Cold-formed steel lightweight concrete (CFS-LWC) composite beams: New design proposal

The authors’ recent experiments and simulations have shown that incorporating composite action in systems comprising built-up cold-formed steel (CFS) beams and lightweight concrete (LWC) deck slabs is feasible and effective in enhancing structural performance. While existing design procedures for steel-concrete composite beams typically address hot-rolled steel beams and concrete deck slabs connected with welded shear studs, the CFS-LWC composite beam systems use headed bolts instead of conventional welded shear studs. In these systems, the ratio of bolt diameter to the CFS top flange thickness exceeds the 2.5 limit specified by EN 1994–1–1. Current design methodologies have not yet established specific guidelines for such built-up CFS-LWC composite beams; this study, therefore addresses this gap by proposing a new strength prediction method tailored to CFS-LWC composite beams. The method’s accuracy was validated through extensive simulation results and parametric studies, demonstrating that it provides a reliable and practical tool for predicting the bending strength of these composite systems. The proposal offers practical design rules for the built-up CFS-LWC composite beams, consistent and applicable to EN 1994–1–1 and AISC-360.