Axial compressive behaviour of concrete-filled steel tubular columns with interfacial damage

In a previous study, 17 rectangular concrete-filled steel tubular columns were tested using a push-out test method to examine the interfacial bond behaviour. In this study, these specimens were subjected to axial compressive tests to study the effects of interfacial damage on the ultimate axial compressive capacity. The variations in both the load–axial displacement curves and load–strain curves were recorded and then compared to study the influences of both the steel tube fabrication method and the D/ B ratio on the axial load–carrying capacity. The axial compressive behaviour of rectangular concrete-filled steel tubular columns with no interfacial damage was then studied using a numerical analysis method. The contact stress distribution along the length and width of the face and at the height of the interface was obtained and discussed. In addition, the ultimate axial compressive capacity of rectangular concrete-filled steel tubular columns with no interfacial damage was calculated using the formulas from three international codes. The influence of interfacial damage on the axial compressive bearing capacity of a rectangular concrete-filled steel tubular column was discussed through a comparison of the results of the numerical simulation, formula calculation and experiments. The influence of the interfacial gaps caused by the push-out tests on the axial bearing capacity of the concrete-filled steel tubular columns can be ignored, because the core concrete was not destroyed and the outside steel tube can provide a sufficient constraint force on the concrete when the two materials yielded. Finally, the influences of the gap type and size on the bearing capacity were discussed.