NEW INSTRUMENTATION FOR DAMAGE AND STRESS IN REINFORCED CONCRETE BEAM-COLUMN JOINT ABSTRACT

Transcription

1 Proeedngs of the 8 th U.S. Natonal onferene on Earthquake Engneerng rl 8-, 6, San Franso, alforna, US Paer No. 4 NEW INSUMENIN F MGE N SESS IN EINFE NEE EM-LUMN JIN Fumo Kusuhara and Htosh Shohara S In the nonlnear analss of strutural frames, eam-olumn jonts are usuall modeled as rgd nodes or lnearl elast shear anels. For PEE desgn, mrovement of the models are neessar to get more rese nformaton suh as stffness degradaton, strength degradaton and damage etent due to nelast l loadng n eam-olumn jonts. However, lttle test data n detal are avalale for ul for the valdaton of the models. Most of test data avalale for eam-olumn jonts are onl average shear stran and stor shear. Hene a new nstrumentaton for damage and stress are roosed for tests of eam-olumn jont sujeted to statall l load. hs aer desres the nstrumentaton method and dsusses the relalt and effetveness showng the eamle of data oserved n a test of eam-olumn jont. Introduton In the modelng of the resonse of uldng frames sujeted to earthquake loadng, eam-olumn jonts are usuall treated as rgd nodes or an elast shear anels wth the assumton that nelast atons are lmted to fleural eldng of eams or olumns. However, eermental results suggest that nelast aton of jonts s sometmes sgnfant for resonse of frame under earthquake loadng. o evaluate erformane of newl desgned or estng strutures, mrovement of the models s neessar to get more rese nformaton on erformane suh as stffness degradaton, strength degradaton and damage etent due to nelast l loadng n eam-olumn jont. eentl, several nonlnear modelng methods for renfored onrete eam-olumn jonts have een roosed (e.g. Lowes ). However, test data for valdaton of the models are lmted the reason that most of test data reorted are average shear stran of eam-olumn jont and stor shear onl. Hene omrehensve nstrumentaton nludng new nstrumentaton method s roosed. he nstrumentatons am to otan measurement nludng () omonents of deformaton n eam-olumn jont, nludng relatve dslaements of memer ends for three degrees-offreedom, or two translatonal dslaements and rotaton twelve dslaement transduers, () esearh ssoate, et. of rhteture, he Unv. of oko, 7-3- Hongo, unko-ku, oko , Jaan ssoate Professor, et. of rhteture, he Unv. of oko, 7-3- Hongo, unko-ku, oko , Jaan

2 omonents of hord rotatons n eams and olumns, and (3) stress n longtudnal ars sujet to l elasto-last stran seal arrangement usng longtudnal ars wth groove and stran gauges. hs aer desres the nstrumentaton method and dsusses the relalt and effetveness showng the eamle of data oserved n a test of eam-olumn jont. Instrumentaton for amage and Stress n eam-olumn Jonts Suassemlages Measurements n tests of eam-olumn jonts are varous. For the erformane ased earthquake engneerng (PEE), not onl the redton of stffness and strength, ut also the redton of damage dstruton n the strutural sstem s mortant. Hene, the test data on damage dstruton are artularl mortant to valdate models used for the PEE. o omare the analtal results wth measurements, t s also neessar that the test data are rovded wth lear defnton of damages and how the are measured. he most oular omonents n eam-olumn jont tests are () hord rotatons of eams and olumns, sometmes, dvded nto suomonents of fleural deformaton and shear deformaton, and () shear deformaton of jont shear anel. ut the are ovousl not suffent to desre omlete ehavor of eam-olumn jont. For eamle, measurement of the lateral eanson of jonts s alwas omtted whereas t s sgnfantl related to the aal fores arsng n the eams. So the authors attemted to measure most of mortant omonents as muh as ossle. o desre suh data, the deformaton needs to e roken nto suomonents wth lear defntons. he roosed suomonents of the deformaton the authors are, (a) hord rotatons of eams and olumns, () rgd-od-rotatons of eams, () dslaements of faes of eam-olumn jont anel, (d) relatve dslaements etween adjoned memer ends, (e) dslaements of memer ends, (f) rotaton of faes of the eam-olumn jont, and others. Hereafter eah defnton of the suomonents and the method to onvert from measured raw data to the suomonents s elaned wth the assumton that the raw data s otaned the measurement sstem shown n Fg., whh was atuall used n a rojet the authors. hord rotatons of eams and olumns he hord rotaton s the total defleton of eah eam or olumn. Eah of them s measured dslaement transduers on the measurng frame fed at the memer ends as shown n Fg. (a). he hord rotaton of left eam l s alulated Eq.. { L ( )} l d l () where, d : oserved dslaement at t of left eam, L : length of left eam, : deth of olumn, l : dstane etween the anhored ont of the measurng frame and eam end.

