www.cafetinnova.org Indexed in Scopus Compendex and Geobase Elsevier, Geo-Ref Information Services-USA, List B of Scientific Journals, Poland, Directory of Research Journals ISSN 0974-5904, Volume 09, No. 04 August 2016, P.P.1421-1428 #02090411 Copyright ©2016 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved. Performance of Plain and Lipped Cold-Formed Channel Sections in Axial Compression G BEULAH GNANA ANANTHI Division of Structural Engineering, College of Engineering, Guindy, Anna University, Chennai - 600025 Email: beulah28@annauniv.edu Abstract: Cold-formed steel (CFS) members are finding increasing acceptance within the construction markets as primary structural elements. Among the members most commonly used is the open channel members that offers simple fabrication and connection. This paper throws light into the behaviour of both lipped and plain channel members with different slenderness ratios comparing with the various international codes of practice for cold-formed sections subjected to compression. The various standards includes, the Indian Standard Code of Practice for use of Cold-formed Light Steel Structural Members-IS:801, the British Code of Practice for Design of Cold-formed Sections-BS:5950 (Part 5) and the North American Standard- NAS Manual. Finite element analysis (FEA) on the post-buckling behaviour of channels under axial compression is compared with the various codal specifications. The load versus axial shortening behaviour of sections is obtained by using a non- linear FEA. The load carrying capacities of plain and lipped channels for seven different slenderness ratios are compared. Load versus axial shortening behaviour for the plain and lipped channels are also presented. The mode of failure observed is combined local buckling in the case of unstiffened element, flexural buckling about minor axis for the slenderness ratio of 30 to 100 and for sections having slenderness ratio 120 to 200 overall flexural buckling about the weak axis. FEA is useful as an alternative and complementary method to the design of CFS structures and predicts the ultimate load with reasonable accuracy. Keywords: Cold-Formed Steel; Columns; Plain and Lipped Channels; Finite Element Analysis; Codal Provisions 1. Introduction Cold Forming is a process where steel members are manufactured by rolling or shaping the steel after it is cold. Thin sheet steel products are extensively used in building industry, and range from purlins to roof materials and floor decking. The broader use of thin walled CFS structural components in many areas of application has elevated considerable interest in the local instability of these members. Generally these are available for use as basic building elements for assembly at site or as prefabricated frames or panels. These thin steel sections are cold- formed, i.e. their manufacturing process involves forming steel sections in a cold state (i.e. without application of heat) from steel sheets of uniform thickness. Sometimes they are also called Light Gauge Steel Sections or Cold Rolled Steel Sections. The thickness of steel sheet used in cold formed construction is usually 1 to 3 mm. Much thicker material up to 8 mm can be formed if pre-galvanised material is not required for the particular application. Sustained research and continuous upgradation of design codes contributes to the maximum utilization of these sections for construction. A problem of particular interest is to investigate their post-buckling behaviour and ultimate load carrying capacity. There are many codal specifications for the design of CFS issued by various countries like IS:801, BS:5950 (Part 5) and NAS manual. Many times it is tedious for evaluating the ultimate load carrying capacity since all these codes involve empirical formulas. Codal provisions also lack in ambiguity with uncommon sections. The basis for the determination of member capacities of CFS sections is either Allowable Stress Design (ASD) or the Limit State Design referred to as Load and Resistance Factor Design (LRFD). Most of the specifications namely British Standards (BS) and the North American Standards have switched over from ASD to LRFD. However, the Indian Standards (IS) is still in the process of conversion to limit state design. In this study, FEA is proposed as an alternative and complementary method to the design of cold-formed steel structures. Ben Young and Jintang Yan [5] presented a design and numerical investigations into the strengths and behavior of cold- formed lipped channel columns under fixed end condition by using FEA. A nonlinear FE model was developed and verified against fixed-ended channel column tests. Geometric and material nonlinearities were included in the FE model. It was demonstrated that the FE model closely predicted the experimental ultimate loads and the behaviour of the cold-formed channel columns. The column strengths obtained from the FEA are compared with the design column strengths calculated by using the American, Australian/New Zealand, and European specifications for CFS structures. It was shown that the design column strengths calculated from the three specifications are generally conservative for lipped