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Experimental Investigations-Correlation W/Analysis Presented at 770711-15 Proceedings of Natl Science Foundation Workshop,Univ of Ca,Berkeley
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Issue date:	07/11/1977
From:	Jennings P, Shepherd R; CALIFORNIA INSTITUTE OF TECHNOLOGY, PASADENA, CA
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EXPERIMENTAL INVESrI;AT IONS - CORREATION WITH ANALYSIS 0

lby Robin Shepierl Visiting Professor of civil nim-i ring

. aliftor nia Institute of TechIlokirgy On Le.iv from the lUnivvrsity of Auckl;ttd, New Zealand and Paul C.

Jnnings Professor of Applied Ah chanis California Institute of Tvihnology A I STR A CT In an attmpt to improvc undcrslandin

,f th (art'ilitake r-sponse of reinforced *-nncrlc Iildings, about onc imitrd sutb strututrs throughout th' worl have been iested or instrimnitted in somen manner.

Predictions of dynamic cIaractrisics hav'e b.

ni Cmnpa red with observed behavior when excitation is provided by wind or olier ambicnt excitations, by a controlled f'trced vibratjion (xcile'r or by st ron2

-arthquake motions.

For some buildings. experimental re'sults are available from more than one type of excitation.

In this artich* referu'ncu's to the various titing techniques and their resuilts are given and, in particular, the tretnds exhibited by forced vibration tests are suanisrized.

In addition, intcrprelations are made of response to strong ground motion and suggestions are advanced for further cxperimntal testing of fill-scale structures.

The greatest needs are for the quantification of the capacity of reinforc.d concrLe strue tures to resist strong ground motion and for additional experimental investigations of soil-structu re interacti on in buildings of the shear-wall type.

0 a coe0 800-1

EXPEIUMEF: NTAL INVESTIGATIONS

- CORRELA ION WITHI ANALYSIS bly tobI) in Sh eplie rd(

Visiting Professor of Civil i

neer Calift-rnia Irisltitiut of Technoitlogy On Leave from the University of Aickland, New Z/.alarol and Paiul C.

Jennings Professor of Applied Mectanics California Institute of Technoloy

SUMMARY

In an attempt to improve undcerstanding of the cariliquake response of reinforced (onc:rtc buildings, about onet hundred such structures throughout the world have been testedr or instruentedc in somei manner.

Predictions of dynmic charac teristics have been compared witi observed behavior when excitation is provictl by wind or other ambient excitations, by a controllel forced vibration excitor or by strong earthquake motions.

For some buildings experimnental results are available from more than one type of excitation.

In this article references lo the various testing techniques and their results are given and, in particular, the trends exhibited by forced vibration tests are sumniarized.

In addition, interpretations are made of response to strong ground motion and suggestions are advanced for further experimental testing of full-scale structures.

The greatest needs arc for the quantification of the capacity of reinfore d concrete at ruc tures to resist. strong ground motion and for additional experimental type..

Sine stigations of soil-structure interacti on in building s of the shear -wall INTRODUCTION In the last twenty years Ithe inproved availability and capabilities of high speedc digital compoters, which have allowed increasingly sophis ticated mathematical models of structures to be used in the seismic design process, has been paralleled by the develonpment of finely con trolled exciting apparatus and sensitive response detection equipment.

This modern instrumentation has made possible detailed experimental investigations on prototype structures, with the object of verifying assumptions made at the design stage and increasing our understanding of dynamic response in general.

Although the principles of vibration measuring instruments have been described thoroughly in classical texts in niclianical vibrations.

only relatively recently have reliable field instruments suitable for testing of buildings been availalblc commercially.

Similarly, effective stady -state testing only became a practical possibility when specd control systems were developed to ensure a satisfactory level of

pe rformantc in Ih adv r' conditions near structural resonance.

These developitwnt" have ic-cn fostvr, d.

in par, by an inc rasing interest in fhiuI-sc I.

t-ine tLht Ihar iIv lopcd over the I last fifcon years L II.

At thir pr. S1n ino wlre nxcitalin systcrns and measuring appara tus ar* ;.ailable front,,aoniurcini s(oir is and increasing activity in -the:

a rca of dynamic testing 'f fuill-scale buildings is expected.

X'C(i l ATION SOURC:ES Proid i

tiat sensit iv, tra iseItic r s ar ' available, a convenient ti'chniqgii used. to 'stabliih Ithi small amplitude natural periods and corrisponling deflictioos

)f strucitres is L.o neasure the response to wvined or microtrimor t'xtitatioin.

Difficultics arising from the presence of 'nois,'" from traffic or nwaianical equipment, from the complexity of. thc building, and from fhi effects of th' non-stationary, gusting, characteristic of Ilie wiid have ben reengnized. and good correlation tsually has bie.1n obtailned totwven observed and predicted responses of r'inforc'd

'.o ui bb'ugt' hniltois

,1-71.

