Failure Mechanism Of Single-layer Reticulated Domes Under Multi-point Impact Considering The Influence Of Joint Stiffness

Reticulated shells are very popular because of its large indoor space and beautiful shape.It is one of the structural forms of long-span spatial structures.Because of its reasonable stress,high stiffness,light weight and various structural forms,these structures are more and more widely used in gymnasiums,museums,exhibition halls and opera houses in large and medium-sized cities.As a landmark building,long-span structure marks the improvement of local modern building science and technology and economic level.However,with the continuous application of reticulated shells in major projects,the failure and collapse of such buildings under accidental load has attracted more and more attention.Whether the latticed shell structure can provide safety guarantee for people's life and property becomes a concern when it is subjected to accidental impact loads such as aircraft impact.Scholars at home and abroad have done a lot of research on this issue and achieved fruitful results.However,many research results are the conclusions of some numerical simulation.Moreover,the uncertainties of the number and location of impacted objects are not considered,and the effect of joint stiffness on the impact dynamic response of reticulated shells is not considered.Based on the previous research foundation,this paper uses the combination of numerical simulation and experimental research to further study this problem,and considers the influence of factors which have not been considered in the existing research resu lts on the conclusion.The specific research contents are as follows:(1)This paper presents a numerical simulation method for the dynamic response of single-layer reticulated spherical shells under multi-point impact loads.Based on ANSYS/LS-DYNA analysis program,this refined modeling method can consider the influence of the size and volume of welded spherical joints on the analysis results.Cowper-Symbols is selected as the constitutive model of steel in this model,which takes into account the effect of strain rate and is especially suitable for impact.The contact algorithm adopts point-to-surface contact algorithm,which is based on penalty function algorithm.At the same time,this paper describes the process of applying multi-point impact load to the reticulated shell structure in the LS-DYNA program.(2)The refined finite element model of K6 single-layer reticulated domes is selected as the research object.The stiffness of the joints is changed by changing the wall thickness and diameter of the welded spheres.The influence of the stiffness of the joints on the dynamic response and failure mode of single-layer reticulated domes is studied.Based on the analysis results of 10 typical examples,the influence of joint stiffness on the dynamic response and failure modes of single-layer reticulated domes under multi-point impact is summarized.(3)The model test of K6 single-layer reticulated domes is used to verify the accuracy of the refined finite element analysis method.Firstly,the tensile tests of welded spherical joints,inclined rods,ring rods and ribs of reticulated shells were carried out respectively,and the mechanical properties parameters of the materials were obtained.The finite element model was modified by using the material performance parameters obtained from the test.Secondly,multi-point impact tests on single-layer reticulated domes were carried out on a self-made impact test bench.The test includes three parts: elastic impact,elastic-plastic impact and destructive impact.The dynamic response data of key members and nodes of single-layer reticulated domes during the whole impact process are obtained by using data acquisition instrument.The whole deformation development of single-layer reticulated domes during the whole impact process was photographed by high-speed camera.The experimental results are compared with the numerical simulation results,and the two analysis conclusions are consistent,which verifies the accuracy of the refined finite element analysis method.(4)LS-DYNA program is used to analyze a large number of parameters of K6 single-layer reticulated domes under multi-point impact loading.The influence of impact velocity,impact mass,impact point number and impact point distribution on failure mode and dynamic response of single-layer reticulated domes is considered in the analysis model.According to the ultimate deformation characteristics of reticulated shells,six typical failure modes of single-layer spherical reticulated shells under multi-point impact loads are defined,and the disadvantageous conditions causing the overall collapse of reticulated shells are discussed.Based on the results of energy analysis,the failure modes of reticulated shells can be predicted by the loss of gravitational potential energy(? U).The ? U can also be used to evaluate the damage degree of reticulated shells after being impacted.At the end of the paper,how to improve the energy dissipation capacity of single-layer reticulated domes is discussed.