3 gd-od-rotatons of eams he rgd-od-rotatons are the relatve rotatons of eah eam end to the jont anel fae. It s measured dslaement transduers fed on the jont anel. he rgd-od-rotaton of left eam at olumn fae e l s alulated Eq.. ( d d ) a e l 5 6 () where, d : oserved dslaements at the end of left eam, a: dstane etween the two dslaement transduers. slaements of faes of eam-olumn jont anel In a lane frame analss, where eams and olumns are modeled lne elements, eah memer end has three degrees-of-freedom. So t s natural to defne deformatons of a jont anel twelve degrees-of-freedom elong to the four memer ends or the four faes of the jont anel as shown n Fg.. So the dslaements of the faes of a eam-olumn jont anel are defned twelve dslaements nludng two translatonal dslaements and a rotaton. However t s not feasle to measure the dslaements dretl wth seal sensors. So the measurement sstem shown n Fg. () was used. he followngs elan how the dslaements are derved from the measurements. elatve dslaements etween adjoned memer ends usng the measurement frames shown n Fg. (), two translatonal dslaements and a rotaton etween adjoned two omonents an e otaned from measurements the transduers,.e. relatve dslaements of left eam end (node n Fg. ) to lower olumn end (node n Fg. ) { } s alulated usng Eq. 3. { } ( d9 d ) d ( d d ) (3) 9 where, d : oserved dslaements, : dstane etween the two dslaement transduers. slaements of memer ends Wth four sets of relatve dslaements; left eam to lower olumn{ }, uer olumn to south eam{ }, rght eam to uer olumn{ } and lower olumn to north eam{ }, dslaements of twelve degrees-of-freedom of four-nodes at eah memer end (node to n Fg. ) are alulated as follows. Frst, n addton to the relatve dslaements of left eam end { }, the relatve dslaements of rght eam end { } and uer olumn end to lower olumn end { } are alulated Eq. 4.

4 { } [ ]{ } { } { } [ ]{ } { } [ ]{ } (4) where, [ ], [ ], [ ] : translaton matres of oordnate l, l : deth of olumn, l, l : dstanes etween the anhored onts of the measurng frames and eam or olumn ends,, : dstanes etween dslaement transduers and enter lnes of the memers. In the net ste, the dslaements of the enter of the jont anel whh s defned as the ross-ont of two lnes whh are onneted the enter lnes of eams and enter lnes of olumns resetvel s alulated Eq. 5. { } ( ) { } ( ) ( ) ( ) { } ( ) ( ) ( ) ( ) ( ) { } ( ) ( ) l u, (5) Fnall, the dslaements of memer ends related to the enter of the jont { } are alulated wth them. { } [ ]{ } { } { } ( ) { } (,,, ) (6) where, [ ] ( ) ( ) ( ) ( ) os sn sn os : translaton matr of oordnate { } ', { } ', { } ', { } ' : loaton of nodes.

