Study On The Selection And Optimum Design Of Double Layer Latticed Shell Supported By Inner Column And Surrounding

The support condition of the reticulated shell structure is one of the important factors that affect its mechanical properties and economic performance.The spherical reticulated shells are usually supported by the surroundings,and the peripheral nodes are rested on the foundation or the lower structure.In recent years,with the rapid development of cultural and creative industries,a variety of real performance theater has become a new kind of large span space structure.Due to the needs of the performance scene,the theater usually has a large span to adopt the formation of the inner column and the surrounding common support of the mixed support.In this paper,the ellipsoid double reticulated shells which is used as a large-scale real performance theater in Xi’an are supported by the inner column and the surroundings.According to the grid generation principle of double-layer reticulated shell,the three-dimensional coordinates of each node of double-layer reticulated shell are obtained by MATLAB program.Using the span ratio,the thickness,the position and shape of the grid column as the control parameters,a parametric finite element analysis model is established and the cross section of the selected bar is optimized by discrete variable cross section In the finite element program ANSYS.Through the comparison of the double-layer reticulated shell with no inner pillar,the stress performance and mechanism of the ellipsoidal double reticulated shells under the mixed support is analyzed.In the double-layer reticulated shells in which the inner and outer joints are co-supported,the force of the double-layer reticulated shells is dominated by compression at the top of the inner column,rather than bending.The diagonal inner column and the network Grid formed X-shaped cross arch significantly enhance the performance of the reticulated shell.After understanding the influence mechanism of the inner pillar support on the double reticulated shells,the position,quantity and form of the inner column are optimized by comparing the steel consumption and the mechanical properties when the double-layer reticulated shells are kept unchanged by means of parametric modeling.The influence rule of each parameter is summarized.The position of the inner column is optimized,and it is found that the internal column position has a significant effect on the mechanical properties of the reticulated shell.By comparing the internal force averages,the internal force peaks and the standard deviations of all the rods after the optimization of the inner column position,the internal force of the reticulated shell is reduced by more than 30%and the internal force distribution is more uniform.More than 80%of the internal force of the rod has changed significantly,which indicates that the inner column has changed the internal force distribution and force transmission path of the double reticulated shell;When the number of inner columns is changed from 4 to 6,the improvement effect of structural force performance is very obvious.The efficiency of the two new columns is basically the same as that of the original four columns.When the span is large and the conditions are allowed,you can consider the six pillars of the program;The inner column is a key component in the double-layer reticulated shell structure.Its bearing capacity and stability are not correlated with the double-layer reticulated shells.The inner column should be designed by the principle of its bearing capacity and stability are not lower than those of the shell.The inner column adopts the truss type lattice column to adjust the component section and the column size flexibly to fully exerts the material utilization efficiency of the component.After the optimization of the relevant parameters of the inner column,the shape,thickness and sag ratio of the double reticulated shell are analyzed.It is found that the truncated line shape of the reticulated shell has little effect on the steel consumption of the double-layer reel without inner column,which has less influence on the steel consumption of the double-layer reticulated shell.It is considered that the sensitivity of the double-layer reticulated shell to the shape of the truncated line is further reduced after the inner column is provided,and the double-layer reticulated shells are available in a larger range;The analysis of the thickness of the double-layer reticulated shells with the inner columns shows that with the thickness increases,the steel consumption decreases and then increases.When the thickness to span ratio in the range of 1/42～1/32,the amount of steel is optimal.The support effect of the inner column increases with the thickness of the double reticulated shell increasing.When the thickness ratio of the reticulated shell is less than 1/42,the double-layer reticulated shell will show obvious stress concentration The negative moment has a negative effect on the double-layer reticulated shell.The analysis of the parameters of the spanwise ratio shows that the larger the span ratio is,the smaller the effect of the inner column is.Double-layer reticulated shells are too flat or too bulging both will lead to an increase in the amount of steel.The amount of steel is fine within the vector ratio between 1/6～1/5.