Axially loaded circular high-strength concrete columns confined by steel tube: Mechanics, modeling, and slenderness effects

Current North American design codes for concrete-filled steel tubes assume that axial load is applied to the entire column cross section, and that the two component materials resist the load independently. Another approach to CFST construction has been proposed, where only the concrete surface is directly loaded. In this form of construction, the steel tube serves primarily to confine the concrete core. With the increasing use of high strength concrete, and the well documented need for it to be confined, this form of construction warrants consideration. Currently there are no design guidelines for this type of CFST element. This thesis addresses this shortcoming by examining the existing database of these CFST columns, and then by developing an experimental program to examine the interaction between the steel tube and the high strength concrete core. Slenderness effects are also examined. Design equations are proposed.