求解车辐式结构自应力模态的逐点去约束法

Constraints removed method for self-stress mode problem of spoke structures

车辐式结构是一种由索桁架、内部受拉环以及外部受压环梁组成的空间结构,确定其初始预应力态是一个"由形找力"的问题,即需要结合建筑设计给定的结构位形,寻找一种预应力分布形式,使结构在预应力和自重作用下,能够达到建筑方案的几何位形要求.求解自应力模态是确定初始预应力的基础.已有求解自应力模态的方法,如平衡矩阵理论,需要使用专门程序,无法在通用有限元软件如Ansys上直接应用.本文在平衡矩阵理论的基础上,提出了针对车辐式结构的逐点去约束法.该方法能够判定车辐式结构是否存在自应力模态并求出它.对于不存在自应力模态的结构,通过一个算例提出了修改结构几何位形使其具有自应力模态的方法.逐点去约束法可以使用Ansys等通用有限元软件计算,为车辐式结构的自应力模态分析提供了方便、有效的途径.

Spoke structures, as spatial structures formed by cable trusses connecting tension rings and compressing rings, are widely used in roofs of stadiums. It is a force-finding problem to determine the initial stress state, which means to find a distribution of pre-stresses so that the structure can satisfy the structural configuration under the pre-stresses and dead loads. Self-stress modes are basic conditions to solve force-finding problem. Several methods, for example, equilibrium matrix theory, have been developed by previous researchers to solve the self-stress mode problem of the cable tension structure. However, since they can not be used directly in general structural analytical software such as ANSYS, these methods are not so convenient for spoke structures. This paper presents constraints removed method for self-stress mode problems of spoke structures based on equilibrium matrix theory. This method can judge whether the structure has self-stress mode and find suitable distribution of pre-stresses. Constraints removed method can be used directly in general structural analysis software and offer an easy and effective way to solve self- stress mode problem of spoke structures.