investigating of the effect of concrete confinement on the axial performance of circular concrete filled double-skin steel tubular (cfdst) long columns

In this study, the cooperation of steel and concrete in composite columns is considered. using numerical modeling to study the behavior of these sections, a new type of sections, namely concrete filled doubleskin steel tubular (cfdst) columns, is introduced. the parameters and techniques that influence the numerical simulation that bring this modeling closer to the laboratory conditions are determined by varying the dimensions and geometry as well as the properties of materials such as the compressive strength of concrete and width to thickness ratio on the strength of circular section columns at internal and external skins are investigated by the abaqus finite element software. the purpose of this paper is to investigate the effect of concrete compressive strength on the axial performance of cfdst columns. in this paper, the effects of concrete with different compressive strength, concrete confinement, bearing capacity and widthtothickness ratio on the overall strength of tubular crosssection columns in their inner and outer skins are investigated. the results of the study indicated that the bearing capacity of cfdst columns under axial pressure increases by increasing the concrete compressive strength in the inner skin and decreases by increasing width to thickness ratio (d/t).also, studies have shown that with increasing crosssectional area, the bearing capacity in circular columns decreases by about 3%.