Low-Cycle Fatigue Performance of the Assembled Self-Centering Buckling-Restrained Brace and its Application in the Bridge Structures

Significant residual displacement in bridge structures caused by strong earthquakes can severely hinder post-disaster rescue. To reduce the post-earthquake residual displacement and enhance the seismic performance of bridge structures, this study proposed the design concept for the application of the assembled self-centering buckling-restrained braces (SC-BRBs) to spandrel columns. While SC-BRBs effectively dissipate seismic energy, the inner core is prone to fatigue damage induced by significant plastic deformation, which leads to the risk of brace fracture under strong earthquakes. For the above problems, this study initially researched the low-cycle fatigue performance of SC-BRB through tests, and a fatigue damage quantification method suitable for SC-BRB was proposed. Then, the spandrel column was extracted as an independent component, and the design parameters of the SC-BRBs utilized on the spandrel column were determined based on the structural “fuse” concept. Finally, the hysteretic performance of the spandrel column with SC-BRBs in the transverse direction was analyzed, and the dynamic responses of the whole bridge under near-fault pulse-like ground motions were also investigated. For comparison, the seismic performance of the bridges with or without link beams on original spandrel columns and the bridges retrofitted with buckling restrained braces (BRBs) on spandrel columns were also studied. The results indicate that SC-BRBs exhibit stable energy dissipation and excellent self-centering capacity. Based on Miner’s rule and Manson–Coffin equation, the fatigue damage of SC-BRBs can be effectively quantified. Compared to the original bridge, the bridges with SC-BRBs and BRBs significantly reduce the lateral displacement of the spandrel columns and the base moment, as well as substantially decrease the post-earthquake residual displacement of the columns. This design application can provide new insights for the brace design of similar bridge structures.