STRENGTH AND DEFORMATION CHARACTERISTICS OF SRC FRAMES HAVING WEAK AXIS BENDING COLUMNS

Transcription

1 13 th Wold Confeence on Eathquake Engineeing Vancouve, B.C., Canada Augut 1-6, 24 Pape o STREGTH AD DEFORATIO CHARACTERISTICS OF SRC FRAES HAVIG WEAK AXIS BEDIG COLS.Haegawa 1 T.Fujinaga 2, I.itani 3,.chida 4,.aihaa 5, Y.Ohtani 6 and T.Fukuumi 7 SARY An expeimental wok of SRC (Steel encaed Reinfoced Concete) fame with weak axi bending column wa pefomed. Total fou pecimen wee ubjected to contant vetical load and cyclic hoizontal load. A the expeimental paamete, the column length to ection depth atio and axial load atio wee elected. Fom the tet eult, the expeimental tength wa compaed with AIJ (Achitectual Intitute of Japan) deign fomula. In addition, the collape mechanim of pecimen, the hyteei chaacteitic and the defomation capacity wee invetigated and dicued. ITRODCTIO Steel-concete compoite tuctue ae being widely ued fo the building in Japan now. And by the development of the indutial technology in ecent yea, high-tength concete and teel ae ued a a building mateial. Theefoe, a column membe hould become lende. In AIJ deign fomula, the tength of lende teel-concete compoite column i calculated by upepoed method conideed additional bending moment. Howeve, the deign method take no conideation about defomation capacity. To evaluate the defomation capacity, it i neceay to etablih pope hyteei model fo teel-concete compoite membe. Fom the above, an expeimental tudy on SRC fame wa pefomed. The objective of the tudy ae to examine the AIJ deign fomula and to evaluate the defomation capability of the compoite column. 1 Gaduate tudent, Kobe niv., Japan. m-haegawa@juno.ocn.ne.jp 2 Reeach Aociate,.Eng., Kobe niv., Japan. ftaka@kobe-u.ac.jp 3 Pof., D.Eng., Kobe niv., Japan. imitani@kobe-u.ac.jp 4 Pof., D.Eng., Kobe niv., Japan. nuchida@kobe-u.ac.jp 5 Gaduate tudent, Kobe niv., Japan. neitatu@k9.o-net.ne.jp 6 Aoc. Pof., Ph.D., Kobe niv., Japan. ohtani@kobe-u.ac.jp 7 Aoc. Pof.,D.Eng., Kobe niv., Japan. fukuumi@kobe-u.ac.jp

2 TEST PROGRA 1. Specimen Total fou SRC pecimen wee teted to invetigate the elatic-platic behavio of compoite fame. The pecimen wee ubjected to contant vetical load and cyclic hoizontal load. The encaed H-ection column wa weak-axi bending. When pefoming the expeimental tudy, two paamete wee choen. One wa L/D (column Length to ection Depth atio) of 12and 6, the othe wa axial load atio (/BDF c =.1,.5 (: axial load, B: width of a column, F c : compeive tength of concete )). The dimenion and popetie, and the detail of pecimen ae hown in Table 1 and Fig.1. The cleaheight of column i 18mm o 9mm. The column, with quae ection of 15x15mm, ae einfoced with 4-D6 (D: defomed ba, SD295A) longitudinal ba and 4φ hoop (@1mm). The encaed H-ection deigned a H-1x5x5x7 i mild teel and i placed o a to be ubjected to weak axi bending. The aea atio of the teel ection to the ection of the column i about 4.6%. The beam, with ection of 15x16mm, ae einfoced with 8-D1 (SD295A) ba and 4φ tiup (@5mm). The encaed H-ection i placed o a to be ubjected to tong axi bending. The pecimen wee deigned o that the column wee collaped ealie than the beam. Theefoe, the numbe of tiup wa aanged in the beam. The main einfocement wee welded to the end plate. All pecimen ae named uch a SRC-6-1. In thi cae, 6 mean L/D (the column Length to ection Depth atio) and 1 mean vetical load atio. Column 4φ@5 4φ@1 Beam Fig. 1 Detail of pecimen

