Probabilistic Evaluation Of Collapse Resistance Of Cable-Stayed Arch-Truss Under Random Parameters

As China’s modernization has entered a new era,the economy and society have been further developed.As a representative form of large-span spatial structure,cable-stayed arch-truss has beautiful shape and spacious internal space,so it is favored by more and more architects.The cable-stayed arch-truss adopts the external prestressing technology,which combines rigid and flexible,but has low redundancy.Especially after the failure of important components such as cable,the load path of the structure changes greatly,which is prone to progressive collapse.At present,in the study of progressive collapse of long-span spatial structures,the evaluation method system of anti collapse ability of cable-stayed arch-truss after failure of important components has not been formed.Based on the nonlinear buckling material model of beam-column element,this paper proposes a rapid analysis method of progressive collapse of cable-stayed arch-truss,carries out the progressive collapse analysis of cable-stayed arch-truss considering random parameters,and evaluates the anti collapse ability of cable-stayed arch-truss under the failure condition of important components.The main research contents are as follows:（1）In view of the current situation that the finite element analysis method for progressive collapse of cable-stayed arch-truss is complex in modeling,time-consuming and inefficient in analysis,a rapid analysis method for progressive collapse of cable-stayed arch-truss is proposed based on the nonlinear buckling material model of beam-column element,through the secondary development of LS-DYNA user subroutine The feasibility of the rapid analysis method is verified by comparing with the existing test;（2）The incremental dynamic analysis method suitable for progressive collapse of truss string is proposed.The IDA curve slope degradation coefficient I₁,bearing capacity degradation coefficient I₂ and nested bearing capacity degradation coefficient I₂’are introduced.At the same time,the sensitivity coefficient SI_jand vulnerability coefficient VI_i are defined with the axial force as the structural response.A multi index evaluation method of important components of cable-stayed arch-truss based on IDA is proposed.The important components of two structural examples are evaluated respectively,and the primary and secondary important components are determined.The importance coefficients of different important members are comprehensively studied,and the nominal continuous collapse bearing capacity of cable-stayed arch-truss is defined;（3）Based on the analysis of the mechanism of progressive collapse under the cable failure condition,the simplified assumption of the force on the mid span section of the cable-stayed arch-truss is proposed,and the simplified prediction formula of the progressive collapse bearing capacity of cable-stayed arch-truss under the cable failure condition is established.The deformation decomposition hypothesis of cable-stayed arch-truss is proposed.The deformation of cable-stayed arch-truss is decomposed into the elastic bending deformation of the whole structure and the elastic axial deformation of members.The simplified prediction formula of deflection of cable-stayed arch-truss is established,and the correction coefficient considering material nonlinearity and geometric nonlinearity is introduced to modify the simplified prediction formula of deflection;（4）The performance level points under different component failure conditions are defined.Based on the incremental dynamic analysis,the probability evaluation method of progressive collapse resistance of cable-stayed arch-truss is proposed.Considering three kinds of random parameters,100 structural samples are generated by Monte Carlo simulation method for progressive collapse analysis.Based on the statistical analysis results of IDA curve,the progressive collapse vulnerability analysis of cable-stayed arch-truss is carried out,and the exceedance probability and progressive collapse resistance under different failure conditions are quantitatively described;（5）The effects of space effect on IDA curve,continuous collapse bearing capacity and ultimate deflection span ratio of truss string are studied.The probabilistic evaluation method of progressive collapse resistance of single truss string is extended to spatial truss string.The exceedance probabilities and progressive collapse resistance of performance level points under failure conditions of cable and support bottom chord are quantitatively described.The influence of spatial effect on progressive collapse resistance of cable-stayed arch-truss is studied by comparing the quantitative analysis results with single cable-stayed arch-truss.