This paper proposes an accurate and efficient 2D nonlinear finite element model to investigate the mechanical behaviour of the shear connection between prefabricated concrete slab and steel girder in composite bridges. Beside material nonlinear constitutive laws and 4-noded plane elements, frictional contact finite elements are introduced in the model at the steel-concrete interface between the girder flange and the concrete slab, between the studs and the embedding concrete and at the base of the concrete slab. Numerical results are compared against experimental results of push-out tests. The tested specimens comprise 4 or 9 studs per slab. Firstly, it is shown that 2D numerical analysis may be accurately used for simulating the original truly 3D problem: a ''layer-equivalence'' methodology is proposed. A numerical investigation is then carried out to study the influence of the friction coefficient on the load- slip behaviour of the specimen and the distribution of internal deformations and forces in the specimen. A parametric study and some practical recommendations could follow this numerical approach for a better design of the connection.