Interaction between local and overall buckling

Abstract Numerical solutions of the equations governing the interaction of local and overall modes on box columns are presented. In confirmation of previous results these solutions show that elastic buckling is highly sensitive to changes in the magnitude of both local and overall small imperfections, and that the strong optimum indicated for coincident mode design is effectively eliminated when this imperfection sensitivity as well as effects of plasticity are included. It is also clearly demonstrated that the reduced modulus approach provides a conservative estimate of the elastic load-carrying capacity. The inclusion of plasticity into the analysis shows that the effects of elastic interaction may also be highly significant in controlling the plastic collapse load, and for most practical cases this plastic interactive buckling will control design. An extension of the Perry-Robertson procedure is shown to provide a convenient means of presenting the design information. Finally, the usefulness of the van der Neut model as the starting point of the analysis is verified.