Comparison between the behaviors of fully encased cold-formed steel joists and hot-formed steel joists with prestressed concrete: Experimental analysis

This paper investigates the behaviors of different types of prestressed concrete beams utilizing fully encased cold- or hot-formed steel joists. Twelve types divided into two sets of composite beams are assessed. Set 1 is composed of six beams utilizing cold-formed steel (CFS) joists distinguished by the cross-sectional steel-to-concrete ratios of 1%, 2%, and 3%, and the presence or absence of web openings. Set 2 has the similar composition but utilizes hot-formed steel joists. Four-point and three-point bending tests were conducted at the mid-span of the composite concrete beams. Key properties, such as strength, stiffness, flexural load capacity, ductility, energy absorption capacity, and failure modes, were used in the analysis. It was found that the specimens with CFS I-beam joists provided better performance compared to those with hot-formed steel joists. Also, the existence of web openings in the encased CFS beams enhances the ductility and energy absorption of the composite concrete beams.