Experimental investigation of steel built-up beam-columns composed of tracks and channels cold-formed sections

In this paper, a built-up column of novel cold-formed cross-section that composed of four elements is investigated. The proposed built-up column is suitable for carrying axial, uni-axial, and bi-axial loading. The web of the new cross-section is composed of back-to-back track sections while the flanges of the cross-section are two lipped channels connected to the web using interconnectors. Elements comprising the cross-section are assembled and connected by enough interconnector bolts depending on the column built-up configurations. The interconnector spacing is varied among specimen cross-section and column length. In the present study, series of axially, uni-axially, and bi-axially compression columns were tested experimentally. Eleven specimens with various cross-section aspect ratios as well as different overall slenderness ratios were tested. Numerical finite element model that accounts for both material and geometrical nonlinearities was developed using 'ABAQUS' software to analyze the tested columns. A good agreement was achieved between the experimental test and the finite element model results. Experimental test results revealed that for axially loaded columns with small, medium, and high slenderness ratios, the failure modes were local buckling, local-flexural buckling, and flexural distortional buckling; respectively. On the other hand, for uni-axially loaded columns having small, medium, and high slenderness ratios, the failure modes were local buckling, interaction between local and lateral-torsional buckling as well as lateral-torsional buckling; respectively. Furthermore, for bi-axially loaded columns, the failure mode was lateral-torsional buckling.