Prediction of the bond-slip law in externally laminated concrete substrates by an analytical based nonlinear approach

To attain a suitable strengthening system for concrete structures, adequate stress distribution between externally bonded fibre reinforced polymer (FRP) materials and the substrate is required. With the growing application of the FRP in strengthening of the structures and in order to be able to sufficiently model the strengthened structure behaviour, the need for a generic bond relationship is increasing. Hence, this article introduces a simplified analytical method to define the bond-slip law of the FRP-concrete interfaces. The advantage of this procedure is that the model is developed only based on boundary conditions and therefore can be applied to any type of the adhesively bonded joints. Subsequently, the bond characteristics obtained from the proposed model is compared with the experimental results and the previous models. A modified single lap shear test set-up is adopted during the experiments. In addition, a new relationship is proposed for determination of the fracture energy corresponding to antisymmetric in-plane shear mode. Analytical analysis indicates that the interfacial fracture energy increases for the samples with thicker bondline or lower FRP-to-concrete width ratio.