Mechanical performance analysis of RC frame beam-column joints considering load–displacement hysteresis curves

This study investigates the seismic performance of damaged RC frame beam-column joints reinforced with external angle steel and three different secondary reinforcement methods (thin-walled steel plate shear walls, diagonal braces, and V-shaped buckling-restrained braces) through low-cycle cyclic loading tests. Based on load–displacement hysteresis curves, the energy dissipation capacity, stiffness degradation, ductility, and failure mechanisms of the joints are systematically analyzed. Test results indicate that all reinforced specimens achieved the desired shift in failure mode from “strong beam-weak column” to “strong column-weak beam.” Among them, specimens reinforced with V-shaped buckling-restrained braces (RC-4) exhibit the best performance. Their ultimate load capacity increases by 455.0% compared to unreinforced specimens, cumulative energy dissipation rises approximately 20.2 times, displacement ductility coefficient reaches 2.88, and stiffness retention rate remains at 77.9% even after cracking. This reinforcement method, employing V-shaped buckling-restrained braces, possesses multiple energy dissipation capabilities and significantly delays the progression of node damage. It is suitable for seismic retrofitting in high-intensity seismic zones and provides experimental evidence and design references for enhancing the seismic performance of existing RC frames.