Cyclic Loading Tests for Hybrid Coupled Shear Wall with Various Reinforcement Details

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1 International Conference Data Mining, Civil and Mechanical Engineering (ICDMCME 215) Feb. 1-2, 215 ali (Indonesia) Cyclic Loading Tests for Hybrid Coled Shear Wall with Varios Reinforcement Details Woo-Yong Lim, and Sng-Gl Hong bstract Cyclic loading tests for for hybrid coled shear walls with varios reinforcement details were erformed. The rimary variables were reinforcement details of the coled shear walls. s a reslt, strctral erformances of the coled shear walls were deendent on the reinforcement details. The vertical reinforcements have inflence on the shear strength of the shear walls. The reqired vertical reinforcement ratio in an embedded length was also roosed by sing the shear strength models of roosed PC coled shear walls. Design method of the recast concrete (PC) coled shear wall was roosed by assming the distribtion of comressive stress acting on the flange of the embedded steel beam in the shear walls. Keywords Design method, coled shear walls, reinforcement detail, shear strength. C I. INTRODUCTION OUPLING beams are resonsible for the energy dissiation caacity for the lateral force acting on the strctre, and have to be designed to exhibit a roer strength, rigidity and deformability. ccording to Palay s researches [1], when shear stress is.5 f c MPa or more, diagonal reinforcements shold be installed at reinforced concrete (RC) coling beams. However, there is a difficlty to install the diagonal reinforcements to the RC coling beams. For these reasons, hybrid steel coling beams have been roosed to imrove the constrctability and to relace the conventional reinforced concrete coling beam by many researchers [2]-[8]. The exerimental researches for hybrid steel coling beams were erformed by Harries et al. [2],[3], Marcakis et al. [4], Mattock et al. [5], Shahrooz et al. [6], and Kent et al. [7]. ccording to revios researches, it is reqired to inhibit the rematre failre of the coled shear walls by secial reinforcement details. Existing design codes, esecially CI [8], have rovided reinforcement details for the secial strctral walls and coling beam at Section 21.9 in Chater 21. However, secific design method of hybrid steel coling beam have not rovided in those codes. Englekirk [9] has sggested that the coled shear walls shold be reinforced by additional reinforcements in arond the embedded steel beam. Woo-Yong Lim is a ost-doctoral researcher in the Deartment of rchitectre & rchitectral Engineering at Seol National University, Korea (corresonding athor s hone: ; wyarch97@sn.ac.kr). Sng-Gl Hong is a rofessor in the Deartment of rchitectre & rchitectral Engineering at Seol National University, Korea ( sglhong@sn.ac.kr). Strctral erformances sch as strength, stiffness, and energy dissiation caacity of the hybrid steel coling beam are greater than those of the RC coling beams. Desite these many advantages, it is difficlt to aly the steel coling beam to conventional RC shear walls owing to the weak constrctability. If the coled shear walls rodced in factories, the PC coled shear walls are likely to be damaged in the transort rocesses. Existing hybrid steel coling beam systems have a roblem with sing in the coled PC shear walls owing to the constrctability. Ths, it is necessary to imrove the new hybrid steel coling beam systems and also to rovide the secial design method for the PC coled shear walls. In this stdy, Design method for coled PC shear walls was roosed based on the exerimental stdies.. Test secimens II. TEST PROGRM Cyclic loading tests for the for coled PC shear walls with steel coling beam were erformed to evalate the shear strength and energy dissiation caacity. The main arameters of the test were reinforcement details of the PC shear walls. Figre 1 shows the reinforcement details of the test secimens. The coled PC shear walls had a dimension of mm ( in.). For (d b = 19 mm or.75 in.) horizontal and vertical reinforcements were installed to inhibit the concrete failre dring the test at the secimen s bondary. Here, d b is diameter of bars. SD4 (Korean Standard, f y = 4 MPa or 58 ksi) reinforcements were sed in each secimen. Design comressive strength of concrete f c is 35 MPa (5.1 ksi). P6NC is a rototye test secimen designed by according to CI 318 design codes [8]. (see Fig. 1) Ten (d b = 13 mm or.5 in.) and