Iow,'ver.

in the field of earthquake engin tring thu relationships botween small ;mplitude vibration proper tis:; and 'trong mltiin seismic responsi is not sufficiently well esta lisiheicd thalt ambin t t,'sting is prefei'rrd to alternative procedures in

'.hi'h lirgir amplitudis

.f moion occnr.

It is difficult to extrapolate from tie armiplituide-s of an ambi nt test to that of earthquake response and the t sting nwthod giving the largest allowable amplitudes is reconunend,"d Spring -back tosts involv e, tih imposition of an initial deflection on a structuro, typically by way

,f a ins mned cable or rocket thrust gene rator, and thu subse-quent recording of the free vibrations of the systim when thn additional load is suddenly released.

This technique has been used with success on certain cat,-gories of structures, including.

tall chimneys and towers, but the nmagnitud of the forces necessary to apply significant distortiuns to reinforced conc ret buildings has dis couraged its application in tiis field.

Fort ed vibration testing using variable frequency exciters enables steady-state coniditions to b achiuved; th,' steady-state response permits dtti rmninatiotn of natural frein quecies, mod,- shapes and damping.

The latter variabcl is particiiarly hard to determine from ambient tests.

Several rotating mass shak'rs have b'tien developed, those having a vertical axis being restricted to generating horizontal loads, whereas machines with hori:nontal axes can Ie used to excite either horizontal or vertical oscillatinis

., 8, 9..

Although the capacity of available shakers is insufficieit to vibrate Ioll-scale rcinfor ccd concrete structures into the range of camage or Cnilap se, sinusoidal firces of a few tons magni tudie can i

genera ted and building rleflectioins several times greater than those arising under ambiint conditions can be imposed.

Synchronous opt ration of mnori than one shaker can facilitate investigations of tor sional dynamic properties, as well as sinplifying the study of transla tional niodes of vibration.

Artificially generated strong ground mootion fromn explosions has b)ieu'n used on several occasions to vibrate rvinforced concrete buildings

[10,121.

Good correlation between th. tibserved elastic response and

that deterrmiird u sing rnatI hen ati al k,

modCll in!

f hniipues has Iweni 9

reported.

The most rearlistic tests, < onducte by r uordirt g the actual behavior of buildings wh-n subjcted to strono ground motion _eincrated by a natural eart.hquake are rc ssa rily infrequent.

It is only in the last decade that arrag:ornts have Ien succssful to install strong motion recording instruments in over one hundred struttures throughout the world.

To the time of writing only the 1971 an [

mrano earth quake has provided more than a few sampls of respornr; even or this occasion no instrurnntet builring was close to that area whih

.xperienced the most severe intensity of grounl shaking, abd the several structures that were severely damaged, or rollapsed, were not instru mented [1l1.

It is to be exp'cted, however, that the continuing programns of instrument installation and mainter'nance will ult.irately yield reliable evidence of the loads and mroveumern associatrt with the earthquake response of severely damaged structures.

MEASUREMENT The difficulirs rncountert d in attemptin in nwasurv absolute deflections in a building vibrating with frequencies the one to tenl hertz rance have r':sulted in detrcti'n rquiprment being selected with careful regard to the object of the investigatior.

Whrem r latie m

ostion arc the primary requrirerrrnt, as in drtermining natural nrdes frecquen cies and mde

shaps, velocity type instruments such as standard Willmore or Rancer seismoarnetrs have frequently Ire used.

These units have the advantage of high sensitiviLy and convenient operation but are difficult t calibrate if absolute amplitudes of displacem nt are required.

For moderate levels of responses, Stathaim accelrrnretr rs capable of convenient absolute ca ibration have proven useful L13, 143.

Where sufficirntly large responses are available, a

in a major earth quake, specially developerd instrumrerts [151 may he usd and the dis placements calculated from t1re measured accvlerations.

The apparatus used to record builting vibration has includel chart recorders, multichannrel oscilloscopes, filimn, magnti tap rrcorders and integrated data processing systrrrs providing digital oturt directly.

The incrvasing.sophistication of the rquipment provides aa vastly improved data -handling capability, in return for much larger initial costs.

RESONANCE TESTS hle objr-tivs rrf forcel vibration trsting arr' basically two-fold.

TI, experinreitally determined mode shapes. frcrreruncies and danmrpings can verify the accuracy of the assumptions maah at the design stage and lead to inrproverent in future hesigns through bettr undranding of the dyna ir behavior of-luildings.

Secondly, if the dynani: proper Lies are cstablished rxperimental.ly both before ain after a structure experiences strong ground shaking, sror't of te effectas of this experience may be inferred [rrm changes in tthese measured properties.

A Brief Rteview of Reson-mncc Testing Abroad Japanese Scexpe rieric in resonanc tedting has included shaking tests on r'infoifrceed concrete and reinforced-cOnC 1111C rete, steel-composite framed buildings.

From these ttests, average values of modal damping were clotermined and expressions for the modal periods as a function of building height were proposed [ 16].

Efforts to clarify the soil-structure interaction effect, which is of particular importance for the many rela tively stiff Japanese buildings founded on relatively soft ground, has included thw forcetd vibration testing of a stiff six story building, which sh evid that rocking vibration can p redominat L 17, 18].

