Effects of BRB on cyclic behavior of resilient RAC composite frames with ultra-high strength steel bars

Abstract

Quasi-static tests were conducted to investigate the effects of buckling restrained braces (BRB) on the seismic performance of resilient recycled aggregate concrete (RAC) composite frames with ultra-high strength steel bars (UHSB). The damage processes, hysteretic characteristics, stiffness and strength degradation, energy dissipation capacity, strain development of steel, residual drifts and residual crack widths of specimens were analyzed. Overall, the effects of BRB on the crack propagation of specimens were minor, both of which exhibited a beam hinge failure mechanism. After setting BRB, the damage to RAC was reduced within the range of gusset plates, and the spalling area of RAC in columns was significantly diminished. When the horizontal drift reached 1.5 %, the stiffness, bearing capacity and energy dissipation capacity were increased by 102 %, 66 % and 186 %, respectively. Moreover, the residual drift was slightly larger, but the residual crack width remained invariable. Considering the weak bonding property of UHSB and fractures of BRB, finite element models of specimens were established. The simulated results indicated that as the stiffness ratios and BRB area ratios increased, the peak bearing capacity of specimens improved. It was recommended that the stiffness ratios and BRB area ratios should be within the range of 0.50–2.00 and 0.50–1.00, respectively.