Research On Static Stability And Dynamic Response For Single-double Layer Reticulated Shells Structure With Large Rise-to-span Ratio

The single-double layer reticulated shell, which has been widely used in recent years, is a spatial structure composed of single layer one and double layer one. Currently, fruitful results have been obtained by many researchers on static and dynamic stability characteristics of single layer reticulated shell or double layer one, however it’s lack of systematical study about stability characteristics of single-double one. This paper will use a double layer reticulated shell based on actual project and six single-double layer ones which are extended from the double layer one as the research projects, compute and analyze the static and dynamic characteristics of single-double layer one. The main contents are summarized as follows:(1) This paper investigates the static behaviors of two kinds of structure respectively, on this basis, the influences of parameter change on single-double layer reticulated shell,which include half-span distribution of live loads and changing form of the joint node of single-double layer, are studied. The results show that the nodes where the maximum vertical displacement happens are close to the joint of single-double layer, and the stiffness of structure declines with the enlargement of single layer region span. Besides, both the node vertical displacement and the axial force of circle members change violently due to the stiffness mutation located in the joint of single-double layer, and the change rate also increases with the augment of single layer region span. Furthermore, both the node vertical displacement and the axial force of circle members are controlled by half-span distribution of live loads, and changing form of the joint node of single-double layer have little effect on the structural static behaviors.(2) On the basis of static analysis, the analysis of impact of geometric nonlinearity and material nonlinearity on two kinds of structure was performed, as well as probing the effects on stability by several parameters and different initial geometric imperfection modes. Besides, the applicability of eigenvalue imperfection mode method is discussed. At last, this paper studied the imperfection sensitive region of single-double layer reticulated shells. The research shows that along with the augment of single layer region span, the impact of geometric nonlinearity on the stability bearing capacity of the perfect double and single-double layer reticulated shell increases, on the contrary, the impact of material nonlinearity declines. It’s suggested that the ratio of single layer region span should not exceed 40 percent of structural span based on the considerations of economy and stability. In addition, the stability bearing capacity of single-double layer reticulated shell is more conservative under the half-span distribution of live loads and can be improved obviously by changing form of the joint node of single-double layer. Furthermore, the structure is sensitive to the variation of initial geometric imperfection, a 1/500 of span as the reasonable maximum value of imperfection is more suitable for large single layer region span ratio, and 1/400 of span for small single layer region span ratio. In the end, the structural imperfection sensitive region locates primarily in single layer region(including the joint of single-double layer).(3) This paper compares the effects of different seismic wave simulation modes and different seismic waves on the structural dynamic response of single-double layer reticulated shell, and also studies initial geometric imperfection modes. The research shows the following three conclusions. Firstly, the variation of structural dynamic response can be measured more effectively by support large mass method, so this method is suggested to be a better method to calculate structural dynamic response. Secondly, compared with the conventional seismic wave records, the dynamic response is more adverse when the severest ground motion which meet certain site and basic period band are adopted. Lastly, when using stochastic imperfection modal method as the baseline reference, although taking structural natural vibration mode as initial geometric imperfection mode is more reasonable, the results of this method are less securable. By contrast, not only it shows a tendency to safety when using eigenvalue imperfection mode method, but the assurance rate of this method is higher.