火灾下约束钢柱临界温度的简化计算方法

在火灾条件下,约束钢柱轴力由于升温而增加,会导致在较低的温度下发生屈曲;但屈曲后,钢柱的轴向温度膨胀得到释放,轴力下降,因此屈曲后钢柱仍能继续承栽。本文通过计算长度系数将转动约束钢柱转换为铰支钢柱,给出了一种轴向约束钢柱在火灾升温条件下的临界温度的简化计算方法——轴力放大系数设计方法。此法通过轴力放大系数将轴向约束钢柱转化为无约束钢柱,再按无约束钢柱计算得到钢柱的临界温度。用验证过的有限元模型对简化计算方法进行了验证,计算结果表明简化方法吻合较好。

Simplified Calculation Method for Critical Temperature of Restrained Steel Column in Fire

The axial load of a steel column will increase because of the axial restraint.Buckling of axial-restrained columns may occur at a lower temperature than that of free columns.But the steel column can still keep working after buckling in a fire for the axial load would reduce after the release of the axial temperature expansion.A rotational restrained steel column is converted into a hinge-support one by using the effective length coefficient,and a simplified calculation method for critical temperature of restrained steel column is proposed.The simplified calculation method can transform the axial restrained column into an unrestrained one by using an axial force amplification factor,and then the critical temperature of the restrained column can be obtained by the design method for unrestrained columns.The simplified calculation method is verified by an ABAQUS model.The critical temperatures predicated by the two methods agree well.