In order to characterize the bond between CFRP and concrete, considerable research has been developed using two-dimensional tools. In several studies the influence of the bond length is dealt with, but only a few focus on the effect of the width of the bonded materials. From this study, an analytical approach is proposed to define an influence width where stress transfer occurs between CFRP and concrete. The main purpose of this work is to contribute to the definition of an effective bond width, which allows for the estimation of the load carrying capacity of the bond connection. A 3D numerical analysis is performed using the finite element method. Pure shear models under both mode-II and mode-III fracture are defined to describe the bond behaviour between concrete and externally glued sheets of carbon FRP. These results are also compared to experimental data obtained from the literature.