Analytical prediction of the shear connection capacity in composite steel–concrete trussed beams

Steel–concrete trussed composite beams are a particular types of composite girders constituted by a steel truss embedded in a concrete core. The truss is typically composed by a steel plate or a precast concrete slab working as bottom chord while coupled rebars are generally used to form the upper chord. Moreover, a system of ribbed or smooth steel rebars welded to the plate and forming the diagonals of the truss, works as web reinforcement. In the present study, the attention is focused on the evaluation of the shear resistance of the connection between bottom steel plate (the bottom chord) and concrete core through the diagonal bars of the truss developing a mechanical model able to account for the particular issues arising in this beam typology. In particular, the proposed formulation is based on the extension of existing formulations for the prediction of the resistance of steel dowels to the case of inclined steel bars loaded against concrete, accounting for the following effects: lateral and top confinement, mechanical non-linearity of materials, length of the plastic hinge arising in the steel bar and influence of moment-shear-axial force interaction effect. The accuracy of the model is verified with the available experimental data collected from the technical literature and with FE results obtained from a parametric analysis carried out by the same authors in a previous work.