Dynamic Response And Failure Mechanism Analysis Of K6 Single Layer Reticulated Spherical Shell Under Multi Point Continuous Impact Load

The reticulated shell structure has the characteristics of good mechanical properties and rich shapes and is widely used in the construction of large stadiums and venues in cities.In recent years,engineering accidents such as terrorist attacks,aircraft falling,and high-altitude falling have caused structural failure even collapse frequently.The dynamic behavior and failure mechanism of space structures subjected to single point impact have been studied at home and abroad,but the dynamic behavior of space structures subjected to multiple points and continuous impact is rarely studied.In this paper,K6 type single-layer spherical reticulated shell is taken as the research object.On the basis of experimental research,the dynamic performance of K6 type singlelayer spherical reticulated shell under multi-point continuous impact is studied by combining theoretical analysis and finite element simulation.The specific work is as follows:(1)By establishing the motion equation of the impact zone of the spherical reticulated shell structure under the triangular pulse load,the dynamic response and response ratio of the structural system are derived.It is concluded that the main influencing factors of the maximum response ratio of the structure are the duration of the impact load and the natural frequency of the structural system.The approximate energy method is used to calculate the plastic deformation of spherical reticulated shell under impact loads,and then derives the radius of the depression area.The results show that the depression radius is affected by the curvature radius,equivalent thickness and edge width of the shell structure.In addition,the yield stress of the structural material and the impact energy absorbed by the structure also affect it.The results provides a basis for the subsequent selection of unfavorable multi-point impact positions of the structure.(2)The impact calculation model of K6 single-layer spherical reticulated shell is established using ANSYS/LS-DYNA,and the experimental test results and numerical simulation results are compared and analyzed.The results are in good agreement and the error is within the allowable range.The accuracy of finite element model and structural impact numerical analysis method is verified,which lays the foundation for the subsequent analysis.(3)By establishing 47 finite element models under impact conditions,the dynamic response of the reticulated shell structure under multi-point continuous impact is analyzed with the rise span ratio,impact position,impact mass and impact velocity as different parameters.The results show that the above factors only have a greater impact on the dynamic response of the structure in the impact zone during the first and second impacts,and have little impact on the structure in the non-impact zone.(4)By comparing the deformation of 35 examples of K6 single layer spherical reticulated shells under different multi-point continuous impact energy,five deformation modes are summarized:(1)multiple local depressions of the structure,(2)multiple local severe depressions of the structure,(3)structural collapse,(4)multiple punching shear failure of the structure with severe depressions,(5)multiple local punching shear failure of the structure.Taking the deformation mode(1)and the deformation mode(2)of the reticulated shell structure under the effective secondary impact as the object,the failure mechanism is studied and analyzed.The deformation of the reticulated shell structure under these two deformation modes spreads outward after the second impact,especially the deformation mode(2),the deformation of the structure between the impact points develops greatly,but the deformation of the lower part of the reticulated shell structure develops less in the two deformation modes.In the deformation mode(1),the structure absorbs less energy,and the members in the impact area do not enter complete plasticity;in the deformation mode(2),the structure absorbs more energy and the members in the core area of the impact enter complete plasticity,which results in that the energy absorption rate of the structure is larger than the deformation mode(1).