横梁荷载作用下单层无侧移刚架的稳定承载力

Stability capacity of single-story non-sway frames with beam loading

分析刚架稳定性能时,常把横梁上的荷载集中于柱顶,这对单层无侧移刚架可能产生较大误差。为推导出合乎刚架实际性能的实用设计方法,首先进行刚架的弹性稳定分析,明确失稳是渐近极值型的。由于失稳时变形过大,不应用其临界荷载来确定柱的计算长度。其次对刚架水平推力是否需要二阶分析进行探讨,结论是否定的。再次,对弱梁刚架和弱柱刚架两种典型情况进行分析,明确设计规范采用的传统设计方法可以用于这类刚架设计,只是必须考虑水平推力的影响。文中强调了把无侧移刚架分为弱梁刚架和弱柱刚架的必要性,给出刚架类型的判别式和弱梁刚架的易位计算法。

In investigating the stability of frames, the load acted on the beam is usually concentrated on the top of the columns, which may cause considerable error for single-story non-sway frames. The present study aims at resolving practical calculation method in conformity with the actual behavior of the frames. The elastic stability of the frames is analyzed, revealing that the loss of stability occurs in an asymptotic mode. Owing to large deformation in the course of the instability, this critical load is unfit for determining the effective length of the column. The necessity of using second-order analysis for calculating the horizontal thrust is examined and the conclusion is negative. By analyzing two typical frames： weak-beam frame and weak-column frame, it is shown that conventional design approach, as adopted in design code, can be used for frames discussed herein, and one has only to take account of the influence of the horizontal thrust. The distinction between weak-beam and weak-column frames is emphasized, and the classification judgment formulas together with the 90°transposition approach for week-beam frames are presented.