ssc-367 - Ship Structure Committee

More documents

Recommendations

Info

Jr 2*$ *dti= Jr 2*S*du eeee. Therefore, the encounter frequency need only be used to select the response amplitude operator and the integration is still over the stationary frequency, u. i.e., re = r(we) = r(w + 2 VU/g) B.2.3.3 Short-Crested Seas The usual mathematical representation of a sea spectrum is onedimensional with the random waves traveling in a single direction with the crests and troughs of the waves extending to infinity on either side of the direction of wave travel. A one-dimensional irregular sea is also referred to as a long-crested irregular sea. In the real ocean the waves tend to be short-crested due to the interactionof waves from different directions. A two-dimensional spectrum (short-crested sea) is created from a standard one-dimensional mathematical spectrum by multiplying the spectrum by a “spreading function.” The most commonly used spreading function is the “cosine-squared”function. f(lp)= (2/Tr)*cos2$ where * is the angle away from the general wave heading, (-lT/2q%/2) The cosine-squared spreading function spreads the sea spectrum over an angle +/- 90 degrees from the general wave heading. To incorporatemulti-directional or short-crested irregular seas into a spectral analysis, the RAOS for a range of wave headings must be obtained. A spectral analysis is performed for each heading using the one-dimensional sea spectrum. The results of the one-dimensional analyses are then multiplied by integration factors and summed. B-n
The following is..a. sample...of..a“.set. of...heading angles integration factors for a cosine squared spreading function. and the $ Factor ~o 0.2200 *2O0 0.1945 *4O0 0.1300 ~600 0.0567 3800 0 ● 0088 6.2.4 Force Spectrum For simple single-degree-of-freedomsystems, generated directly from the calculated or forces. a force spectrum can be measured regular wave The force on the structure is calculated by empirical or theoretical methods, or is derived by analyzing measured strain records from tests on the structure or on a model of the structure. This force is the right hand side of the equation of motion as described in Section B.2.2.1. The force itself has an in-phase and an out-of-phase component relative to the regular wave which generates the force. The force can be written in complex form, F(u) = A*[FI(u) + i*FO(m)] or in force RAO and phase form, F(w) = A*RAOf(w)*cos(wt+$(w)) where RAOf = SQRT (F12 + F02), and @ ‘ATAN (FO/FI). B–12
Page 1:
SSC-367 - FATIGUE TECHNOLOGY ASSESS
Page 4 and 5:
SHIP STRUCTURF COMMllTFF The SHIP S
Page 6 and 7:
—.--— 1. Report No. 2. Gowotnmr
Page 8 and 9:
FATIGUE TECHNOLOGY Assessment AND D
Page 10 and 11:
6. FATIGUE STRESS HISTORY MODELS 6,
Page 12 and 13:
APPENDICES A. REVIEW OF OCEAN ENVIR
Page 14 and 15:
D. VORTEX SHEDDING AVOIDANCE AND FA
Page 16 and 17:
LIST OF FIGURES (cent.) FIGURE TITL
Page 18 and 19:
HOT-SPOT STRESS . The hot-spot stre
Page 20 and 21:
QA/Qc : Quality Assurance/QualityCo
Page 22 and 23:
1. INTRODUCTION 1.1 BACKGROUND The
Page 24 and 25:
general assessmentof fatiguewhile t
Page 26 and 27:
2. OVERVIEW OF FATIGUE 2.1 FATIGUE
Page 28 and 29:
2.2 FATIGUE ANALYSIS 2.2.1 Anal.vsi
Page 30 and 31:
● Loads generated as affected by
Page 32 and 33:
A deterministic method is sometimes
Page 34 and 35:
1 APPLICATION OF NUMEROUS CYCLIC ST
Page 36 and 37:
I MOBiLEANDSTATIONARY MARWE STRUCTU
Page 38 and 39:
3. FATIGUE DESIGN AND ANALYSIS PARA
Page 40 and 41:
and in-plane/out-of-planeangles,and
Page 42 and 43:
the general quality of fabrication,
Page 44 and 45:
3.2 REVIEW OF FATIGUE ANALYSIS PARA
Page 46 and 47:
frequencies of interest, requiring
Page 48 and 49:
