A model for the bond between concrete and reinforcement

The bond mechanism between deformed bars and concrete is known to be influenced by a number of parameters, such as the strength of the surrounding structure, the presence of splitting cracks and yielding of the reinforcement. However, when reinforced concrete structures are analysed with finite element models, it is quite common to assume that the bond stress depends solely on the slip. A new model has been developed, which is specially suited for detailed three-dimensional analyses. In this new model, the splitting stresses of the bond action are included, and the bond stress depends not only on the slip, but also on the radial deformation between the reinforcement bar and the concrete. Bar pull-out tests with various geometries and with both monotonic and cyclic loading have been analysed. The results show that the new model is capable of predicting splitting failures and the loss of bond if the reinforcement is yielding, as well as dealing with cyclic loading in a physically reasonable way.