Experimental Study for Multiple Friction Pendulum System

Transcription

1 3 h old Confeence on Eahquae Engineeing Vancouve, B.C., Canada Augus -6, 4 Pape No. 669 Expeimenal Sudy fo Muliple icion Pendulum Sysem C. S. sai, su-cheng Chiang, Bo-Jen Chen 3 SUMMARY he Muliple icion Pendulum MPS which is a ind of base isolaion sysems has been developed in his sudy o povide as a means fo poecing sucues fom eahquae damage. he doubled concave sliding inefaces, aiculaed slide and advanced eflon composie ae vey diffeen fom he adiional PS device. he developmen of he MPS isolao is aimed a impoving he duabiliy and upgading he eahquae-poof capabiliy of he adiional PS isolao unde nea-souce exciaions and song gound moions wih long pedominan peiods. his sudy mainly consiss of he componen ess of he advanced eflon composie, he pooype MPS isolao and he shaing able es of a full-scale sucue wih MPS isolaos. he expeimenal esuls of componen es show ha he new lubican maeial possesses low ficion coefficiens and excellen duabiliy unde high compessive loading, and ove 4 cyclic loadings wihou any sign of deeioaion. uhemoe, he MPS isolao has been equipped beneah each column of he hee-soy sucue a he Naional Cene fo Reseach on Eahquae Engineeing o demonsae is seismic esisance capabiliy. he expeimenal esuls fom he shaing able ess of he 94 El Ceno, 995 Kobe, 999 Chi-Chi and 33 Hua-Lien eahquaes show ha he poposed isolao can educe he undesiable seismic esponses of he sucue by lenghening he fundamenal peiod of he sucue duing eahquaes, and ha he MPS isolao povides povide he sucue wih excellen isolaion funcion unde he fa- and neasouce exciaions and song gound moions wih long pedominan peiods. om hese expeimenal obsevaions, i can be concluded ha he poposed MPS isolao is a poweful ool fo enhancing he seismic-esisibiliy of sucues. INRODUCION Base isolaion is a pomig echnique fo conolling he seismic esponse of sucues duing eahquae moions. Among he base isolaion devices, he PS isolao poposed by V. A. Zayas [] has been poven as an effecive ool fo isolaing seismic ansmied enegy hough compehensive expeimenal and numeical sudies [-7]. Howeve, he expeimenal Pofesso, Depamen of Civil Engineeing, eng Chia Univesiy, 47 aichung, aiwan, R. O. C. Ph. D. Candidae, Gaduae Insiue of Civil and Hydaulic Engineeing, eng Chia Univesiy, 47 aichung, aiwan, R. O. C. 3 Assisan Reseach ellow, Depamen of Reseach and Developmen, Eahquae Poof Sysem, Inc, aichung,aiwan, R. O. C.

