高强度Q690钢柱受火后受力性能试验研究

为了获得高强度Q690钢柱受火后的受力性能,采用电炉将2根高强度Q690钢焊接H形截面柱升温至800℃后自然冷却至常温,对受火后钢柱进行受压试验,得到钢柱的承载力和破坏模式。为考察受火对钢柱承载力的影响,对2根同尺寸不受火钢柱也进行受压试验。使用ABAQUS软件建立了试验钢柱有限元模型,考虑钢材受火后力学性能的退化和截面残余应力的影响,模拟试验构件的结构响应,并与试验结果进行对比。研究表明:钢柱均发生了绕弱轴的整体失稳破坏;经800℃受火作用后的钢柱承载力与不受火相比降低30%左右;有限元分析结果与试验结果吻合良好。进而采用有限元模型分析受火温度、冷却方式、长细比等参数对受火后Q690钢柱整体稳定系数的影响,有限元分析发现:受火后Q690钢柱稳定系数随受火温度升高呈先增大后减小的趋势,转折点为800℃左右;受火温度较低时冷却方式对Q690钢柱稳定系数影响较小,受火温度高于800℃后影响显著;受火后Q690钢柱稳定系数随长细比增大而降低,长细比小于80时,降低幅度较大,长细比超过80时,降低幅度减小。

Experimental study on post-fire load capacity ofhigh strength Q690 steel columns

In order to obtain load capacity of high strength Q690 steel columns after fire exposure, two welded H-section Q690 steel columns were heated to 800℃ by a furnace and then cooled down in air to room temperature. Compressive tests on the two columns were carried out and the load capacity and failure mode were recorded. To investigate the influence of fire exposure on load capacity of steel columns, two specimens with similar dimension without fire exposure were also compressed. Finite element models of tested specimen were established by ABAQUS software and residual mechanical properties and residual stress were considered. The structural responses were simulated and compared with test results. The study shows that all the specimens fail with flexural buckling around weak axis. The load capacity of specimen after exposure to 800℃ is 30% lower than that of specimen without exposure to high temperature. Good agreement is found between finite element analysis and test results. The effect of exposure temperature, cooling method, slenderness ratio on the stability coefficient of Q690 steel columns were furtherly analyzed by employing established finite element model. The finite element analysis shows that the stability coefficient of Q690 steel column increases first and then decreases with the elevation of exposed temperature, and the turning temperature is about 800 ℃; when the exposure temperature is low, the cooling method has a little influence on the stability coefficient of Q690 steel column, and the influence is significant when the exposure temperature is higher than 800 ℃; the stability coefficient of Q690 steel column decreases with the increase of slenderness ratio, and the decreased value is obviously for slenderness ratio lower than 80, and the decreased value is not significant for slenderness ratio exceeding 80.