Experimental and numerical investigations on an assembled self-centering buckling-restrained brace with high post-yield stiffness

Abstract

In order to facilitate the replacement of damaged components and prevent the weak-story mechanism of frame structure after strong earthquakes, a novel assembled self-centering buckling-restrained brace (ASC-BRB) is proposed in this paper. The proposed bracing system is comprised of the buckling-restrained brace (BRB) system and the self-centering (SC) system. The SC system consists of two sets of steel strands and one group of disc springs stacked in series to achieve the goal of large deformability and post-hardening behavior. The detailed configuration, fundamental working mechanism, and restoring force model of the ASC-BRB are first presented. Different from SC systems with bilinear elastic behavior of existing SC-BRBs, the SC system of ASC-BRB exhibits trilinear elastic behavior due to its special configuration. Then, quasi-static tests are conducted to validate the effectiveness of the proposed ASC-BRB. The experimental results indicate that the ASC-BRB has a flag-shaped hysteretic response with excellent self-centering capability, stable energy dissipation capability, and appreciable deformation capacity with a maximum ductility coefficient of 25.58. More importantly, the specimen can exhibit the anticipated post-hardening behavior. The refined numerical model of ASC-BRB is established and verified by the experimental results, which can effectively analyze the mechanical behavior of the main components of ASC-BRB, making up for the deficiency of the tests. According to the problems discovered in the tests and numerical analyses, an improved configuration of the ASC-BRB is proposed and validated by the numerical simulation of the BRB system before and after improvement. The numerical results indicate that the improved BRB system exhibits more stable hysteretic behavior, and the stress levels of the inner and outer tubes become much lower after replacing 1-shaped cores with steel angle cores.