ssc-367 - Ship Structure Committee

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Member Agencies: United States Coast Guard Naval Sea Systems Command Maritime Administration American Bureau of Sh@ping Military Sealifi Command Transpmt Canada Ship Structure Committee An Interagency AdvisoryCommittee May 17, 1993 Address Correspondence to: Executive Director Ship Structure Committee U.S. Coast Guard (G-Ml/R) 2100 Second Street, S.W. Washington, D.C. 20593-0001 PH: (202) 267-0003 FAX: (202) 267-4677 SSC-367 SR-1324 FATIGUE TECHNOLOGY ASSESSMENT AND STRATEGIES FOR FATIGUE AVOIDANCE IN MARINE STRUCTURES .—.. This report synthesizes the state-of–the-art in fatigue technology as it relates to the marine field. Over the years more sophisticated methods have been developed to anticipate the life cycle loads on structures and more accurately predict the failure modes. As new design methods have been developed and more intricate and less robust structures have been built it has become more critical than ever that the design tools used be the most effective for the task. This report categorizes fatigue failure parameters, identifies strengths and weaknesses of the available design methods, and recommends fatigue avoidance strategies based upon variables that contribute to the uncertainties of fatigue life. This set of Appendices includes more in-depth presentations of the methods used in modeling the loads from wind and waves, linear system response to random excitation, stress concentration factors, vortex shedding and fatigue damage calculation. G.P.Y&n .. A. E. HENN Rear Admiral, U.S. coast Guard Chairman, Ship Structure Committee .-.
T*chnical Report Documentation Poge 1. Report No. 2. Governmtmt Acc*ssioti No. 3. Rocip,~ntrs Catalog Ne. 4. Title and subtitle 5. Rcportiko June1992 FATIGUEDESIGNPROCEDURES 6.Performing Organization Cod= 7. AuthorIs) 8. PorfaminQ 0r9anizatisn R9part No. CuneytC.Capanoglu SR-1324 9. Prrfnrmin9 Or~anization Namm rnd AdAmss 10. Work Unit No. (TRAIs) EARL AND WRIGHT 11. Controctar Gr~nt N*. 180 Howard Street DTCG23-88-C-20029 San Francisco, CA 94105 13. TYP. of R-part ondPried C-word ~2. 5POm~Or~mQ Aq~n=yNa~~ ~mdAddr*~~ Ship Structure Committee Final Repoti U.S. Coast Guard (G-M) 2100 Second Street, SW IS. supplementary Notes Washington, DC 20593 I 14. Sponsoring Agency Cod. SponsoredbytheShipStructure Committeeanditsmembersagencies. G-M ABSTRACT This report provides an up-to-date assessment of fatigue technology, directed specifically toward the marineindustry, A comprehensive overview of fatigue analysis and design, a global review of fatigue including rules and regulations and current practices, and a fatigue analysis and design criteria, are provided as a general guideline to fatigue assessment. A detailed discussion of all fatigue parameters is grouped under three analysis blocks: ● Fatigue stress model, covering environmental forces, structure response and loading, stress response amplitude operations (RAOS] and hot-spot stresses ● Fatigue stress history model covering long-term distribution of environmental loading ● Fatigue resistance of structures and damage assessment methodologies The analyses and design parameters that affect fatigue assessment are discussed together with uncertainties and research gaps,to provide a basis for developing strategies for fatigue avoidance. Additional in-depth discussions of wave environment, stress concentration factors, etc. are presented in the appendixes. 17. Key Words 18. Distribution Statwn.nt Assessment of fatigue technology, fatigue stress models, fatigue Available from: stress history models, fatigue National Technical information Serv. resistance, fatigue parameters U. S, Department of Commerce and fatigue avoidance strategies Springfield, VA 22151 19. .lecunty Cl=$sif. (~f this r-pert) Unclassified I I 20. s~curity Classif. (of this POW) Unclassified Form DOT F 1700.7 (8-72) Reproduction Oi completed page authorized I 21. No. O{ PU9*S I 22. Pri CC 194 EXCI, Appendixas
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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
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The finite element models of increa
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The stressmodel parametersdiscussed
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While API S-N curves are applicable
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DESIGN Osn40H rAnNsirsR8 FAMcA~ M P
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Primarily Affect .--------+’ & In
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MOTIONS MODEL — .—. ● ;LOADS
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loa 1 10 -— — — -t-i-nT 1[ -t
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4. GLOBAL REVIEW OF FATIGUE 4.1 APP
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An allowable stress method, also co
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esults of work covering assessment
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location. Thus, the method should b
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1. SDectral FaticlueAnalvsis Althou
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2. Weibull AtIDroach The Weibull sh
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energy about the central direction
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Although considered to be an emergi
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many design rules implement this ap
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Detailed Anal.vsisMethods The detai
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The DnV X-curve and the DEn Guidanc
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ending restrictions. Cruciform and
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period, are also designed tomeet th
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incorporates inspection-strategy(Re
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‘Thereare numerous finite element
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LOCATIONs oF FATIGUE CMCKS Figure 4
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TW=’T ——— ———___ __ r
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1 —. — — — — -.. - .. - .
