Q235焊接工字形钢支撑的低周疲劳性能试验及数值模拟

Experiment and Numerical Simulation on Low-cycle Fatigue Behavior for Q235 Welded I-section Steel Bracing Members

对19根Q235材质焊接工字形钢支撑进行了等幅轴向循环位移作用下的低周疲劳性能试验,基于观测到的翼缘出现可见裂纹时的循环次数提出了估算支撑低周疲劳寿命的经验公式。在试验基础上,对支撑滞回性能和低周疲劳性能进行了数值模拟。试验及数值模拟结果表明:试件在第1个弹塑性循环受压时就发生了出平面的整体失稳;从第3或第4个循环开始,支撑的抗压、抗拉承载力及单循环耗能进入到稳定退化阶段。将试验及数值模拟得到的支撑稳定承载力及跨中最大横向变形与相关规范、文献计算结果进行了对比,证实了相关规范、文献的可信性。总体上,数值模拟结果与试验结果吻合较好,但离散性小于试验结果。在数值分析得到的应力-应变结果基础上,利用2种临界面损伤模型预测了支撑裂纹萌生时的低周疲劳寿命,预测的裂纹萌生位置与实测位置一致,预测结果基本位于实测结果的3.5倍分散带以内,偏于安全一侧,同时发现残余应力对支撑的低周疲劳寿命基本没有影响。

The low-cycle fatigue behavior tests of nineteen welded Q235 steel I-section bracing members under constant amplitude cyclic axial displacement were carried out,and based on the cyclic numbers of macroscopic crack initiation in the flange monitored,an empirical formula for estimating the low-cycle fatigue life was presented.Based on the test results,the numerical simulation on the hysteretic and the low-cycle fatigue behavior of the bracing members was conducted.The results of analysis and test showed that,the specimens lose their overall stability around the weak axis during the first cycle compression loading,after the third or four cycle,the tensile and the compressive resistances,as well as the single-cycle energy dissipation of the specimens are all gradual decrease.The test and analysis results about the maximum compressive resistance and the maximum lateral deformation of these specimens were investigated and verified in comparison with the results calculated by the relevant literatures or codes.In general,the simulation results agreed well with the test ones.Based on the stress-strain results gained by the numerical analysis,numerical simulation of the low-cycle fatigue lives for the bracing members was estimated using two critical plane damage models.It was found that the predicted location of the crack initiation is in accordance with the test results,and the predicted low-cycle fatigue lives basically fall within a safe scatter band of 3.5,moreover,the residual stress has no effect on the low-cycle fatigue life of the bracing members.