for reinforcements for horizontal reinforcement and ten for vertical reinforcements were rovided in this secimen. Horizontal and vertical reinforcement ratios were ρ h =.5 and ρ v =.54, resectively. H6NC is the secimen that reinforced the length as mch as the embedded length by horizontal closed hoos. The length of those bars is consistent with the length of embedded steel beam. Details of the reinforcements of this secimen are very similar to rototye test secimen P6NC as shown in Fig. 1. Since eight (d b = 16 mm or.62 in.) horizontal reinforcements were rovided, the horizontal reinforcement ratio of this secimen is ρ h =.64. Sh6NC htt://dx.doi.org/ /iie.e

2 International Conference Data Mining, Civil and Mechanical Engineering (ICDMCME 215) Feb. 1-2, 215 ali (Indonesia) is the test secimen reinforced by the vertical reinforcements to the entire length of the wall as shown in Fig. 1. Forty ties with 6 mm (23.6 in.) of length were rovided at each 6 mm (2.4 in.) of sacing. Horizontal and vertical reinforcement ratios are ρ h =.5 and ρ v =.54, resectively. SP6NC is the roosed test secimen, which was reinforced by three closed ties in the embedded length at each 2 mm (7.9 in.) of sacing, two (d b = 22 mm or.9 in.) and horizontal reinforcements, and for diagonal reinforcements as described in Fig. 1. Length of the closed ties which are installed in embedment length is 62 mm (24.4 in.). Horizontal and vertical reinforcement ratios are ρ h =.1 and ρ v @27 φ6 8 - section 8 - section section 18 - section @27 φ6 8 - section 8 - section section section Fig. 1 Details of the test secimens: P6NC; Sh6NC; H6NC; and SP6NC Steel coling beams were designed in accordance with ISC design codes [1] as shear dominated members. Overall length of the steel coling beam inclding the steel late shear connection is 72 mm. The dimension of the steel coling beam is mm ( in.). Steel late connection had the length of 12 mm (4.7 in.) and thickness of 2 mm (.8 in.), resectively. Total length of the steel coling beam is 9 mm (35.4 in.) and the distance from the srface of the PC shear wall to the loading oint is 595 mm (23.4 in.). The length of the embedded beam (l e ) was 6 mm (23.6 in.), which was obtained from the existing shear strength models as shown in Table 1. Dimensions of the I-shaed beam were mm ( in.). To minimize the excessive deformation in the embedded steel beams, For stiffeners were installed at both side of the embedded beam in distance of 2 mm. To and seat angles were set to indce the shear deformation of the steel coling beam. Steel coling beam and to-seat angels were assembled by sing for high-tensile bolts, which diameter (d b ) are 24 mm (.94 in.). The yield and tensile strength of,, reinforcements sed in the PC coled shear walls were : f y ()= 462 MPa (67. ksi), f () = 594 MPa (86.1 ksi), : f y ()= 417 MPa (6.5 ksi), f () = 667 MPa (96.7 ksi), and f y () = 425 MPa (61.6 ksi), f () = 63 MPa (91.4 ksi), resectively. The strength obtained from the material tests was f c = 38 MPa (5.5 ksi). Design yield strength of the steel coling beam was F y = 3 MPa (43.5 ksi).. Test set- Figre 2 shows test set-. Test secimens were loaded at the distance of 72 mm (28.3 in.) from the srface of the PC shear wall ntil the ltimate failre by dislacement control. Figre 2 shows the loading schedle. Rotation angle was incremented by.25 % from.25 % (1.5 mm or.6 in.) to 2. % (12. mm or.47 in.) and after that was increased by.5 % from 2. % (12. mm or.47 in.) to ltimate failre. LVDTs were sed to measre lateral and vertical dislacement of the test secimens. Nmbers 1 for horizontal dislacement measrements at the to of the steel coling beam (LV1), and Nmber 2 and 3 for vertical dislacement of the coling beam (L and LV3), and Nmber 4 and 5 for vertical dislacement of the embedded steel beam (LV4 and LV5), and Nmber 6 and 7 for shear distortion of the PC shear wall (L and LV7), and Nmber 8 and 9 for lateral dislacement at lower art of the steel coling beam and to seat angles (LV8 and LV9), and Nmber 1 for sli of the coled PC shear walls (LV1), resectively. LV1 LV8 LV9 LV1 L LV4 LV5 18 LV3 2,kN ctator Drift ratio (%) Fig. 2 Test set- and loading schedle III. TEST RESULTS. Load-rotation angle relationshi Nmber of cycles Figre 3 shows the load rotation angle relationshi of the test secimens sbjected to cyclic loading. The rotation angle is the lateral dislacement divided by the effective distance (72 mm) of the steel coling beam. The terms of V reresent the lastic shear strength of the steel coling beam for ositive and negative loading, resectively. The yield strength V y and dislacement δ y were defined as the oint when the strain of the steel coling beam has reached the yield strain. The dislacement at the imm strength reresented by δ and ltimate dislacement δ are also resented in Fig. 3. htt://dx.doi.org/ /iie.e

