Experimental behaviour of steel-concrete composite box girders subject bending, shear and torsion

The results of two unique experimental campaigns carried out on composite box girder sections subjected to moment-shear interaction and moment-shear-torsion interaction are presented. They involve the behaviour of the box sections both in positive and negative bending. The effect of the flexibility of the connection is measured and accounted for. A finite element model is implemented to account for this effect, resulting in an improvement in the accuracy of the stiffness of the sectional behaviour. One of the main results is a significant over-resistance in relation to the shear capacity of the sections, which is very clear in the tests involving bending shear and torsion. This effect is attributed to the contribution to the shear capacity of the concrete slab.