2 effos in hose sudies have meely focused on he effeciveness of he scaled PS devices unde eahquae gound moions away fom acive fauls. In ecen yeas, hee have been significan sudies on he efficiency of he base isolao as subjeced o nea-faul gound moions [8]. I is suggesed ha he eahquae wih long pedominan peiods always give he base-isolaed sucue a significan impac. In view of his, an advanced isolao called he Muliple icion Pendulum Sysem MPS has been poposed in his sudy [9, ]. As shown in ig., he MPS consiss of wo spheical concave sufaces and a special aiculaed slide which can be anohe sliding suface. Based on his special design, he displacemen capaciy is wice of he PS isolao wih a gle sliding suface. Moeove, he fundamenal fequency is lowe han ha of he PS due o he seies connecion of he doubled sliding sufaces. Hence, he poposed device can be given as a moe effecive ool o educe he seismic esponse of sucues even subjeced o he eahquaes wih long pedominan peiods. he conens of his sudy ae mainly gouped ino fou pas which ae: i componen ess fo he advanced eflon composie, ii componen ess fo a full-scale MPS isolao, iii shaing able ess fo a full scale seel sucue wih MPS isolaos, and [iv] numeical analyses by ug he mahemaical model poposed in his sudy. he esuls fom componen ess and shaing able ess show ha he poposed device is a pomig one o upgade he seismic esisibiliy of he sucues. uhemoe, he numeical sudy show ha he fomulaions pesened in his sudy can well pedic he behavio of he sucue isolaed wih MPS isolaos. COMPONEN ESS OR ADVANCED ELON COMPOSIE AND ULL SCALE MPS ISOLAOR he duabiliy of he eflon composie, which is an impoan ey o decide whehe he beaing is capable of susaining high compessive sess and housands of cyclic loadings wihou any deeioaion. he mechanical behavio of he eflon composie is vey complicae and some esuls on expeimens and heoies has been poposed by Moha e al. [] and Consaninou e al. []. In his sudy, an advanced eflon composie wih new fomula has been developed as he lubican maeial on he sliding sufaces of he MPS base isolao. As shown in ig., he seel plaes wee coaed wih he advanced eflon composie and he high densiy chome especively o ub agains each ohe. Duing he ess, he axially compessive sesses impog a he ineface ae 4.34Mpa, 55.33Mpa, 68.95Mpa, 8.7Mpa and Mpa, especively. he ampliude of he cyclic hoizonal displacemen is se o be mm, and he ess wee pefomed a he fequencies of.hz,.5hz,.hz,.hz,.4hz,.6hz,.8hz, Hz,.Hz,.4Hz,.6Hz,.8Hz and Hz, especively. he shape of he displacemen cycles duing he ess ae amp waves. ig. 3 shows he ecoded ficion coefficien of he advanced eflon composie unde an axial sess of 4.34Mpa and hoizonally evesal loadings. I is evidenly demonsaed fom he figue ha he coefficiens of ficion ae almos idenical unde he same sliding velociy. heefoe, he duabiliy of he poposed maeial can be guaaneed houghou hese ess. he ficion coefficiens of he eflon composie unde diffeen axial sesses ae given in ig. 4. I is evidenly shown fom he figue ha he mechanical behavio of he advanced eflon composie is vey simila o ha poposed by Moha e al. []. he ficion coefficien appoaches a consan value while he sliding velociy is highe han a ceain value, howeve, he ficion coefficien gadually deceases as inceag he axially compessive sess. In ode o assess he feasibiliy of he MPS isolao fo he pacical use and is behavio unde an axial loads in he pacical siuaion, full scale MPS base isolao ess wee conduced unde an axial load of 9ons and hoizonally cyclic loadings in his sudy. ig. 5 shows he dimensions of he base isolao and he ouline of he biaxial machine. he adius of cuvaue of he polished-seel sliding ineface is.36m, and he diamee of he aiculaed slide is 6mm. Duing he ess, he hoizonal sliding velociy had been se o be.43cm/sec. In he expeimenal sudies, 8 cycles of evesal

3 loadings wee caied ou o invesigae he behavio of he MPS base isolao. he es esuls given in ig. 6 show ha he behavio of he MPS base isolao duing he 8 cycles is vey sable. uhemoe, hee is no any sign of degadaion of he eflon composie line coaed in he sliding ineface fom visual inspecion. he shea foce of he h cycle is 9.5% of ha of he s cycle due o he consideable enegy accumulaed in he sliding ineface. he hoizonal siffness measued 8.87 ons/m fom hese ess is vey close o he heoeical value of.5 ons/m, hence, he accuacy of he manufacue of he poposed device can be conolled wihin a desiable ange. SHAKING ABLE ESS O A SEEL SRUCURE IH MPS ISOLAORS In ode o evaluae he effeciveness of he MPS base isolao on seismic miigaion, he shaing able ess of a full scale seel sucue isolaed wih he poposed isolaos wee conduced a he Naional Cene fo Reseach on Eahquae Engineeing in aiwan. ypical song gound moions of he 94 El Ceno eahquae which is usually adoped in shaing able ess have been given as inpus duing he ess. Addiionally, he nea faul and sof-soil-deposi sie eahquaes which conain long pedominan peiods have also been imposed on he base isolaed sucue o invesigae he effeciveness of he poposed device. As shown in ig. 7, he hee-soy sucue is 9m in heigh and he oal weigh of he sucue is abou 4ons. he popeies of columns and gides of he seel sucue ae H 8 and H 5 6 9, especively. In ode o incease he igidiy of he supesucue, diagonal seel bacings L 3 had been insalled on he sucue duing he ess. he MPS isolao adoped in he shaing able ess has doubled concave sufaces of.36m in adius of cuvaue, and he diamee of he aiculaed slide is 7.8cm. he compaison of he ime hisoy of he oof acceleaion esponse beween he bae and base-isolaed sucues unde he uniaxial El Ceno eahquae NS componen of.47g in PGA is shown in ig. 8. I is shown fom he able and he figue ha significan educions of seismic esponses can be achieved by he insallaion of he poposed devices. Even duing he sevee eahquae of.47g in PGA, he maximum oof acceleaion is meely.396g. Hence, he poposed device can be egaded as a poweful ool fo upgading he seismic esisibiliy unde eahquaes. he aveage hyseesis loop esponse of he MPS base isolaion sysem unde he El Ceno eahquae of.47g in PGA is also given in ig. 8. he ficion damping povided by he sliding ineface can help o dissipae he accumulaed seismic enegy, heefoe, he maximum sliding displacemen is only 3.6cm even subjeced o 3% El Ceno eahquae. he compaisons of he oof acceleaion and he hyseesis loop esponse of he MPS isolaed sucue unde he Kobe eahquae ae given in ig. 9. Significan educion in acceleaion esponse and highly nonlinea behavio of he poposed isolao can be obseved in his figue. Duing he shaing able ess, he sevee eahquae of he CU84 Chi-Chi eahquae of.g in PGA had also been adoped. I is shown fom ig. ha he acceleaion esponse of he supesucue can be lessened by ug he poposed isolaos. Moeove, he efficiency of ficion damping on dissipaing he seismically accumulaed enegy can also be shown fom he figue. In ecen yeas, some eseaches suspec he efficiency of he base isolaion sysems unde gound moions wih long pedominan peiods. Song gound moions measued a he aipei ba, which conain long pedominan peiods in he ange of.~.6sec, have been adoped in he shaing able ess. In his sudy, he ecoded PGA of.76g,.48g and.58g in NS, E and veical componens of he Hua-Lien eahquae AP98 was scaled up ove enfold of he oiginal o invesigae he behavio of a base-isolaed sucue locaed a he aipei ba unde sevee eahquaes. he expeimenal esuls of he oof acceleaion and aveage hyseesis loop ae given in ig.. Due o he doubled concave sufaces and he lubican maeial, he poposed isolao can easily shif he fundamenal peiod of he sucue ino he ange of 4~5sec wih sufficien damping. he maximum floo acceleaions unde sevee eahquaes ae mainly in he ange of.5~.3g, heefoe, he poposed isolao can be adoped as a good ool in miigaing seismic esponses of a sucue locaed a a sof-soil-

