Abstract:
Built-up box sections are becoming increasingly popular as column members in cold-formed steel (CFS) structures; uses of such sections include CFS trusses, space frames, and portal frames. In this paper, the built-up box sections are fabricated by two identical lipped channel-sections connected at their flanges with self-drilling screws. This paper presents an experimental investigation on the axial capacity of CFS built-up box sections. Compression tests were conducted for different values of slenderness’s covering stocky to slender columns. In total 8 built-up box columns were tested. For comparison, 8 single channel sections were also tested and reported herein. Prior to the compression tests, material properties and initial imperfections were measured for both the single channel and CFS built-up box sections. Load-axial shortening relationship, failure modes, and deformed shapes at failure are discussed for CFS built-up box columns. Test results show that all short columns failed through local buckling. However, for slender columns global buckling was observed. The experimental test results were also compared against the designed strength calculated in accordance with the AISI & AS/NZS. From the comparison, it was found that the AISI & AS/NZS are conservative by around 15-19% on average, while predicting the axial capacity of such CFS built-up slender columns.