冷弯薄壁四肢拼合箱形截面柱抗火性能研究

冷弯薄壁型钢四肢拼合截面柱是一种常用的拼合柱，主要用于多层冷弯薄壁型钢结构建筑结构中承受集中荷载。对8根拼合箱形截面柱进行了高温下整体稳定试验研究，主要考虑了不同的温度纵向分布模式和螺钉布置方式对其抗火性能的影响。试验中测得了炉温、柱温、轴向荷载、轴向位移和侧向位移等，并且得到了钢柱在高温破坏后的残余变形。根据试验结果可以判断钢柱在高温下首先发生整体屈曲，再发生局部屈曲，最后在二者相互作用下失去承载能力。试验结果表明：当螺钉间距小于300 mm时，构件截面的协同变形能力良好，单肢构件间未出现分离的现象，且随着螺钉间距减小，钢柱失效的临界温度有较大的提升；在拼合柱端部设置抗剪螺钉群对其抗火性能的提升不明显；当构件由全长受火变为上半部分受火时，构件侧移最大点位置会由中部区域向上移动靠近柱端，且达到耐火极限时，钢柱失效的临界温度升高。基于ABAQUS建立了有限元模型，模型中考虑了材料与几何非线性以及高温下螺钉的抗剪刚度。有限元模拟结果与试验结果对比发现，该有限元模型不仅可以很好地模拟该类构件高温下的变形，也可准确地预测其耐火极限与临界温度。

Study on fire behavior of cold-formed steel quadruple-limbbuilt-up box-section column

Cold-formed steel quadruple-limb built-up box-section column is a type of commonly used composite member, mainly used for multi-story cold-formed thin-walled steel structure buildings to bear concentrated load. In this paper, fire tests on eight columns were carried out to study the fire resistance of this type of built-up column against global buckling. Different heating modes and screw arrangements were experimentally studied. The furnace temperature, specimen temperature, axial load, axial displacement, and lateral displacement were measured, and the post-fire residual deformation of the specimens was obtained. According to the test results, the specimens first undergo global buckling, then local buckling, and finally lose their load-bearing capacity under the interaction of the two buckling modes. The test results show that when the screw spacing is less than 300 mm, the collaborative deformation ability of the cross-section is satisfactory，and there is no separation between the single component. Moreover, the smaller the screw spacing is, the higher the critical temperature is. The screw group set at the ends leads to limited improvement of the fire resistance. When the fire condition changes from full-length fire to upper part fire, the location of the maximum lateral displacement of the member would move upward from the middle region, and the critical temperature would increase when the fire resistance is reached. Finally, a finite element model was established based on ABAQUS, considering the material and geometric nonlinearity as well as the shear stiffness of the screw at elevated temperatures. By comparing the simulation results with the test results, it is found that the finite element analysis could simulate the deformation of the specimen at elevated temperatures and accurately predict the fire resistance and critical temperature of the specimen.