Enhancing Seismic Stability in Steel Buildings: A Numerical Evaluation of the Novel Seismic Stability Provisions Proposed for the CSA S16:24 Commentary for Stable and Resilient Post-earthquake Performance

This article assesses the novel seismic stability provisions proposed for the Commentary of the Canadian Steel Design Standard CSA S16:24 to enhance the seismic stability performance of steel buildings and replace the classic strength amplification approach. They mitigate inelastic drift concentrations over the building height and reduce residual drifts. They also allow for the relaxation of existing stringent height limitations. The provisions stipulate that the seismic force-resisting system is required to develop a specified minimum positive post-elastic lateral storey shear stiffness and maintain this stiffness for a storey drift of at least 2.5% of the storey height. Extensive validations of this proposed new approach have been carried out, including on eccentrically, buckling-restrained, and friction-braced frames, to assess their effectiveness. This study focuses on nonlinear response history analysis of 10- and 20-storey eccentrically and buckling-restrained steel-braced frames in Vancouver, BC. It compares two approaches: one following the classic strength amplification approach, as prescribed in the CSA S16:19, ignoring the height limitations and another incorporating the newly proposed provisions for the CSA S16:24 Commentary. Results indicate that while the currently used approach of amplifying the yielding strength is inefficient in mitigating soft-storey response and collapse by dynamic instability when ignoring the height limitation, the proposed method effectively ensures stable inelastic response with uniform storey drifts and with reduced residual storey drifts across the studied building heights.