工程结构整体屈曲的临界荷载分析

很多工程结构的承载力取决于整体屈曲分析所确定的稳定承载能力．一般认为特征值屈曲计算值是非线性屈曲计算值的上限,而且按照第一阶屈曲模态施加初始缺陷必将减小临界荷载,通过数值计算表明实际工程中会出现相反的结果,并根据屈曲理论研究了上述现象的机理．比较了不同的屈曲类型屈曲后平衡路径的发展特征及其缺陷影响,采用若干典型结构作为算例对特征值屈曲分析进行探讨,发现其适用范围为直柱、框架及平板结构,并以实际结构为例进行了验证．通过分析得知:不同类型的屈曲形式有着不同的缺陷敏感性;屈曲后平衡路径的发展特征决定了特征值屈曲分析的偏差情况;对极值点屈曲的结构进行临界荷载分析,需要施加正负缺陷进行比较以得到最低临界荷载值．

Analysis of the Overall Buckling Load for Engineering Structures

The bearing capacity of many engineering structures is determined by the buckling analysis. In general , it is believed that the critical load calculated by the eigenvalue buckling analysis is larger than that by the nonlinear buckling analysis, and imperfections applied according to the first eigenvalue buckling mode will reduce the critical load of the structure. Some contrary cases are presented with numerical results and the mechanism of the above phenomenon is investigated. Based on the classification of critical points, the post-buckling paths of each type are traced and their characteristics observed. The influences of the imperfections are analyzed. From the example of several typical finite element models,it is found that the eigenvalue buckling analysis can only be used in straight bar, frame and plate structures, which is further tested by analyzing an actual engineering structure. The results show that the imperfection sensitivity differs for different types of critical points and the inaccuracy is controlled by the growing characteristics of the post-buckling path. In order to find the lowest critical load value, both positive and negative imperfections should be considered and their results compared.