Seismic performance of steel braced frames with innovative assembled self-centering buckling restrained braces with variable post-yield stiffness

Abstract

An innovative assembled self-centering buckling restrained brace (ASC-BRB) with variable post-yield stiffness is proposed in this study, aiming to better control structural responses under earthquakes of different intensity levels. The proposed ASC-BRB consists of the buckling restrained brace (BRB) system and self-centering (SC) system, where the SC system provides the variable post-yield stiffness with trilinear elastic behavior. The overall configuration and restoring force model of the brace are first described, and six independent hysteretic parameters are determined to comprehensively describe its hysteretic behavior. A simplified truss model of the ASC-BRB is established using OpenSees, and the experimental and numerical hysteretic curves coincide well with each other, indicating that the simplified model has satisfactory accuracy. The simplified model is then utilized to investigate the effect of the design parameters on the hysteretic behavior of the ASC-BRB. Nonlinear dynamic analyses are also conducted for three 6-story steel frames with different types of braces. The comparison results indicate that the proposed ASC-BRB with high post-yield stiffness can effectively limit the displacement development at the lower floors, but the structural high-mode effect will be further amplified. Finally, system level parametric analyses are performed to study the influence of brace design parameters on the structural responses, and reasonable values for these design parameters are recommended according to the parametric analysis results.