Shear interaction effect between transverse reinforcements in FRP-strengthened RC beams

An important phenomenon that characterizes the behavior of shear-strengthened beams with FRP at ultimate is the shear interaction effect between internal and external transverse reinforcements, which represents a key factor that significantly affects the shear capacity of the FRP-strengthened beam. The present paper is finalized to study the mechanism of shear interaction and to quantify the effect of the under-mobilization of the internal steel stirrups. By adopting some rationale simplifications to describe the bond-slip behavior, the problem is developed in a way that a closed-form solution can be obtained which is, therefore, particularly useful for practical design purpose. Furthermore, a parametric analysis was carried out to identify the sensitivity of the theoretical solutions to the variation of some principal mechanical and geometrical parameters. Finally, a comparison with some experimental data available in the literature shows the consistency and reliability of the proposed model.