Interested n

raders are referred to the literature for details of the extensive JapanesI testing program.

Itvostieations in New Ze:aland have included comparison of pre dlicted dynamic pr'pertic s with measurad ones for a framed building with spandrel blcams

19.

for four shiear-wall buildings EZI, 22] and for a simple framed structure 23].

Hland shaking excitation of a sixt-n fnor apartiernt building ienaIled thi two fi si niad(

translation frequencies to be established.

The measoretd values lay leiwien those predicted in the design when plane frame axial defo rmtion effects werte firstly negc'tleLd and secondIv included.

Correlation bett.r than 10/,, was obtained when the first mode periods were recalculaled using an increased value of elastic niodulus and including ti flange action of the exterior frames trans verse to the direction of movement wh eni determining the structural stiffness L19).

The requirnicnt to include flange action in buildings of the type tested, in which virtually all the lateral resistance is provided by the perimater frames, was probably the roost significant result derived from IIhis test.

Ihe nec e ssity for including the effects of shiearing deformations in deep licam reinforcr concrete frames -

as distinct from shallow girder frames -

had been recognized at the design stage [20].

@L SteadIy state resonancet ttesting has been undertaken on one six story [ 21 1 and thrue adjaccnt eight story biildings [22],

each being of the pierced sicar-wall type.

live moo s of vibration were examined in tile lower building and a total of seventeln in the eight story.complcx (Figure 1).

It was established that whereas the dynamic characteristics of the structural systemn may be predicted reliably, the effects of soil structure interaction proved difficult to assess with any degree of cer taiity.

Damping of up to 10% critical was measured and foundation complianci' contributions of almost 40% of the maximum top story deflection were noted.

Forced vibration int" tht post-la stic ra ngl: of a two story -full scale.reinf rced conerete frant: has been accomplished using a variable speed exciter nounted on the frame C 23].

The structure was designed and erected to the standards applicable somic ten years ago, consequently t is anticipated that the observeid performance of the test frame will be reprt-svntative of that which could be expected of a typical building erected in the same period.

As no recent New Zealand carthquake has resulted in even moderatc shaking of reinforced concrete buildings, no 4'.

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L a er

f1, r tile Sa ll I t mrra d, e ~ rtl q u a lce o f F e b ru a ry 9, 19 7 1,

fouidatinn, translation and rot at innl evvr,, found to conltri bute

'uhmecto Lil roo 1 lt On, sk-,

o tl

~ of III,'

N-S fuendamental nmd e C 14, 29, 3t lec;1, 1se tile

(co hlanyti g change.s in pu rind are consistent w ith tile Chanllges In Iliteeh 5fi'0J),s aindlleas.tn n

o pr,cnt s

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l t~oalydch fatrigo e dcVQ'of initeracti on t e S ru t i, w ich i c u e rctailei neg w alls Nx lk ay a cd a n l p

z.

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M I i a n L ib ra ry is c o n sis te n t wi~

tht nted fce a ~ nCret.

ha r-walI streucture. by ituay and Shepherd NZ fr byi force;,fd aunr sleur wall struature by Stephen, C

l co ntrbtin ah.

lei n a ~

A"I ss interaction ece t i

ot o

a oe t

~ to til e r o o f M A W,o 0 w a s r p o rte d b y N ie lse n f ur a conc retc-f rarnci building (271.

Amot,""

pr r sn in thce temts is thc, change( of resonant I cried with am-plitude.

'l*hi s is Sholwnc cltea rly in the Ic suht by

,,uroiwa 4I3, 28]

showvn icl Figu~rt. 2.

Tiis efethas also beennodbyNesuf27ad b ye o r d e r O n vf t i3 o r s.

a o e n f

l a e n f p e r i o d i s t y p i c a l l y o f fate o r of 3 or o% eve r tM c r n e Of an yleitud e. of testi n g, w hich is a fac b r f

5 to 10.

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t. of c a g,

is itsv f noet signific ant, but it

~Inhlrgetr

resp lity of5iNa larses in perioddurin the j I jui q8 c-spec ted ducrineg en cthe cakc response.

The earthqu~ake rigtec.

erad le mleasu red re pspc~

&f buji dcis istle' only Wytocermli val ts eef daepii 1

.as niethes o c alcu lte it are still in te c rie t

stages of de.elopn,,

1 t.

I-or eceec ret t st ructurICs n the rit tests typically show values rp s force vibdme c a ic ej. 5 o ra fin-,1 I te 3 of Criicl, Vi the a cluar tendcc.y t owa rd-inc rasing v l e Oif darnpiinLn%.ith inc l-a sicU alplitudcs; cf re spciele Ex -X evtaoltoth s

glue ral f ron a are higher p

odes,

,hccsulyshi oeplhanto highe values.

Also, on feature of tMe tests rvertM yS epitn t ah.gh31r asthe highe values of damnpingm appr,achinm 9,

that ere ebterl.[for m o d s w th e-l ti ely la rg e a m n~ t s o f in o ra c icec t w sh o u ld b e re a liz e d.

that these values o f daripicng are only rcprcvstctatite o h

mltd levels Of the tests.

