Mechanical behavior and design method of low-yield-point steel buckling-restrained brace and connections

A novel assembled low-yield-point steel buckling-restrained brace (ALYBRB) was proven to have favorable and stable seismic performance. However, the absence of optimized brace-to-frame connection and design methods restricted the realization of its superiority. The influence of design parameters on the performance of ALYBRBs and brace-to-frame connections was evaluated through parameter analysis. Considering the synergistic interaction among frame, gusset plate, and ALYBRB, design recommendations for optimized configurations of gusset plates were given, and a design method for ALYBRBs and connections based on damage control concepts was proposed. Results indicated that the upper limit of the gap between core and external restraint system and core width-to-thickness ratio could be relaxed to half of core thickness and 15, respectively, compared to specifications. Within the recommended range, ALYBRBs exhibited insensitivity to gap-size variations, improving processing and assembly efficiency. The double-angle steel cross-sectional dimensions should accommodate the spatial requirements for the core, bolts, and spacers. The core can be effectively constrained by the external restraint system with four equally spaced bolt groups and two groups of end-strengthening bolts. Unreliable gusset plates limited the load-bearing capacity of ALYBRBs, resulting in lower load-bearing capacity in beam-column-ALYBRB models compared to ALYBRB models. The stability and strength of gusset plates were improved by optimized stiffener configuration, ensuring full utilization of seismic performance of ALYBRBs. End stiffeners should be positioned along the entire free edge of the gusset plates. The intermediate stiffener length should ensure the stiffened gusset plate length is at least 0.69 times its total length.