Behaviour of partially encased composite columns with high strength concrete

The behaviour of partially encased composite columns under eccentric and concentric axial loading tends to be complex because of the interaction of the concrete with the thin-walled steel section. When constructed with high strength concrete, developing numerical simulations of the response of these columns under load is particularly challenging. In this paper, a finite element model capable of simulating this response is presented. A constitutive model that has the capability of predicting the overall stress–strain behaviour of high strength concrete, including the post-peak softening branch and residual strength, is selected. The finite element model has been validated by conducting simulations of the behaviour of partially encased composite test columns with high strength concrete. The load-deformation response, ultimate capacity, and failure mode are predicted accurately by the model for both concentric and eccentric axial loading conditions. Finally, a parametric study is presented that uses the validated finite element model to identify the key differences in strength and failure behaviour of partially encased composite columns when using high strength instead of normal strength concrete.