Influence of residual stresses induced by cold curving on the resistance of I-Section steel members
The cold curving process is today the most common way to produce curved members from straight members. This process which is continuous along the length of the member changes the distribution of the residual stresses in the cross section and consequently the way they influence the elasto-plastic behaviour. The use of interaction curves made for straight beams for the design of curved members might thus lead to unsafe or uneconomical design of structures. There is thus need for specific design criteria for curved members. In this paper, first the main features of the cold curving process of I-beams will be presented. Then, residual stresses due to cold curving with patterns available in the literature will be compared to finite elements results. Next, these residual stress distributions will be use to build moment-curvature curves and moment-axial force interaction diagrams. To this end, an analytical model based on a non-dimensional forming ratio depending on the aspect ratio of the cross section and on its radius of curvature will be proposed and validated by comparison with numerical models of arches submitted to various combinations of opening and closing bending moments and axial forces. The presented study is limited to members curved along the strong axis and loaded in their plane of curvature; however the method is general and might easily be extended to more complex cases.