杆系结构可动性判定准则

基于矩阵的奇异值分解法,提出了杆系结构在考虑荷载作用下的可动性判定方法,包括含机构的杆系结构可动性判定和瞬变结构的判定。通过分析结构的平衡矩阵,计算自应力模态、机构位移模态,归纳出了荷载态下杆系结构可动性判定公式。结果显示若机构位移模态与荷载向量正交,则几何意义上的机构可演变为可以承受外界扰动、相对稳定的结构。另外对瞬变结构给出瞬变判定公式,弥补了体系分类的空缺。最后辅以算例验证,给出结论,系统列出细化后的结构体系分类表。

NEW CRITERIA FOR THE MOBILITY OF 3-D BAR STRUCTURE

Based on the singular value decomposition(SVD)scheme,a new method for determining the mobility of bar assemblies considering the effect of loads is proposed.It mainly consists of the criteria for mobility of mechanisms and the method of how to distinguish transient assemblies.The independent modes of inextensional mechanisms and the states of self-stress are obtained by analyzing the equilibrium matrix.The criterion formulae for mobility of bar assemblies are listed.The results show that mechanisms would become stable structures when the vector of joint forces and the modes of inextensional mechanisms are orthogonal to each other.Transient assemblies are analyzed separately and the corresponding criterion formulae are obtained.Some typical examples are discussed.The conclusions are shown at the end,and the structural system is further classified.