Multistage performance design for enhancing progressive collapse resistance of earthquake-resilient steel frame joints

The anti-collapse performance of earthquake-resilient steel frame joints has received limited attention, and this study presents the first investigation of this topic. Collapse resistance tests were conducted on three specimens: a welded joint as a reference, a typical earthquake-resilient joint, and an innovative joint with multistage performance design. For the typical joint, the damper fractured, followed by subsequent failure of the web connection; prior to fracture, the load-bearing capacity increased linearly to the peak load during the large deformation stage. By contrast, the innovative joint exhibited a significantly higher peak load and deformation, with the weakened region remaining intact. These results demonstrate the feasibility of the multistage performance design. The finite element analysis was then validated against the test results and employed to investigate the anti-collapse mechanisms. The energy dissipation contribution of the catenary mechanism increased from 35% to 52% owing to the multistage performance design. Based on the validated model, a new earthquake-resilient joint was proposed to improve the multistage performance. The anti-collapse performance and seismic resistance were simultaneously enhanced. A critical joint rotation of 6%–10% is recommended. This study not only extends the current understanding of collapse resistance in earthquake-resilient structures but also contributes to enhancing their multi-hazard resilience. The proposed method provides a valuable reference for future designs.