AbstractA new type of composite column consisting of y-shape steel sheets and L-shape steel angles with concrete being poured into the external surface of steel has recently been developed and used in real construction projects. This yLRC (Reinforced Concrete with y-shape steel sheets and L-shape steel angles) composite column aims at alleviating the restrictions founded in composite members, being applied in construction practice with more pliability. The yLRC composite column is expected to provide good sectional capacity due to the composite action of steel and concrete and reduce the construction times considerably because of the elimination of form-work and rebar placing work. Experimental tests on the axial behavior of yLRC composite columns were conducted as a basic study on the practical use. A total of six test specimens were prepared with testing variable of the width-thickness ratio of the Lshape steel angle. To investigate the axial behavior, the specimens were tested under concentric axial loading, and the peak load and failure mode were analyzed based on the test results.