Influence of design load determination method for SC-BRBs with trilinear flag-shaped hysteresis behaviour on the seismic performance of braces and structures

Abstract

Self-centering buckling-restrained braces (SC-BRBs) can effectively reduce the residual deformation and seismic damage of the main structure. Because the first loading curve and subsequent loading curve of SC-BRB trilinear flag-shaped hysteresis behaviour do not coincide, there are two ways to determine the design load of a brace, i.e., the design load is taken as either the bearing force Fy1 at the first stiffness change point of the first loading curve or the bearing force Fy2 at the stiffness change point of the subsequent loading curve. In this study, a numerical analysis method is used to study the differences in the hysteresis performance of braces (i.e., SC-BRB-Fy1 and SC-BRB-Fy2) and the seismic performance of structures (i.e., SCBF-Fy1 and SCBF-Fy2) based on different design load determination methods. The results demonstrate that when the strength ratio β and the first stiffness ratio αc are similar, the hysteresis performance of braces and the seismic performance of structures are basically the same regardless of the method of design load determination. Decreasing β or increasing αc significantly increases the maximum axial force of SC-BRB-Fy1 but has little effect on that of SC-BRB-Fy2. Decreasing β can enhance the energy dissipation capacity of braces, reduce the maximum displacement of structures during earthquakes, and reduce the deformation concentration effect of SCBF-Fy2 but has no obvious influence on the deformation mode of SCBF-Fy1. Increasing αc can improve the energy dissipation capacity of SC-BRB-Fy1 but weaken the energy dissipation capacity of SC-BRB-Fy2, which has the opposite effect on the displacement response of SCBF-Fy1 and SCBF-Fy2.