A plastic design method based on multi-objective performance for high-strength steel composite K-shaped eccentrically braced frame

Abstract

A plastic design method based on multi-objective performance (PDMP) for high-strength steel composite K-shaped eccentrically braced frame (HSS-KEBF) is developed in this study, which explicitly considers the different seismic fortification objectives of the structure and the shear distribution relationships of the brace-frame system. The performance objectives of the structure under three seismic hazard levels were obtained by combining different roof drift ratios and displacement ductility demands, and a trilinear capacity curve of HSS-KEBF considering the change of post-yield stiffness was proposed. The energy balance principle was used to calculate the elastic and elastic–plastic shear distributions of the brace-frame system under different performance objectives, to facilitate the elastic–plastic design of HSS-KEBF. A ten-story HSS-KEBF structure was designed using the proposed design method, and an elastic-plastic finite element model of the structure was established using OpenSees for analysis. The results show that the structural model achieves the expected performance objectives in terms of capacity curves, roof drift ratios, base shears, and failure modes. From the SLE level to MCE level, the base shear distribution ratio borne by the frame component increased from 36% to 46%, which satisfies the design idea of multi-aspect fortification.