Research On Progressive Collapse Resistance Of Large-span Truss String Structure

In recent years,frequent collapse accidents of large-span spatial steel structures show that,although it has high redundancy,failure of the key members may develop catastrophic progressive collapse.Since the truss string structures is widely used in public buildings,it will cause great property loss and casualties once it collapses under unexpected loads.Therefore,it is of great significance to analyze the progressive collapse of long-span string truss structure.The main research contents and conclusions of this paper are as follows:(1)The key techniques and related problems of the numerical analysis of continuous collapse of spatial structures are described,and various parameters and criteria adopted in this paper are clarified.(2)The numerical analysis of the existing tests(the dynamic failure test of single truss cable)shows that the ABAQUS /Standard solver can accurately simulate the progressive collapse of the truss structure.After the failure of the cable and the bottom chord of the support,the force mechanism and failure mode of the single truss structure are analyzed.The influence of different restraint forms of supports on the collapse behavior of structures is studied.The results show that the single string structure has a single transmission path,and the failure of the bottom chord at the support and cable will lead to the collapse of the structure.For the progressive collapse simulation of the string structure,the sliding hinge bearing with measuring range should be used.(3)The theoretical basis of the double-cable design is discussed in depth,the structure of the double-cable design can make full use of the tensile strength of the cable under the accidental load,and reduce the possibility of progressive collapse caused bythe failure of the cable,which has certain economic and engineering feasibility.The dynamic response of the structure with double cable design under the failure of single cable is analyzed,and the collapse performance of the structure with single cable design and double cable design under the failure of single cable is compared,draw the conclusion: the two-cable string truss design changes the internal force redistribution mode of the residual structure caused by the cable failure,and the residual structure changes from the tubular truss structure to the string truss structure.The structural stress mode and collapse mechanism do not change qualitatively,and the collapse resistance of the structure is greatly improved.The failure of the bottom chord of the support easily leads to the collapse of the structure.(4)The progressive collapse behavior of space truss string structures is studied by numerical simulation.Three types of members: cable,column and support are selected as the initial failure member,and the dynamic response to the residual structure(displacement,internal force of the member)is analyzed.The mechanism of force transfer and collapse mode of long-span string truss structure are discussed,and the dynamic response and progressive collapse resistance of two-cable structure and single-cable structure under cable failure are compared.Finally,according to the failure of initial members in different locations,measures to enhance the resistance of long-span string truss structure to progressive collapse are proposed.