Seismic Performance of Glubam Frames with Bamboo-Steel Composite Buckling-Restrained Braces

Buckling-restrained braces (BRBs) with timber casings have demonstrated effective energy dissipation, yet the application to orthotropic engineered bamboo (glubam) raises unresolved questions regarding confinement mechanics under high-mode buckling. This study proposes a novel bamboo-steel composite buckling-restrained brace (B-BRB) using a glubam casing and self-tapping screws (STSs). Reversed cyclic loading tests on eight full-scale frames were conducted to investigate the effects of bracing type, stiffener length, and connection configuration. Results show that B-BRBs mitigate brittle failure modes observed in conventional braces. Compared with the bare frame, strength and stiffness increased by approximately 500% and 800%, respectively, with ductility improved by up to 78.8% and stable energy dissipation achieved. Higher-mode local buckling of the steel core induces glubam splitting or STS withdrawal, governing system failure. A stiffened segment length of at least 10% of the core yielding length and the use of multi-bolt connections are recommended to ensure stable behavior. A numerical model in OpenSees accurately captures the global hysteretic response, supporting system design and optimization.