Experimental study of the behavior under axial compression of steel tube confined concrete with a circular hollow section (STCC-CHS)

A new type of steel tube confined concrete columns (STCC) in which the outer steel tube only confines the core concrete and does not directly bear the axial load. Based on this, a new type of steel tube confined concrete with a circular hollow section (STCC-CHS) column was presented in this article. It demonstrated high strength and relatively light weight, high economic efficiency and promises easy installation. Axial compression tests were conducted to quantify the effects of the diameter-thickness ratio and the hollow ratio on the failure modes, the ultimate strength in axial compression, strain and stiffness. Constraint effects and ductility were also analyzed. The test results show that the outer steel tube effectively delays local buckling failure. The smaller the hollow ratio and the smaller the diameter-thickness ratio, the greater a column's bearing capacity. The observed ultimate compressive strength is compared with STCC and CFDST components. The experimental data are used to test the utility of the recommended formulas for predicting the axial bearing capacity of such columns, with several different models of the confined concrete strength.