It is gene rally niot puOs sitl,- tof traoe anlthe to6x r po a e M s

VaIucs wilI runfilnce:

t tIhl" hiher anmrplitud-:;

r LIrth i qo.

mi 1tiun ;

such valuis of damping are hest obtained from thw analysis of miasurd carthquakc rernnre.

The prirrntI.:

usod techiqs (if r"slrit testing arc <apal ol dlfining in sic'nifi. ant detail ti dforniation

,f a st ructurc as it vibrates in its resonant nidi

s.

To dalte, th most del;iled resi lts h;ve been presented by FoRvlh, it al. [1, Z

who rneasurcd three coiplontnrts if notion at each of ;0 linIts, for each of six levils if Millikan Library.

With these iirienwirnts h-was alt to nwniasure the ouit-of-plane and in-plane drnrmi oniis of lbn flour slabs, the niulurc of the interaction between shear-walls and the fr-aIne, and other details of structural response.

Th-amount if in-plane mition of loor slabs was also measured by.Steiphen, t al.

311 who noted that for structures in which the in-plane !tiffm;c s

if the flmor is comparable to

,Ir less than fti stiffness of Ii lateral lund resisting systeln, hlit-assumption if in-plani rigidity of floor slabs may b-invalid.

MFASUREMIENTS OF EARTIQUAKI;

RESPONSE

The instrunn'ntal rrcoirds if the responsc of building; to string ground shiking con-almiost cxi lu!ively fromt tli San Fclrnandlo narth tiake ll, 30 O er fifty multistory buildings provided sets of acclerograrms frnm tihe arthquakc, and many of thes structures were of reinforced

ipoirte costruction.

The records included sone buildings shaken strongly enough to receive strinctural damage, althounqh none of the few concrete buildings ihat collapsed or were ir reparably darnaged wvere instrumented.

[he measured levels of maximum acceleration varied from a few percent of gravily to over 10'>. g, with niany buildings receiving shaking of the order if J0 0

g.

The maximurn driflection of the structures vari ed, o ou. rs, bht intirstory displacement. s of 10 to 20 rnm wer- ;rchievid by manry instruinited structuris.

Selected samples of aicilerograms and dcrivved displacnti records obltaiel in reinforced concrete structures chnring the San Fernandr earthquake are shown in Figures 6, 7 and 8 L3 1, 34.

One of the must not(rd results from the ibuilding records obtained during the San Fernand" earthqualte was. thi clear evidroer it longhening of the natural periods of vibratinn.

Ihis increase in period tiok two forrs.

First, there was a general increase in piriids shown in earth quake respons-over those fomnd from anIient. or forced vibratien tests.

Iis had been anticipatcd from the behavior of struturis during resonance tests, but the magnitudes cf tie changes, some as great as 5071 or more, were larger than mist enginrers anrtiipated.

Secondly, in soime records it is clear that theri is a lengthening of the natural period during tie earthquake resposi itself.

This behavior can te secn upn

<areful examination of the responses of the lidiray Inn ard Mtillikan Library, shown in Figures 6 and 8.

It is thought that. this decrease in stiffne ss during the earthquake is the result of a combinatior of cracking, non-structural damage and, in snme cases, minor structural danage.

Tbis conclusion is supported by the tendency of tie periords shown dou iring earthquake resprnse to be in agreement with those calculte-d consitering only the structural resistance of lite building..TIe rathlnr large change's in period that a st ructure can show under the fort es of wind, resonance

ft*-siIig ;tnI( different ls of a rtIIqiake eXtitation point to thev nec essity of 'onsi dering thI natit p riiods of individual buildings as temporal quantities associated w"it substantial degrees of uncertainty.

As mentioned previously, the increas in damping values with increasing aniplituuts of response tbsirved in resonance tests indicates that the damping <bserved in Bhe tests may be much lower than that shown in the earthquakv response of structures.

This fact was demon strated clearly by the analysus made of individual building responses to the San Pernando earthqunk

, W, 34-36],

Theme analyses showed that the buildings typically ishibited effective viscous damping values ranging Trom 5 to 10 percent or more, with the high.r values associated with the larger arnplitudes of response. This trend in the effective damping values exhibited by reinforced concrete buildings is seen also in the result shown in Figure 9 which is taken from a recent study by Hart and Vasuch-van [371.

Tii figure shows the relation between damping values and th livel of the undaruipd respon e spectrum of the accelero grari recorded at the base of the bilding.

rhe results show that the damping values dtveloped in the San Fnmand" earthquake ranged from 2 t) 12

, with a tendency for concrete structures to show larger values than steel buildings.

As a final note, it is emphasized that the concept..

of -quivalnt viscous daniping is a convenient way to describe what is, in fact, a very complex, poorly udirstood process by which buildings dissipate vncrgy.

The concept appears adequate for earthquake response up to levels associated with minor structural damage, but it is generally agreed that it is nout adequaLe for larger levels of response.

