Nonlinear Dynamic Response Analysis Of Reticulated Shells Based On Dynamic Substructure Method

Reticulated shell structure has the advantages of beautiful shape,reasonable stress and large structural stiffness,which are widely used in civil and industrial construction and public buildings.At present,the dynamic nonlinear studies on reticulated shells are all based on the finite element dynamic time history analysis.However,due to the large number of degrees of freedom of reticulated shells,the calculation is complicated and time-consuming.Based on cellular automata technology,the cell automata numerical modes of K6 and K8 single-layer spherical reticulated shells were established by finite element software and programming software in this paper,and the similar node domains of basic reticulated shells and objective reticulated shells were matched.The nonlinear relation index between the reticulated shells was proposed,and the plastic bars of the objective reticulated shells were identified.At the same time,the parametric analysis of the reticulated shell numerical model is carried out to study the main factors that affect the identification rate of the plastic bar,including the ratio of vector to span,span,load,direction of seismic action,etc.According to the results of the parametric analysis,the requirements for improving the identification rate of the plastic bar are put forward.After identifying the plastic members of the reticulated shell,the substructural elements of the reticulated shell are divided based on the dynamic substructure method,the modal analysis and dynamic time-history analysis of the reticulated shell are carried out,and the calculation results of the reticulated shell using the substructural elements and the ordinary finite element elements are compared,including mode diagrams,node displacement and the equivalent stress of bars.The main conclusions are as follows:1)The logarithmic strain energy density in the node domain of the reticulated shell is linearly related to the amplitude of seismic acceleration.2)Maximum logarithmic strain energy density of bars(lg(E_jmax))and Maximum logarithmic strain energy density of nodal domains(lg(I_imax))are close to linear relationship.And when taking the same lg(I_imax),different span,ratio of vector to span,bar section and load have almost no effect on lg(E_jmax).Different seismic wave and seismic action direction have great influence on lg(E_jmax).3)Span,vector-span ratio,load and bar section have little influence on the recognition of plastic bars of K6 and K8 objective reticular shells,and the recognition rate is more than 80%.However,different seismic waves and seismic action direction have great influence on the recognition of plastic bars,and the recognition rate is between 60%and 80%.The vertical seismic wave has the greatest influence on the recognition of plastic bars of K8 objective reticulated shells,and the recognition rate is 0.Therefore,in order to improve the recognition rate of the plastic bars of the objective reticulated shell,the seismic wave and seismic action direction of the base reticulated shells and the objective reticulated shells should be consistent.4)Based on the identification results of the plastic members of the reticulated shell,the reticulated shell is divided into substructural elements,and then dynamic time-history analysis is conducted under the action of earthquake.The reticulated shell without substructural elements is compared.The modal shapes of the two are similar;under the earthquake action,the displacement error of K6 reticulated shell nodes is within 8%,the maximum node displacement error is within 2%,the error of the equivalent stress of bars is within 6%and the error of proportion of plastic bars is within 2%;the displacement error of K8 reticulated shell nodes is within 11%,the maximum node displacement error is within 3%,the equivalent stress error of bars is within 6%and the error of proportion of plastic bars is within 2%.