The Analysis of Interface Normal Stress of Short Column of Square Concrete-Filled Steel Tube with Axial Compression

The interface normal stress reflects the interaction between the steel tube and the concrete in the tube, which is helpful to distinguish the time and size that begin to appear confinement effect of the concrete filled steel tube. The typical CFST members in engineering applications may be loaded such as loading through the whole cross section, loading through steel alone and loading through concrete alone, etc. Establishing nonlinear finite element model to analyse the interface normal stress between steel and concrete along the section width, short column height and with the change of axial compressive load, the results show that the different loading mode of CFST column interface normal stress along the width of the cross section showed a "trough" distribution, but the value is different, sorted by size in descending order is loading through concrete alone, loading through the whole cross section, loading through concrete alone. When steel tube and concrete are subjected to loads, the effective length of steel tube confined concrete is about 0.55 times the width of the section, and the normal stress of the interface is almost 0 in the unconstrained area after 0.5 times of the ultimate load.