ssc-367 - Ship Structure Committee

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SSC-<strong>367</strong> ‘ FATIGUE TECHNOLOGY ASSESSMENT AND STRATEGIES FOR FATIGUE AVOIDANCE IN MARINE STRUCTURES This document has been approved for public release and srilq its distribution is unlimited SHIP STRUCTURE 1993 COMMITTEE
Page 1: SSC-367 - FATIGUE TECHNOLOGY ASSESS
Page 5 and 6: MemberAgencies: United States Coast
Page 7 and 8: -. —---- —-...-. . COMVEflSION
Page 9 and 10: 4. GLOBAL REVIEW OF FATIGUE 4.1 App
Page 11 and 12: 8. FATIGUE DUE TO VORTEX SHEDDING 8
Page 13 and 14: B. REVIEW OF LINEAR SYSTEM RESPONSE
Page 15 and 16: LIST OF FIGURES
Page 17 and 18: COMMON TERMS USED IN FATIGUE AND IN
Page 19 and 20: MODELING ERROR (Xme) : Typically de
Page 21 and 22: SIMPLE JOINT : An intersection of t
Page 23 and 24: imperfections, fabrication defects,
Page 25 and 26: including environmental conditions,
Page 27 and 28: complete the three-phasestable crac
Page 29 and 30: diagram boxes are normalized so tha
Page 31 and 32: carrying out similar tests for diff
Page 33 and 34: 2.4 FATIGUE FAILURE AVOIDANCE Fatig
Page 35 and 36: ENVIRONMENTAL CRITERIA (DEFINITIONO
Page 37 and 38: -. (THIS PAGE INTENTIONALLY LEFT BL
Page 39 and 40: 3*1*1 Desiqn Parameters There are n
Page 41 and 42: not three but five Charpy specimens
Page 43 and 44: elsewhere). Both thermal stress rel
Page 45 and 46: -- analysis process is often initia
Page 47 and 48: analysis of a fixed platform. As di
Page 49 and 50: wind loading on a structure is due
Page 51 and 52: stresses several times greater than
Page 53 and 54:
Selection of S-N Curve The S-N curv
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D is the cumulative damage, k is th
Page 57 and 58:
Primarily Affect ---------+ r I GLO
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Primarily Affect .~:--------+. ENVI
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SCAITER DIAGRAM Y WAVE DIRECTIONALI
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,,- ... , . . . . . . . . . . . :.:
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The different methods and their app
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● Vertical bending moment - neede
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Offshore structures such as a semis
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analysis is likely to be requiredwh
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dynamic loads on vessel bottom may
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In general, the minimumrequirement
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port are also subjectedto different
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the sensitivity of fabricationdefec
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4.2.1 Applicable Methods Simplified
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4.2.2 SCFS, S-N Curves and Cumulati
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Cumulative Damaae The use of the Pa
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Although additionalresearch is need
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● Optimize the design details to
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5. 6. 7. 8. DETAILED ANALYSIS 5.1 S
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and by providing sufficientmargin w
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ICOMPUTER MODEL I MASS MODEL I I I
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tl MASSMODEL 1 I r * RIGID 600Y MAS
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“k- N ++’ b. -- 0 N 0 NOTE - PE
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~ AMERICAN ETPOLEUMlNSTITUTE )tiotS
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TOPIC U.K.DEPARTH~NT(lFENERGY(lJEn)
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(THIS PAGE INTENTIONALLY LEFT BLANK
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● The effect of modeling complexi
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shall have sufficiently fine mesh a
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The ship motion and wave action res
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● Preparationof a table of offset
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analysis program can be used, a thr
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approach, also called “consistent
Page 119 and 120:
For each load component (in-phase a
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energy of the water particle (drag
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for a pre-definedwave height, wave
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where: u = defined as the net veloc
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simulations of random waves. The ba
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The analysis effort must be kept co
