Seismic Performance of Shaped Steel Tubes

Buckling-restrained braces (BRBs) have seen rapid adoption in structural engineering due to their superior seismic energy dissipation. These assemblies typically consist of a core brace, confinement elements, and an unbonded interface layer. Among these, the confinement elements play a critical role; their design dictates the overall seismic resilience of the brace and the connected structure. Conventional BRBs using rectangular steel tubes often suffer from pronounced stress concentration and inefficient material usage. To overcome these drawbacks, we introduce a non-rectangular steel tube concrete-confinement buckling-restraint brace—a novel structural system that enhances confinement effectiveness through geometric innovation. This study systematically evaluates the performance of this new system by first building a library of special-shaped steel cross-sections, including elliptical and corrugated profiles. We then employ ABAQUS finite element simulations complemented by physical testing to analyze how key parameters—such as cross-sectional shape factor and wall thickness—govern the hysteretic behavior of the components. These findings will inform standardized design guidelines for non-rectangular confinement members. Compared with conventional BRB designs, our approach offers two principal advantages. The optimized geometry of non-rectangular sections promotes more favourable stress redistribution, improving minor-axis bending resistance.