轴向约束钢柱温度应力影响因素研究

建筑结构多为超静定结构.火灾条件下,组成结构的各构件在受到不均匀温度作用时,构件内将会产生温度应力.温度应力增加了构件的作用荷载,并影响受火钢柱的稳定性,是导致约束钢柱屈服破坏的主要原因.根据文献分析,轴向约束钢柱的温度应力影响因素主要有轴向约束刚度、长细比、初应力水平和构件升温.采用试验方法研究各因素对约束钢柱温度应力的影响规律.在温度应力增长阶段,构件所产生的温度应力与构件的温度升高值之间为线性关系,温度越高,温度应力越大.温度应力随轴向约束刚度和长细比的增大而增大；初应力水平越高,温度应力值越小.初应力水平的大小不影响温度应力的增长,但决定构件何时进入塑性状态.

Study on the influence factors of thermal stresses of axial-restrained steel columns

Most of steel structures are statically indeterminate structures.Under fire condition,the compositions of a structure will give rise to thermal stress when exposed to non-uniform temperature.On the basis of analysis on reference,the influence factors of thermal stresses of axial-restrained steel columns were investigated.They were temperature increment,axial restraint stiffness,slenderness ratio and initial stress ratio.A series of tests were carried out by using crossover trial method to study the influence rules of these factors.The end restraint stiffness was set as 3 levels,slenderness ratio was set as 4 levels and initial stress ratio was set as 3 levels.The results showed that the relationship between temperature increment of columns and its thermal stresses was a linear relation.The higher temperature,the larger thermal stresses.Before buckling,because of the bigger end restraint stiffness,the bigger restraint for axial elongation of steel column,the axial thermal stress increased with the increasing of restraint stiffness.The axial thermal stress increased with the increasing of slenderness ratio.The columns of large slenderness ratio brought about elastic buckling,and earlier failure,while that of small slenderness ratio brought about elastoplastic buckling,later failure.Initial stress ratio was insensitive to thermal stress,but it could impact steel columns entering into elastic-plastic behavior.