Numerical studies on the torsional behavior of octagonal concrete‐filled linked double steel tubes

The concrete confinement is improved in octagonal concrete‐filled double steel tubular (OCFLDST) columns by linking the steel tubes with steel plates and thereby it enhances ductility. It has the potential to improve the torsional resistance in concrete‐filled steel tubular cross‐sections. This paper investigates the torsional behavior of OCFLDST through analytical and numerical investigations. The numerical model for OCFLDST is developed in ABAQUS and validated using test data available in the literature for axial loading conditions. The validated model is then subjected to pure torsion to study the torsional behavior of OCFLDST. In comparison with bare steel tubes, concrete filling of linked steel tubes has increased the torsional resistance by 33%. Further, parametric studies are conducted to understand the influence of various parameters like yield strength and thickness of the outer steel tube, compressive strength of concrete, the thickness of the linking plates, and axial load ratio. The numerical results are compared with the proposed expression for finding the torsional capacity based on St. Venant's torsion theory. The proposed capacity prediction is in good agreement with the numerical results.