约束高强钢柱受火后轴压剩余承载力试验研究

设计了3根截面尺寸、长度均相同的Q550高强度钢柱，其中两根受到轴向约束，并对其进行了恒载作用下升温、降温的受火全过程试验，以及自然降温至室温后的轴压剩余承载力试验，对未受火的钢柱进行了常温下的极限承载力试验。研究了高温试验中钢柱的轴向位移-温度和中点侧向挠度-温度关系、极限承载力试验中钢柱的轴力-轴向位移和轴力-柱中点侧向挠度关系，并进行了有限元模拟。试验以及有限元模拟分析显示，若约束钢柱在高温过程中发生屈曲，则降温后钢柱会有明显的残余弯曲变形，并且柱中截面会产生比初始残余应力更为显著的残余应力，从而显著降低钢柱的剩余承载力和轴向刚度。试验结果与有限元分析结果吻合较好，验证了有限元分析模型的有效性。

Experimental study on residual capacities of axially restrained high strength steel columns after fire

In this paper, three columns with the same section dimension and length made by Q550 high-strength steel were prepared for the experimental study. Two columns were axially restrained and tested under entire fire phase including heating and cooling down to ambient temperature and then tested to get the residual load-bearing capacity,while the other one was tested at ambient temperature to get the ultimate load-bearing capacity. For fire test, the axial displacement-temperature curves and deflection-temperature curves of the columns were obtained and analyzed. For the test at room temperature, the axial force-axial displacement curves and axial force-deflection curves of the columns were obtained and analyzed. These experiments were simulated through finite element method. Both experiments and finite element simulation analysis show that if the axially restrained columns buckle during the heating stage of fire, the residual bending deformation becomes obvious after cooling, and the residual stress in the cross section at the mid-height of the column will be increased significant and exceed the initial residual stress, leading to significant reduction of the residual load bearing capacity and axial stiffness of steel columns.The numerical results agree well with the experimental results, which proves the correctness of the finite element model.