A hybrid analytical-finite element approach has recently been developed to assess the effect of cold work on the structural behaviour of steel columns of press-braked sections, in which the manufacturing process is modelled by means of two analytical solutions for the two manufacturing stages (i.e. the coiling-uncoiling and the press-braking operations) respectively. These analytical solutions, which predict the residual stresses and equivalent plastic strains resulting from cold work in a section, treat both stages as a plane strain bending problem, but this assumption is invalid near the edges of the steel sheet. During the coiling-uncoiling process, the width of the edge zones for which the plane strain assumption is invalid may become significant compared with the width of the steel sheet. The present paper aims to clarify the effect of the plane strain assumption employed in modelling the coiling-uncoiling process on the predicted column behaviour. To this end, a finite element investigation into the width of the edge zones is first presented. The effect of this assumption on column behaviour is then clarified through comparisons of results from the hybrid approach with those from a fully finite element approach in which both stages of the manufacturing process are modelled using finite element techniques. These comparisons demonstrate that the hybrid approach predicts column behaviour accurately.