Effect of contact on the elastic behaviour of tensile bolted connections

Both experimental evidence and 3D finite element analyses indicate that contact forces between the connected parts influence the behaviour of bolted T-stub and L-stub connections in tension. In the present paper, a mechanical model that predict the elastic behaviour of such connections is developed. The model relies on the enhanced beam theory, proposed by Baluch et al. [13], to describe the mechanical response of the flanges in both the contact and the non-contact regions. The model response shows that the contact stresses distribution strongly depends on the ratio between the length of the contact area and the flange thickness. Furthermore, the length of the contact zone in a non-preloaded connection appears to be independent from the magnitude of the external force. Several simplifications have been proposed to facilitate the determination of the separation length which is the primary unknown of the problem. To validate the analytical and calculation models, a 3D finite element model has been developed. Analytical and numerical results are in good agreement which demonstrates the validity of the proposed mechanical model. The theoretical and numerical results confirm that prying action increases with decreasing value of the ratio between the flange stiffness and the bolt stiffness.