Stability And Dynamic Analysis Of Reticulated Shell Considering Stiffness Of Welded Hollow Spherical Joints

In the design of single-layer reticulated shell,the welded hollow ball joints have the advantages of clear transmission force,simple structure and convenient connection,and are widely used in engineering practice.In practical engineering,the welded hollow ball joints are usually designed as rigid joints.In fact,the welding hollow ball joints will also deform,which is a semi-rigid joint between rigid connection and hinge joint.Therefore,the research on semirigid joints will be of certain application value to the actual project.In this paper,the stress process of welded spherical joints in elastic-plastic stage is analyzed.The stress changes of joints from elastic to plastic stage under axial force are studied.The elasto-plastic stiffness of the joint under axial force is solved.The factors affecting the axial stiffness of the joint are analyzed.At the same time,the failure process of the joint under the action of bending moment is analyzed,and the bending stiffness of the joint in the elastic stage is calculated.The bending stiffness of the joint in the elastic-plastic stage is fitted,and the stiffness degradation coefficient is derived.The relationship between the bending stiffness of the joint in the elastic-plastic stage,the ratio of pipe diameter to ball diameter and the thickness of the ball wall is studied.The pre-processing model of welded spherical joint shell is established by 3D3 S software.The stability analysis of the shell considering the stiffness of welded ball joints is carried out by ANSYS software.The influence of the initial defects,span and vector span ratio are considered.The linear buckling analysis and nonlinear buckling analysis are carried out for the single-layer reticulated shell structure with different node stiffness.The results show that the ultimate bearing capacity of the welded hollow ball joint is 0.68% lower than that of the rigid joint for the shell structure with a span of 50 m and a ratio of 1/4 of the vector span.In this paper,the dynamic response analysis of the keweitt type latticed shell structure considering the elastic-plastic stiffness of the joint is analyzed,and the influence of different parameters such as span,vector span ratio and member section are considered.The natural frequency,node displacement response and acceleration response of single layer keweitt shell structure under different seismic conditions are analyzed,and the displacement time history curve and acceleration time history curve are drawn.The results show that the maximum displacement differences between the nodes and the rigid connections of the reticulated shell structure considering the elastic-plastic stiffness of the nodes are 8.74%,1.84% and 8.71%respectively under horizontal seismic action,vertical seismic action and three-dimensional seismic action.The results show that the maximum displacement differences between the nodes and the rigid connections of the reticulated shell structure considering the elastic-plastic stiffness of the nodes are 8.74%,1.84% and 8.71% respectively under horizontal seismic action,vertical seismic action and three-dimensional seismic action.Because the distribution of internal force of the keweitt type latticed shell is uniform,the seismic performance of the joint grid shell is better,and the advantages of the single grid shell structure can be combined with the keweitt-United grid shell structure.Therefore,the dynamic analysis of the joint elastoplastic stiffness of the keweitt-joint square latticed shell is carried out.The influence of span and vector span ratio are considered.The natural frequency of the keweitt-joint square latticed shell under different stiffness is calculated,and the influence of of each node on the deformation of the latticed shell under earthquake action is analyzed.