● 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 100 and 101:
TOP[C U.K.DEPARTMENTOF ENERGY(OEn)
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
Page 150 and 151:
In many cases wind informationmay b
Page 152 and 153:
q = 3.3 s = 0.07, for f< fm s = 0.0
Page 154 and 155:
Seasonal Variation The annual wave
Page 156 and 157:
4. ~arpkaya spreading. (Reference 6
Page 158 and 159:
~. \“ life of a structure,cannot
Page 160 and 161:
6.3 TIME-DOMAIN ANALYSES Nonlinear
Page 162 and 163:
The wave environmentdefinitionsbase
Page 164 and 165:
.,..,, ....- ., ;., .. .... .- .. .
Page 166 and 167:
● Fatiguetest data should be care
Page 168 and 169:
assessmentis typically identifiedas
Page 170 and 171:
damage accumulation similar to that
Page 172 and 173:
“FabricationRestrictions Fabricat
Page 174 and 175:
Fatigue strength of a tubular joint
Page 176 and 177:
Current recommendations,rules and s
Page 178 and 179:
n NB=T 1 [p=+pi Ei . ‘c where: NB
Page 180 and 181:
(2) Damage computation does not acc
Page 182 and 183:
DNB = (f. T/K) (2/2 U)m r (f+ 1) wh
Page 184 and 185:
interactionof multiple fatigue crac
Page 186 and 187:
amplitude loading and loading seque
Page 188 and 189:
n“ CAP PASSES ROOT = * { A A 4 I
Page 190 and 191:
It should be pointed out that the e
Page 192 and 193:
v= flow velocity normal to the cyli
Page 194 and 195:
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
Page 200 and 201:
failure data on various structures,
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 246 and 247: Member Agencies: United States Coas
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
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: 9 is the acceleration of gravity in
Page 295 and 296: is the damping ratio,..the ratio of
Page 297 and 298: the set of extreme conditions, and
Page 299 and 300: A response scatter diagram could be
Page 301 and 302: 2.4 2.2 2 1 ‘Sen &-”Swull$p~ctr
Page 303 and 304: L ‘2
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
Page 350 and 351:
-— T-joint CtkuHlane ELFSaddlePci
Page 352 and 353:
I 1 1 1 1 ~. l~o ~ ha= 1s0 : ~. ~J
Page 354 and 355:
1 ! ! O.fi ;0.762 %841 0,769 O,= !0
Page 356 and 357:
Ikrdwth-kdlw SF l%quiaiifm K-joint
Page 358 and 359:
hdsmthqwdhy W Camputatim l-joint Ax
Page 360 and 361:
Ejrnnt flkf+lane SF SaddlePmitim ~,
Page 362 and 363:
MAXIMUM PRINCIPAL STRESS SCF = ----
Page 364 and 365:
‘-W, .\ I Ill I : II m -,, !) .
Page 366 and 367:
’ \./ ““’ w~”mm m ““-
Page 368 and 369:
. . I Column L’ Longitudinal Gird
Page 370 and 371:
C.8 Underwater Engineering Group,
Page 372 and 373:
APPENDIX D VORTEX SHEDDING AVOIDANC
Page 374 and 375:
a an b d f“ f ar f~ ‘bmax f~ fn
Page 376 and 377:
D. VORTEX SHEDDING 0.1. INTRODUCTIO
Page 378 and 379:
Vortex Shedding Frequency (f”) fv
Page 380 and 381:
waves. When only isolated members u
Page 382 and 383:
member’s nominal diameter and thi
Page 384 and 385:
\Lf-! of cycles. Thus, the reduced
Page 386 and 387:
s ; J steady current, by substituti
Page 388 and 389:
Step 3: Obtain a new valueof 1/10 b
Page 390 and 391:
vortex shedding will occur, i.e., V
Page 392 and 393:
h. The fatigue life may -be modifie
Page 394 and 395:
NOTE: The relationship given is bas
Page 396 and 397:
CELL C7: KINEMATIC VISCOSITY = U CE
Page 398 and 399:
COLUMN N: THE STRESS AMPLITUDE IS C
Page 400 and 401:
D.8.3 Devices and Spoilers Devices
Page 402 and 403:
D*9 REFERENCES D.1 King, R., “A R
Page 404 and 405:
Fint Insmbility Rtgion I !%mmd Inat
Page 406 and 407:
.—____ *U.S. E.P.O. :1993-343-273
Page 410 and 411:
COMMllTEE ON MARINE STRUCTURES Comm
Page 412:
4!! . ,—.-.,
show all

ssc-367 - Ship Structure Committee

Create successful ePaper yourself

Delete template?

Save as template?