EXPERIMENTAL STUDY OF CONCRETE-FILLED STEEL TUBULAR DUMBBELL SHAPED SHORT COLUMNS UNDER CONCENTRIC LOADS

concrete-filled steel tubular (CFST) dumbbell shaped columns under concentric loads are tested. The distance between two tubes and the distance between two webs with or without tie rod to connect the two webs are taken as experimental parameters. The load-displacement relations and the failure mechanisms of the specimens, the load-strain relations of both circular steel tubes and steel webs, and the load-Poisson抯 ratio relation of the composite material are analyzed. Experiment results indicate that the property of the circular CFST in the dumbbell shaped member is the same as a concentrically-loaded CFST single tubular column. The concrete inside the web space is also constrained by the link steels. The rupture of welding seam connecting the web plates and the steel tube is the most pronounced failure mechanism. A simple calculation method for the ultimate load of dumbbell shaped CFST concentrically-loaded columns is proposed.