火灾后栓接Q690角钢净截面受拉承载力研究

Study on Net Section Tension Bearing Capacity of Bolted Q690 Angle Steel After Fire

对栓接Q690角钢在火灾后的净截面受拉承载力展开研究,参考过火后高强钢Q690材性试验结果,利用ABAQUS建立栓接Q690角钢的有限元模型,分析面外偏心距、螺栓连接长度、过火温度对火灾后栓接Q690角钢净截面受拉承载力的影响;将已有相关公式及规范公式的计算结果与模拟得到的角钢支撑受拉极限荷载进行比较;基于最小二乘法,提出了Q690角钢净截面受拉承载力的有效截面系数公式,对比了数值结果及其他文献试验结果;基于数值模拟数据库,进行了可靠度分析。结果表明:有效截面系数随着螺栓连接长度的增大而增大,随着面外偏心距的增大而减小,而过火温度对有效截面系数几乎没有影响;美国规范AISC 360-16对不同过火温度下Q690角钢净截面受拉承载力预测结果偏于不安全,中国现行《钢结构设计标准》预测结果偏于离散;提出的计算公式对于不同过火温度下的栓接Q690角钢净截面受拉承载力均能进行较好预测;推荐所提出公式计算火灾后栓接Q690角钢净截面受拉承载力的抗力分项系数为1.061。

The net section tension bearing capacity of bolted Q690 angle steel after fire was investigated.The finite element model of bolted Q690 angle steel was established by ABAQUS with reference to the material property test results of high strength steel Q690 after fire.The effects of out-of-plane eccentricity,bolt connection length and fire temperature on the tension bearing capacity of the net section of bolted Q690 angle steel after fire were analyzed.The calculation results of existing research related formulas and code formulas were compared with the tensile limit load of angle steel support obtained by simulation.Based on the least square method,the effective section coefficient formula of the net section tension bearing capacity of Q690 angle steel was proposed,and the numerical results were compared with the experimental results in other literatures.Based on the numerical simulation database,the reliability analysis was carried out.The results show that the effective section coefficient increases with the increase of bolt connection length and decreases with the increase of out-of-plane eccentricity.The fire temperature has little effect on the effective section coefficient.The net section bearing capacity of Q690 angle steel after different fire temperatures calculated by the formula in AISC 360-16 are unconservative,and the prediction result of the current Chinese Standard for Design of Steel Structures are in discrete distribution.The proposed calculation formula can well predict the net section tension bearing capacity of bolted Q690 angle steel under different fire temperatures.It is recommended that resistance factor of the proposed equation for calculating the net section tension bearing capacity of bolted Q690 angle steel after fire is 1.061.