Experimental behaviour of RC beams strengthened in shear by frp sheets

Reinforced concrete beams strengthened in shear by FRP are characterized by a failure behaviour where the ‘classical’ shear resisting actions of the un-strengthened elements, relied on concrete and steel, are combined to additional mechanisms activated by the FRP sheets. The final result is, undoubtedly, an enhanced performance in shear of the elements but, clearly, a major complexity in understanding and modelling the modified response. Many analytical formulations aiming at modelling such behaviour have been published in the scientific literature and some of them provide satisfactory results. However, it is evident that most of the theoretical models would require some improvements. Indeed, the preferred approach in calculating ultimate shear strength is based on a simple sum of independent terms, due to concrete, transverse steel and FRP, neglecting possible interactions among those contributions. The present paper shows and discusses some of the results obtained within an experimental program performed at the University of Cassino. In particular, the objectives of the experimental campaign are to explore the possible interaction between FRP and steel transverse reinforcement resisting actions, analysing the deformation behaviour of both the materials and the modes of failure of the strengthened and not strengthened beams.