Construction Defects Influence On Structral Stability Of Freeform Surface Single-Layer Reticalar Shell

The design trend of modern space structure is to simulate space, work model and analysis by means of computer to fulfill many different types of 3-D relationship. This trend has brought extreme liberalization of architectural style. Thus, free-form surface spatial grid structure is introduced. In the process of designing free-form surface grid structure, checking component strength, stability and stiffness of grid structure is needed, in addition, checking structural overall stability and sensibility of initial imperfections is also very significant. How to accurately calculate the influence of structural stability and defects to structure should be taken into account in the process of designing grid structure. This thesis analyzes single-layer shell with general laws of free surface, it shows bending stress is larger than axial stress by comparing the axial stress and bending stress of cross-section. Thus, the influence of defects to this type of grid structure is different with that of spherical shell and cylindrical shell.This thesis has carried out eigenvalue buckling analysis, geometry nonlinear stability analysis and geometry-materials double nonlinear stability analysis on general free-form surface monolayer shell under dead load plus live load and study the stability of such shell and sensitivity of shell to initial imperfections. Then, eigenvalue buckling analysis, geometry nonlinear stability analysis and geometry-materials double nonlinear stability analysis on Shenzhen Bay Sports Center shell are carried out under dead load plus live load, dead load plus live load plus temperature reduction, dead load plus live load plus temperature increase to study the stability of this structure and compare the stability under this three load condition, but also analyze the influence of temperature and initial imperfections to the stability of grid structure. It shows that local buckling occur in these two grids when considering geometric nonlinearity, but It can bear load and the stability problem does not exist in this structure. When considering geometry-materials double nonlinear, critical load occur in these two grids and the stability problem exists. But critical load factor is greater than the factor in standard and the overall stability satisfies the requirements. The temperature load has little influence to the stability of Shenzhen Bay Sports Center.Defects are introduced for general free-form surface monolayer shell and Shenzhen Bay Sports Center shell by consistent mode imperfection method and man-made defects (construction error) method and then analysis about influence of imperfection on stability is carried out. The results show that initial imperfection has some influence to the stability, but less than that of spherical shell and cylindrical shell. It indicates that this type of structure is not sensitive to initial imperfection.