For larger response, in which significat dainage is expected, a more direct con sideration of the energy dissipation in the structure is recommended.

An examination of the analytical investigations of the earthquake response t

eleven instrurm te d builings, including six of reinforced ciociete, was rtade by Gates 1.35 1 in the same volumes where these studies ar presented 132 3. In addition to sonm1 of the items noted above, Gates makes soet important points applicable to reinforced concrete structures, which aq parapirased below.

1.

Modern analytical tiwihniqus can r.eproduce adequately the recorded earIthquke mtions of the bulings, and these same tichiques can be applied effectively in design.

2.

All of the buildings, including thos e of reinforced (toncrtc, expe'irienced forcu levis greater than the design values of thi

code, in soie cases the response eas large enough to cause significant. yielding and nonlinear response

3.

uilding displaicenitits ranged fron two to four times the values computed for the dsign forcs prescribed by tih code.

Thes large story drifts produced sig niuicant cracking of partitions in all te buildings.

Ti rvsponse if rinfir<

.,<onei rtIc bui ini s

durinL-Ih San IF'crna nd-o carth'IteiII antI I th I I I n i) onk Ii O Of I' IrIh([ IaIke reI sponlsc to. that tindeIr code fmr( Is make-s it cl-wr that lhe rueatiOn b we n

S se smsc l.-sign criteria for a iuilding a11 t1IW actual njinit y of 11 strutuire i.eeds to bt iiivistigatid.

Th r-suits if ooe rs-arch in progirss on this question at thu California Institute if Ichnology are showi in Fi curr 1).

'Th, fi gure is limitid to riniforced co rt-Ie building s and shows three quantities fir iach latiril (lirectlin Iof viiration if sev ral st ructitres.

Th-abscissa ofI the figure is thi pIerioi if vibratiun o

otbserved during the earthquake.

The ordint-;

ploitted ar tle base shear used in dh sign expresseid tn a pirntiiit;ic Of gravity, the base ihear experieiced during th earithiuake as delrmi ned from the dis placement of the bitilding in the fundaniital moodi., ;in the rnimun acceleration at the top of the building, given by th strong-rnation acceleromneter.

Bujilrlings which showed structural dantage are inelicntid by ticks..

The data in Figure 10 are too few o d-fine trends prieis.ly.

but there is c lea r-irl-nce that, on ave rag,-, reiif, rci-I cmnic ret st ruc hIres are capahl-of vitIstandin lib1;Le shea i-s itre' or more times the Ialues usedC-in.lesi 1i before stril. ittral danag-becimes significant.

It iir exprctr-d that the st ru.IiturI-s ouldi have withst ond suistanitially larger r-sponsi's withalt bhin in dangmr If collapse.

As mire data accimiites nii the ruspons-

-f buildintgs Ili string artlipuak.

motioii, plnts so. i as thesv sho l

help quanti(% thi

-gre of t onsIrvatina that is itplicit in modr-rn buildin celes ani design prcidr-i-s.

Tis knowle-dg is

'-ssential to a realistic deteririiation of scismic ha-.ard.

A major eartliqunke strongly shaking a lirg.

inmer of instrume!nted buildings has not yet occurred in lapan, bot ecords obt.ained on instru nened structures in Japan during noderate ground shaking indicate hat.

the ineasuired acceleration at lie bas, of

)io rieinforc.d concrie building Nwas less than that recorded on th ground surfac-ni-arby, wtereas that at the top of li(- buildinc

.as two to four tincs larger than that rccordcd at the bas L171.

A tnidency for longer iodal piriorls and larger damping to be exhibit.d by buildings shaken by groind motion rather than dynaicii exciter is also riported [.161, as is the fact that ill earth quakes the miaxintmii acceleration dos not rii-c-ssarily Occir at the top floor.

The reliability if r-spoiis predictions tas-I toi carefilly selected mathematical models was cionfirmtel by sturlis of inasiiran nts-mad in two different iarthquakes L1".

A similarly satisfactory result has also b(eon repirted from Yugoslavia [391 DISC LSSION This bri-f sianiniry of ixicriniti tal r-silts for rcinforcid ioncrete structures rivials a numbir if ar-as wher-risi-arch

,ii fIll-sceil structures is needid tli clarify li-ability of suc.h.

uildings to witlistand strOng eartfinquake motio.ns.

Foremost among ttis-is ti.i fact that ti, reisponsi of.a building subiecti-d i extrenily strong shaking has not yet been rneast red.

Thus. '.

are lacking tli full-scale virification that odn-Iern tmi-thods Of analysis and design ari l-ading to structur,-s. which pi-rforn as int eicdeil under

sever.

loading.

Although ainy buiildinigs a riV 1on.

instirnentid

toi givc useful data if subjected III strong shaking, the.

well-known probl-ms if instrumenting for eartiquak-ri-spins-hav.

so far precluded the detailed instrumentation if any single building.

It i'ay

he' possibl, ho.

ver, in w

,ar future to do this, and recover from the earthquake reslons iNforiiation concerning the mechanics of plastic hinge fornalion, the beha ior f meismic joints. the progress of dcterio ration, thu lo(d redistribition( during the prouression of damage, and oth-r nei ded data.

