Post-earthquake fire behaviour of a self-centring connection with buckling-restrained plates and pre-stressed bars: An experimental investigation

Abstract

Earthquake is recognised as one of the most destructive hazards not only because of the loss and casualties caused by itself, but also the secondary disasters triggered by it. Among hazards following the earthquake, fire is the most common and threatening one that should be paid more attention. For the self-centring system initially proposed to mainly serve the seismic demands, it is necessary to understand its behaviour in post-earthquake fire scenarios to ensure comprehensive performance. However, neither the actual experimental response nor the systematic analysis has been conducted, leading to a lack of relevant knowledge. Based on that, this study mainly aims to explore the structural response and understand the failure procedure of a self-centring steel system under the earthquake-fire sequence. The focused configuration consists of buckling-restrained plates for energy dissipation and pre-stressed bars for self-centring. The quasi-static cyclic tests and standard fire tests were conducted on the cross-shaped self-centring connection derived from a prototype frame. Besides, a thermal-only test was supplemented to clearly distinguish the thermal and mechanical effects under fire. Results show that the target connection has excellent seismic performance under a peak drift ratio as high as 6%. In the meantime, it appears satisfactory post-earthquake fire resistance with endurance over 1.5 h and failure temperature higher than 900 °C. Thermal and mechanical effects are found to separately dominate the global response under post-earthquake fire, first the uneven thermal expansion and then the mechanical degradation at elevated temperatures. Moreover, buckling-restrained plates serve as the major damage element throughout the earthquake-fire sequence and fracture is detected on the side with severer seismic damage. Pre-stressed bars provide self-centring capacity under cyclic loadings but fail to retain the pre-tension in the subsequent fire. The findings reveal the actual response of the self-centring system for fundamental understanding, and can be extended for thermo-mechanical numerical calibration and further analysis, to help improve the comprehensive performance of self-centring structures under earthquake-fire sequence.