索桁张拉结构形状设计及找力分析

Shape design and finding force analysis on cable-truss tensile structure

为研究索桁张拉结构的形状判定和自应力求解问题,通过ANSYS有限元软件,提出了基于合理位形改进的力迭代法.首先,基于索桁张拉结构所特有的拓扑关系,从其合理位形出发,推导了形状判定的简洁判断公式.然后,提出了改进的力迭代法,用以求解索桁张拉结构的自应力模态.迭代过程中,更新后的索力逐渐逼近目标值,并在目标预应力作用下得到结构的不平衡位移.算例结果表明,所提方法可一次性确定索桁架的合理形状,且迭代5次左右便可求得结构的自应力模态,所得结果与已有方法的结果相比最大误差为0.48%,满足精度要求.将基于平面索桁架得到的自应力模态代入空间索桁张拉结构中,计算结果接近,内力最大误差为0.030%,且不平衡位移较小,从而证明了由平面索桁架组装成空间索桁张拉结构的可行性.

To study the shape determination and solve the self-stress modes of cable-truss tensile structures, an improved force iteration method based on reasonable shape was proposed by the finite element software ANSYS. Firstly, a simple formula for shape determination was derived from the rational shape based on the topological relation of the cable-truss tensile structure. Then, an improved force iteration method was proposed to solve the self-stress modes of the cable-truss tensile structures. In the iteration process, the updated cable forces were gradually close to the target values, and the unbalanced displacements of the structure under target pre-stresses were obtained. The results of examples show that the cable-truss frame with reasonable shape is determined by one-time, and the self-stress mode is obtained after about 5 iterations. The largest error between the results of the proposed method and those of the existed method is 0.48%, meeting the engineering requirements. After the self-stress mode obtained from the plain cable-truss frame is put into the spatial cable-truss tensile structure, the calculation results are close, and the largest error of the internal forces is 0.030%. The unbalanced displacements are small, proving the feasibility of the assembly of spatial cable-truss tensile structures by plain cable-truss frames.