Another related topih: concerns the amplitude dependent charac turistica of reinforced concret structures in the range of response up to and including minor at ructural d;miagi.

This response can be decribd for many purp'ses by li ni niheniatical models, in parti cular such mindels are usiefl in analyses fir design.

It is important in using such models, however, to employ realistic values of natural periods and damping.

The present data is sufficient to establish general trends of these quantities with amplitude, but more data is required to determine he most apprnpriate values to use for a given structure.

R.inforced concret e shear-wall buildings. reinforced masonry buildings, and other stro ores such as in-filied frames which respond to ground motion as shar-wall strutur s show a much larger degree of soil-structur inlteraction tIhan has hein obserived in steel-frame or concrete-framue buildines.

ThO data arc too few to draw definite conclusiiis, but it does appear fairly rlar that when such structures are found(u oni alluviiumi, ti aiount if soil-structure iiteraction can be larje enough to influen e si!gniificantly the earthquake response.

Inter action of this amount should b ionsidenrd in design, as the periods, deflc'tions, and drifts can le affected sustantially.

The amount of soil-stroutui re interaction and. tHe details of the rotational-and transla tional compliance s of the foundati' n are rconiniexided as ceNtral parts of future tests of reinforced uoncrti buildiigs.

A CiKNO0WLEDG);MENTS The. ailim rs wish to

'xpriss their appreciation to the National Sc i inc i Foundation for financial sipport under Grant No. ENV\\74-19135 AO].

The effort of Albert Tin, who pcrrd suroe of the calculations reported above, is also ackniwledgeid Any pinions, findings, and con cluions or rinnunendatins erxprese in iWs paper are those of cie authors and do not nvcessarily rilect the views pf re National Science Foundation, 10

9~~ ~

I t.

RINU Er's

1.

Ifudso,~

" Ro'oan lsiinI!

of Fill *~c.Ll-Struchtirs.

Jurnal of dici Enuvinuuring MliatiLS 1)ivlimi

AMYI, Wol 90, n".

EX13, Join

1941, pp.

1-19.

Of B uiri(ic!,, I lulIl. Scisil. So AT inr.

,vol.

5.100.,

Dc(

'Y)4,(1 pp, 1743-1710.

3.

0 rawfr'i.. P~. asnd

WNardu, If. S..

"Win tn uwood Vibrat ion s and B~uilding~ Nlid:r

". Bull. Sci sim.

Soc. Ame r.. vol. 56(4), Aug.

1 96, PP. 793-81t 1.

iAnalvss

-4 NHbHHl'"" library fitri Aridnol Vibration,"

1:arttr Science t a Hyp.i,

11l ym' c(roiiiany; hub.

I1968.

5.

Ghvrry, S. an't Di.if U. A.,

"D(tcrmiiiain if fio( Dlynaic Prupertiv:i'

-( a uv Strrinturc from Ambient VibratiOns,'

Structural R-stcml (upod.

U. MG.C.. Vanwov~r Supt.

176.

0. TaQN Ihu..u.

M., iKhan, F.

and~ Snanlait, Rt. IL., -AmIen Itesponsr iAoal ys of Sotin all Structurcs, '

P noc.

ASCIK. %'ol. 101, no STI, Jan.

1975, pp. 49-05.

7.

Ward, It.

S. and RAuiur,.1. NI.,

EaxpvrimoiiI Dciotriinatin of Structure and V~moldition Pa taiotors using: Wind lttd Vibration.,'

Proc. Inst. Civil Engra., %,,.

53. Svpt. l')7,-, pp. 30';-3-'_'

.9 Uurouil 1).

E..,

Dynonrit I.sts Of Full Stilv trcor,'Erh (updated in irocn digs Of ASCEI/EMD Spui4lt

(:ofi'ri'ccit Dynamic R spun so ol St ructouvs U. G. L. A.

,1176).

9.Shcpir:. f.. and Runy, A.

N4., 'Sonow ApI~tr~

h-Siil Ann p Iiluch(I' Dynan Ihit T1U ti IIg of MuIItltist ory I, IlIdioIIgs, "St rain11, volI.

10(.

[rut-ran, S. A.,

GIn, C,

K. an to (zjrmut.i Ri.

N1.. Dynamic Rc spouse-,hia rac t.,i ati s of ui ifo rc od Concrt t-Stuc ti ro s.

P'roc.

if ASCEI/ EM I SpccialIty Confcrno nc o on D ynammi c Ru ~sponso (i

St ruc ture s, U. C. L. A.

1976.

Il1. Jezuiinrns, P. C.

, Eit.,

IEginuu i g Fcaturus of thuc San Vcrnando Eariticlako., Vutt 9, 1971,-

La rATtqkv Engiir-ng itisun Li Labor-atory, Ruprt Nw. EIKIL 76t01, Calfornia Instiuto Of Technology, Join 1971.

IZ. Itujatt, C.

arlt

iiaulav.

