Experimental study of the influence of welding space in cold-formed built-up box flexural members

Current building codes for cold-formed steel structures specify flexural design guidelines for C open sections. Nevertheless, there are no guidelines to estimate the capacity for a cold-formed built-up box-beam composed of two C-sections in contact, considering weld seam spacing as a relevant constraint. This research compares the nominal flexural strength of a beam section, determined by theoretical formulations described in AISI S100-16, and experimental investigation on 20 beams, considering four seam-weld spacings (ranging from 0 mm -continuous- to 900 mm). The length of the specimens was 1800 mm, with a cross-section of 220 mm x 160 mm; the base material thickness was 1.5 mm. The experimental and analytical evidence suggests that a maximum separation between seam welds (a(max)), calculated as a mean value between the theoretical distortional buckling lengths for the single C-section (Lcrd-S) and the box-section (Lcrd-D), results in a reasonable parameter to guarantee the maximum capacity of the box section. It is imperative to continue performing tests and computational modeling for these profile configurations and, thus, suggest an improved formulation.