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from a removnl of the stiffening contribution of tho dnmnpwl mcmbor(s). In the experimental hydm-dastic modol, all lllo joinlr arc nrilhcr ~,c,r- fectly rigid nor flexible. (Jonnts were fastened with ABS ralvrnt gltr.) Therefore, when the slructareunderwent damngo, the excess stwm tmnssil- ted lo the rcmniningmombma, pnrticulnrly thc nneiglnhotnring onm, nnllcl Ih~vc. resulted in a weakening of romc of tho joinla of llne remnining s!cmhc~(x)-- especially the joint(=) closest lo lhe d~mngcd mombcr(s). Tho ttcl cffcel 01, the total stiffneaa of the atroclure would be greatec than lhnt of thc then- retical model. This, in turn, would resull in lnrgcr sl~ilts in frqamcicx of the modes in which the flcxibilily Is greatly influencal by the romovd of lhr particular member(*) (e.g., modo 4 and mombec 70). From the overall struclaral gmmdry, il wolnld scan tbnt, in 11~1: tlwo- retical resulte, the percentage shift in frequcncica resulting lrnm tlr: rnnevul of member 68 would be equal to thal of member TO. An cxnnni!~nlion crl Table 1.4 shows that thcrc arc discrepancies in thc roaults for time ainlilnr structural damage canfigurations. This may have malted from lhe ilen~1.i~~ acheme used. The rubspare itcrnlion method was used to ~olvc for thc m1.1- ural frequencies. There is an error asrociatcd with lhe melltocl tilnt is sandl lor the first few modes, and hemmos larger as the nurnhcr el nnorlra in lhr: solution increases.
Chapter 9 Concluding Remarks and Recommendations 'This treatise dealt with adetoiled design and construction of a hydm-elastic modol of a lypicnl four-legged jacket offshore platform. Both an indepth ll~eorcticnl and experimental anniysis wore carried out. Experiments were conduetod in a w~vc tank cquipped with a pseudo random wave making fa- cility. To obtain lhe neeesary modal parameten (e.g., resonant frequencies, and damping mtios) Imm the ambient response dats, the recently devd- opcd Mnrple algorithm was used with the wry powerful Maximum Entropy Mcthod (MBM). Regarding structural integrity monitoring, structural damage was 8imulded by saw cutting lhe member(#) under mnsiduatio~. In the lhmretical analysts, this was done by making the member(.) inactive in tllc 'rllc dewion damage war bed on the changw in monant lrequslcics mmpnred with the intact structure. 9.1 Concluding Remarks Bass an the reported mulls and evaluations, important conclusions can be rcachcd. Among lheae are lhe Lllowing:
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NOTICE The quallty of this microfor
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I*I Et"" :lbL="*"" k.. bpilmsa7d Di
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Acknowledgements I should like lo t
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Abstract As a result of the increas
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Contents List of Figures xii List o
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4.6.3 Fnbrieatiox of tllc Rcduced M
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A Selected Algoilthma 278 A.1 Diago
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4.5 Member Configuration at level #
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7.21 Dynamic Mode # 6 (Intact Model
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7.49 Typical Measured lnput Wnve Sp
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7.66 hulls fmm Accelerometer A2 due
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D.ll DynamicMode # I (Intact Model)
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List of Tables 4.1 Symbols, Units a
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8.9 Pacent Changes in Resonant Frrq
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List of Symbols d(k) .i(k) A A(L1 1
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autosp~trni density of r(t) cms-spe
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0,1,2
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[@I a Pu. P. P:,," P.. o2(k) instan
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een recorded, then it is beneficial
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Associated with every vibration mod
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Such s model is called a dynamicall
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presenlcd. Chapter 3 contains the t
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al frequcncic. occurred when member
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detwM from the data roeorded (later
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y Duggan d a!. [a]. This study inve
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~~lidity of the results war rompsro
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nic~~~aan:immcdiateiyuseful, they a
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tlncayatem hehavior oftrusswork pla
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Chapter 3 Theoretical Modelling Tll
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3.2 Wave Theories Works by earlier
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F;-RY% WAVE THEORY) 1/20 I "w/Lw DE
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DIRECTION OF WAVE PROPAGATION FIG.
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liero, d and ita wlocity component
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and and a+ "=-. OY = wA~inl~IW(1+ s
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FIG.3.4 ARBITRARILY ORIENTED CYLIND
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~i n long c mtd wave is being conai
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inrther. Ultimately, the resulting
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equcncia and mode shapes, equalion
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Toestablish tho relationship betwee
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Furthermore, from equation (3.56),
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lG.3.6 SIMULATED 3-D AND STICK MODE
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1. priam&tic heam members, 5. sir d
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The equation of motion for each ele
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From tho ~tatic dispiaeemont muita,
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instance, the non-dimensional equal
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functional relationship relating th
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whcre F, 't iinstantanmua force at
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Table 4.1 Symbols, Unit. and Dimens
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thc Buckinghm r-Thmrem (i.c., I2 te
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That is, equations (4.28) and (4.29
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C. Ilence, if the dynamic amplifica
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where (2) is the general gmmdric or
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the prolotype. Damping is dcfincd b
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2 LEVEL # 7 1 28956DO NOTE: ALL DIM
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Mataial= Structural Steel, E = 206.