If.,

lForcuit Vit~rattoi losts of a Tb ru-Stury Hkinbircud Cotc roc Fraic and Slit-cr-Wall.i idi ng in Tadizhik S. S.K.,"

P roc.

i A SCE/EMI)

SPLH Gulty onormwc oin Dynamic tiesponst. if St rtclu rug, U. C. L.A.

1970.

it

it r! I'i it

. 11.,i~

it 0i~ 'If

I Mitlti-Story B3oiliotQ EaV-rth quait' i III-( rim-, iR -: ;c;t rcli Laborat-'r y, California Institute (i Techni'l'iv, Pa sadtii.(Cali fitriiia, 19?67.

1 -.

1-oititt 1 ). A.

,'A

-Stuidy If thri Vibirational Characteristics of Two Molt st 'rNy bIiliii ng a ' EII, L Rport No. 76-01, Ea rthquake Lot,' ite ri ng Re s-a rch Laboratory, California Institute of. Techinology, P asad,-na. California, l')7(,

15.

lill-rsoil. 11. 1.,

I\\ -t Irnt al (i-vicw of Pir'ent Strongt Motion Accch1-rqograihs,"

lr-ii.

Iifib Winrd (Xonfi'r-I'rwe on Earthiquake!

Eogin tiring. pp 10-(,- 104.Ii. I'Rm,-,

19)73.

16.

OhI ai, T.. A da (iti, N..

U ( It i yat itsia, S..

N iwa, M. a nd Takalia si, K.,

"IUlts o f Vi brat ito I

on Tall.Itiring s~ and Their Earthquakc Ile spons-," ' Pr' i.

Sixthi Wo'rld Confi rent.* ott Ea rthquake Enginee ring, (9,It, Ne-w Delti,

I'977.

17.

Osawa.

Y., Nftrvakatii

, M..- Miuiaooi, T. andu Isitida, K.,' "Observa tion-il Studijia 'ilie w t rtltrqnak,- Rr-spo,wi~

of Butildinegs inl Japan,"

Prot.. Inst. Sytiptstitim

'in Iartliqral,-

St rurttrral Engintce ring, pp. 1123-11-19, St.

Linuis, Missouri, 1970.

18'-.

1-awasutri, II. arnd lKairai, K.,' Smal~l Amrplitudre Vibration of Actual Pit1ildiig a., P-roce - if the WVo rid Conf,' rent r in Earthquake Engineer

iorq, 13-rkeL'I-y, California, 19fpp.

7 1-1 to 7 11.1.

1').

Sin p-lin-rd,.It.

"'A C ornpa r i strif If Ca ltirlat rd a nd M ca sircd Pe rioads of a Tail B~nuiing,

Nt.-v Zealatnr Engiovering, vol. 22, no. 9,

1967,

'0.Sh..

.rd It.,.FTht Dyntarmic Analysis o'f at, A partnment Building,"

Bll1. - Stisni. Sotc. Art-r., viii. (MO. no.

1, 1'906, pp. 13-36.

11.

i.ay. A. M. atnd Slicii-rii. It.,Stcafiy State' Vibration Tests of a Six St'rr' I-inftorc(ii ('ni ret' Buiildling, -

[Bull.

N. Z,. Sor. for

/--A Eartbtlitaki Enriiuriiiit. vii. 4I rio.

I, 1?71. pp. 4I-107.

2.itcay, A. M.

aidc Sh,-pin-rI.

"D,'lyirarit:c Chiarsctcri stic a-of Th rce Aflia'.'-rtt iti-irnfitrC,'eI LIIInIC ni' liiliiriS,

' ProC.

Inst. Civil Lngrs.

vol. 50,. 1971, pp. 25--47.

'3. Sli-pbtrd, R, arid Ros, I). A., Intlastic Chtaracteristics if a R,,i rforcc t(:otnc rt'te-Frano," I rit.

SouthI Pacific Cnnfe rernce on La rthcquaki: Engi nrc ri ne.

N. Z.. Mal. Soc. for Earthiquake Engineering, 1975.

2.1.

Cai r rit. r, 1). S., FEd.

, La Irlak,- In.- t iit liins in tie X,stern Uritid SHtehs 1',31 -19614.

P'tblikatiion '1,

.. Deritntof Cornterkt-. Coasat and G eodietic Sitrvey.

25.

AX~m rc, J. L., a nid Ilt i,

('.

W.-, 'A Dynamic Test of a Four Story iteirifirree Cncri-ti-BiIldinig, i1ti. Sti si. Soc. Anter., vol.

.143,

1953, pp. 7-16.

IEiglc-sIby

[tic',

cd Qm r, B'c1ilding,.

" ~tc~ci I

Enicr'rinig.

R-po' Ont Gf. i-H, ttoivcrsity aC ';c~irnia, Los Angt-l's'-916.

7.

icilslin, N1.

Jt,:io'M; of of c:'nf'i-'i y o Lmil( 1odT 30*

Knc,

3.

