Accurate determination of asymptotic postbuckling stresses by the finite element method

Abstract Koiter's method for initial postbuckling and imperfection sensitivity analysis of elastic structures is conveniently formulated in terms of finite elements. Special care must, however, be taken in the computation of the postbuckling stresses and the postbucklmg constant determining the initial curvature of the postbuckling path. The cause of the problem lies in the different degree of approximation of in-plane and lateral displacements and is inevitable in a standard compatible finite element formulation. It is shown that only a minor change in the computation of the postbuckling stresses is needed. The procedure is extended to cover Byskov and Hutchinson's method for cases with nearly sinultaneous buckling modes.