Effectiveness of Stiffeners in CFDST Columns: Comparative Study

AbstractConcrete-filled double-skin tube (CFDST) columns are considered one of most efficient forms of steel-concrete composite columns, which provide higher axial strength and better ductility compared with their counterpart concrete-filled tube (CFT) columns. This paper aims to numerically investigate and compare the performance of axially loaded circular CFDST short columns provided with stiffeners in inner tubes and outer tubes. Circular steel hollow sections have been adopted for inner as well as outer tubes, and rectangular steel stiffeners were fixed in inner and outer tubes to check the effectiveness of stiffeners in stiffened CFDST columns. These CFDST columns were investigated numerically by using a verified finite-element (FE) model from commercially available software. Behavior of 36 unstiffened, inner-tube stiffened, and outer-tube stiffened CFDST columns (12 each) was studied. The FE results were verified by comparing them with previous test results. The FE analysis study has exhibited an increase in peak load (load-carrying capacity) up to 26% and 15% in outer-tube stiffened CFDST columns compared with unstiffened and inner-tube stiffened CFDST columns, respectively. Also, enhanced ductility has been observed in case of these stiffened CFDST columns.