Axial Strength and Stability Behaviour of Cold-Formed Steel Battened Closed Section Columns

Due to numerous favorable features of cold-formed steel (CFS) members, there has been a good demand for their utilization in civil engineering construction. The need for built-up members arise, when the load demands on the structural members are large. The past research on CFS built-up columns has mostly focused on the performance evaluation of open built-up cross-sections. Closed CFS sections perform better than the open ones, particularly in terms of their torsional stability. Furthermore, very less research output on CFS battened columns has been reported so far. Therefore, there is a need to study the strength and stability behavior of CFS battened columns with closed sections.

This study presents an experimental investigation on CFS built-up columns connected with battened plates. Pin ended support conditions allowing uniaxial bending were adopted. Since the ratio of unbraced chord slenderness to overall column slenderness is crucial in influencing the performance of battened columns, two groups of built-up columns were formed such that the ratio of unbraced chord slenderness to overall column slenderness falls in three zones (0.25, 0.5 and 0.75). In the first group, to achieve the above ratios of slenderness, the unbraced chord slenderness was kept constant and the toe-to-toe spacing was varied. In the other group, the first parameter was varied whereas the latter parameter was kept constant. Furthermore, the design strengths of the built-up columns were computed using North American Specification and Eurocode for CFS structures. The design strength predictions of both these standards were found to be un-conservative.

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