Seismic performance of fish-bone shaped buckling-restrained braces with controlled damage process

A new type of all-steel fish-bone shaped buckling-restrained braces (FB-BRBs) with large maximum ductility and cumulative ductility have been proposed, and their excellent seismic performance and failure mechanism have been verified through a series of experiments in a previous study. The proposed FB-BRBs can fully utilize ductility of a material through a multiple-neck deformation mechanism. This mechanism can achieve a well-controlled damage process of different segments of the FB-BRBs. In addition, the proposed FB-BRBs can sustain tensile load-carrying capacity even after rupture of the core plate, which is owing to the interaction between the multiple stoppers of the core plate and corresponding filling plates. Both experimental and numerical studies have been conducted. However, the previous study failed to achieve the expected failure mechanism due to unexpected failure at the stoppers of the FB-BRBs. This paper aims to experimentally investigate the optimal values of the design parameters of the FB-BRBs, and further clarify the failure mechanism. Quasi-static cyclic loading tests were carried out using eight specimens with different configurations. Different failure modes of the newly proposed FB-BRBs are verified, and high seismic performance of the dampers is proved through the experimental results.