Study on Cross-shaped Concrete Filled Steel Tubular Stub Columns Subjected to Axial Compression: Experiments and Design Method

Abstract

Despite its wide application prospect, researches on the cross-shaped concrete filled steel tubular (CFT) columns are scarce, and no design method can be used. This paper concerns with the axial load behavior of cross-shaped CFT stub columns. Five specimens were tested to examine the influences of three parameters on the characteristics of failure, the bearing capacity and deformability. The parameters include the width-thickness ratios of steel plates, the yield strengths of steel and the sectional dimensions. Experimental results demonstrate that the global outward bulge of steel tube near the concave corners is significant, so that the stresses on the steel tube distribute unevenly and the confinement effects on the concrete are inferior to the rectangular CFT columns. By decreasing the width-thickness ratio of each steel plate, the global outward bulge near the concave corners was smaller, but the ductility could be improved only when it decreased by 2.08 times. By increasing the yield strength of steel to 1.47 times, the bearing capacity and deformation were inversely smaller, but the ductility was increased. By increasing the length-width ratio of each leg to 2.25 times, the global outward bulge was increased and local buckling occurred earlier. Then the application scopes for evaluating the maximum strength of specimens by the methods in design codes are provided. A new method is also proposed by considering the confinement effects of concrete and the strength loss of steel tube. The results predicted by the proposed method show good agreement with the experimental ones.