火灾全过程下10.9级高强螺栓断裂性能试验研究  

Experimental study on fracture behavior of grade 10.9 high-strength bolts in whole process of fire

作　　者：陈桥 姜健 蔡文玉 杨卫明[1] 陈伟[1] 叶继红 Chen Qiao;Jiang Jian;Cai Wenyu;Yang Weiming;Chen Wei;Ye Jihong(China University of Mining and Technology,Xuzhou 221116,China;Hainan University,Haikou 570228,China)

机构地区：[1]中国矿业大学,江苏徐州221116 [2]海南大学,海南海口570228

出　　处：《土木工程学报》2023年第7期55-68,共14页China Civil Engineering Journal

基　　金：国家自然科学基金(52078478)。

摘　　要：火灾下钢梁悬链线效应产生的附加作用力易造成梁柱节点断裂破坏,掌握高强螺栓的高温力学性能和断裂性能是研究钢节点高温断裂破坏机理的基础。考虑应力三轴度和温升历程的影响,设计10.9级高强螺栓平滑圆棒和缺口圆棒试件,分别进行火灾升温段、升温-降温段和火灾后螺栓拉伸断裂试验,获得高强螺栓火灾全过程下工程和真实应力-塑性应变曲线;研究高强螺栓在复杂应力和高温共同作用下的断裂性能,并通过电镜扫描试件断口,研究其微观断裂机理。研究表明:火灾全过程下高强螺栓呈现韧性断裂特征;温度高于400℃时,EC3结果偏不安全,弹性模量折减系数偏大约0.15,屈服强度偏大0.3~0.4;不同温度工况下,应力三轴度越大,高温屈服强度和极限强度越大,断裂应变越小,但超过600℃时应力三轴度影响被削弱;断裂应变随温度升高而增大,降温段螺栓材性与峰值温度有关,直接采用升温段材性代替会造成不安全结果,弹性模量差异可达常温值的15%,屈服强度相差达20%;升温段材性直接代替火灾后材性则会造成材料浪费,强度折减系数差异达0.36。The additional force generated by the catenary effect of steel beams under fire is easy to cause the fracture and failure of beam column joints.Understanding the high-temperature mechanical properties and fracture properties of high-strength bolts is the basis for studying the high-temperature fracture and failure mechanism of the steel joints.Considering the influence of stress triaxiality and temperature rising history,the smooth and notched round-bar specimens of grade 10.9 high-strength bolts are designed.The tensile fracture tests of bolts in the heating stage,heating-cooling and after-fire stage are carried out,respectively.The stress-plastic strain curves of high-strength bolts are obtained,and the fracture performance of high-strength bolts under the combined action of complex stress and high temperature was studied.The fracture surface of the specimen is scanned by electron microscope to study its micro fracture mechanism.The results show that all high-strength bolts present ductile fracture characteristics in the whole process of fire.For temperatures above 400℃,the EC3 results are in the unsafe range.The reduction factors is about 0.15 higher for elastic modulus,and 0.3~0.4 higher for yield strength.Under different temperature conditions,the greater the stress triaxiality,the greater the high temperature yield strength and ultimate strength,and the smaller the fracture strain.However,when the temperature exceeds 600℃,the effect of stress triaxiality is weakened.The fracture strain increases with the temperature.The material properties of bolts in the cooling stage are related to the peak temperature.Directly using the material properties of heating stage instead of cooling stage will cause unsafe results.The difference of elastic modulus can reach 15%of the normal temperature value and the difference of yield strength can reach 20%.If the material properties in the heating stage directly replace the material properties after fire,it will cause material waste.The maximum difference of strength reduc

关 键 词：火灾全过程 10.9级高强螺栓 断裂性能 微观断裂机理 

分 类 号：TU391[建筑科学—结构工程]