Development of an Innovative Assembled Self-Centering Dual-Stage Yield Buckling-Restrained Brace for Improving Seismic Resilience

An innovative assembled self-centering dual-stage yield buckling-restrained brace (ASCDYB) is introduced to enhance seismic resilience of building structures. The energy-dissipating system of ASCDYB is a buckling-restrained brace with dual-stage energy-dissipating properties, and the self-centering system consists of high-strength steel rods and pre-compressed disc spring combination. First, the basic configuration and working principle of ASCDYB are introduced, followed by which a simplified theoretical hysteretic model is developed. Then, quasi-static tests and refined and simplified numerical analyses are conducted to analyze the hysteretic behavior of ASCDYB in depth. Nonlinear time history analyses of ASCDYB single-degree-of-freedom (SDOF) systems are conducted at last. Experimental results indicate that the ASCDYB specimens can achieve the expected dual-stage energy-dissipating characteristics and have stable hysteretic performance. No strength degradation occurs before the energy-dissipating cores fracture. The ASCDYB specimen with longer slotted holes in second-stage energy-dissipating cores can achieve better self-centering performance in a larger range of loading displacements. The developed theoretical hysteretic model, refined and simplified numerical models can well predict the hysteretic behavior of the ASCDYB specimens throughout the entire loading process, and both numerical models have higher accuracy, with errors of analytical indicators generally within 10 %. For the SDOF system with significant partial self-centering properties under rare earthquakes, the use of ASCDYB increases the peak displacements by less than 9 % but reduces the residual displacements by about 40 % compared with the use of existing self-centering buckling restrained braces (SCBRBs). Therefore, when the structural post-earthquake target residual displacement is certain, the proposed ASCDYB can have a lower pre-stress requirement and is more convenient for engineering applications compared with existing partial SCBRBs.