考虑柱间相互作用的阶形柱计算长度系数

Effective length factors of stepped columns considering interaction effect among columns

柱间相互作用对阶形柱的稳定性有很大的影响,而我国现行规范及已有文献所给出的阶形柱计算长度系数的计算方法不能准确考虑该作用。利用等截面压杆的转角-位移方程得到阶形柱的刚度矩阵,由此推导了轴力对阶形柱刚度削弱的表达式,并构建了可考虑柱间相互作用的阶形柱计算长度系数的计算式。研究表明该计算长度系数计算式具有较高的精度,使用方便,可用于多跨框架的计算,同时也适用于柱高不等的情况。对钢梁起坡的山形门式刚架,给出了实用的计算方法,参数分析表明采用该方法计算得到的柱计算长度系数具有良好的精度,可满足设计需要。

The interaction effect among columns has a great influence on the stability of stepped columns. As provided by current design codes and existing literatures, the effective length calculation methods of stepped columns can not accurately to account for this effect. In view of this, the stiffness matrix of stepped column was obtained by using the rotational displacement equations of the member with constant cross section. The expression of the negative lateral stiffness for stepped column was derived and then used to establish the effective length factors formula with consideration of the interaction effect among columns. The results show that the formula is accurate and easy to use. It can be used to calculate the multi-span frames and the frames with different column heights. A practical method to account for the influence of the roof inclination angle for pitched-roof portal frames with stepped columns was also presented. The parametric analysis shows that the practical method has good accuracy, which can meet the design requirements.