To study the mechanical performance of concrete-filled double-skin steel tubular long columns under compressive and torsional loads

two ordinary circular steel tube reinforced concrete columns and two double-layered steel tube reinforced concrete columns were subjected to low-cycle reciprocating tests under pure torsion and torsion-compression loading using a developed Stewart six-degree-of-freedom loading platform. Based on the tests

the bearing capacity

torsional deformation

energy dissipation

and hysteresis performance of each specimen were compared and analyzed

and finite element parameter analysis was conducted. The study shows that both ordinary circular steel tube reinforced concrete columns and double-layered circular steel tube reinforced concrete columns have good torsional resistance. Compared with ordinary circular steel tube reinforced concrete columns

the initial stiffness and bearing capacity of double-layered steel tube reinforced concrete columns are slightly improved

the hysteresis curve is more full

and the energy dissipation capacity and ductility are greatly improved. Parameter analysis shows that when the steel content is constant

the larger the thickness ratio of the inner steel tube

the more beneficial it is for torsional resistance; and within a certain range of axial loads

the torsional resistance of steel tube reinforced concrete columns can be improved.