Shear strength and moment-shear interaction of steel-concrete composite beams: Experiments, numerical analyses, and design models

Current structural codes do not address the shear strength and the moment-shear interaction in composite beams explicitly. The shear is commonly assumed to be resisted by the steel beam alone neglecting the contributions of the slab and the composite action. This paper presents an experimental and numerical study to cover this gap. Fourteen composite beams and one steel beam were tested in order to investigate the contribution of the concrete slab to the shear strength of a composite section and the moment-shear interaction in compact composite beams. A nonlinear finite element model was also developed to complement the experimental results. It was found that the moment capacity of a composite beam is significantly reduced when high shear forces are present. The reduction in moment capacity is accompanied by failure modes consisting of web buckling in the steel beam and brittle shear failures in the concrete slab, while the ductility is largely compromised. A significant contribution of the concrete slab to the shear capacity of the composite section was determined by the tests and verified by the numerical analyses. Based on the experimental and numerical results design models are proposed for the robust and economical design of compact composite beams under high shear forces, and for incorporation into design standards.