震后火灾下内置单环加强T形圆管节点受火性能分析

Fire resistance of tubular T-joints with internal single ring stiffener under post-earthquake fire

为了分析火灾作用下考虑震损的内置单环加强T形相贯节点的抗火性能,开展了基于试验验证内置单环加强T形相贯节点计算模型的有限元分析。根据实际工程应用情况,考察参数支管与主管壁厚比、支管与主管的直径比、主管直径与两倍壁厚比及加强环厚度与主管壁厚比对节点抗火性能的影响,合理确定参数取值范围,利用Pushover分析法考虑地震引起的损伤,引入损伤变量,然后采用ANSYS中重启动分析方法,将地震引起的残余应力和残余变形全部传递到节点的抗火性能分析中,对不同损伤变量及不同参数下单环加强T形相贯节点的临界温度、耐火性能和失效机理进行分析。结果表明:损伤变量对内置单环加强T形圆管节点的抗火性能影响较大,节点临界温度随损伤变量的增大而大幅减小;支管与主管壁厚比对内置单环加强T形圆管节点的抗火性能影响效果不明显;随着支管与主管的直径比和加强环厚度与主管壁厚比的增大,内置单环加强T形圆管节点的临界温度呈下降趋势;随着主管直径与两倍壁厚比的增大,内置单环加强T形圆管节点的临界温度有较明显的上升趋势。

To analyze the fire resistance performance of tubular T-joints with internal single ring stiffener considering earthquake damage, finite element analysis(FEA) was carried out to verify the calculation model of internal single ring stiffener tubular T-joints by using existing test results. According to the application of tubular T-joints in engineering field, important parameters, i.e., brace to chord wall thickness ratio, brace to chord diameter ratio, chord diameter to twice wall thickness ratio, and reinforcement ring thickness to chord wall thickness ratio, were selected to study the influence on the fire resistance of the tubular T-joint. Then, setting the parameters in a reasonable range, using the Pushover analysis method considering the earthquake damage, and introducing the damage variable, the residual stress and residual deformation caused by the earthquake were transferred to the fire resistance analysis by the restart analysis method in ANSYS. The critical temperature, fire resistance and failure mechanism of tubular T-joints with internal single ring stiffener under different damage variables and parameters were studied comprehensively. The results show that the damage variable has a great influence on the fire resistance performance of tubular T-joints with internal single ring, and the critical temperature decreases greatly with the increase of the damage variable. The effect of brace to chord wall thickness ratio on the fire resistance of tubular T-joints with internal single ring is not obvious. With the increase of brace to chord diameter ratio and reinforcement ring thickness to chord wall thickness ratio, the critical temperature decreases. The critical temperature increases obviously when the chord diameter to twice wall thickness ratio increases.