5 eformaton of eam-olumn jont Wth the dslaements of memer ends whh are desred aove, jont shear deformaton and rgd-od-rotaton of four jont omonents shown n Fg. 3 s otaned as elow. he jont shear deformaton γ s alulated Eq. 7 and the rotatons of faes of eamolumn jont are alulated Eq. 8. γ ( ) ( ) (7) l r l u γ γ γ γ el (left) (rght) e r (lower) (uer) (8) d3 uer olumn uer olumn L d d d3 d4 L d left eam L l d5 d6 d4 a d7 d8 lower olumn L rght eam (a) for hord rotaton and end rotaton Fgure. Measurement sstem l d left eam l d d d9 d9 d8 lower olumn d5 d6 d7 l rgh ea dslaement transduer () for eformaton of jont ds s ds / L u uer olumn E F L s south eam es u γ s l n north eam n en lower olumn l Fgure. slaements of memer ends L Fgure 3. omonents of deformaton

6 Suomonents of stor drft he stor drft d s n Fg. 3 an e dvded nto deformatons due to the hord rotatons of eams and olumns, the rgd-od-rotatons of eams, the jont shear deformaton and the to rotatons of faes of eams-olumn jont. he suomonents of stor drft are alulated Eq.9. s se ss s u l, L el er L γ L L u l L, s s l l r L r L (9) where, s, s : stor drft angles due to hord rotatons of eams and olumns, se : stor drft angle due to rgd-od-rotatons of eams, ss : stor drft angle due to jont shear deformaton, s, s : stor drft angles due to rotatons of faes of eams-olumn jont. Strans and stresses n longtudnal ars o measure the stresses after eldng n the longtudnal ars s asall mossle. So o shae grooves were made on the two sdes of eah deformed ar (See Photo ) to get redued seton. he setonal area of the ars was redued along the length eet the loatons where stran gauges were laed, suh that renforng ars should not eld and reman n lnearl elast range adjaent to the stran gauges. he grooves were made along the longtudnal r of the deformed shae so that the grooves does not sgnfantl nfluene on the ond roert gauge(ε) gauge(ε) gauge(ε) gauge(ε) load, kn 3 d stran, mm/mm Photo. etal of grooved ar Fgure 4. ensle test of grooved ar

7 Setonal area of grooved seton was estmated tensle test wth ee shown n Fg. 4 on the ass of measured strans ε and ε as elow. n eamle of the load-stran relatons are shown n Fg.. η ε ε () where, η: reduton fator of setonal area, ε, ε : oserved strans n the test. est rogram Eamle of laton n a eam-olumn Jont est Fve half-sale renfored onrete eam-olumn suassemlages wth nether transverse eam nor sla were onstruted. he were loaded dslaement ontrol to falure under quas-stat l loadng wth nreasng amltudes smulatng sesm loadng ondton. he test rogram onssts of two seres of tests and eamles of oserved test data are shown for one of the fve semens. For the semen, amount of eam ars were hosen so that the jont shear demand s.9 tmes of the allowale for jont shear stress sefed n the IJ Gudelnes (IJ, 999), whle sum of moment aates of olumns are.3 tmes of that of the eam. he longtudnal ars n eam are assng through the jont. onstant aal load 6 kn was aled at the to of olumn durng whole the test. he test results of the semen he stor shear-stor drft relaton s shown n Fg. 5. Yeldng of eam ars and onrete rushng at the enter of the jont ourred. In the stor shear-stor drft relaton, no sudden degradaton of stor shear and no lear nhng loos due to dea of resstane of the jont were oserved. str shear / mamum stor shear stor drft angle, % Fgure 5. Stor shear-stor drft relaton

8 otatons of the jont faes served rotatons of uer and lower jont faes are shown n Fg. 6. he rotatons of uer and lower faes have dfferene after degradaton of stffness due to rakng n the jont. Usuall, the jont deformaton s alulated as the average shear stran from dagonal deformatons of the jont anel wth an assumton that the jont anel deforms unforml. he assumton ovousl nludes that the two oules of oosed faes of jont anel kee arallel. However, as Fg. 6 ndates, the anel n asmmetr ondton lke an eteror jont don t alwas deform to arallelogram orresondng to jont shear. elatve rotatons etween the jont faes In Fg. 7, relatve rotatons of uer and lower faes of the jont to south fae of the jont are lotted aganst to stor shear. he relatve rotatons are alulated as dfferenes etween rotatons of two adjoned faes, and the are nrement or derement of angles etween adjoned olumn and eam n ase of the end rotaton of memers an e negleted. s the ar of uer olumn and south eam s oenng n ostve loadng whle the ar of lower olumn and south eam s losng, FIg. 7 ndates the stffness n the ase of oenng s smaller than that of losng. It seems that the dfferene n stffness of oenng and losng ars of two memers auses asmmetr deformaton of the jont anel. stor shear / mamum stor shear south eam uer olumn u l lower olumn u l stor shear / mamum stor shear south eam π/us s π/ls uer olumn u l lower olumn uer fae to south fae (us) us u - s lower fae to south fae (ls) ls l - s rotaton, % Fgure 6. otatons of jont faes relatve rotaton, % Fgure 7. elatve rotatons of jont faes

