火灾后Q690高强钢超低周疲劳性能研究  

Study on post-fire ultra-low cycle fatigue properties of Q690 high strength steel post fire

作　　者：薛暄译 王斐 石宇[1,2] 王卫永[1,2] XUE Xuanyi;WANG Fei;SHI Yu;WANG Weiyong(School of Civil Engineering,Chongqing University,Chongqing 400045,China;Key Laboratory of New Technology for Construction of Cities in Mountain Area(Chongqing University),Ministry of Education,Chongqing 400045,China)

机构地区：[1]重庆大学土木工程学院,重庆400045 [2]山地城镇建设与新技术教育部重点实验室(重庆大学),重庆400045

出　　处：《建筑结构学报》2023年第6期119-128,共10页Journal of Building Structures

基　　金：重庆市博士后特别资助项目(XmT20200011)。

摘　　要：为评估经历火灾的钢结构剩余抗震性能,需要明确火灾后结构钢材超低周疲劳性能。以受火温度、冷却方式和疲劳应变幅为变量,对23组高温后的Q690高强钢进行了超低周疲劳试验,获得了高温后Q690高强钢的疲劳寿命和循环应力应变曲线。在此基础上,分析了Q690高强钢的超低周疲劳性能以及耗能能力,讨论了火灾后Q690高强钢的超低周疲劳破坏形态,并对其微观金相组织进行了观测,讨论了微观组织对超低周疲劳性能的影响。结果表明:高温后Q690高强钢仍具有良好的耗能能力,其循环应力-应变曲线呈现出饱满的梭形;经历600℃后自然冷却可以起到回火的效果,使Q690高强钢的疲劳寿命较常温的提高了23.4%;经历900℃高温后,冷却方式对Q690高强钢的峰值应力影响显著,浸水冷却的Q690高强钢的峰值应力是自然冷却的1.77倍;高温后Q690高强钢金相组织发生变化并影响其超低周疲劳性能;除经历900℃浸水冷却的Q690高强钢外,断口可以观察到明显的疲劳源、疲劳弧线和瞬断区,疲劳应变幅的增加使疲劳弧线间距增大。To evaluate the residual post-fire seismic performance of steel structures,it is necessary to clarify the ultralow cycle fatigue performance.Ultra-low cycle fatigue test of 23 groups of Q690 high strength steel(HSS)after high temperature was carried out,considering temperature,cooling method and fatigue strain amplitude as variables.The post-fire fatigue life and cyclic stress-strain curve of Q690 HSS were obtained.The ultra-low cycle fatigue performance and energy dissipation capacity of Q690 HSS were analyzed,the post-fire ultra-low cycle fatigue failure mode of Q690 HSS was discussed.The microstructure of Q690 HSS was observed,and the influence of microstructure on ultra-low cycle fatigue performance was discussed.The results show that Q690 HSS still has good energy dissipation capacity after fire,and its cyclic stress-strain curve shows a full shape.Natural cooling after experiencing 600℃can play a tempering effect,which increases the fatigue life of Q690 HSS by 23.4%compares to that without heating.The cooling methods have a significant influence on the peak stress of Q690 HSS after experiencing 900℃.The peak stress of Q690 HSS cooling from 900℃by water immersion is 1.77 times that of natural cooling.The metallographic structure of Q690 HSS changes after high temperature and affects its ultra-low cycle fatigue performance.Except for the Q690 HSS cooling from 900℃by water immersion,there are evident fatigue source,fatigue arcs and instantaneous fracture zone in the fracture of Q690 HSS.The increase of fatigue strain amplitude increases the spacing of the fatigue arc.

关 键 词：高强钢 过火温度 超低周疲劳试验 耗能能力 金相组织 

分 类 号：TU391[建筑科学—结构工程] TU317.1TU311.41