Experimental study on seismic performance of assembled buckling-restrained brace with low yield point steel

Based on the design concept of seismic resilience, which aims to achieve controllable damage during earthquakes and rapid post-earthquake functional recovery within the structure, an assembled buckling-restrained brace with low yield point steel (ALYBRB) was proposed. To evaluate its seismic performance, quasi-static cyclic loading tests were conducted on five ALYBRB specimens. The influence of core steel material, bolt spacing of the external restraint system, and the gap between the core and the external restraint system on the seismic performance of ALYBRBs were investigated. The results indicated that the ALYBRBs exhibited superior plastic deformation capacity, stable energy dissipation capacity, and exceptional fatigue performance, as well as significant cyclic hardening characteristics and hysteretic properties with good symmetry. The cumulative plastic deformation coefficient (CPD) of ALYBRBs with LYP100 and LYP160 steel were 2.33 times and 1.51 times greater than that with Q235 steel, respectively. The maximum equivalent viscous damping coefficients of all specimens can achieve a range of 73.0 % to 86.2 % of the theoretically maximum value. The strain hardening adjustment factors of all specimens ranged between 1.34 and 1.90. The average compression strength adjustment factor for the properly designed ALYBRB specimens was 1.12. Reducing the bolt spacing can effectively inhibit the multi-wave buckling of the core, which is conducive to the improvement of energy dissipation efficiency in ALYBRBs. ALYBRB specimen with excessive gap exhibited decreased ductility, energy dissipation efficiency, and fatigue performance, and its out-of-plane deformation mode was a combination of bending deformation in the constrained yield segment and the transition segment deformation.