Probability Analysis Of Progressive Collapse Of Steel Framed Structure

Since the progressive collapse of Ronan Point apartment in the UK in 1968,the characteristics of the low probability of the progressive collapse,which would cause great loss of life and property once it happened,have attracted extensive attention of scholars in various countries.With the extensive use of steel structures in buildings in recent years,it is of great social significance to prevent the progressive collapse of steel structures from accidental loads.However,at present,most researches on the progressive collapse of building structures are based on deterministic analysis,and the impact of the uncertainty of structures themselves and external loads on the progressive collapse resistance of structures is rarely mentioned.Aiming at this problem,this paper will conduct a fragility analysis of the progressive collapse resistance of the steel frame structure by numerical simulation.Firstly,a three-dimensional finite element numerical model of the substructure of the steel frame with the floor is established by means of macro modeling method,and the model is systematically verified by using the experimental data at multiple scales,such as material,joint and steel frame model,so as to ensure that the numerical model has good reliability and accuracy while having high operational efficiency.The influence of load distribution form and beam-column stiffness ratio on the collapse resistance of the structure was discussed through the macro-numerical finite element model.Secondly,the mechanical mechanism analysis of the steel frame structure’s collapse resistance was carried out to find the parameters that might have a greater impact on the structure’s collapse resistance.The tornado diagram method was used to analyze the sensitivity of related parameters of the structure.Tornado diagrams of the influence of various parameter uncertainties on structural performance under concentrated and uniformly distributed loads were drawn,and the three most important parameters affecting the collapse resistance of the structure were determined,namely concrete strength,steel beam height,and floor thickness.Finally,according to the sensitivity analysis results,the improved Latin super-cube sampling(CLHS)sampling method was adopted to establish the random finite element model,referring to the "three levels" in the seismic design of the building and the code ASCE 41-13,The limit states of IO(Immediate Occupancy),LS(Life Safety)and CP(Collapse Prevention)with different damage degrees were defined.Under the failure conditions of middle column,side column and corner column,the fragility of the structure to collapse resistance is analyzed by corresponding concentrated load and distributed load respectively,and corresponding fragility curves are drawn.