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alternative, the accuracy of hot-sp
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classified as a K joint. If the loa
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Details of Equations The details of
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Screeninq Process For a preliminary
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-“ 30 Calculation l.iaoas 6 Beck
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PlatlOrmDetailed 3-D ModW 1 I Gener
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I ‘-l !1r.“N%%’, QN SECTION A
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JOINT IN=PLANE OUT-OF-PLANE CLASSIF
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6. FATIGUE STRESS HISTORY MODELS Cr
Page 149 and 150:
Actual recordedwave elevationdata i
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Wave informationis calculatedfrom w
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6.1.3 Scatter Diaqram Wave scatter
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waves in a short crested sea approa
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evaluated as explained in Section 5
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judgement errors) and facilities ca
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6.3.1 Stress Statistics The resulti
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Ss@e WaveScatt@rDiagram s i 9 n : i
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7. 7.1 BASIC PRINCIPLES OF FATIGUE
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The S-N curves that can be used dir
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The primary factors that influence
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‘b = fatigue strength of a joint
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Maddox (Reference 7.11) provide the
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frequency of loading identify sever
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fatigue damage predictions. Fatigue
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Typically, the sea state represente
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When the structure response yields
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Following the weighting of the shor
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thickness effect is necessary and t
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:Ilo I Cn 80 to 40 . 20 T- m 10 m -
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8. FATIGUE DUETO VORTEX SHEDDING Th
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frequency (i.e. fc = fn = fv), memb
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8.2.2 VIV Response and Stresses A s
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Verification of a member’s struct
Page 197 and 198:
9. FATIGUE AVOIDANCE STRATEGY Most
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● An indirect fatigue design wher
Page 201 and 202:
“!M91! ● Global Configurations
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Fatigue avoidance strategy for mobi
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improve the fatigue strength. The m
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to the electrode position, so the s
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structures. A comprehensive discuss
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second objective is to accurately e
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elative slippage--betweenjacket leg
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h!!!u Fatiguestrength is not analyz
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● Stress concentrationfactors; in
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should be carefully reviewed and th
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and regulations. These and other st
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UNDERCUT CWCK-LIKE DEFECT & .’i ~
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SOMEOF THERELEVANT FATIGUERESEARCHP
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10. REFERENCES 1.1 Fatigue Handbook
Page 229 and 230:
4*3 Munse, W.H., Wilbur, T.U., Tell
Page 231 and 232:
4.21 Weidler, J.B., and Karsan, D.I
Page 233 and 234:
5.13 Rodenbush, G., “Random Direc
Page 235 and 236:
6.4 Study of Environmental Design C
Page 237 and 238:
7.11 Maddox, S.J., “Fitnessfor Pu
Page 239 and 240:
8.1 Bel1, E.R.G. and Morgan, D.G.,
Page 241 and 242:
StatisticalCharacterization,”Ship
Page 243 and 244:
SHIP STRUCTURE COMMITTEE PUBLICATIO
Page 245 and 246:
~HIP STRUCTURF CO MMllTEF The SHIP
Page 247 and 248:
T*chnical Report Documentation Poge
Page 249 and 250:
FATIGUE TECHNOLOGY ASSESSMENT AND S
Page 251 and 252:
A. REVIEH OF OCEANENVIRONMENT The o
Page 253 and 254:
The recommended form of displaying
Page 255 and 256:
where, f is the circular frequency.
