A cost-effective design procedure for cold-formed lipped channels under uniform compression

Cold-formed lipped channels are extensively used in commercial steel buildings. Current design provisions provided by the American Iron Steel Institute (AISI), and Canadian Standard Association (CSA-S136-07), ignore the geometric interactions between the channel components. The development of the design equations is based upon treating the web and the flange in isolation. Furthermore, the influence of the lip size on the local stability of the web and the flange is not accounted for. The paper presents a cost-effective procedure that can be utilized in the North American steel industry for efficient design of cold-formed lipped channels. An efficient modelling strategy that stimulates the “actual” boundary conditions between the channel components is presented. The influence of the lip and flange sizes on the buckling and post-buckling strength of the web and the flange is highlighted. It is shown that the web buckling stress is largely affected by the sizes of the channel components and is not a constant value as treated by the North American cold-formed steel codes. A noticeable increase in the post-buckling stiffness of the web and the flange can be attained by accounting for the geometric interaction. Graphs are presented showing the design space of various channel sections that can be utilized in practice to achieve economical design. Comparisons with the existing AISI and CSA-S136-07 provisions are also made. It is shown that the present procedure yields substantial material savings. The paper provides useful guidelines to the cold-formed steel fabricators to determine the optimum section sizes that maximizes the buckling strength.