高温下铝合金板式节点刚度退化及其对网格结构抗火性能的影响研究

Study on stiffness degradation of aluminium alloy plate joints at high temperatures and its effect on fire resistance of mesh structures

采用有限元数值模拟分析方法,研究了200~400℃时铝合金板式节点的弯曲刚度退化机理。给出了不同温度对应的弯曲刚度退化折减系数,并分析了节点的破坏模式。分析结果显示,上节点板局部变形明显,下节点板出现拉剪破坏,翼缘板沿着周围螺栓孔位置断裂,随着温度的升高腹板应力集中位置逐渐向下发展,腹板发生断裂破坏。在上述基础上,通过典型铝合金网格结构的案例分析,研究了节点弯曲刚度退化对网格结构整体抗火性能的影响。结果显示,高温下,相较于未考虑节点弯曲刚度退化网格结构,考虑节点弯曲刚度退化的网格结构变形在高温区集中,竖向变形增加了4.5%,竖向承载力下降了46%。节点弯曲刚度退化对结构抗火性能影响明显,在铝合金结构整体抗火分析中应予以考虑。

The finite element numerical simulation analysis method was used to study the bending stiffness degradation mechanism of aluminum alloy plate joints at 200~400℃.The bending stiffness degradation reduction coefficients corresponding to different temperatures were given,and the failure modes of the joints were analyzed.The analysis results show that the local deformation of the upper gusset plate is obvious,the lower gusset plate has tensile-shear failure,the flange plate breaks along the surrounding bolt holes,and the stress concentration position of the web gradually develops downward as the temperuture rises and the web fractures.On the basis of the above,through the case study of a typical aluminum alloy mesh structure,the influence of bending stiffness degradation of the joints on the structural overall fire resistance was studied.The results show that at high temperature,compared to the mesh structure without considering bending stiffness degradation of the joints,the deformation of the mesh structure with considering bending stiffness degradation of the joints is more concentrated in the high temperature area,and the vertical deformation increases by 4.5%,the vertical bearing capacity decreases by 46%.The bending stiffness degradation of joints has obvious influence on the analysis of structural fire resistance,and it should be considered in the overall fire resistance analysis of aluminum alloy structures.