空间网架结构竖向抗震性能的简化计算

Simplified Analysis of Space Grid Structures under Vertical Earthquake Action

将网架简化为考虑剪切变形的交叉梁系，用有限元法分析其竖向抗震性能．在动力分析中，忽略转动惯量的影响，对总刚矩阵进行刚度集聚，建立网架竖向振动方程，然后通过子空间迭代计算其自振频率和振型，再利用振型分解反应谱法求各振型下竖向地震作用效应并进行组合．文章同时给出了梁元法与空间桁架位移法精确解的误差比较，其精度满足工程要求，并且计算速度快、所占存贮空间少．

In this paper, the space grid structure is simplified into an intersecting beam system, and the finite element method, with the shear deformation taken into account, is adopted to analyse the vertical aseismatic behaviors. In the vibration equation, a condensed stiffness matrix is formed by transforming the rotation stiffness matrix into the submatrix caused by vertical displacements, the rotational inertia being neglected. Then the natural vibration frequencies and modes can be obtained through the method of subspace iteration. Finally, the maximal seismic effects of each vibration mode are calculated and then combined, using the mode resolution response spectrum method. Comparisons of the results by the beam method and the space truss method show that the simplified method is practical and precise.