The use of externally bonded fibre reinforced polymer (FRP) plates and sheets to strengthen and rehabilitate existing reinforced concrete structures has recently received a great deal of attention within the Civil Engineering community. However, many gaps remain in the knowledge that is required in order for the technique to gain widespread acceptance. For instance, the bond between FRP and concrete as well as the wide variety of bond failure modes are incompletely understood and require further investigation. In an attempt to provide insight into the behaviour of the FRP/concrete bond, an experimental and theoretical investigation is undertaken. Both pull-off specimens with the FRP/concrete joint loaded in pure shear, and bond beam specimens with a joint loaded with a combination of shear and flexure, are examined in extensive laboratory tests. Strains in the FRP at different load levels are monitored along the length of the bond to produce bond strain and stress profiles that can then be compared with the predictions of a simple theoretical model. The theoretical model, developed from previously published work, is based on a shear lag approach and simple mechanics. Details of the model are provided and a comparison is made between the theoretical and experimental data. Results indicate that the strains and stresses in an FRP/concrete joint can be adequately predicted by the model at service load levels. However, before the ultimate capacity of an FRP/concrete joint can be determined with accuracy, the effects of bond slip and interface cracking, currently not considered, as well as a variety of other bond issues, must be accounted for in the model.
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