Influence of cold bending on the resistance of wide flange members

Cold roller bending is commonly used for bending straight members with hot rolled wide-flange sections to create arches. This process induces plastic deformations along the member, so that it can acquire the desired curvature. The resulting residual stress distribution is different from the wellknown residual stress pattern due to hot rolling. Extensive studies have shown that the influence of residual stresses due to hot rolling on the resistance of wide-flange steel sections is non negligible. On the contrary, the residual stress pattern due to roller bending has been only recently clearly identified and its effects on the elasto-plastic behavior of curved members have not been studied sufficiently. Thus, in this paper the influence of such residual stresses on the resistance of both wideflange sections and corresponding arch members is investigated in detail. Taking into consideration the residual stress pattern due to cold bending, interaction diagrams are developed for combined axial load and bending moment, as well as buckling curves for cold bent steel arches. The results are quantified and compared with those for hot-rolled and stress free members. This will allow designers to appreciate the available margins of safety when using standard residual stress pattern for cold bent members. Furthermore, the results suggest the necessity for the development of buckling curves for curved members including initial imperfections.