Behavior Of Concrete-filled Steel Tubular Composite Frame After Exposure To Fire

With the increasing use of concrete-filled steel tubular (CFST) structure in engineering, especially fire disaster happens frequently in recent years, it is severely significant to further the research on the mechanical behavior of CFST structure after exposure to fire.The paper describes the research studies on the mechanical behaviors of CFST composite frame after exposure to fire. The main achievements can be summarized as follows:(1) Accurate thermal model was assumed, and CFST column to steel beam composite temperature field FEM model was also developed. The results obtained from the FEM model were verified against those experimental results. Meanwhile, the temperature distribution was analysised with the CFST composite model under fire.(2) Reasonable material model, element type and solution method were assumed. The mechanical behavior model of CFST columns to steel beam composite frame was developed considering the restrained effect and interface model of steel tube and concrete. The results obtained from the FEM model were verified against experimental results. And comparison of mechanical behavior between CFST frame at ambient temperature and post fire was also analysised.(3) Typical examples of CFST composite frame were modeled using the FEM model. Parametric analysis was performed to investigate the mechanical behavior of the composite frame after exposure to fire. The strength of steel tube, the concrete strength of column, the steel ratio of column, slenderness ratio, the axial compression ratio, the depth of fire protection, the beam to colums linear stiffess ratio and the beam to column strength ratio were considered as parameters. The influence of parameters to the load to displacement curve of CFST composite frame after exposure to fire was received. A simplified P-Δcurve model was also given.