life may -be modifie
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NOTE: The relationship given is bas
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CELL C7: KINEMATIC VISCOSITY = U CE
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COLUMN N: THE STRESS AMPLITUDE IS C
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D.8.3 Devices and Spoilers Devices
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D*9 REFERENCES D.1 King, R., “A R
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Fint Insmbility Rtgion I !%mmd Inat
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.—____ *U.S. E.P.O. :1993-343-273
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COMMllTEE ON MARINE STRUCTURES Comm
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4!! . ,—.-.,
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