Page 257 and 258:
particular wave spectrum formula, t
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T~ = 0.9457*T P’ New The first eq
Page 261 and 262:
H = 2*[2*ln(n) ]+*Hs 1/n For n = 10
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H~ = 0.1610*g/(um)2 ‘m = o.4o125*
Page 265 and 266:
‘P = 1.1671*TS . For Y = 1, the f
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A.4.1 Wave Hindcastinq Wave hindcas
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The wave height exceedance diagram
Page 271 and 272:
Using the significant wave height a
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The equation for the Weibulldistrib
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Z1 = reference height, 30 ft (10 M)
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n = fluctuating frequency 2 S(n) =
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‘GiiQH1 REGULAR WAVES TI T2 T3 I
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B. REVIEW OF LINEAR SYSTEM RESPONSE
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the sea. By assuming thatthe respon
Page 286 and 287:
B.2.2.1 Equation of Motions By assu
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X(w) = A*RAO(w)*cos(wt+ O(W)). When
Page 290 and 291:
[dn/dx]max= aW2/g . Squaring the eq
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Jr 2*$ *dti= Jr 2*S*du eeee. Theref
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The force..spectrum can be created
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0.3 EXTREME RESPONSE The extreme re
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Significant response, (DA): R5 = 4.
Page 300 and 301:
From this process, the original num
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APPENDIX C STRESS CONCENTRATIONFACT
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c. STRESSCONCENTRATIONFACTORS. C.1
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Ma and Tebbett also state that whil
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C.2.2 Smedley-Wordsworth The Smedle
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C.3.l(a) Kuang Chord SCF’S for T-
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ChordSide BraceSide K-Joinlx SCFCX
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Chord Sidg SCFCX= 1.7yT~(2.42 - 2.2
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(3) Table 2 only .. (l)-~f~ ~ 0.95
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‘1 ——. -.— ——. . ..-—
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5 4 L u w 3“ 9 t o -. ii Ic Kuang
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C.3.l(b) Smedley-Wordsworth Chord S
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— &. 15 Smedley-Wordsworth SCF Co
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— -. .... 5 Smedley-Wordswotih SC
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— 5 Kuang SCF Computation 4 IL L)
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j K Out— ~lanq SCF ‘?’ + F .
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, 5 Smediey-Wordswotih SCF Computat
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Smedley-Wordswotih SCFComputation *
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C.3.l(e) Smedley-Wordsworth Chord S
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\ Smedley-Wordswoti SCF Computation
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C.3.2 Tables The Kuang and Smedley-
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I@q W ~tim T-juint Axial W Owd Side
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-- -- -- .- -- -- -- -- -- -- .- --
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— T-joint hid S5 Crm i%itim 1 1 1
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. T-joint In-PlaneSE UM P~itim ., 1
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— i : m ! 0.3: O*5: 0.7: o*?: 0.3
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Ku&W Cr@atim K-jrnntiht++laae SF M
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!WsA-MIEy SF bqutaticm K-joint Axia
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-- ..—--- ------ -- ------ ------
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kbrdwmii%dl~y SCFComputation ,..-,
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C.4 FINITE ELEMENT ANALYSES RESULTS
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,. .. ..-. __ _________ ._ _ ______
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—..—.— -.. — 7 a . LOWER HU
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. Loading ~ Figure C.4-4 Equivalent
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C.5 REFERENCES C.1 Kuang, J.G. et a
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(THIS PAGE INTENTIONALLY LE~ BLANK)
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NOMENCLATURE co CLj CLO o ‘tot DI
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x (THIS PAGE INTENTIONALLY LEFT BIA
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shedding frequency to synchronize w
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deflection and stability parameters
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a fn = ~ (EI/mi L4)% where: the mom
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0.3.1 In-Line Vortex Shedding . In-
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0.4.1 In-LineVortex Sheddinq Amplit
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CLO = base lift coefficient = 0.29
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The vortex shedding bending stress
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a. Depending on marine structure in
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c constant (See Vr reduced velocity
Page 395 and 396:
D.7.2 Analysis for Wind-Induced Cro
Page 397 and 398:
I . + [ (+)-L (+ - t)4] (cm4) COLUM
Page 399 and 400:
Experiments have shown- that for a
Page 401 and 402:
Shrouds Shrouds consist of an outer
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Harmonic Flow, Royal Institute of N
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o.: Q., 0“.. 0.1 0.1 * REGION 0 9
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(THIS PAGE INTENTIONALLY LEFT BIANK
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SHIP STRUCTURE COMMITTEE PUBLICATIO
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