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TOP[C U.K.DEPARTMENTOF ENERGY(OEn)
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:1 U.K.DEPARTMENTOF ENERGY(DEn) AME
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TOPIC U.K.DEPARTMENJOFEIWRGV(oEn) O
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5. FATIGUE STRESS MODELS 5.1 REVIEW
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● The water particle kinematicsar
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“radiation pressure” of waves,
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influence on the applied loading. H
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their function, selecting appropria
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hydrostatic stiffness is introduced
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structure is unique and an allowabl
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loads directly. Since the diffracti
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typically from 0.6 to 0.8 and 1.5 t
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therefore be defined uniformly alon
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load analysisof adetailed three-dim
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esponsesare required , or where con
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either multiple stick elements (for
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Braces may have stubs or cones, whi
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Whatever the basis for an empirical
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The SCF equations currently in use
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life. During the comprehensive desi
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?.s I z - ]LEvE~ ~ 1,5 \ i i+ 11 Is
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-. Figure 5-5 Comparison of Detaile
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( -t ) ( T-JOINT Y-JOINT ( \ I / K-
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SMEDLEY-WORDSWORTH 0 d =— = D 600
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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
Page 196 and 197: Ra < S REGIME OF UNSE?ARATE~ FLOW 5
Page 198 and 199: ages. The designer has no control o
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Page 202 and 203: connections, knife edge crossings,
Page 204 and 205: 9.3.1 Fabrication Effects The fatig
Page 206 and 207: ● Controlled Erosion An alternate
Page 208 and 209: after a given number of stress cycl
Page 210 and 211: A second pass with polishingdisc is
Page 212 and 213: others. Extensive analytical and ex
Page 214 and 215: d) Stress SDectrum Hot-spot stresse
Page 216 and 217: Cumulativefatiguedamagecomputations
Page 218 and 219: as a parametric study intended to i
Page 220 and 221: Additional areas requiring further
Page 222 and 223: GROUP Modification of Weld Profile
Page 224 and 225: 400 ‘,, . . 350 - I I 300r [ ~ ,0
Page 226 and 227: TOPIC SUBJECT INVESTIGATOR COMPLETI
Page 228 and 229: 3.1 Soyak, J. F., Caldwell, J. W.,
Page 230 and 231: 4.12 Daidola, J.C., and Basar, N.S.
Page 232 and 233: 5.4 Papanikolaou,A. and Zaraphoniti
Page 234 and 235: 5.21 -”’ ” ”---”---”
Page 236 and 237: “7.2 Jordan, C.R., and Cochran, C
Page 238 and 239: 7.19 Niemi, E.J., “FatigueTests o
Page 240 and 241: 9.1 Skaar, K.T., “ContributingFac
Page 242 and 243: COMMllTEE ON MARINE STRUCTURES Comm
Page 244 and 245: U.S.Department of Transportation Un
Page 248 and 249: ‘ METRIC CONVERSION FACTORS Appro
Page 250 and 251: APPENDIX A REVIEW OF OCEAN ENVIRONM
Page 252 and 253: The most distinctive feature-of a r
Page 254 and 255: s(w) = 2*(4*112) - For a “height
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Page 258 and 259: T: v. Visually Observed Period, or
Page 260 and 261: The characteristic wave heights of
Page 262 and 263: H~ is the significantwave height, a
Page 264 and 265: a = 0.09, for UJ>wm The U value of
Page 266 and 267: H~ is the significant height, ‘m
Page 268 and 269: If the wind duration is less than t
Page 270 and 271: Sample Wave scatter Diagram s 12 +.
Page 272 and 273: Nm is the total number of waves in
Page 274 and 275: turbulence largely a function of te
Page 276 and 277: Applied Wind Speed Vz(t) ft/s (m/s)
Page 278 and 279: A.1O REFERENCES A*I Mechanics of Wa
Page 280: APPENDIX B REVIEW OF LINEAR SYSTEM
Page 283 and 284: Awhite noise function-may be used t
Page 285 and 286: Multiplication of the wave spectrum
Page 287 and 288: B.2.2.2 Response Amplitude Operator
Page 289 and 290: 0.2.3 Wave Spectra The wave spectru
Page 291 and 292: 9 is the acceleration of gravity in
Page 293 and 294: The following is..a. sample...of..a
Page 295 and 296: 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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