Finite element analysis of all-steel cantilever-stiffener buckling-restrained braces

초록

This study develops and evaluates a cantilever-stiffened buckling-restrained brace (CAS-BRB) designed to enhance energy dissipation and cyclic stability while remaining compatible with conventional fabrication practice. A finite element framework was established to simulate a subassembly with a 2.0 m core, incorporating nonlinear steel behavior through combined isotropic-kinematic hardening, low-friction unbonded contact between the core and restrainer, initial geometric imperfections, and a quasi-static loading protocol consistent with seismic qualification practice. A low-yield steel equivalent to HSA80 was adopted for the core, while a conventional structural steel comparable to SS275 was used for restraining and stiffening components. The model was verified by benchmarking against published experimental results and by checking its response against recognized seismic design provisions. Parametric analyses were then conducted by varying the lengths of the welded and cantilever segments to isolate the role of staged engagement during compression. The results show that the cantilever segment delays the onset of strength degradation from the first compressive cycle at 1.5 Δbm in the baseline case to 2.0 Δbm for a 150 mm cantilever, while no strength degradation occurs within the applied loading protocol for a 550 mm cantilever. The interaction between the welded and cantilever segments indicates that shorter welded segments require longer cantilever segments to satisfy stability requirements. The welded segment provides the primary compressive resistance, whereas the cantilever segment governs post-contact stability. In addition, the partial-weld detail reduces heat input and residual distortion and is compatible with standard shop fabrication. Overall, the findings demonstrate a practical approach to improving the seismic performance of BRBs and support the development of cyclic qualification procedures and design guidance that link detailing parameters to target performance objectives. © 2026 Techno-Press.

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