To Improve Axial Compressive Behavior of Concrete Filled Double Skin Tubular (CFDST) Short Column

Abstract

Concrete filled double skin tubular (CFDST) are promising members in recent decades which was proven to be a competitive structural member compared to traditional steel tubular members. It provides an efficient composite action between steel and concrete. Concrete filled double-skin tubular has been studied for its strength and ductility. This research aims to experimentally investigate the compressive behavior of circular concrete filled double-skin steel tubular (CFDST) short columns, in which both the sandwiched concrete and steel tube is under axial compression. For this purpose, Steel tubes of two different diameter one of larger diameter and other of smaller diameter were used with high strength concrete sand-witched between them. Total 8 specimens were prepared in the study and their axial load-shortening curves, ultimate strength and failure modes were briefly discussed. Two sample were prepared for the comparison of concrete filled double skin tubular column having no shear studs with the column having shear studs on the inner face of outer steel tube and the outer face of inner steel tube. For strengthening the strategic location of outer steel tube. In the first series, we're starting with the outer steel tube having wall thickness of 1mm. In 2nd series we've taken different approaches for strengthening of outer steel tube. This strengthening has been applied at various strategic locations. Such as top mid and bottom. In series 3 the entire thickness of steel tube increase to 2 mm. At the end we have to compare series-2 sample with series1 and series3. Result suggest that Shear studs significantly enhance load-carrying capacity in C-SC columns compared to C-WSC. Shear studs reduce susceptibility to sudden failures from local buckling o instability. Bonding strength and prevention of local buckling are key roles of shear studs in CFDST columns. With the increase of the wall thickness and yield stress at critical area of outer steel tube, the failure mode of the specimens gradually changes from diagonal shear failure to axial compression failure. The CFDST short column having extra strengthening on the outer steel tube increase the maximum load carrying capacity from 10 to 20% with respect to the control mix. The load-carrying capacity increases as the confinement of the outer steel tube increase due to the larger confining pressure provided to the infilled concrete.