Study On Numerical Simulation And Experimental Research Of Progressive Collapse For Large-span Truss String Structure

In 1968, the collapse of the Ronan Point Apartment in the United Kingdom caused by explosion raised the attention of the researchers to the progressive collapse of the structures for the first time, and the relevant research has been carried out for more than forty years so far. At present, the research on the progressive collapse mainly focuses on the frame structures as the representative of the high-rise buildings. However the study of the large-span space structures is less in-depth. The truss string structure which has the characteristics of simple construction and low redundancy is a new type of large-span space structure, and the problem of its resistance to the progressive collapse deserves more attention.The progressive collapse analysis of the truss string structure was conducted by the numerical simulation and the dynamic tests in this paper. The failure mechanism of the progressive collapse of structures was discussed, and meanwhile the design method of the reinforced structures against progressive collapse was proposed. The main work in this paper is as follows.Firstly, the existing method for the numerical simulation of the progressive collapse of structures was introduced. Based on explicit dynamic finite element analysis program ANSYS/LS-DYNA, the numerical simulation of the progressive collapse of the truss string structures was carried out in this paper. The using method and the key problems of this program for the truss string structures were described in detail.The cable of the truss string structure has higher sensitivity as the key component in the structure. The cable was selected as the initial failure members and the dynamic response of the remaining structure after failure of the cable was studied. Accordingly to the numerical example of 72m-span truss string structure, the progressive collapse analysis of this structure under different loads was carried out. The response of this structure after failure of the cable was analyzed and the dynamic magnification factor was calculated, revealing the failure mode and the mechanism of the progressive collapse. In addition, the support stiffness of the large-span truss string structure, the cable area and the failure time of the cable were changed in the numerical simulation model respectively, and comparative analysis of the dynamic responses and the dynamic magnification factor of these structures was conducted to explore the influence of these factors on the progressive collapse of the large-span truss string structures.A 6m-span truss string structure plane system was designed and experimental research of the progressive collapse under the sudden failure of the cable was conducted. A failure trigger device which could effectively simulate the sudden failure of the cable was developed. The device could be used for remote operation, and had the advantages of simple, reliable and repeatable use as well as good applicability. The material tensile test of the structural members was carried out to obtain the stress-strain relationship of the material. The strain of the structure was measured by TST3826F-L test system and the joint displacement was measured by UI-3370CP and SA3type 120K-M3. By measuring the strain and the displacement, the dynamic response of the remaining structure was collected. By analyzing and comparing the experimental results and the numerical simulation results, the failure mechanism of the progressive collapse of the truss string structure were obtained further, and the accuracy and feasibility of the progressive collapse analysis of the truss string structure conducted by the numerical simulation based on the ANSYS/LS-DYNA program were verified.A method was presented to improve the anti-collapse performance of large-span truss string structure with fuse cable. Accordingly to the numerical example of 72m-span truss string structure as well, and four kinds of fuse cables were designed for it. The collapse resistance of the large-span truss string structures with different fuse cables after failure of the cable were investigated. Comparative analysis of the dynamic responses and the dynamic magnification factor of these structures was conducted to reveal the influence of the fuse cable on redistribution mechanism of internal forces for the structure. The fuse cable increased the structural redundancy and alternated the load path. Thus the resistance to progressive collapse of the structure was improved.