Numerical modelling of fibre reinforced concrete-filled stainless steel tubular columns

The nonlinear behaviour of fibre reinforced (FR) concrete-filled stainless steel tubular columns is discussed in this paper. A nonlinear 3-D finite element model was developed for the analysis of the composite columns. The pin-ended axially loaded composite columns had different lengths, which varied from stub to long columns. The nonlinear material properties of the composite column’s components comprising stainless steel tube and FR concrete were incorporated in the model. The effect of FR concrete confinement and interface between the stainless steel tube and FR concrete infill was also considered allowing the bond behaviour to be modelled. In addition, the measured initial overall (out-of-straightness) geometric imperfection was carefully incorporated in the model. The finite element model has been validated against tests recently conducted by the author on FR concrete-filled stainless steel tubular columns. The composite column strengths, load–axial strain relationships and failure modes were predicted from the finite element analysis and compared well against that measured experimentally. Furthermore, the variables that influence the composite column behaviour and strength comprising different lengths, external diameter-to-plate thickness (D/t) ratios and FR concrete strengths were investigated in a parametric study. The parametric study has shown that the increase in column strengths owing to the increase in concrete strength is more significant for the columns having L/D ratios less than 6 as well as for the columns having D/t ratios less than 50. The composite column strengths obtained from the finite element analysis were compared with the design strengths calculated using Eurocode 4 for composite columns. It is shown that the EC4, in most cases, accurately predicted the design strength for axially loaded FR concrete filled stainless steel tubular columns.