Experiment on debonding in concrete-filled steel single tube columns subjected to eccentrically loading

The confinement on concrete core by the steel tube is the main advantage of concrete-filled steel tubular (CFST) column under compression. However, the debonding of concrete from the steel tube common and it ruins the confinement effect. In this paper, the influence of debonding on the behavior of CFST stub columns subjected to eccentrically loading is investigated experimentally. The debonding was formed by inserting galvanized sheet in the steel tube before the concrete is filled and pulling them out after 5~6 hours. The test validates this method to form a debonding in specimens. The parameters in the tests include the debonding arc-length ratio and steel ratio. All the specimens failure in flexural mode, which indicates that the debonding has no influence on the failure mode, but the curvature of the debonding specimen is a little smaller than that of the normal specimen. The ultimate load capacity and the ductility of the specimens are significantly decreased with the increase of debonding arc-length ratio, which can be relieved by a larger steel ratio.