In this paper, an experimental study on the ultimate load behavior of web stiffened intermediate length cold-formed steel rack column with lateral stiffener is described. An approach of transforming the open-rack column section to a partially closed section is used with lateral stiffener as a means to increase the axial stiffness and compressive strength. A total of 4 rack column sections, with and without lateral stiffener, were tested under axial compression. The length of the columns is selected by performing elastic buckling analysis using CUFSM software. The failure behavior of cold-formed steel rack column sections is closely studied for different intervals of lateral stiffeners. The results indicate that a significant increase in axial stiffness and ultimate strength of cold-formed steel rack column sections is observed when appropriate numbers of lateral stiffeners are used.

In recent years, there has been a growing demand for cold-formed steel members, in the field of automobile and construction industry due to their light weight, high performance structural system with reduced cost, easy installation and erection and production time. The instabilities of cold-formed steel compression members are local, distortional and overall buckling and their interaction. The buckling behavior of the column depends on the geometry, dimensions and the length of the member. The occurrence of the distortional and buckling mainly depends on the cross-section profile and the length of the member. Distortional buckling occurs at intermediate length between the lengths where local and overall buckling occurs.

Hancock (1985) investigated on lipped channel sections over a range of buckling modes (local, distortional and flexural-torsional). Lau and Hancock (1990) provided design curves for channel sections where the distortional buckling stress and yield stress were approximately equal. Kwon and Hancock (1992) discussed the design expression for sections undergoing interface of local and distortional buckling modes in a lipped open channel column section with or without intermediate web stiffeners under fixed end condition. Leach and Davis (1996) conducted an experimental verification on the generalized beam theory applied to interactive buckling problems of channel columns. Narayanan and Mahendran (2003) studied the behavior of intermediate length innovative and complex geometrical sections which underwent distortional buckling. Recently, thin walled open column section has attracted the attention of several researchers to improve the distortional strength of intermediate (Talikoti and Bajoria, 2005). Similarly, Veljkovic and Johansson (2008) proposed an innovative idea open thin walled section by making the section partially closed by using spacers/closers.

Structural Engineering Journal, Intermediate length columns, Cold-formed steel columns, Rack columns, Thin walled members, Distortional buckling, Lateral stiffeners