3 International Conference Data Mining, Civil and Mechanical Engineering (ICDMCME 215) Feb. 1-2, 215 ali (Indonesia) The ratio of the imm strength to the lastic shear strength (V /V ) showed that P6NC:.98, H6NC: 1.19, Sh6NC: 1.18, and SP6NC: The strength of the rototye test secimen P6NC did not reach the lastic strength. On the other hand, the imm strength of the other secimens were exceeded the lastic shear strength P6NC V V H6NC V V Sh6NC V V SP6NC V V Fig. 3 Load-rotation angle relationshi: P6NC; Sh6NC; H6NC; and SP6NC. Failre mode Figre 4 shows the damage and crack atterns of the test secimens at the end of the test. The initial crack of all test secimen has occrred at arond the embedded steel beam in the coled shear walls de to increasing the bearing stress of concrete. For P6NC, initial cracks has occrred at 1.% of rotation angle. The vertical and horizontal cracks has occrred at the embedded steel beam as well as the connection between concrete and to seat angles. Diagonal cracks have initially occrred at the end of the embedded steel beams and roagated to the fondation. Initial crack of H6NC secimen was observed at 1.75% of rotation angle and diagonal crack has initiated at 3. % of rotation angle. Initial crack and diagonal cracks of Sh6NC have occrred at 3. % and 3.5 % of rotation angle, resectively. SP6NC showed that initial crack has occrred at -1.75% of rotation angle and diagonal cracks has observed at 3. %. Shear yielding of the steel coling beam occrred at 5.5 %. Diagonal cracks develoed to 4. % and at -4.5 %, horizontal cracks was observed at the center of the initial crack occrred. s a reslt, P6NC secimen designed as secial concrete strctral walls by sing CI 318 codes showed that initial and diagonal cracks has occrred in 1.75 % of rotation angle. Sh6NC secimen reinforced horizontal hoos at embedded region was effective to revent the crack roagation. For SP6NC and H6NC, initial and diagonal cracks was observed in the same time. The steel coling beam of H6NC has yielded at 6.% of rotation angle and that of SP6NC has yielded at 5.5%. Fig. 4 Damage and crack atterns C. Strain of the vertical and horizontal reinforcements Figres 5 and 6 show the strain variation of the vertical and horizontal reinforcements for the rotation angle. The strain of the vertical reinforcement was measred by sing strain gages attached at 4 mm, 24 mm, 44 mm, and 66 mm of distance from the end of the PC shear wall. (,, V1, ) The strain of the horizontal reinforcement was measred at the end of the vertical wall reinforcement, which is located in the center of the embedded steel beams by a strain gage. The strain of the vertical reinforcement showed a tendency to increase more raidly as vertical reinforcements are closer to the face of the PC shear wall. The otermost vertical reinforcement of the test secimens excet SP6NC has yielded at 4 % of rotation angle. However, three vertical reinforcements measred vertical strain remained elastic state ntil the end of the exeriment. On the other hand, all reinforcements of SP6NC did not yield ntil the end of the tests. reslts of the comarison of the strain of the vertical reinforcement, the vertical reinforcements within 25 mm from the interface are likely to yield before they reach the imm strength. However, if the vertical stirrs were installed arond the embedded steel beam, it is ossible to revent the rematre yielding of the vertical reinforcement ntil reaching the ltimate strength. Strain of the horizontal reinforcement in most of secimens excet rototye secimen P6NC did not reach yield strain. s a reslt of comaring the strain of the horizontal reinforcements, if the additional reinforcements were not installed arond the embedded steel beams, test reslts showed that the rematre yielding of the horizontal reinforcements has occrred. The bearing failre of concrete is likely to occr owing to the yielding of the horizontal reinforcement when the design method of existing model codes is alied to the design of the coled shear walls. Therefore, the additional reinforcement shold be installed at the embedded region in the htt://dx.doi.org/ /iie.e

