ABSTRACT
When a concrete slab rests on a steel girder without any connection, it deflects like the girder but has its own neutral axis so that its top fibers shorten while its bottom fibers elongate. The fibers of the steel girder are also subject to similar displacements in longitudinal direction, so a differential displacement appears at the concrete-steel interface (Figure 12.1a) due to the fact that the bottom fiber of the slab elongates, while the top fiber of the girder shortens. If the differential displacements at the interface are restraint, the slab and the girder behave as a composite girder with a single neutral axis (Figure 12.1b). The restraint is provided by shear connectors, while any natural bond between concrete and steel is ignored. The shear connectors transfer a longitudinal shear that develops due to vertical shear. In the case of box girder bridges an additional transverse shear (Figure 9.4d) is developed and resisted by the shear connectors. If the shear connection ensures the full development of the moment resistance of the composite member, it is characterized as full, otherwise as partial. This chapter presents the rules for design of the shear connection, which must be a full connection for bridges designed by the rules of EN 1994-2 [1].
