INFLUENCE OF SECTION SLENDERNESS ON THE AXIAL PERFORMANCE OF HIGH-STRENGTH COLD-FORMED STEEL BUILT-UP COLUMNS

Abstract

Cold-formed steel (CFS) sections are widely utilised in roofing and framing systems due to their lightweight properties and ease of fabrication and construction. The application of CFS built-up sections was introduced to enhance the strength and stability of single channels. However, typical CFS channels possess slender profiles with a high section slenderness ratio (w/t)max, making them susceptible to buckling and limiting their effectiveness. Consequently, this study examined the axial compression behaviour and cost-effectiveness of G550 high-strength CFS built-up sections with a reduced (w/t)max compared to conventional industry sizes. Experimental and numerical studies were conducted to assess the effect of member slenderness (KL/r)m and screw arrangement on the CFS built-up sections with different section slenderness. The results demonstrated that the proposed sections, with a lower (w/t)max, significantly improved buckling resistance for members with (KL/r)m less than 90. This improvement is attributed to their more compact profile design, which restrained the occurrence of local buckling. Furthermore, these sections were found to be more cost-effective, offering greater strength at a reduced weight.