新型自复位耗能钢框架抗震及震后抗火试验研究

Experimental Study of a Novel Self-centering Energy-Dissipation Steel Frame Under Earthquake and Post-Earthquake Fire

地震易诱发次生火灾从而加剧结构破坏和生命财产损失。自复位耗能钢框架作为一种新型可恢复功能体系,已有研究聚焦其抗震性能评价,但尚且缺乏对其震后火灾下的灾变行为和失效机理的相关研究。针对一种以预应力钢棒和屈曲约束板为自复位和耗能元件的新型钢框架,基于节点试验对其抗震及震后抗火性能进行研究。抗震试验结果表明,设计合理的自复位耗能节点在转角高达6%时,仍可实现预期的损伤集中和震后复位机制。震后抗火试验结果表明,在经历幅值6%的转角变形后,自复位耗能节点仍具备长达1.5 h的耐火极限和高于900°C的耐火温度。不均匀温度场导致的热效应和材料性能退化导致的机械效应分前后两阶段对结构响应起控制作用。屈曲约束耗能板在灾害序列中始终作为主要损伤构件,并以前序地震损伤更甚的耗能板断裂作为节点在次生火灾下的失效模式。预应力钢棒在地震下发挥重要的复位作用,但在震后火灾中由于热膨胀和高温拉伸的共同作用而最终失效。

Earthquake can trigger secondary fire to exacerbate structural damage and loss of life and property.The self-centering energy-dissipation steel frame is a novel resilient system,and the seismic performance of this structure has been evaluated in existing studies.However,there is a lack of research on its structural behavior and failure mechanism under post-earthquake fire.This study presents a seismic and post-earthquake fire performance of a novel steel frame with pre-stressed bars and buckling-restrained plates served as self-centering and energy-dissipation elements of the target frame,respectively.The results of the seismic study show that with the appropriate design of target configuration,the mechanism of damage concentration and self-centering can be achieved even when the maximum drift ratio reaches 6%.The results of the post-earthquake fire test show that even after seismic loadings of a 6%drift ratio,the target self-centering energy-dissipation connection still has a fire endurance of more than 1.5 h and a failure temperature higher than 90o C.Thermal effects caused by uneven temperature conditions,as well as mechanical effects caused by the deterioration of material properties,separately dominated the structural response in the entire process.Buckling-restrained plates serve as the major damage element throughout the earthquake-fire sequence,and the fracture of the one with more severe damage during the preceding earthquake is considered as the failure mode of the structure under the subsequent fire.Pre-stressed bars significantly contributed to the self-centering mechanism under seismic loading,but they can fail during post-earthquake fire due to the combined effects of thermal expansion and high-temperaturestretching.