非均布荷载下扣件式脚手架的随机缺陷稳定分析

Stochastic imperfect stabUity of fastener scaffold under non-uniformly distributed load

针对有缺陷的扣件式钢管脚手架,研究了其在非均布荷载下的全过程受力性能,提出了一种改进随机缺陷法,系统地分析了架体在不同荷载分布和各种缺陷随机耦合情况下,其相应失稳形态及极限荷载的随机分布规律,并进行了相关试验.发现架体立杆、水平杆及斜撑的应力均为阶梯状分布,架体在非均布荷载作用下呈现出立杆波浪形失稳形态,并且其极限荷载符合正态分布规律.研究表明架体中的水平杆和斜撑均参与架体受力,内力通过这两种杆件的传递在架体立杆中实现再分配,从而使得立杆应力从上到下逐渐减小,并使每根立杆均参与架体的受力.此外,由规范计算得到的架体稳定承载力具有很高概率可靠性,但是并不是架体稳定承载力的下限,在某些情况下,可能会存在安全隐患.

The whole process of mechanical performance was studied for fastener scaffold with imperfections under non-uniformly distributed load and advanced stochastic imperfections method was put forward. Based on these, considering different load distribu- tion and random coupling of various imperfections, buckling modes and random distribution of ultimate load were adopted and rela- tive experiments were made. It was pointed out that the stress of vertical bars, horizontal bars and braces presented step distribution, and instable mode of scaffold was undulating form under non-uniformly distributed load, and the limit load conformed to normal distribution. The results indicate that the horizontal bars and brace participate in the work of the scaffold. The internal force goes through the two types of bars to realize redistribution in every vertical bar in order to decrease the stress from the top to the bottom of the vertical bar and involve them in the stress of the scaffold. In addition, the stable capacity calculated by specification has the very high probability but it is not the stable capacity limit. In some cases, it may pose a safety hazard.