Regression models for predicting the inelastic seismic response of steel braced frames

This paper describes the development of regression equations to predict the peak inelastic drift and acceleration response of steel concentrically braced frame (CBF) building structures. A database of Engineering Demand Parameters (EDPs) is developed by performing a large number of nonlinear time-history analysis (NLTHAs) in OpenSEES for a set of 24 case study CBFs. A consistent and realistic set of mechanical models is achieved by designing each case study frame using Eurocode 8. Multi-variable regression models for peak drift and accel-eration response at each storey level are fitted to the NLTHA results data. A nonlinear formulation and robust regression are employed to capture the influences of the Eurocode 8 behaviour factor and brace slenderness and overstrength limits on the EDP profiles over the height of a building. Comparison with existing models shows that the fitted regression equations achieve improved agreement with NLTHA results across a wide range of structural parameters. The regression models can be applied in performance-based design or assessment to predict the peak inelastic response of CBF structures without performing additional nonlinear analyses.