Numerical modelling of concrete-filled steel box columns incorporating high strength materials

In this paper, an accurate finite element model which accounts for the effects of initial local imperfections and residual stresses is developed for the nonlinear analysis of high strength steel box columns infilled with high strength concrete. The inelastic behaviour of the steel box and the concrete core is modelled using an elastic-plastic model with linear hardening and a concrete damaged plasticity model, respectively. In addition, an extensive numerical analysis based on a wide range of width-to-thickness ratios, yield stresses of steel tubes and compressive strengths of concrete core was also carried out to propose a new empirical equation for estimating the confining pressure on the concrete. The predictions of ultimate strengths, behaviour and failure modes are compared with experimental results to verify the accuracy of the present model. Parameter studies indicate that both the Eurocode EC4 and Australian Standard AS 5100 approaches can be safely extended to predict the ultimate strength of concrete-filled steel columns with high strength materials.