New composite beams having cold-formed steel joists and concrete slab

Abstract

A new composite beam and floor system has been developed to achieve a higher strength and ductility, as well as to yield a more economical design purpose. This new composite beam system consists of three elements: reinforced concrete slab on corrugated cold-formed metal deck, back to back cold-formed steel joists, and continuous cold-formed furring shear connector. The continuous shear connector is screwed through the metal deck and the top flange of the support joists in order to provide vertical interlocking and horizontal shear resistance between the concrete slab and the cold-formed steel joists. The self-drill fasteners are used for fastening the furring shear connector through the metal deck into the supporting joists.To understand the behavior of the new composite beam, a total of six 12ft long composite beam tests were conducted to obtain the positive moment capacity, vertical deflection, and end slip of proposed composite beam system. Comparing with the non-composite section, the proposed composite section presents a better performance for both strength and ductility. Based on present beam tests the ultimate load and mid-span deflection of the proposed composite section can be increased by 14–38% and 56–80%, respectively. According to the experimental bending test results, the composite section can reach the ultimate strength without local shear or compression buckling failure when the proposed shear connector is presented in the composite section. Analysis and design of composite beams with cold-formed steel joists and concrete slab are also studied to validate the present test results.