A new steel jacketing method for RC columns

This paper introduces a new steel jacketing method for reinforced concrete (RC) columns with lap splice and evaluates its performance by a series of axial tests of concrete cylinders. At first, 45 concrete cylinders were fabricated with varying design compressive strengths of 21, 27 and 35 MPa and then part of them was jacketed with two split-steel jackets under lateral confining pressure. The parameters in the first test were the steel jacket's thickness and the existence of adhesive between steel and concrete surface. In the second test, whole steel jackets were used to wrap cylinders with lateral pressure. Also, a double-layered jacket consisting of two steel plates was introduced; a cylinder was jacketed by two steel plates one after another. The effect of the new method was verified through comparing the results of the compressive tests for plain and jacketed cylinders. The steel jacket built following the new method showed good results of increasing the compressive strength and ductility of the jacketed cylinders with respect to the plain cylinders. The thicker steel jackets showed that the increased compressive strength, and the ductility at failure depended on the welding quality of the steel jackets. The adhesive between steel and concrete surface reduced the confining effect of the steel jackets. The whole jacket showed more ductile behaviour than the two split jackets. The double-layered jackets were estimated to possess an equal performance to that of a single steel jacket having the same thickness of the double-layered jacket. Finally, the experimental results were compared with the constitutive model of steel-jacketed concrete; which showed a good agreement between the experimental results and the models.