Finite element modelling of concrete-filled spiral-welded mild-steel tube short and long columns

Abstract

The capability of finite element modelling (FEM) to predict the experimentally observed behaviour of concrete-filled spiral-welded mild-steel tube (CF-SWMST) columns was assessed in this study. FEM was carried out of 24 previously reported CF-SWMST short and long column tests using the ABAQUS software. The tube length to outside diameter ratio (L/D) of the short and long columns were 3.0–3.3 and 9.0–10.0 respectively while the nominal outside diameter to thickness ratios (D/t) of the specimens were in the range 51–114.5. Load eccentricities of 0, 0.15D, and 0.4D had been considered for the specimens in the respective tests. Widely used and well-established modelling procedures, previously reported for concrete-filled steel tube (CFST) columns, were adopted for the analyses. The concrete damaged plasticity model in ABAQUS was used as the constitutive model for concrete. The specimen geometries were represented using solid hexahedral elements, while the spiral weld seam was also explicitly modelled. With respect to the reported experimental axial capacities, the FEM provided conservative load capacity predictions for the CF-SWMST specimens with D/t ratios less than 100. The prediction conservativeness increased with increasing load eccentricity and decreasing section slenderness. For the eccentrically loaded CF-SWMST columns, the predicted globally deformed states agreed with those observed experimentally, though the local buckling patterns were not replicated in the FEM. The results indicated that the decrease in strength enhancement of the concrete core due to confinement with increasing section slenderness was possibly underestimated by the material models that were used. The FEM results were also found to be negligibly sensitive to the explicit consideration of the spiral weld seam geometry with equivalent behaviour being predicted even when the spiral welded tubes were modelled as plain tubes.