Investigation On Several Problems Of Progressive Collapse Analysis Of Steel Frame Structures

In recent years,with the development of economy,more and more high-rise buildings and large public buildings use steel structure.Once progressive collapse of such structures is induced,it will inevitably lead to great economic losses.Therefore,it’s of great theoretical significance and engineering value to study the problem of progressive collapse of steel structures.The alternate path method was employed to analyze the influence of space effect and floor slab on the resistance performance of progressive collapse of steel structure,and the global stability of steel frame structure in the process of progressive collapse analysis,the main contents are as followed:(1)The alternate path method was employed to analyze two-dimensional finite element model and three-dimensional finite element model separately through nonlinear static analysis(pushdown analysis).By comparing the results of two models,the influence of space effect on the resistance performance of progressive collapse for steel frame structure was studied.The results showed that,without considering the space effect of the steel frame structure,the resistance of progressive collapse for residual structure could be overestimated,and which led to unsafe results.(2)A three-dimensional finite element model with floor slab was built with the software ANSYS 10.0,the effect of floor slab on the resistance performance of progressive collapse for steel frame structure was investigated by nonlinear static analysis(pushdown analysis).The results showed that considering the effect of floor slab of steel frame structure can improve the resistance progressive collapse for residual structure,which could play a certain role in preventing the structure from progressive collapse.(3)By comparing the pushdown analysis results from two-dimensional finite element model,three-dimensional finite element model with and without floor slab,the effect of the position of failure column on the resistance performance of progressive collapse for steel frame structure was studied.The results showed that the loss of corner column may be more likely to cause progressive collapse of steel frame structure than middle column and inner column,and which can have a more negative effect on the structure.(4)By comparing the nonlinear buckling analysis results from two-dimensional finite element model,three-dimensional finite element model with and without floor slab,the global stability of the structure during the process of the progressive collapse was studied.The results showed that the global instability could have been occurred before the yielding-type beam mode progressive collapse.Therefore,attention should be paid to the global stability of the steel frame structure in the process of progressive collapse analysis.