Dual-objective control of braced steel frame using asynchronized parallel two-stage yielding BRB

A novel buckling restrained brace (BRB), called the asynchronized parallel two-stage yielding buckling restrained brace (APTYBRB), is proposed to achieve dual-objective control of the maximum inter-story drift ratio (MIDR) and damage concentration effect (DCE) of braced steel frame structures. The APTYBRB features asynchronized two-stage working and yielding mechanisms. First, the feasibility, seismic performance, and fatigue performance of the APTYBRB were evaluated based on full-scale tests. Subsequently, simplified numerical simulation methods for the proposed APTYBRB, existing asynchronized series two-stage yielding BRB (ASTYBRB), and existing synchronized parallel two-stage yielding BRB (SPTYBRB) were recommended and validated. Based on non-linear time history analyses of a ten-story steel braced frame structure equipped with APTYBRBs, ASTYBRBs, SPTYBRBs, and conventional single-stage yielding BRBs (SYBRBs), the advantages of the APTYBRB in dual-objective control over the SYBRB, ASTYBRB, and SPTYBRB were identified. Compared to braced frame structures using SYBRB, SPTYBRB, and ASTYBRB, the MIDR using APTYBRB was reduced by 17 %–23 %, 10 %, and 7 %, respectively, and the damage concentration factor was reduced from 1.5 to 1.54, 1.51, 1.38, and 1.3, respectively. Finally, parametric studies were carried out to investigate the influence of the two-stage activation deformation (Δa2) on the dual-objective control effect of APTYBRB. This study provides a high-performance BRB for achieving dual-objective seismic response control of braced steel frames.