Experimental investigation on the moment-shear interaction in steel-concrete composite beams

![CDATA[Current structural codes do not provide specific rules for the determination of the reduction in moment capacity of a composite beam when significant shear forces are present. In addition, the plastic shear capacity of a composite beam is typically assumed to be the shear capacity of the steel section alone. This can lead to uneconomic design of composite structures. The moment-shear interaction in composite beams is investigated in this paper. Fourteen tests were carried out on composite beams with different moment-to-shear ratios to study the reduction in moment capacity due to the presence of high shear forces and to quantify the contribution of the concrete slab to the shear resistance of a composite section. 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 brittle failure modes consisting of web buckling in the steel beam and sudden shear cracking in the slab, whilst the ductility is largely compromised. A moment versus shear interaction diagram is constructed and a design model is proposed for the calculation of the shear strength of a composite section and the reduced moment capacity in situations where high shear forces are present.]]