大长细比约束杆件屈曲后承载力简化计算方法

Calculation Method of Slender Restrained Tubular Member for Post-buckling Load-bearing Capacity under Fire

大跨度建筑空间中的火灾属于局部火灾,局部受火的网架结构由于其整体性会产生杆件间的约束效应,实际工程中网架结构的杆件长细比往往大于钢框架柱。目前对于网架结构中的约束杆件屈曲后承载力未见研究报道。根据假定的高温下约束杆件的变形形态建立内外力平衡方程,提出考虑初弯曲的网架结构中轴向约束杆件屈曲后轴力的简化计算方法,得到受火全过程轴力—温度的关系曲线,并发现初弯曲会使得长细比较大的约束杆件的应力增长速率明显减小。通过ABAQUS软件对网架结构中轴向约束杆件受火力学反应全过程进行了数值模拟,本文提出的简化计算方法与数值模拟结果吻合较好,为进一步分析网架杆件屈曲后承载力对整体结构抗火性能的贡献提供了理论依据。

Fire in the large volumn spacial buildings is defined as localized fire. The structural in- tegrity can cause restriant effect in the members of grid structure subjected to localized fire. The slenderness ratio of members in actual grid structure is often greater than that of the steel frame structure column. There is no research on the post-buckling loading-bearing capacity of restrained members in grid structure. A simple method for calculating the post-buckling load-bearing capac- ity has been derived from the force equilibriums of restrained steel members in fire condition and is verified by the ABAQUS software. The axial force-temperature relationship of a restrained steel member can be obtained. It is also found that the initial crookedness can slow down the growth rate of stress, especially for the members with high value of slenderness ratio. The post- buckling load-bearing capacity of members can improve the fire-resistance capacity of the steel grid structure.