The present article is based on a master’s thesis project on the study of steel columns buckling resistance. The primary focus is on the non-linear buckling region, where both imperfections and residual stresses influence the buckling strength of a column. In the current European Standard, this is carried out by applying the Ayrton-Perry model. In this model, residual stresses are equated as geometrical imperfections. In addition, a model proposed by Lehigh University is considered. This model expresses the buckling strength of a column based on the residual stress distributions influence on the gradually yielding of its cross-section. In order to optimize the Lehigh model, a modification which include the influence of geometrical imperfections is proposed. Furthermore, the Lehigh model and the Ayrton-Perry model are combined, in an effort to investigate their combined influence on the buckling strength of a column. Additionally, the article investigates the basis for establishing a model based on energy principles, in which the influence of residual stresses are accounted for. It is concluded that the modified Lehigh model reduce the buckling strength in relation to the original model, however not as much as the Ayrton-Perry model. Generally, the article draws the conclusion that it is highly troublesome to establish a simple model, in which the actual influence of residual stresses are included. This is primarily due to the erratic behaviour of residual stresses.
