Seismic performance assessment of steel braced frames with segmentally controlled steel braces

Abstract

A novel segmentally controlled steel brace (SCSB) featuring a simplified configuration analogous to conventional steel braces was proposed to enhance energy dissipation capacity primarily through repeated axial yielding in both tension and compression. The SCSB can be directly incorporated into traditional concentrically braced frames (CBFs), thereby forming a steel braced frame with segmentally controlled steel braces (SBF-SCSB). Seismic energy is predominantly dissipated via inelastic deformation of the link segments located at both ends of the SCSB. The detailing and design of the SCSB were presented, and a simplified finite element model was developed and validated against experimental results. Furthermore, three global structural models representing a steel moment frame (SMF), a CBF, and a proposed SBF-SCSB were established using OpenSEES. Time history analyses under various seismic intensities and incremental dynamic analyses were performed to comprehensively investigate the seismic response and fragility. Results indicate that the SBF-SCSB demonstrates significantly improved seismic performance compared to both the SMF and CBF. Under service level earthquakes, both conventional braces and SCSBs effectively increase lateral stiffness and reduce inter-story drift ratios. When subjected to severe earthquakes, the SCSBs develop stable and full hysteretic loops, enabling efficient energy dissipation and reducing base shear demands, thereby mitigating damage to primary structural members. Moreover, the residual inter-story drift ratios of the SBF-SCSB are substantially lower relative to those of the SMF and CBF. Additionally, the average peak ground accelerations corresponding to various performance limit states are consistently higher for the SBF-SCSB than for the SMF and CBF, highlighting its superior capacity for seismic damage control. Overall, the SBF-SCSB serves as an optimized and practical alternative to traditional steel braced frames.