Effect of Concrete Slab on Built-up Double Web Castellated Steel Beam under Combined Flexural and Torsion Load

The research examines the behavior and reactions of six double-web steel sections of non-composite and composite-reinforced concrete deck slabs and castellated steel beams. The composite beams with concrete slabs and non-composite steel beams with different levels of castellation were isolated from the specimens at 0%, 25%, and 50%. The ultimate strength, load at cracking, failure mechanism, load/deflection relationship at midspan, stiffness, and ductility were evaluated. The concrete slab increased the ultimate load by 61.1%, 63.3%, and 55.5% for castellation ratios of 0%, 25%, and 50%, respectively. The non-composite and composite castellated beams' shear strength decreased as the expansion ratio increased. The angle twist of non-composite samples was greater than that of composite samples due to their greater ductility and lower stiffness. The concrete slab also restricted the samples and reduced their rotation.