Seismic damage drift limits of self-centering friction beam-column joints: Prediction and application

In recent years, self-centering structures have garnered significant attention as an effective strategy to enhance structural resilience, minimize residual displacements, and reduce seismic losses. However, research on the damage criteria for self-centering components remains limited-particularly in determining the inter-story drift ratios (IDRs) corresponding to various damage states. This gap has hindered advancements in performance-based seismic design and resulted in a lack of foundational data to support resilience assessments for self-centering systems. To address this issue, this study focuses on the self-centering friction beam-column joint (SCFJ) as the primary research subject. First, four distinct damage states for SCFJs are defined, and a finite element (FE) model is developed and validated. Sensitivity analyses are performed to identify key design parameters affecting the seismic performance of SCFJs. Based on typical engineering practices, a total of 432 FE models with varying section dimensions and design parameters are constructed, establishing a comprehensive seismic damage database for SCFJs. Subsequently, statistical analysis is used to determine the IDR thresholds for each damage state, and fragility curves are fitted accordingly. These fragility curves are then applied to evaluate damage and seismic losses in two six-story frame structures. Results indicate that damage in SCFJs is primarily concentrated in the reduced section, and the mean IDRs corresponding to slight, mild, moderate, and severe damage are 0.52 %, 1.07 %, 1.74 %, and 3.48 %, respectively. Under the maximum considered earthquake, SCFJs predominantly exhibit slight to mild damage, with associated seismic losses amounting to 30,500 CNY-representing a 41.6 % reduction compared to ordinary reinforced concrete joints (ORCJs). These findings demonstrate that SCFJs exhibit significantly reduced damage and lower seismic losses than ORCJs, providing a theoretical basis for future seismic performance and resilience evaluations.