3 Table 1. Popetie and Size of pecimen b(mm) D(mm) mp(%) p(%) ce(gpa) F c (pa) (k) n n' batch Column SRC A L/D=6 Beam Column SRC B Beam Column SRC A Beam L/D=12 Column SRC B Beam b: width of co ection, D: depth of co ection, m p: einfocement atio ( m A/bD, m A: go aea of eba) p: teel atio ( A/bD, A: aea of H-ection), ce: modulu of elaticity of concete, F c : compeive tength of concete, : applied axial load, n: axial load atio, n': / 2F c bd Specimen: SRC-L/D-n 2. echanical popetie The popetie of concete uch a the modulu of elaticity and the compeive tength ae hown in Table 1. The mechanical popetie of teel obtained fom the coupon tet ae hown in Table 2 and the ize of H-ection i ummaized in Table 3. Table 4 how the mix popotion of concete. The deign tength of concete wa 27Pa. The tength of concete hown in Table 1 wa the eult of compeive tet uing cylinde (1φx2mm) at tet age of the pecimen. The maximum aggegate diamete wa 15mm. Table 2. echanical popetie of teel diamete Young' odulu yield point tenile tength yield tain yield atio elongation φ(mm) E(GPa) σ Y (Pa) σ u (Pa) ε Y ( σ Y / E) σ Y / σ u (%) flange web D1 A B D φ A B Table 3. Size of H-ection height width flange thickne web thickne H (mm) B (mm) t f (mm) t w (mm) Table 4. ix popotion of concete weight pe unit volume (kg/m 3 ) W/C S/a F G AX Slump C W S1(ea) S2(cuhed) G AE agency (%) (%) (Pa) (mm) (cm) F: deign tength of concete, G AX : maximum diamete of coae aggegate, S: S1+S2 A B

4 3. Loading Appaatu toy dift angle(ad.) The loading pogam i hown in Fig.2. The.4 amplitude of toy dift angle of the fame wa inceaed in incement of.5ad..3 The expeimental appaatu i hown in Fig.3..2 Though the Loading beam, the contant vetical load wa applied on the pecimen by hydaulic jack 1, and.1 kept contant duing hoizontal loading poce. The cyclic hoizontal load wa applied to the pecimen by -.1 hydaulic jack 2. And the applied foce wee meaued by load cell. -.2 Fig.4 how the poition of meauement. Hoizontal -.3 diplacement wee meaued uing diplacement tanduce at the cente of the beam. Axi -.4 cycle diplacement wee meaued by diplacement tanduce at the top of the both column and 1.5D (D: Fig. 2 Loading pogam depth of column) below. The tain of concete, encaed H-ection, and main einfocement wee meaued by wie tain gauge placed at D apat fom the face of column and beam. 4 Wie tain gauge Diplacement tanduce Slide Slide Jack 1 Load cell Loading beam D Load cell Specimen Jack 2 D 1.5D H Reaction wall 4 Fig. 3 Loading appaatu Fig. 4 Poition of meauement RESLTS AD DISCCTIO 1. Load-diplacement elation Fig.5 how the Q-R elation of all pecimen, whee Q mean the lateal foce applied to the pecimen and R mean the toy dift angle defined a the elative lateal diplacement between top and bottom of the column divided by height of the column H (See Fig.4). Additionally, the tage obeved flexual cack and bond cack ae hown by mak A and B, epectively. And the tage that main

5 einfocement and H-ection teel eached thei yield tain ae hown by C, D, E and F. In that cae, the occuence of the cack wa judged by eye obevation and yielding of the teel mateial by tain gauge. In Fig.5, the olid line how the expeimental behavio. The chain line how initial igidity of the fame, which i calculated by diegading the igid zone and uing linea-fame model. The dotted line how the igid platic collape mechanim line baed on the fully platic moment of the column co ection, which i calculated by auming that a platic hinge ae fomed at the uface of the beam (the 1 Q(k) 8 Initial igidity A 6 echanim line C B AIJ fomula Q(k) B 8 D 6 A 4 F 2 E E D SRC-6-1 C SRC Q(k) 4 3 C 5 Q(k) 4 3 C D E 2 A A 2 F D -2-3 F -4-5 SRC SRC-12-5 A : flexual cack wee obeved B : bond cack wee obeved C : occuence of main einfocement at top of column yielding D : occuence of main einfocement at bottom of column yielding E : occuence of teel at top of column yielding F : occuence of teel at bottom of column yielding Fig. 5 Hoizontal load - toy dift angle elation

