大型钢网架穹顶结构弹塑性稳定性分析

针对大型LNG储罐钢网架穹顶结构的弹塑性稳定性分析,基于刚体准则与改进塑性铰模型建立适于几何与材料双非线性分析的空间弹塑性梁单元,研究局部荷载扰动与整体模态扰动两种不同的初始缺陷处理方法以及材料非线性对结构稳定承载力影响的差异。结果表明:初始缺陷、材料非线性与约束刚度减小均会降低网架穹顶结构稳定承载力;荷载干扰下,结构稳定承载力对干扰大小敏感而对位置不敏感;模态干扰属于整体几何缺陷,结构整体初始变形较大,荷载位移曲线平滑。与ABAQUS相比,所建的弹塑性刚体准则空间梁单元及其相应的非线性分析方法效率与精度兼优,适用于大型复杂工程结构非线性分析,在处理局部缺陷对结构稳定性的影响上具有优势。

Elasto-plastic stability analysis of large steel grid dome structure

Based on the rigid body rule, an improved plastic hinge model is adopted to produce a spatial elasto-plastic beam element for the stability analysis of the steel dome structure of LNG storage tank by the consideration of the nonlinearity of geometry and materials.Two different methods of considering initial imperfections between local load disturbance and global modal disturbance and whether to consider the influence of material nonlinearity on the stability of the structure are studied. The results show that the initial defects, material nonlinearity and reduction of restraint stiffness will all reduce the stable bearing capacity of the grid dome structure. The stable bearing capacity of the structure under load interference is sensitive to the magnitude of the interference but not to the position; the modal interference is an overall geometric defect, the overall initial deformation of the structure is large, and the load-displacement curve is smooth.Compared with ABAQUS, the elasto-plastic rigid body criterion spatial beam element and its corresponding nonlinear analysis method are more efficient and accurate. It is suitable for nonlinear analysis of large and complex engineering structures, and has advantages in dealing with the effects of local defects on the structural stability.