Seismic Behaviors of Shuttle-Shaped Double-Restrained Buckling-Restrained Braces: Experimental, Numerical, and Restoring Force Model Parameter Identification

The research aims to explore seismic behaviors of a novel shuttle-shaped double-restrained buckling-restrained brace (SDR-BRB). To this end, three SDR-BRB specimens showing various restraining ratios were first prepared to conduct low-cycle cyclic loading tests to investigate their failure modes, hysteretic performance, and fatigue performance. Afterwards, the ABAQUS finite element (FE) model verified by experiments was established, and effects of multiple critical factors upon seismic behaviors of SDR-BRBs were discussed through parametric analysis. Finally, an improved dung beetle optimization (DBO) algorithm considering global optimization and local exploration was proposed by combining Tent chaotic mapping, adaptive T-distribution perturbation strategy, and Osprey optimization algorithm. Based on this algorithm, the parameter identification method was developed for the improved Bouc–Wen model of SDR-BRB. Results indicate that hysteretic curves of SDR-BRBs are plump and symmetrical, showing excellent energy-dissipation capacity and fatigue performance, and obvious strain-strengthening characteristics. The restraining ratio, core yield length, initial imperfection, and core diameter-thickness ratio have significant effects upon seismic behavior of SDR-BRBs, while the gap of the core and the external tube merely exerts a slight effect. As recommended, the restraining ratio should exceed 2.0, the diameter-thickness ratio need to be less than 15, and the gap should not be less than 2[Formula: see text]mm. The proposed parameter identification method for the restoring force model of SDR-BRB has high accuracy and agrees well with experimental and numerical results. It provides reference for applying SDR-BRBs to analyze elastoplastic seismic responses of a structural system.