6 top and bottom of the column). The dahed line epeent the tength that i calculated by AIJ fomula fo lende column. In all of the pecimen, the table hyteei popetie wee obeved until thei maximum tength wa obeved. And the yielding of H-ection wa obeved in the final tage of all pecimen. The expeimental tength of all pecimen exceed the tength calculated by AIJ deign fomula. eithe pecimen excluding SRC-12-5 eached the igid platic collape mechanim line. Two pecimen whoe axial load atio i.1 howed thei maximum tength at R=.2ad. On the othe hand, two pecimen whoe axial load atio i.5 howed thei maximum tength (at about R=.1). Afte peak, the tength of all pecimen deteioated lage than the mechanim line. 2. Poce of collape The final cack patten of the tet pecimen ae illutated in Fig.6. The L/D=12 pecimen collaped flexual failue. On the othe hand, the L/D=6 pecimen collaped hea bond failue that wa diffeent fom that aumed in AIJ deign fomula. In cae of the L/D=12 pecimen, flexual cack wee obeved at the top and bottom of the column (R=.5 ad.). Subequently, the numbe of cack inceaed a the defomation wa inceaed. The SRC-12-1 pecimen eached maximum tength at R=.25ad. and the SRC-12-5 pecimen ha aleady eached at R=.1ad. And afte that, cuh of concete ection wa obeved at R=.3ad in both pecimen. bond cack SRC-6-1 SRC-6-5 flexual cack SRC-12-1 SRC-12-5 Fig. 6 Cack patten (final tage)

7 In cae of the L/D=6 pecimen, flexual cack obeved at R=.5ad. At R=.1ad, bond cack between teel and concete wa obeved. Afte that, the cack have pogeed fat. Finally, the cacked cove concete fell off gadually. 3. Compaion of tength between Tet and AIJ fomula In AIJ deign fomula, the tength of lende compoite column i calculated by Equation 1, whee a conventional equation of imple upepoition i modified. The tength of lende compoite column i obtained a lage value of the two upepoed tength. One i pefeable fo bending about the tong axi of teel membe, the othe one i pefeable fo bending about weak axi. pefeable fo bending about the tong axi When o (1 / k ) =, = + 1 k When o (1 / ) k = +, = 1 (1-1) k pefeable fo bending about the weak axi When o (1 / k ) =, = + 1 k When o (1 / ) = +, k = 1 (1-2) k whee : ultimate compeive tength of membe, : ultimate flexual tength of membe, : ultimate compeive tength of RC potion, : ultimate flexual tength of RC potion, : ultimate compeive tength of RC potion ubjected to compeion alone, : ultimate flexual tength of RC potion ubjected to bending alone, : ultimate compeive tength of teel potion ubjected to compeion alone, : ultimate compeive tength of teel potion, : ultimate flexual tength of teel potion, : ultimate flexual tength of teel potion ubjected to bending alone, k : elatic buckling tength of column defined by Equation 2 π E I = 2 c c k + E I 2 lk 5 whee ce and E: modulu of elaticity of concete and teel, epectively, ci and I: moment inetia of concete potion and teel, epectively, l k : buckling length of column (2)

