ABSTRACT
Concrete-filled steel tube (CFT) columns have several advantages over reinforced concrete or steel columns. The participation achieved by composite action improves the behavior of the structures. CFT columns can obtain strength and ductility by steel tubes, and high compressive strength and stiffness by concrete core. Moreover, the steel tube can work as a mold which will decrease the expense of labor, and it can prohibit the spalling of concrete, too. Furthermore, concrete can prolong the buckling of steel tubes. (Hajjar 2000).
