Yield - line analysis of cold - formed steel members

The objective of this paper is to provide a state of the art review of the application of yield-line analysis to cold-formed steel members, and present a newly developed solution to the stresses that develop in an inclined yield-line. Yield-line analysis in cold-formed steel members is shown to be distinct from traditional yield-line applications. Challenges in the application of yield-line analysis include (1) the need for an a priori definition of the spatial collapse mechanics of interest and (2) the widely varying solutions that are provided in the literature for the bending strength of yield-lines. Based on the von Mises yield criterion, in the fully plastic state (ν=0.5), and assuming only normal and transverse stresses exist for bending about an inclined yield-line axis, new expressions are provided and verified for the stresses in an inclined yield-line. Although the assumed local stress state is verified, it is found that development of the correct load-deformation response requires a more complete treatment of the kinematics of the actual deformation and the developed forces. Finally, despite current challenges, future applications of yield-line analysis are discussed for the study of imperfection sensitivity, ultimate strength prediction, ductility, and energy absorption. All of which are important problems for future research in the behavior and design of cold-formed steel members.