张弦空间结构的非线性分析

运用非线性有限元基本理论研究张弦空间结构的非线性特征。针对5个张弦空间结构工程,研究结构的几何非线性、材料非线性和边界条件的状态非线性特征,揭示其基本力学特性。分析表明:张弦空间结构的刚性构件体系贡献了结构的线性刚度,结构的变形协调使拉索应力刚化进而增大结构的几何刚度;对索施加初始预拉力可以增大结构几何刚度,但不影响结构总刚度增量的变化规律;结构总刚度的非线性部分随荷载步的改变而更新,结构分析须先确定结构所处的荷载工况;结构材料进入塑性后表现为结构总切线刚度中线性部分的降低,当结构达到弹塑性极限承载力时表现为结构材料失效。基于张弦结构的自平衡特性,当张弦空间结构滑动支座滑移达到滑程时,结构的边界条件转变为相应的铰支座或弹性支座。通过屋盖结构支座附近同位置且同方向的下部支承结构体系的刚度与屋盖邻支座区域杆件体系刚度的比较,可方便准确地对屋盖单独模型进行屋盖结构在实际工作环境中边界条件的模拟。

Nonlinear analysis of spatial string structure

The nonlinear characteristics of the spatial string structure were studied by using nonlinear finite element analysis.The nonlinear characteristics,such as geometric nonlinearity,material nonlinearity and state nonlinearity of structural boundary conditions,were revealed by examining several spatial string structural projects.The results show that the frame system of the spatial string structure contributes to the linear stiffness,and stressing of the cables increases the geometric stiffness.The initial tension of the cables can enhance the structural stiffness,but not affect the variance ratio of increment of the total stiffness.The total structural stiffness is updated with the load steps,so the loading status should be determined prior to the structural analysis.The linear stiffness of the total tangent stiffness is reduced as soon as the material enters the plastic state,and the structure collapses are due to material damage when the structure arrives at its elasto-plastic ultimate capacity.The sliding support of the spatial string structures is set based on the structural self-balance characteristic.When it reaches the limit of the slippage,the boundary condition becomes hinge or elastic spring support.By comparing the stiffness between the roof frame system and the supporting system adjacent to the roof supports along the same direction at the same point,the boundary condition of roof structure under actual loading condition can be simulated exactly.