Experimental Assessment of the Flexural Behaviour of Cold-Formed Steel and Concrete Composite Flooring System Built with C-Shaped Profiles

This research proposes a new flooring system formed by a concrete slab supported by composite beams made of built-up cold-formed steel (CFS) profiles with U-shape and concrete filling. This solution enables a decrease in materials consumption and weight over existing flooring systems, thus presenting economic and environmental benefits. The CFS beam is an assemblage of commercial C-shaped profiles and the edges of the CFS profile placed at the bottom of the beam are embedded in concrete to improve the shear transfer already provided by the CFS-concrete bond. Push-out tests were previously conducted to assess the load-slip behaviour and shear load capacity provided by the CFS and concrete interface. The present work addresses the bending behaviour of these composite beams considering static and short-term load tests. The experimental tests involved variations in the span and in the configuration of the CFS profiles assemblage (bolts and welding). The experimental load-deflection behaviour was characterized by a linear elastic response up to the initiation of slip at the CFS-concrete interface. The initiation of slip led to the formation of cracks and, consequently, to a load capacity decrease. By increasing the deflection, the beams could recover some load capacity. The strain evolution on the CFS and concrete composite beams demonstrated deformation compatibility between materials in contact, up to the initiation of slip. The configurations of the CFS profiles assemblage influenced the structural performance. The beams that use bolts demonstrated higher load capacity and ductility. The failure of the beams was caused by horizontal and vertical shear effects.