4 International Conference Data Mining, Civil and Mechanical Engineering (ICDMCME 215) Feb. 1-2, 215 ali (Indonesia) coled shear wall. In addition, it is necessary to revise the existing shear wall design eqation for the secial concrete strctral walls % V1 () () (V1) () 5% 4% V1 () () (V1) () % 4% Fig. 5 Strain of vertical reinforcements 4.26% Yielding y 3.99% y Yielding () () (V1) () V1 4% 5% () () (V1) () V1 5 4 Yielding Yielding Fig. 6 Strain of horizontal reinforcements D. Strain of the steel coling beam Figre 7 shows the strain variations of the steel coling beam. The strain of the steel coling beam of the P6NC did not reach the yield strain ntil the end of the tests. On the other hand, the steel coling beam of the H6NC, Sh6NC, and SP6NC yielded at rotation angle of y = 6.2 %, 6.5 %, and 5.3 % for ositive loading and at y = -5.9 %, -6. %, and -4.7 % for negative loading, resectively. The reason why the steel coling beam of P6NC, which is designed in accordance with CI 318 design codes, did not yield is that the bearing failre of the shear walls occrred at abot 4 % of the rotation angle before the strain of the steel coling beam has reached the yield strain. On the other hand, the steel coling beams of the other test secimens reinforced by additional vertical and horizontal reinforcements, esecially SP6NC showed the lastic behavior after the imm strength. 5 4 yielding 3 W y 6.5% y 6.% W y 6. 3 W y 5.9% y 5. 3 W y 4.7% Fig. 7 Strain of the steel coling beam E. Energy dissiation caacity Figre 8 shows the energy dissiation caacity in accordance with the rotation angles. Figre 9 reresents the energy dissiation caacities er secific rotation angle and Fig. 9 shows the cmlative energy dissiation caacities. Energy dissiation caacity was defined as the area of the load rotation crves er rotation angle and that was obtained in the third cycle of the target dislacement. The energy dissiation caacity of the roosed test secimen SP6NC showed the imm vale and aeared the lowest vale in P6NC designed by CI s a reslt, the energy dissiation caacity of the test secimens reinforced by the horizontal or vertical reinforcements was greater than the others as described in strain variation of the reinforcements. In other words, energy dissiation caacity of the PC coled shear walls deends on the reinforcement details. Energy dissiation (knmm) SP11 SP12 SP13 SP CUmlative energy dissiation (knmm) SP11 SP12 SP13 SP Fig. 8 Energy dissiation caacity er rotation angle: Energy dissiation caacity; and Cmlative energy dissiation caacity IV. DESIGN METHOD OF COUPLED SHER WLL Figre 9 shows the roosed design model of the PC coled shear walls with steel coling beam. Stress distribtion of the embedded steel beam was assmed to be rectanglar stress block based on the exerimental reslts. When alied shear force occrs at the steel coling beam, comressive strength C f and bearing strength C b act at αl e ( < α < 1) and (1-α)l e of er and lower art of flange, resectively. Comressive strength of concrete is assmed to be.85f c. Ths, shear strength is obtained by sing eqilibrim condition as follows: V C f Cb.85 fclebef 1 2 (1) where C.85 f l b, C.85 f 1 l b. f c e ef b c e ef htt://dx.doi.org/ /iie.e

5 International Conference Data Mining, Civil and Mechanical Engineering (ICDMCME 215) Feb. 1-2, 215 ali (Indonesia) For shear dominant hybrid steel coling beam, the embedded length of the steel beam is obtained when the shear strength V calclated by Eq. (1) is eqal to lastic shear strength V as given: l e Va 2.85 fb c ef 2 1/ 2 where a is the distance from the face of the shear wall to loading oint. y sing Eqs. (1) and (2), α is obtained as follows: 2 X 2 X / 2 X (3) X 4 where X V /.85 fcbef a. Ths, the length (1-α)l e occrring the bearing failre of concrete is given: 2 X 2 X / 2 X 1 le 1 le (4) X 4 The redicted shear strength was relatively good agreement with the exerimental data..85 f ck Embedded steel beam l e Coled PC shear wall l e 1 le a Steel coling beam.85 f ck Fig. 9 Proosed design model of the coled PC shear wall Reqired vertical reinforcements of the PC coled shear walls can be obtained by sing the comressive forces at the flange of the embedded steel beams. s a reslt, the redicted bearing stress of the coled shear walls is reresented by C b = xc f. That is, the bearing