PROGRESSIVE COLLAPSE ANALYSIS OF COMPOSITE FRAME WITH CONCRETE-FILLED STEEL TUBULAR COLUMNS SUBJECTED TO MIDDLE COLUMN FIRES

摘要

This paper presents a finite element(FE) model of planar frame with concrete-filled steel tubular (CFST) columns to investigate the mechanism of progressive collapse under loading and middle column fires.A static-dynamic analytic conversion procedure has been developed based on the restart and predefined-field function in the FE model using ABAQUS.The analytic procedure switch between static and dynamic analysis is effective to investigate the progressive collapse of composite frame subjected to fire which shorten the calculation time and show the dynamic characteristics of progressive collapse.The failure modes, displacement and internal force of composite frame were calculated caused by the damage of column subjected to fire.The results shown that the displacement of top column including four stages when exposure to fire, such as inflation deformation in early heating stage,localized failure of heated column, transient equilibrium phase and the progressive collapse phase.