Stability Analysis Of Concrete Folded-plate Pseudo-spherical Densely Ribbed Reticulated Shell

The concrete folded plate pseudo-spherical reticulated shell is formed by cutting the plane on the spherical surface and then meshing.The structure is formed by the ribbed flat plate at the ridge line,which is a new concrete space grid structure.In the process of structural construction,the spatial position can be determined by the ridge line coordinates,and the construction technology of the ribbed slab is used to avoid the complicated process of the general curved mesh shell formwork and the bracket,which greatly reduces the construction difficulty and shortens the construction period.At the same time,the concrete space structure has better durability and fire resistance,and reduces the maintenance cost of the structure.It is a new type of shell structure with good engineering application prospects.For large-span concrete shell structures,structural stability problems cannot be ignored,because during concrete construction,casting defects,concrete cracking,and component lap offsets can cause changes in the overall stiffness of the structure.For this reason,this paper systematically studies the stability performance of concrete folded-plate pseudo-spherical reticulated shells with finite element software,and discusses the bending stiffness of main ridge line,sub ridge line,ribbed beam and bearing ring beam in detail.The effect of the ratio of the span ratio and the thickness of the roof panel on the structural stability.The analysis of structural elastic stability shows that the structure exhibits overall deformation in the low-order instability mode,and the main ridge line is symmetrical,and the plate shell near the bearing ring beam is the first to be unstable;The influence of load is large and should not be lower than 1/8;the bending stiffness of bearing ring beam has limited influence on critical load;the bending stiffness of dense rib beam has great influence on critical load of structure,and increasing the height of section is beneficial to enhance structural instability.The main ridge line is the pitch line of the structural low-order instability mode,and its bending stiffness has little effect on the critical load of the structure;the critical load increases linearly with the increase of the stiffness of the auxiliary ridge line;increasing the thickness of the roof panel is not effective.To improve the critical load;in order to ensure better overall stability and material utilization,it is recommended that the division of the side length of the ribbed grid is controlled at about 1.5m.The geometrical nonlinear calculation of the structure shows that the structural sagittal ratio is the main factor affecting the ultimate load,and the two have a parabolic growth relationship;the load-displacement curve under different bearing ring beam stiffness has a high degree of coincidence,that is,the bending stiffness of the bearing ring beam The ultimate load has little effect;as the stiffness of the rib beam increases,the ultimate load increases significantly,but the height of the rib beam is not higher than the height of other beam members;the thickness of the roof slab cannot improve the ultimate load of the structure,too thick The roof panel will increase the weight of the structure.It is recommended that the roof panel take a smaller thickness when the bearing capacity is satisfied.The geometric initial defect reduces the structural ultimate load,and the maximum defect value is 1/800 of the span.Based on the large-scale parameterization results,regression analysis is performed.Fit the formula for the ultimate bearing capacity.Through the failure analysis of structural local components: the ultimate load of the rib beam is reduced;the failure of the shell and shell will cause the overall collapse of the structure;the failure number of the main ridge beam will have little effect on the ultimate load within a certain range;The effect of the load is significant;when the bearing ring beam fails,the ultimate load decreases sharply,and the deformation concentrates toward the failure,causing local collapse.This paper concludes with a summary of the current research work and points out the issues that need to be addressed in the next step.