考虑蠕变效应的钢柱高温承载力计算方法

高温蠕变对火灾下钢构件的内力和变形影响较大,现行《建筑钢结构防火技术规范》(GB51249—2017)中未考虑蠕变对钢柱高温承载力的影响。采用ANSYS软件分析考虑蠕变后钢柱在高温下的受力性能,并与钢柱的抗火试验进行对比,发现考虑蠕变的钢柱有限元模拟结果与试验数据吻合更好。利用验证的有限元模型进行参数分析,结果表明:考虑蠕变效应后,钢柱的高温承载力受初始缺陷(残余应力、初弯曲、初偏心)、弯曲方向、荷载比、长细比、升温速率的影响较大,受截面形式和钢材屈服强度的影响较小。给出了考虑蠕变效应后计算钢柱高温承载力的简化方法。

Determination of load bearing capacity of steel columns at elevated temperature considering creep effect

The creep deformations developed in steel significantly affect the deformation and bearing capacity of steel structures in fire. However, such creep effect was not considered in fire-resistance calculation method of steel columns in current specification of Code for Fire Safety of Steel Structures in Buildings (GB 51249-2017). Load bearing capacity of steel columns at elevated temperature after considering creep effect was analyzed by ANSYS soft package. A comparative study is performed in this paper to compare the finite element results with measured data obtained from fire test,and it is found that the numerical results and measurements show good agreement when considering the creep effect. Subsequently, the validated model was used for parametric studies. It is shown that the initial imperfection (i.e., residual stress, geometric imperfection, and load eccentricity), bend direction, load ratio, slenderness ratio and heating rate have a significant influence on the load bearing capacity of steel columns when considering high temperature creep. In contrast, the load bearing capacity of steel columns is less sensitive to the section shape and yield strength of steel. A simple design method is proposed to calculate the load bearing capacity of steel columns at elevated temperature.