9 Eansons of the jont served eansons of the jont n horzontal and vertal dretons are shown n Fg. 8. he horzontal eanson s alulated sutratng horzontal dslaement of south fae from that of north fae and the vertal eanson s alulated sutratng vertal dslaement of lower fae from that of uer fae. s Fg. 8 shows, the oth eansons nreased as the stor drft nreased and the eanson n horzontal dreton s eeted to lead the aal fore n eams and onstran fore n the jont n atual frames. Suomonents of stor drft served erentages of suomonents of stor drft angle are lotted n Fg. 9. In ase of ths semen, whh ndated fleural falure of eam, the stor drft due to the rgd-odrotaton of eam end radl nreased after eldng ourred at.% of stor drft. Furthermore the total of the suomonents was nearl equal to %, and t shows the defntons of the deformatons, the nstrumentaton method and the oserved test data usng the method have relalt..5 etenson of the jont, %..5. horzontal vertal erentage of deforamatons, % s s ss se s s stor drft, % Fgure 8. Etenson of the jont stor drft, % Fgure 9. Suomonents of stor drft Stress and stran n longtudnal ars n eamle of the strans of grooved ars of eams at olumn fae s lotted n Fg. (a). s the stran gauges were laed not-grooved seton, the stran were smaller than eld stran of,84µ. So the stress n the ar an e alulated onl wth multlng the oserved stran setonal area and Young s modulus. Fgure (a) shows that the stress n eam longtudnal ar was ket eld stress n large deformaton when the stress was n tenson, whle the stress was degraded n large deformaton when the stress was n omresson. he stress s lotted aganst the stran n ooste ar; west sde of the seton, n Fg. (). o am of measurng the strans of grooved setons, the grooved longtudnal ars on west sde dd not have non-redued seton to lae stran gauges. he stress-stran relatonsh n Fg. () seems to e smlar to tal relatonsh of suh ars and t shows stresses are ale to e measured wth ths method even after eldng of ars.

10 4 grooves stran gauges west stran, µ stress, MPa stor drft, % stran, µ south eam (a) stran-stor drft relaton () stress-stran relaton Fgure. Stress and stran measured on grooved ars east north eam onludng emarks New nstrumentatons for damage and stress for tests of renfored onrete eamolumn jont are develoed and used n atual tests. the nstrumentatons, () dslaements of twelve degrees-of-freedom elong to the four memer ends or the four faes of jont anel are suessfull measured, () some suomonents of deformaton n eam-olumn suassemlages nludng shear deformaton, rotaton orresondng to shear resstane and moment resstane n eam-olumn jont anel an e alulated searatel and (3) stresses n longtudnal renforement are ale to estmate wthout assumton of stress-stran relatonsh even after l loadng eond eam fleural eldng. In alaton to a test, the nstrumentaton s avalale to desre the jont deformaton n detal. knowledgment hs work was suorted a Grant-n-d for Sentf esearh (), No. 5369, from Jaan Soet for the Promoton of Sene (JSPS). eferenes Lowes, L. N. and. ltoontash,. Modelng the resonse of uldng eam-olumn Jont Sujeted to Earthquake Loadng, Proeedngs of 7NEE. rhtetural Insttute of Jaan, 997. esgn Gudelnes for Earthquake esstant enfored onrete uldngs ased on Inelast slaement onet (n Jaanese).