4 deposi sie. he expeimenal esuls afoemenioned demonsae ha he MPS base isolao can enhance he seismic esisibiliy of a sucue subjeced o an eahquae wih long pedominan peiods. INIE ELEMEN ORMULAIONS OR MPS BASE ISOLAOR In ode o simulae he nonlinea behavio of he MPS accuaely, as shown in ig., a wo-node finie elemen has been poposed in his sudy. As shown in ig. 3, he elemen includes a nodal poin a he cene of he lowe concave sliding ineface nodal poin and anohe nodal poin a he cene of he uppe concave sliding ineface nodal poin. As shown in ig. 3, he equilibium equaion of he lowe concave sliding ineface in he veical diecion can be given as: P he equilibium equaion in he hoizonal diecion can be expessed as: P whee is he veical loading esuling fom he supesucue; P is he conac foce nomal o he sliding suface; is he hoizonal foce impog on he lowe concave sliding ineface; is he angen componen of he ficion foce in he plane. Reaangemen of Eqs. and gives: an D 3 whee D R 4 5 R in which R is he adius of he lowe concave sliding ineface. Similaly, as shown in ig. 3, he equilibium equaion of he uppe concave suface in he veical and hoizonal diecions can be shown as: and he soluion o Eqs. 6 and 7 is: P 6 P 7 an D 8 in which D R 9 R whee R is he adius of he uppe concave sliding suface. Accoding o Eqs. 3 and 8, one can obain he hoizonal sliding displacemens fo he lowe and uppe concave sliding sufaces: D and

5 D he oal sliding displacemen, D, is he summaion of he sliding displacemens of he uppe and lowe concave sufaces, and can be expessed as: D D D 3 Because of he equilibium of shea foces impog on he lowe and uppe concave sliding sufaces mus be held, accodingly, ug, Eq. 3 can be ewien as: D 4 he foces acing in he plane have been esablished. Howeve, he foces in he moving coodinae sysem should be ansfomed ino he fixed local coodinae sysem, ξ, ς and η. As shown in ig. 4, he angle beween he veical plane and he ς -diecion of he local coodinae sysem can be expessed as: u 3 an 5 u he oal sliding displacemen of he advanced PS in he local coodinae sysem can be given as: D u u3 6 whee u and u epesen he elaive displacemen beween nodal poins and in he ς and η 3 diecions, especively. Bacsubsiuion of Eq. 6 ino Eq. 4 leads o: [ u u3 ] 7 By ug he coodinae ansfomaion, he hoizonal foces acing in he moving coodinae sysem in he plane can be ansfomed ino he local coodinae sysem: [ u u ] 3 [ u u ]

