大跨度斜拉立体桁架的极限承载力及影响因素分析

本文针对常用的斜拉立体桁架两塔柱三跨结构形式，基于UL列式，采用混合有限元，分别按空间（面外自由）和平面（面外自由度约束）两种模型，进行了线性、几何非线性、材料非线性以及同时考虑两种非线性的屈曲分析和比较，得出了结构的极限承载力。研究表明，空间模型比平面模型的安全因子低。线性屈曲和只考虑几何非线性屈曲两种模型的安全因子差别较大，而考虑材料非线性和双重非线性两种模型的安全因子比较接近。几何非线性对斜拉立体桁架的极限承载力影响较小，其结构极限承载力主要由材料非线性控制。立体桁架的塑性部位出现在塔柱附近的腹杆和弦杆，以及跨中附近的弦杆以及拉索附近的弦杆。此外，探讨了塔高、桁架高度、索距以及拉索刚度对结构极限承载力的影响，其中索距对结构的极限承载力影响最大。

Analysis of Ultimate Load Capacity and Its Influence Factors of Long Span Cable-stayed Space Truss

Based on the equation of updated Lagrangian formulation, through mixed finite element method, buckling analyses of linearity, geometric nonlinearity, material nonlinearity, geometric and material nonlinearity about system of three spans with two towers for cable-stayed space truss, by use of spatial and planar model, are investigated in this paper. The ultimate load carrying capacity is achieved. It is shown that safety factor of spatial model is lower than that of planar model. Safety factors of two models have great distinct between buckling analyses of linearity and geometric nonlinearity, but these are closer between material nonlinearity and geometric and material nonlinearity. Geometric nonlinearity has less influence and the ultimate load carrying capacity is mainly controlled by material nonlinearity. Plastic zones of space truss are concentrated on web members and chords near tower, chords near the middle of span and cables. In addition, the effects of different parameters inelading heights of tower and truss, distances between cables as well as cable stiffness, on the ultimate bearing capacity of cable-stayed space truss are discussed, in which distance between cables is more important.