Experimental Study of Shear-Critical Reinforced-Concrete Shear Walls under Tension-Bending Shear-Combined Cyclic Load

Four shear-critical RC shear walls were tested under a tension-bending-shear load to replicate seismic behavior of the bottom shear wall in high-rise buildings. The axial tension ratio ranged from 0 to 0.5 and the aspect ratio was 1.06. The shear compression failure mode was observed for each specimen, characterized by the formation of an inclined crack at 45 degrees and direct strut action. The shear displacement was a dominant deformation component throughout the loading history. When the axial tension force increased from 0 to 1,293 kN, the ultimate drift ratio increased from 0.90% to 2.38%, while shear capacity linearly decreased from 1,507 to 895 kN. The load-displacement curve showed a significant pinching effect and strength degradation effect. In addition, this paper reports an innovative experimental method to obtain shear resistance of transverse reinforcement (Vs) based on the plasticity theory and strain measuring result. Test results using this method show that not all horizontal distributed rebar yield simultaneously at the ultimate capacity. The US code-specified shear strength contribution of horizontal distributed rebar was found to be unsafe for each test specimen. Finally, a database of RC shear walls subject to combined tension-bending-shear load was established to evaluate shear strength formulas in design codes. The comparison showed the Chinese code predicted spuriously higher tension-shear capacity, while the US code predicted conservative capacity. Based on the developed database, a simplified design formula is proposed with adequate safety concerns and accuracy. (C) 2020 American Society of Civil Engineers.