Local-overall interaction buckling of inelastic columns: A numerical study of the inelastic Van der Neut column

The elastic Van der Neut column has been a very useful tool to enhance our understanding of local-flexural interaction buckling of columns. In particular, Van der Neut′s work has (a) illuminated the basic mechanism behind interaction buckling and (b) demonstrated that local-flexural interaction buckling is a highly imperfection sensitive phenomenon. In this paper, a component of inelastic behaviour is added to the classical Van der Neut column and its influence on the column buckling curve and the imperfection sensitivity is investigated. Numerical calculations are carried out using a finite differences scheme which is first explained in detail. In general, plasticity gives rise to a second ‘plateau’ in the buckling curve, curtailing the column capacity at low column slenderness values. This plateau typically exhibits low to moderate imperfection sensitivity. However, for yield stresses of the order of the local buckling stress of the flanges, both plateaus merge to form an extended zone of very high imperfection sensitivity.