Study On The Collapse Behavior Of The Huge Reticulated Structure Under The Action Of Strong Earthquake

As a new type of large span space structure,the cylindrical reticulated mega structure has many advantages,such as clear transmission line,various forms,convenient construction and so on.At present,the research on this structure are mostly concentrated in the structure form,mechanical properties,calculation method and optimization analysis,and the research of structure under dynamic load is less.For large span structure,progressive collapse in recent years is more concerned about.So it is necessary to study the collapse performance of the new structure system under dynamic loading.Based on the finite element theory,the dynamic analysis software of ANSYS/LS-DYNA is used to simulate the collapse of large cylindrical structure and the collapse process under the action of strong earthquake.It is clear that the node and substructure have an influence on the collapse resistance of the cylindrical reticulated structure,and the effects of the stiffness of the joint,the structure of the sub structure,the structure of the sub structure and the arrangement mode on the collapse resistance of the structure are studied.The main contents are as follows:(1)The failure mode and failure mechanism of the huge reticulated structure under the action of strong earthquake are studied.According to the structural response of the structure under a series of amplitude modulated seismic waves,it is concluded that the collapse of the structure belongs to the unstable collapse caused by the geometric nonlinearity.According to the order of the failure bar in the collapse process,the structure,the surrounding bearing upper chord and bottom chord,chord,and bearing adjacent grid longitudinal truss and arch truss to the intersection of grid diagonal and upper chord,bar,in the collapse loads for the first possible failure region and failure extended to the surrounding and the cross.(2)The effect of the joint stiffness on the collapse resistance of the cylindrical reticulated mega structure is studied.Based on the existing two kinds of assumptions about the joint stiffness of the spatial structure(rigid joints and joints),a quantitative analysis is given.The results show that the stiffness of the joint has little influence on the collapse resistance of the structure,and the design of the cylindrical reticulated mega structure is more conservative and reasonable.(3)The effect of substructure on the collapse resistance of the huge reticulated structure of the cylindrical surface is studied.The results show that,compared with the main bearing structure separately,the collapse resistance of the whole structure is related to the form of substructure when the substructure is involved in the cooperative load: When the sub structure is a cylindrical shell,the collapse resistance of the whole structure can be improved by taking part in the cooperative loading.When the sub structure is a double-layer grid,it can reduce the collapse resistance of the whole structure.(4)The influence of connection arrangement,the sub structure of the fork tube net shell structure and span ratio between rod specifications,double net shelf structure and main structure(surrounding supporting or supporting four corners),double net shelf structure height and rod specifications on the collapse resistance of the whole structure are analyzed when the substructure is taken into account.The analysis results show that the sub structure layout more substantial,more uniform,the collapse resistance of the structure is stronger;The smaller the span ratio,the stronger the ability to resist collapse;With the fork tube net shell bar specifications(cross-sectional area)increases the collapse-resistant capacity first increased and then decreased;Double net frame structure supporting four corners when the collapse resistance of the structure is greater than the surrounding support;The higher the height of the double deck net frame structure,the larger the rod size,the smaller the collapse resistance of the structure.