Investigation On The Elasto-plastic Dynamic Response Of Double-layer Spherical Reticulated Shells Under Rare Earthquake

The elasto-plastic response characteristics is the main basis of reticulated shell's seismic design and aseismic measures in rear earthquake, but the related research is relatively weak. Systematic analysis and research about double-layer reticulated spherical shell's dynamic response characteristics and it's influence factors under rare earthquake dynamic response characteristics and influence factors is made. The main improvement on existing research:the collaborative work of the lattice shell and substructure is considered; the condition that the reticulated shell's bar is buckled under pressure is considered; the sections of model's bar is determined by the full stress optimization method. This paper mainly analyzes the influence,that four kinds of structural factors such as the span of shell, rise-span ratio, connection condition of abutment, layout of substructure exert, in the elastoplastic response characteristics on the double-layer reticulated spherical shell in rare earthquake. The main study contents and conclusions are as follows:(1) Influence that four kinds of structural factors exert on the model's dynamic characteristics and the seismic responses of structures under small earthquakes is investigated. Research shows that, when the substructure is asymmetric or reticulated shell span is large, the contribution of vertical seismic action is larger and greater internal forces are generated in the bar in the middle span of the shell, when the substructure is symmetric or reticulated shell span is small, the contribution of horizontal seismic action is larger and greater internal forces are generated in the bar near the abutment. The sections of 72 models which are designed under non seismic conditions don't need adjustment because of frequently occurred earthquake checking.(2) The stiffness of substructure and connection condition of abutment are the main factors that influent the difference between dynamic response in rear earthquake and non-seismic load effect of the double-layer reticulated spherical shell.When the abutment of shell is elastic connection or substructure stiffness is weak, the plastic rod is mainly distributed in the area near the abutment; when the abutment of shell is rigid connection or substructure stiffness is strong, the plastic rod is mainly distributed in the middle of span. (3) Large rise-span ratio is also the important reason that causes the differences between the dynamic responses under rare earthquake and the non-seismic load effect of the double-layer reticulated spherical shell. Especially to the large span reticulated shells the upper and lower parts of which are connected rigidly, large rise-span ratio is the prime factor that affects its seismic response, actually it will even causes changes of the distribution of the plastic bars and visibly increasing the number of plastic bars and values of the plastic strain.(4) Different earthquake waves will give rise to the change of the number of plastic bars and visible difference of the value of the residual plastic strains to the reticulated shell structures.(5) From the viewpoint of the residual deformation, collapse appears rarely in the double-layer spheral reticulated shells under 8 degree rare earthquake, it proves that these structures can easily meet the seismic design demand that structures are not allowed to collapse during rare earthquakes.