6 whee and 3 epesen he hoizonal foces acing in he ς and η diecions, especively. Because he MPS base isolao is highly igid in is veical diecion, heefoe, he infinie veical siffness has been adoped in numeical analysis. u E whee u is he elaive displacemen beween nodal poins and in he veical diecion, E is he paamee o descibe high veical siffness of he MPS base isolao. Reaangemen of Eqs. 8, 9 and gives: 3 3 u u u E By viue of he pinciple of viual wo, he foces acing in he - plane can be ansfomed ino he global coodinae sysem. 3 E BU B B B A B BU K B Howeve, he ficion foce nomal o he - plane as shown in ig. 5 should also be aen ino accoun[-4]: G BU K B B S 3 whee

7 S Q Q 4 Q Q he compaisons of he oof acceleaion esponse beween he expeimenal and numeical esuls unde he El Ceno eahquae ae given in igs. 6 and 7, especively. I is shown fom hese figues ha vey good pedicion can be achieved by ug he poposed mahemaical model. No only he oof acceleaion esponse can be pediced accuaely, bu also he highly nonlinea behavio of he MPS is calculaed wih good accuacy by ug he poposed heoy. he compaisons beween he acceleaion esponse and hyseesis loop of he MPS isolaed sucue unde he AP98 Hua-Lien Eahquae given in igs. 8 and 9 also demonsae he accuacy of he poposed fomulaions. CONCLUSIONS In his sudy, he shaing able and he full scale componen ess of a ecenly poposed isolao called he Muliple icion Pendulum Sysem have been conduced o invesigae is effeciveness and duabiliy. he esuls fom shaing able ess show ha he MPS isolao can miigae he acceleaion esponse in he ange of 7 o 9 pecen as compaed wih ha of he bae sucue unde diffeen ypes of gound moions. As he base isolaed sucue subjeced o gound moions wih long pedominan peiods, he poposed isolao also possesses an excellen eahquae-poof benefi wihou significan sliding displacemens. he componen es esuls of he eflon composie and he full scale MPS isolao eveal ha he poposed isolao coaed wih he new composie behaves vey sably duing evesal loadings. uhemoe, he mahemaical fomulaions pesened in his sudy can accuaely pedic he nonlinea behavio of he sucue isolaed wih MPS isolaos. heefoe, i can be concluded ha he poposed conceps in heoy and engineeing pacice can be egaded as poweful ools in designing and enhancing seismic esisibiliy of sucues locaed a vaious ypes of foundaions. REERENCES V. A. Zayas, S. S. Low and S. A. Mahin 987, he PS Eahquae Resig Sysem Expeimenal Repo, echnical Repo, UBC/EERC-87/. C. S. sai, Seismic behavio of buildings wih PS isolaos, Second Congess on Compuing in Civil Engineeing, ASCE, Alana, GA, pp C. S. sai, inie Elemen omulaions o icion Pendulum Seismic Isolaion Beaings, Inenaional Jounal o Numeical mehods In Engineeing, vol. 4, pp.9-49, C. S. sai,. C. Chiang, C. K. Cheng,. S. Cheng and C.. Chang An Impoved PS Isolao fo Seismic Miigaion on Seel Sucues, he ASME Pessue Vessels and Piping Confeence, Vancouve, Canada, Vol. 445-, Y. P. ang, L. L. Chung and. H. Liao, Seismic Response analysis of Bidges Isolaed wih icion Pendulum Behavio, Eahquae Engineeing and Sucual Dynamics, 998, Vol. 7 pp Jose L. Almazan, Juan C. De La Llea and Jose A. Inaudi, Modelling Aspecs of Sucues Isolaed wih he icional Pendulum Sysem, Eahquae Engineeing and Sucual Dynamics, 998, pp C. S. sai,. C. Chiang and B. J. Chen, inie Elemen omulaions and heoeical sudy fo Vaiable icion Pendulum Sysem, Engineeing Sucue, 3, Vlo. 5, pp

