Analytical prediction of load-deformation behaviour for bearing at bolt holes

Although bolted bearing-type connections are widely used in steel structures, knowledge of their deformation behaviour is limited. Deformation behaviour is particularly important for nominally pinned connections, lap connections and other connections with bolts in bearing. Bolted bearing-type connections are characterised by non-linear deformation behaviour in terms of yielding of the material in front of the bolt hole, which occurs at the beginning of the deformation path due to the embedding of the bolt in the steel plate. The paper deals with the formulation of a non-linear analytical expression that describes the embedding of the bolt and allows the designer to estimate the deformation of the bolt hole due to the bearing. The expression was derived based on numerical analysis and confirmed by tests on bolted lap connections made of mild and high-strength steels. Test results of lap joints with different geometries, number of bolts, steel grades and failure modes are also used to demonstrate the applicability of the prediction model. Comparison to the existing Eurocode linear load-deformation model for bearing is also shown. It is shown that the load-deformation relationship for bearing at bolt holes proposed in this paper, which is already included in the new generation of the Eurocode for the design of joints in steel structures, can predict the load-deformation behaviour well. The bearing resistance limit to control the bearing deformation and a simplified linear load-deformation model based on the proposed non-linear model are also presented.