Axial Compression Behavior of Symmetrical Full-Scale Concrete Filled Double Skin Steel Tube Stub Columns

To investigate the bearing behavior of symmetrical full-scale different strength concrete filled double skin steel tube (CFDST) stub columns, 19 full-scale specimens were designed, considering the slenderness ratio (lambda); the compression strength of core concrete and sandwich concrete (f(cki), f(cko)), the thickness of the inner and outer steel tubes (t(i), t(o)); the diameter of inner and outer steel tubes (D-i, D-o); and the tensile strength of the inner and outer steel tubes (f(yki), f(yko)) as the main parameters. Nonlinear constitutive models for concrete considering constraint effect were adopted, and a finite element (FE) model was established using ABAQUS software. By comparing the results between simulations and experiments, the rationality of the modeling method was verified. Based on the FE model, the parameter analysis for CFDST columns were conducted, and the force mechanism, stress distribution, and deformation process were analyzed. The results showed that the axial compression bearing capacity (Nsu) increased significantly with an increase in f(cki), t(o), D-o, and f(cko), while Nsu decreased gradually with an increase in lambda. Finally, according to the calculated results of the specimens, the calculation formula for Nsu of full-scale composite columns was statistically regressed using 1stOpt software and showed a good agreement with the FE.