单阶柱上下柱弹塑性阶段的相互作用

Elastic-plastic interaction between upper and lower columns of singly-stepped columns

单阶柱屈曲时上、下柱存在相互作用,对顶端自由和顶端受转动约束的阶形柱进行了弹塑性有限元极限承载力分析,研究了这种相互作用在弹性阶段和弹塑性阶段的变化。结果表明,在弹塑性阶段,这种相互作用总是朝着增加阶形柱的承载力方向变化,说明目前规范采用依据弹性假定确定的计算长度系数,应用于弹塑性工作的柱子是偏于保守的。通过分析弹塑性阶段上、下柱相对刚度的强弱的变化和柱顶弹性约束相对于柱子刚度的变化,对产生这种结果的原因进行了分析。

There is an interaction between upper and lower columns in the sway-buckling of singly-stepped columns. Finite element analysis of the load-carrying capacity of top free and rotationally restrained stepped columns in the elastic-plastic stage was carried out to study the influence of the interaction in elastic stage and elastic-plastic stage. It is found that the interaction in the elasticplastic stage always increases the overall load-carrying capacity of the stepped columns, which verifies the conservativeness of the current code method where elastic effective length factors are used regardless of the stress level of the columns. Explanations are presented on such results by changing the relative rigidity between the upper and lower columns, and that between the elastic rotational restraints and the stepped columns.