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截面温度不均匀钢柱火灾下将发生热弯曲及扭转屈曲破坏,同时对热变形的约束导致钢柱内在升温阶段产生附加压力,在降温阶段出现附加拉力。分别考虑3种约束刚度比和3种截面温度分布形式,进行了9根受约束钢柱的抗火试验,量测了受约束钢柱达到最大轴力时的温度(屈曲温度)、轴力恢复至初始荷载对应的温度(临界温度)及破坏温度,研究其在火灾升温和降温阶段的受力性能、破坏特征。试验结果表明,截面温度不均匀导致钢柱在绕截面对称轴弯曲时同时发生扭转;约束刚度比越大,钢柱的屈曲温度越低,破坏温度与屈曲温度之差越大;截面温差越大,钢柱屈曲温度和破坏温度越高。同时对试验钢柱进行了有限元分析,分析结果与试验结果基本一致,验证了所建立的有限元分析模型的正确性。
Thermal bending and torsional buckling damage will occur under the column cross-section temperature nonuniformity. At the same time, the restraint of thermal deformation will lead to additional pressure in the inner temperature rise of steel column and additional tension in the cooling phase. Three kinds of constrained stiffness ratios and three kinds of cross-section temperature distributions were respectively considered. The fire resistance tests of nine constrained steel columns were carried out. The temperature (buckling temperature) of the restrained steel column when the maximum axial force was reached and the axial force recovery To the initial load corresponding to the temperature (critical temperature) and the destruction of temperature, temperature and cooling during the study of the stress performance, failure characteristics. The results show that the nonuniform temperature of the cross section causes the steel column to twist at the same time around the axis of symmetry of the cross section. The larger the restrained stiffness ratio is, the lower the buckling temperature of the steel column is and the larger the difference between the failure temperature and the buckling temperature is. , Steel column buckling temperature and destruction temperature is higher. At the same time, the finite element analysis of the test steel column was carried out. The analysis results are in good agreement with the experimental results. The correctness of the established finite element analysis model is verified.