force determined by the roosed method is greater abot 3 than the comressive force occrring in the er flange of the embedded steel beam. Ths, the reqired amont of the vertical reinforcements can be calclated as given:.85 f c l e b ef f (5) f b y V (2).85 fc 1 lebef (6) f y where f y reresents the yield strength of the vertical reinforcement (in MPa). The vertical reinforcement ratio is obtained as follows: Cf Cb sc (7) l b f e w y V. CONCLUSIONS In this stdy, cyclic loading tests for the hybrid PC coled shear walls with varios reinforcement details were erformed in order to evalate the strctral erformance. The reslts obtained from the exerimental stdy is as follows. 1) The strctral erformance of the hybrid steel coling beam showed the different deending on the reinforcement details of the PC coled shear walls. s a reslt of the tests, bearing failre has occrred early at the face of the PC coled shear walls designed as secial strctral walls and coling beams by CI 318 design rovisions. Test reslts showed that rematre failre of the PC coled shear walls has been revented by the stirrs reinforced in embedded length. 2) s a reslt of the measrements of the strain variation of the reinforcement, it has been shown that the vertical reinforcements of the coled shear walls have more inflenced on the ltimate failre than the horizontal reinforcements. lthogh the coled shear walls were designed in accordance with CI design codes, the strain of the vertical reinforcements in 25 mm from the wall face has reached the yield strain at abot 4 ercent of rotation angle. It is necessary to imrove the design method of the secial strctral walls and coling beams resented to the CI codes. The vertical reinforcements shold be installed additionally in the region of embedded length. 3) Test reslts showed that energy dissiation caacity deends on the details of the reinforcement details of the PC coled shear walls. Energy dissiation caacities of the roosed test secimen reinforced by the stirrs arond the embedded steel beam (SP6NC) were greater than those of the test secimen designed in accordance with CI codes (P6NC). 4) Design method of the PC coled shear walls was roosed by assming the distribtion of comressive stress in the steel flanges of the embedded steel beam. ccording to the roosed design method, it is reasonable that the amont of the vertical reinforcements as mch as 4% of reinforcement ratio was installed in the region of the embedded length. CKNOWLEDGMENT This research was financially sorted by the Ministry of Constrction and Transortation of Korea (3 R&D 7-6); The athors are gratefl to the athorities for their sort. REFERENCES [1] Palay, T., and inney, J. R., Diagonally Reinforced Coling eams of Shear Walls, Secial blication CI, Vol. 42, Detroit, [2] Harries, K.., Mitchell, D., Redwood, R. G. and, Cook, W, D., Seismic Design of Coling eams Case for Mixed Constrction, Canadian Jornal of Civil engineering, Vol. 24, No. 3, 1997, [3] Harries, K.., Seismic Design and Retrofit of Coled Walls sing htt://dx.doi.org/ /iie.e

6 International Conference Data Mining, Civil and Mechanical Engineering (ICDMCME 215) Feb. 1-2, 215 ali (Indonesia) Strctral Steel, Deartment of Civil and lied Mechanics, McGill University, Montreal, Canada, [4] Marcakis,. H. and Gaffar, G. H., Precast Concrete Connections with Embedded Steel Member, PCI Jornal, Vol. 25, No. 4, Jly-gst 198, [5] Mattock,. H and Gaffar, G. H., Strength of Embedded Steel Sections as rackets, CI Jonal Vol. 79 No. 9, March-ril 1982, [6] Gong,., and Shahrooz. M., Steel-Concrete Comosite Coling eams ehavior and Design, Engineering Strctres, 23, 21, [7] Kent, D. C. and Park, R., Flexral Members with Confined Concrete, Jornal of Strctral Division, SCE, Vol. 97, ST 7, Jly 1971, [8] CI , ilding Code Reqirements for Strctral Concrete and Commentary, CI Committee 318, merican Concrete Institte, 28, [9] Englekirk, R. E., Seismic Design of Reinforced and Precast Concrete ildings, John Wiley and Sons, 23, [1] ISC, Manal of Steel Constrction Load and Resistance Factor Design Third Edition, ISC, Inc., Chicago, IL, 22. htt://dx.doi.org/ /iie.e

INVESTIGATION ON THE LOAD TRANSFER MECHANISM FOR THE JOINT OF REINFORCED CONCRETE COLUMN AND STEEL BEAM

INVESTIGATION ON THE LOAD TRANSFER MECHANISM FOR THE JOINT OF REINFORCED CONCRETE COLUMN AND STEEL BEAM Seng Hn KIM 1, Sang Whan HAN 2 And Li Hng LEE SUMMARY The composite framed strctres, which consist