SMA-Activated Double-Stage Yielding BRB: Experimental and FEM Insights

To address the limitations of traditional buckling-restrained braces (BRB), which feature a single-stage yielding and inadequate energy dissipation under small earthquakes, this study proposes a novel double-stage yielding buckling-restrained brace (DSY-BRB). The proposed design integrates a sliding friction damper with shape memory alloy (SMA) bolts and conventional BRB components, enabling effective energy dissipation at small deformations and adaptive performance across varying displacement amplitudes compared with traditional BRBs. Leveraging SMA superelasticity, the DSY-BRB also exhibits self-centering capability that distinguishes it from prior DSY-BRB configurations. Experimental investigations were conducted on DSY-BRB specimens with varying core plate widths under cyclic quasi-static loading to evaluate hysteresis behavior, energy dissipation capacity, and self-centering performance. Results demonstrate that DSY-BRBs exhibit symmetric flag-shaped hysteresis curves with enhanced energy dissipation and excellent self-centering capabilities, achieving minimal residual deformation compared to traditional BRBs. Complementary finite element modeling with parametric analysis was performed to establish design guidelines for optimal double-stage buckling behavior. The findings reveal critical stiffness ratio requirements between BRB and SMA bolt-based friction damper components, providing valuable design criteria for engineering applications. This hybrid approach offers significant advantages in seismic energy dissipation and structural resilience compared to existing DSY-BRB systems.