Strength and ductility of concrete confined circular columns

The design procedure of capacity and ductility on the concrete columns with circular cross section depending on the amount of the confining reinforcement is presented in this paper. The stress-strain model in which the longitudinal compressive strain of the concrete at failure is corresponding to the first fracture of the transverse reinforcement, is presented. The cross section capacity and the ductility factor corresponding to the longitudinal force and stirup distance is analyzed. Use of the similar design procedure on concrete-filled steel tubular columns and in strengthening of columns using still straps or FRP is possible.