Axial load behaviour of concrete-filled steel tubular columns

This paper reports an experimental study of concrete-filled steel tubular columns. Six short columns subjected to concentric load were tested. Columns of square, circular and rectangular cross-sections with two steel tube thicknesses were considered. The experimental results showed that the ductility of high-strength concrete increases when confined by a steel tube, but the load-carrying capacity remains the same. The confinement effect does not increase the capacity of the columns because the axial strain of the high-strength concrete core is low up to the point where the column reaches its ultimate load. A model to predict the load against strain behaviour was proposed and the pre-peak and post-peak behaviours of concrete-filled steel columns axially loaded could be predicted from the behaviours of steel tube and concrete core.