Fire Resistance Of Concrete Filled Steel Tubular Components Subjected To Post-earthquake Fire

Fire is one of the most common and largest hazard secondary disaster after earthquake.After the earthquake,the structure of the building will have many damage,such as the falling off of the protective layer and the degradation of the strength of the material,resulting in the decrease of structure fire resistance.The occurrence of post earthquake fires(PEF)would exacerbate the damage of structure and cause the structure collapse.Concrete filled steel tubular(CFST)structure is widely used in engineering practice because of its many advantages.In recent years,the research on the seismic performance and fire resistance of concrete filled steel tube structures or components is relatively more,while the research on fire resistance after the earthquake is relatively small.Therefore,this paper uses the finite element software ABAQUS to study the fire resistance of concrete filled steel tubular members after the earthquake.The main work is as follows:(1)Research on seismic performance of CFST membersThe constitutive relation model of steel and core concrete under cyclic load is determined,and the hysteretic model of CFST column is established by ABAQUS.The rationality and correctness of the modeling method is verified by the finite element calculation of the existing tests.On this basis,the whole process of concrete filled steel tubular column under cyclic load is analyzed through typical examples,and the important parameters affecting the seismic performance are analyzed.(2)Research on fire-resistance performance of CFST members124 fire resistance data were collected,mainly including ordinary CFST columns,concrete filled steel tubular column with encased profiled steel and concrete filled double skin steel tubular columns.The reasonable thermal parameters and the thermal constitutive relationship at high temperature of steel and concrete have been established.The temperature field model and fire resistance model of CFST members are established by ABAQUS,and the temperature field and fire resistance of existing tests are numerically simulated,which verifies the rationality and correctness of the modeling method.Finally,the calculation formula of the fire resistance of concrete filled steel tube columns is summarized.(3)Research on concrete filled steel tubular columns subjected to post-earthquake fireThe damage index is used to evaluate the damage of CFST members after the earthquake.A reasonable damage index model of CFST column is selected,and based on this model with 45 square concrete-filled steel tubular column hysteretic test data,given the seismic damage index model of concrete filled square steel tubular column.A finite element model of fire resistance of CFST columns after earthquake is established by the data transfer function in ABAQUS.The failure model and damage mechanism of CFST members subjected to post-earthquake fire were analyzed,and the influence of damage index on the fire resistance of CFST member is studied.