ssc-367 - Ship Structure Committee

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From this process, the original number of sea spectra, which may have been thousands, is reduced to the number of wave height bands times the number of spectra in each representative set. B.4.2 Wave Spectrum Method A reduced set of sea spectra can be generated to represent the variation of Hs and Tz as given in a wave scatter diagram. If the original sea spectra are not available, a set of sea spectra can be created directly from the wave scatter diagram. In this case the shape of the spectrum must be assumed. For various areas of the world’s oceans, preferred mathematical spectrum equations exist. For the,North Sea, the mean JONSWAP spectrum is preferred. For open ocean, the Bretschneider (ISSC) spectrum is preferred. For the Gulf of Mexico, the Scott spectrum has been recommended. Using the Hs and Tz for each populated box in the wave scatter diagram, and the selected sea spectrum equation, a set of wave spectra are defined. With this method the number of sea spectra is reduced to the number of populated boxes in the wave scatter diagram, but no more than the number of wave height bands times the number of wave period band. B–19
2.4 2.2 2 1 ‘Sen &-”Swull$p~ctru 1.8 SEA 1.6 1,4 M’ 1- SWELL 1.2- 0.8- 0.6- I / 0.4- #---- 0,2- 0 I 1 # i 1 I i 1 0.2 0,8 1 1.4 1.8 2,2 2.5 3 3.4 RodialFrequency(md~see) z I E 1.2 I 1.1 - 1- 0.9- 1 Iicspmse A-nplitudcOpcrotur 0.8- 0.7- 0.6- 0,5- 0.4- 0.3- 0.2- 0.1 - 0 0.2 0.8 1 1.4 1.8 2.2 2,8 3 3.4 Radial Frcqurwmy (md/see) 0.9 I Rtspcmse Spectrum k 0.8- 0.7- 0.6- 0.5- 0.4- 0.3- 0.2- 0.1 - 0 # 1 1 # 1 1 [ 1 I 1 i ! 0.2 0.8 1 1.4 1,8 2.2 2.s 3 3.4 Figure Rsdbl Frsqusney (rod/%w) B-1 Sea Spectra, Response Amplitude and Response Spectrum Operator (RAO) &
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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
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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
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
Page 256 and 257: common probability distributions, t
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
Page 297 and 298: the set of extreme conditions, and
Page 299: A response scatter diagram could be
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Page 305 and 306: o Kuang (ReferenceCl) “ o Wordswo
Page 307 and 308: C.2 STRESS CONCENTRATION FACTOR EQU
Page 309 and 310: C.3 PARAMETRIC STUDY RESULTS . C.3.
Page 311: 30. 2s , 20. 15. 10. 5. & wORDSWORT
Page 314 and 315: ChordSide Brace Side K-Joints SCFU
Page 316 and 317: Definition of Parameters, Validitv
Page 318 and 319: -, l— I + ?1 -— I . 4> a ,- I I
Page 320 and 321: Kuang SCF Computdion 1 L u UI \ f-
Page 322 and 323: ., I , 1- out— FIano SCF m tg n I
Page 324 and 325: — 6 Smedley-Wordswoti SCF Computa
Page 326 and 327: T ln— Plan- SCF CrOwn POsltlon o
Page 328 and 329: C.3.l(C) Kuang Chord SCF’S for T-
Page 330 and 331: 5 Kuang SCF Computation 4 IL u M 3
Page 332 and 333: C.3.l(d) Smedley-WordsworthChord SC
Page 334 and 335: . ,i 5 Smedley-Wordsworth SCF Compu
Page 336 and 337: I I K Out— Plan= SCF —— Saddl
Page 338 and 339: - 10 Smedley-Wordsworth SCFComputat
Page 340 and 341: ‘\, ?v x out— Plan- SCF ——
Page 342 and 343: C.3.2(a) Kuang Chord SCF’S for T-
Page 344 and 345: KuwqSE _im T-joint In%neW UrrdSicko
Page 346 and 347: C.3.2(b) Smedley-HordsworthChord SC
Page 348 and 349: 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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