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LEVEL C6 NOTE: ALL DlMENStONS IN m
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Table 4.5 Relevant Materiel Propert
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FlG.4.9 COMPLETED STRUCTURE. 89
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Since the de& sertioo of the struct
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% FINITE ELEMENT ANALYSIS (COMPUTER
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3 53 I CONTROL RM SECTION A-D. MEZZ
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I I SERVO CONTROLLER MODEL 408.1% j
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LEGEND FI B F2 FREE VlBllTlDN INITI
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5.1.4 Response Circuit Data acquisi
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I ~T.UG~U~E LEGEND: DYIIYT I., 10 A
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the basis upon which the irregular
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then manipulated by the computer ro
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,.. G STRUCTURE IN STILL WATER STRU
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dter every set of hen wave excitati
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To gather spectral information fmm
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is the timelag between silrnplev~l~
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ics, with a lew notable exceptions,
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If bath aides of the dove cguntion
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Conversely, r(1) can be estimated b
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quires ahout N(M + 1) + 9Y1 arithme
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So equation (6.18) become: I, i = C
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At each resonant frequency, the hdl
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6.5 Impact Testing Impact testa wer
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Chapter 7 Theoretical and Experimen
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Table 7.1 Natural Wequeney Comparis
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Therefore, with the natural freluen
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Pi7 Be: kD! SF:& iid id . -5 i#@ Ba
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(i.o., at noder 6, 12, 18, 22 and 2
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tirne dntn;lis reprcsez~lnlioti of
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-CUI~IW~~~ anstmr 9~1sn-mmu3n DL um
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the posilivc and nogntivr peaks. Re
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Table 7.7 X-Direction Results From
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2 GEhEnnlEO FRDM TdE WrllTE hOISE l
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FIG. 7.53 MEASURED INPUT WRVE FROM
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'IUnU133dS 3SIR1 31IHI 9NISn--91 30
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Table 7.9 MEM Damping Estimates fro
Page 246: 7.2.3 Impact Test Results In Chsptc
Page 252 and 253: (K 01 0 01- OZ- DE- 0,- OBI (KI 09
Page 257 and 258: Chapter 8 Discussion of Results In
Page 260 and 261: of rnemhcr removal can he visually
Page 263 and 264: emoved is a cancellation offecl, an
Page 265 and 266: Force Variation Along the Jacket. P
Page 267: fi~t on the lower rrequency end of
Page 271 and 272: pond approximately to thasc which c
Page 273 and 274: 'Ikble 8.1 Measured Resonant Rsquen
Page 275 and 276: Table 8.6 Measured Resonant Wequenc
Page 277 and 278: After a close look at the measured
Page 279 and 280: Table 8.11 Percent Changes in Reson
Page 281 and 282: Table 8.16 Percent Changes in Reson
Page 283: apprmiably. Since the tmnsa of the
Page 286 and 287: '*~+12 \5 \8 h4 h7 $0 FREOUENCY IHz
Page 288 and 289: 8.2.4 Impact Test Results 'l'incobj
Page 293 and 294: I able 8.20 Comparison of the Reson
Page 295: 'Phc invalidity of thc lumped mass
Page 299 and 300: general agreement. 5. An investigat
Page 301 and 302: mode, br example, might have been e
Page 303 and 304: References K I'o,lnt~n~. 'A Sludy o
Page 305 and 306: [21] .I.K. Vandiver, "Structo~ral D
Page 307 and 308: 1431 D.J. Kartewcg and G. d-Vria "O
Page 309 and 310: 1671 I..S. Marplo, "A NCW Autorepes
Page 311 and 312: (111 J. Zhou "Ocean Wave Simulation
Page 313 and 314: [Ill M.C. Ilallsm, N.J. Hcaf and L.
Page 315 and 316: Appendix A Selected Algorithms Tllr
Page 317 and 318: - M = the total mass of the slructu
Page 319 and 320: Suhrtituting qualion (A.5) in equal
Page 321 and 322: ..3 Longuet-Higgins and Cokelet Smo
Page 323 and 324: Appendix B Sample Calculations Typi
Page 325 and 326: The dcnsity of ABS plsstic (p.,,) i
Page 327: C.l Calibration and Instrumentation
Page 330: D.l Mode Shape (Members 70 and 68 R
Page 340 and 341: D.2 Results for an Impact Initiated
Page 343: i W 4 P Li I 2: 5: E B '5 2- d :" i
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oa m 01 o or- QZ- oe- om Q Z ~ oo a
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D.3 MEM Damping Estimates for the D
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Table D.4 MEM Damping Estimate. fro
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4 - Memorial University of Newfoundland DAI

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