4 - Memorial University of Newfoundland DAI

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1. The methodsused in the design, modelling and adjual~nenta, conatn~r- tian, instrumentation and in pmcessing the data arc rcliable atal valid techniques tocarry out struel!trnl intebrity monilori~~gololfsl~orc alnnr- tures, through the analyses of reduced hydm-elnslic models. 2. The Maximum Entmpy Metllod (MEM) proved lo bc n v e powcrhnl ~ meansolobtaining high resolution amootln spcclrn fmm "cry short lime aerie records. Since the spectral density ~ esull~obtni~~~l frosn thc, lirnr aerie data enn be attained in funclionnl lonn, resoand. freqac~aic~x and damping ratios could be ntamcricslly coxnpatcd. Tllis ihhrrcnl facet ol MEM may have very imporlanl npplication~s in experi~rn~slid modal analysis-particularly in the are& of system icle~,tificatio~n fmts ambient vibration data. (It is not suggested thnl the MliM I.cchniq\nr is a replacement of the eonvenlionnl PPT procrdureu.) 3. A predictalrie relationship exists between physical clamagc artd ~:lniatg% in the modes of vibration of lhc strudltm. Ilovovcr, R* ill~~nl.n~lrd ia Table 1.4, the succes of tho slructurnl Integrity monitlrring trrll~!iiqt
general agreement. 5. An investigatim into the effect of s member cracking suggested that the Sl~eluml InlcgrZy Mclhod is limited because of the low sensitir ily/resoiution regarding resonant frequcney versus eraeks. This, there- for~, implies thal only major damages (i.e., primary structural element lailurc) can be dokcled. 6. At each roaonant frequency, the structure deformed in a different man- ner. ilcnce, the relative magnitudes between the various remnant f m quencies should provide an indication of tho general location at which the structure had b m weakened. The prima~y benefit of such a gs- tem is that any damagorl mombcr which has a large influence on the ati~Tnoas of a pnrticuinr mode of the structure will, obviously, rault in as annlugous large change in the exdtstion frequency of that mode. Thus, il is imperative that the stiffness characleristics of the atruc- tore bc completely underrtaod; sa any large changes in the resonant freguoncy of s specific mode may be localized. 7. Worn the thcorelicaiiy computed mode shapes, it was possible to ob- serve lile effecl of damage on the most affected mode(r) fmm theshear- iog of llre panel containing the damaged mcmbcr(s). Thia could not be ailown experimentally, since it would require an array of transducers to computc the mode shapes from the experimentaldata. 8. Esiimates of damping for the lat mode (from the wave induced vibra- tions sludies) are lower than that obtained with the transient decay tests. The values computed from the wave tests are: 2.02% and 2.4'196,
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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
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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 and 296: 'Phc invalidity of thc lumped mass
Page 297: Chapter 9 Concluding Remarks and Re
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
Page 347: 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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