8 8R. S. Jangid and J. M. Kelly, Base Isolaion fo Nea-aul Moions, Eahquae Engineeing and Sucual Dynamics,, Vol. 3, pp C. S. sai,. C. Chiang and B. J. Chen 3 Seismic Behavio of MPS Isolaed Sucue Unde Nea-aul Eahquaes and Song Gound Moions wih Long Pedominan Peiods 3 ASME Pessue Vessels and Piping Confeence, Cleveland, Ohio, U. S. A., Vol. 466, Edied by J. C. Chen, C. S. sai,. C. Chiang and B. J. Chen 3 Shaing able ess of a ull Scale Seel Sucue Isolaed wih MPS 3 ASME Pessue Vessels and Piping Confeence, Cleveland, Ohio, U. S. A., Vol. 466, Edied by J. C. Chen, A. S. Moha,, M. C. Consaninou and A. M. Reinhon, eflon beaing in base isolaion. I, eg, Jounal of Sucual Engineeing, ASCE, Vol. 6, pp M. C. Consaninou, A. S. Moha, and A. M. Reinhon, eflon baeing in base isolaion. II, Modeling, Jounal of Sucue Engineeing, ASCE, Vol.6, pp , 99. 3C. S. sai Nonlinea Sess Analysis echniques-nsa, Depamen of Civil Engineeing, eng Chia Univesiy, aichung, aiwan, R. O.C.. Uppe Spheical Sliding Suface Lowe Spheical Sliding Suface Aiculaed Slide as a oaion hinge ig. Coss Secion of Muliple icion Pendulum Sysem icion Coefficien Sliding Velociy m/sec -3 cycles 3-6 cycles 6-39 cycles 39-5 cycles 5-65 cycels cycles 78-9 cycles 9-4 cycles ig. 3 icion Coefficien duing -4 Revesals eflon composie 5 ons hydaulic acuao chome icion Coefficien Sliding Velociy m/sec 5 ons dynamic hydaulic acuao ig. es Seup Specimen fo eflon sliding ineface 4.34Mpa 55.33Mpa 68.95Mpa 8.7Mpa Mpa ig. 4 Relaionship beween icion Coefficiens and Sliding Velociies unde Diffeen Axial Sess

9 ig. 7 A ull Scale Seel Sucue wih MPS Base Isolaos ig. 5 Specimen and es Seup fo Componen ess Shea oce on Shea oce on cycles 5ons Isolao Displacemen mm 5-54 cycles 5ons Isolao Displacemen mm Acceleaion g Base Shea oce f ime sec wihou MPS wih MPS Isolao Displacemen mm Shea oce on cycles 9ons Isolao Displacemen mm ig. 6 oce-displacemen Loop fo MPS Base Isolao duing Componen ess ig. 8 Roof Acceleaion Response and Aveage Hyseesis Loop of MPS Base Isolaion Sysem in Longiudinal Diecion duing Uni-axial El Ceno Eahquae NS Componen, PGA.47g

10 Acceleaion g ime sec Acceleaion g ime sec wihou MPS wih MPS wihou MPS wih MPS Base Shea oce on Isolao Displacemen mm Base Shea oce on Isolao Displacemen mm ig. 9 Roof Acceleaion Response and Aveage Hyseesis Loop of MPS Base Isolaion Sysem in Longiudinal Diecion duing Kobe Eahquae NS Componen of.858g in PGA Acceleaion g ime sec ig. Roof Acceleaion Response and Aveage Hyseesis Loop of MPS Base Isolaion Sysem in Longiudinal Diecion duing Hua-Lien Eahquae NS Componen, AP98 of.75g in PGA spheical sliding suface aiculaed slide D node node wihou MPS wih MPS D spheical sliding suface Base Shea oce on Isolao Displacemen mm ig. wo Node inie Elemen fo MPS R ig. Roof Acceleaion Response and Aveage Hyseesis Loop of MPS Base Isolaion Sysem in Longiudinal Diecion duing CU84 Chi- Chi Eahquae E Componen of.g in PGA lowe sliding suface u D node P slide

11 slide P node uppe sliding suface η ξ D Q node ς u 6 u 4 R node foces in he uppe suface u 5 ig. 3 oces a Lowe and Uppe Concave Sufaces uppe sliding suface η node u lowe sliding suface node D ς u 3 ig. 4 op View of Moion of MPS Isolao η u 3 node ξ u foces lowe Q in ς he suface u Acceleaion g ig. 5 oces Acing in - Plane 5 5 ime sec Expeimenal Resuls Numeical Resuls ig. 6 Compaison of Roof Acceleaion unde El Ceno Eahquae NS Componen PGA.47g Base Shea oce N Base Shea oce N Expeimenal Resuls Isolao Displacemen m Numeical Resuls Sliding Displacemen m ig. 7 Compaison of Hyseesis Loop unde El Ceno Eahquae NS Componen PGA.47g

12 Acceleaion g ime sec Expeimenal Resuls Numeical Resuls ig. 8 Compaison of Roof Acceleaion unde AP98 Hua-Lien Eahquae NS Componen, PGA.75g Base Shea oce on Expeimenal Resuls Isolao Displacemen m.5 Numeical Resuls Base Shea oce on Isolao Displacemen m ig. 9 Compaison of Hyseesis Loop unde AP98 Hua-Lien Eahquae NS Componen, PGA.75g