8 The expeimental tength ae compaed with the tength calculated by AIJ deign fomula in tem of moment axial load elation in Fig.7. In Fig.7, thick olid line ae the tength of AIJ SRC Standad deign fomula. The thin olid line ae baed on fully platic moment. The tength of mateial compoing a co ection i ued value hown in Table 1 and 2. And the cicle how the expeimental maximum tength. 14 u(k) 14 u(k) 12 Section Section 4 2 AIJ Standad Tet u(km) SRC Tet 2 AIJ Standad u(km) SRC u(k) 14 u(k) 12 Section Section 6 AIJ Standad 6 AIJ Standad 4 4 Tet 2 Tet u(km) u(km) SRC-12-1 SRC-12-5 Fig. 7 oment-axial load elation

9 The expeimental ultimate flexual moment obtained by tet eult ae compaed with the tength calculated by AIJ deign fomula (See Table 5). AIJ deign fomula etimate the tet eult conevatively and eaonably. Becaue the atio of tet eult to AIJ tength i (L/D=6) and (L/D=12). Table 5. Compaion between meaued tength and AIJ tength ex AX AIJ p ex AX / AIJ (k) (km) (km) (km) SRC L/D=6 SRC SRC L/D=12 SRC : applied axial load, AIJ : calculated ultimate flexual tength, p : fully platic moment ex AX : maximum expeimental tength ( ex Q AX L/4, ex Q AX : maximum meaued tength ) 4. Limit toy dift angle Some of the limit toy dift angle (R AX,R 95, R 9 ) ae hown in Fig.9 and Table 6. They ae defined a hown in Fig.8. i.e. R AX i the toy dift angle at the maximum tength. R 95 and R 9 ae one at 95% and 9% tength afte peak tength, epectively. Datic deceae of the tength i obeved afte peak tength in all pecimen. Theefoe, thee ae few diffeence between R AX and R 9 (See Fig.9). In all the pecimen, the tength deceae moe than 1% of the maximum tength at the next cycle afte eaching maximum tength. Q AX Q 95 Q 9 Q(k) R AX R 95 R 9 Fig. 8 Definition of limit toy dift angle Table 6. Limit toy dift angle.4 R AX R 9 exq AX R AX R 95 R 9 (k) (ad.) (ad.) (ad.) SRC SRC SRC SRC Ru(ad.) SRC-6-1 SRC-12-1 SRC-6-5 SRC-12-5 Fig. 9 Limit toy dift angle

10 5. Equivalent vicou damping atio The loop dawn by the hyteei chaacteitic of tuctue bea impotant ole of the damping pefomance. The equivalent vicou damping atio h eq i defined by Equation 3 and epeent the damping pefomance at each loop (See Fig.1). 1 W h = eq 4π We whee W: aea of one cycle W e : equivalent potential enegy = 1 2 k e a 2 Fig.11 how the tanition of the equivalent vicou damping atio at R=.1 to.2. The equivalent vicou damping atio of all the pecimen i between about The H-ection of all the pecimen yielded at final tage (See Fig.5), theefoe it i thought that the damping pefomance doen t inceaed geatly. (3) Q W W e =k e a 2 / SRC-6-1 SRC-6-5 SRC-12-1 SRC a k e a δ heq Fig.1 Definition of equivalent vicou damping atio Fig.11 Tanition of equivalent vicou damping atio COCLSIOS To examine the AIJ deign fomula and to evaluate the defomation capacity of the compoite column, an expeimental wok of SRC fame with weak-axi bending column wa pefomed. Fom eult, it ha become clea that: 1) In all of the pecimen, the table hyteei popetie wee obeved until thei tength eached thei maximum tength. And afte that, the tength of all pecimen deteioated lage than that of the mechanim line. 2) The atio of the meaued tength to the value by AIJ deign fomula wa (L/D=6) and (L/D=12). The AIJ SRC Standad deign fomula wa conevative compaed to the tet eult.

11 3) In all of the pecimen, the equivalent vicou damping atio (R=.1-.2) wa between about.5-.1 and damping pefomance didn t inceaed geatly. 4) The L/D=12 pecimen collaped flexual failue. The collape mechanim of L/D=6 wa hea bond failue that wa diffeent fom that aumed in AIJ deign fomula. REFERECES 1. Achitectual Intitute of Japan. Standad fo Stuctual Calculation of Steel Reinfoced Concete Stuctue, 21.