11.

in Ku-I a 1)

1.,~ V'l'Vihr-jc. im

.'.'\\

S '.N[)riillc'nf Stuyrccl Psisccc W) lcra NicnSw Ga i nfl

.. !y (:,-Sit'c rtcrc Icctcraio."

Bullrc.

ccl iii S-.

'\\Anw.

(:ccIf'i 58'c 1), cin.~ctcc~k* Icgicc;ic 8 1-1.

"I. S tch I). A.

F:ci c~.

I, 8ulcuw N. D.1 and o acia c'I.. lti

'dyrngaFricd

'1 itjs', an Ili Stcry Kasiccyr Iccc(:,bcit.

'Er

(:lifcciii,

" 'rkl, Ii-

. S

'l1

.Il a tq a

3L. Mu rh.r~.

At!,, Arr i'ci i

ll h'cigcaior..i P)an Ici). 206-

'c, tc;,'m Lil rt;,ua o.F,'

I oa,.y

9.

1.I V. S Idwada -~in of. 1 nm:.o c Ai Extrncni Stu y f (r-nI1)

(,r ani Ciic d~ by'il turf. lutuc cic aic i on, Prpc.~

of ilt N

llsca CoIf'rit i

1:rh u

k r

ig Lrjruakc

EuinI. Rcpccrtc Crntcr 75 or No.~ 75-'hr 10,' i;OgincciO of Californi, tHIcrtccry.

Gaicrc975. ~

jct' c

ccccgy,17 31Z.

Murphycc~, I... C., S(cifit io C;c.rii iiysr.,

Sallrnc ra ic

33.

Foth

1.

A.

Iloisi-rc' Go I

and' Jcnings, P, ;cr CMtjc "D lli ncc VcI~spnca ry 9 ix 191,u.lmt S 1iT6iTFTicgTh

drng, t

Sa n Occanch an Earnoh'ric A'RLxcs Rrin.

'.7-0, Eat973.

Ingnurn J6.

h art,(.C

, imb rsial,

1. "o,Insit..fTr itc h t,'1'1 ciin

34.

J p occfq ;

I oU i Uct, ad

!'cirjccH.j, NccniiCcc'auik~s

'y, :I' IISC~c 'If hc Nillk Story~c Rccnfcrclcsd on Erthcjc

k.

Sr lc cc,"ic111..

pp.-ia (if.10 - 4t'c, Rc I')73.

ig n

ot D nvL I

o 94, p

N W

35 W -,

W.

E_

-Iih-,.sv Pm ld,, s wih tr ng M,ti n

li t,1113rl

1 ~ii ral'(,.11Urad)

37. 11art.

G. C. and V.,: -

evan, R.,

Earthcuake Desi n of I'uildin S:

Damping,"

Proc. ASCI, vol. 101, no. STI, Jan. 1975, pp. 11-30.

38. Muto, K.,

Tangawa, T.,

Niwa,M. and Shimizu, 11.,

"Simulation Analysis of a High Rise Reinforced Concrete Building in Two Different Earthquakhs," Proc. of the Sixth World Conference on Earthquake Engineering, (3),

pp. 85-90, New Delhi, 1977.

39.

I.'trovski, J., Jurokovski, D., anl Nauniovski, N.,

"Evaluation of Math-matical Models f Structures fron Full-Scale Forced Vibration SIndics and Record, f Moderate Earthquakes," Proc. of the Sixth World Conference on Earthquake Engineering, (3),

p. 422, New Delhi, 1977.

141

, 1s rrn~as c, e

" ode 270cps)I I

Rccf Md H 2

6th Floor Mid H 3 2od Floor M d H 4 Ground Floor Md

2) v.

25ff.lb twenric a

weight moment 4

CL 20teractiontof Ph cs.d

'I,/

I.

Chemsitry bu,(den s

( 4 62 ps) 4 0

05 0.3 02 01 PERIO ktcs.)

Figure 1.

Building Response vs. Period of Excitation.

Peaks Indicate Resonances as Noted [21, 22].

14 TE S T IOg O

EST 10 f 10 T TEST 10c

.8 j

15 10 d U

4

- TESTIlOd o6 TEST Oc

-[

<TEST tob z

F R 1 U I NC Y (C F )

Figure 2.

Steady-state Response of Millikan Librar Measured at Different Levels of Forced Vibration L13, 28].

DEFORMM VION OF SECTION THIROUGH CEN IfEMINE SHEAR WALL OF IK6N t.IRARY OF ELEVATOR CORE OF MILLIKAN LIORARY N

X E-W EXCITATION E-N 7.[7 Figure 3.

Fundamental Translational Modes of Millikan Library.

Including Vertical Motion and Soil-Structure Interaction [14, 29].

A B

C D

E 0'

0 0

I ST TRANSLATIONAL MODE f 2.78 C*PS 2ND TRANSL A rONAL MODE.

f 5.R2 CPS iSr TOPON ?.'l o

E 2.8. CPS HORIZONTAL MODE SHAPES AT iI TH FLOOR, E-W Figure 4.

Top View of Mode Shapes of an 11-Story Reinforced Masonry Building.

ML13311A239

Text

SUMMARY

RESPONSE

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