Study on self-centering mechanism of different yield strength hybrid buckling restrained braces

Conventional buckling-restrained braces (BRBs) exhibit stable compressive and tensile strengths and excellent energy dissipation characteristics. Nevertheless, the low post-yield stiffness limits the capacity of BRBs to control the peak displacement of the structure. This leads to large residual displacements in structures, which increases the probability of collapse under strong earthquakes. Consequently, introducing a reliable system that dissipates seismic energy, and provides an adequate self-centering capability, is necessary. This study has been carried out to investigate the hybrid BRBs response with different yield strengths (DY-HBRB) using numerical analysis. The cyclic responses, residual displacement, energy dissipation, and equivalent damping coefficient of the DY-HBRB models have been assessed. A simplified core-spring finite element model was utilized to model DY-HBRB elements. Moreover, an innovative trilinear kinematic hysteresis (TKH) model is proposed to simulate the cyclic behavior and facilitate the application of DY-HBRBs to seismic designs. The proposed model has been validated with the experimental investigation and numerical analysis results. The results indicate that selecting appropriate combinations of steel cores with different yield strengths in DY-HBRB provides a stable cyclic response with adequate energy dissipation and eliminates a significant part of the residual displacement. In addition, it was confirmed that the proposed TKH model could logically represent the double yield point of the DY-HBRBs with remarkable precision.