Enhancing the seismic stability of buckling‐restrained steel braced frames in subduction interface seismic regions using viscoelastic dampers

This article proposes a stability‐enhanced alternative to traditional buckling‐restrained steel braced frames (BRBFs) for application in tall‐rise steel buildings located in high seismic regions. The viscoelastic (VE)‐BRBF is a BRBF featuring V or inverted‐V bracing configurations and integrates vertically aligned VE dampers at beam–brace intersections on each story. The incorporation of VE dampers addresses two significant drawbacks of traditional BRBFs. First, it enhances the post‐elastic lateral story shear stiffness, crucial for mitigating P‐delta‐induced inelastic drift concentrations and global instability, particularly under subduction interface events. Second, it augments inherent damping, a parameter typically low in conventional steel buildings. These improvements alleviate the need for the stability‐related stringent height limitations imposed by design codes, such as the 40 m limit for SC4 buildings in Canada. Utilizing nonlinear response history analysis, the seismic stability performance of the proposed system is assessed against traditional BRBFs designed with classical strength amplification through an inelastic stability coefficient. The assessment is conducted on 10‐ and 20‐story steel buildings in Vancouver, BC, considering seismic excitations involving the subduction interface. The results demonstrate that traditional BRBF designed overlooking height limitations failed to meet design code acceptance criteria, with several stability cases exhibiting global instability and excessive drifting. In contrast, the incorporation of VE dampers in the VE‐BRBF demonstrated responses that met the design code acceptance criteria, with uniform drift distributions and mitigated P‐delta effects and with residual post‐earthquake drifts within repair limits, regardless of building height or seismic excitation type.