Strength, stiffness and ductility of r.c. beams strengthened with FRP sheets

In the last decades, the rehabilitation of civil structures has become increasingly an important challenge in the construction market. Among the various methods used to strengthen and repair r.c. beams, wet lay-up systems of fibre reinforced plastic (FRP) sheets represents an effective and convenient method. The advantages of bonding FRP sheets to the concrete derive from the light weight due to low density, the high mechanical characteristics in terms of strength and stiffness, the high resistance to corrosion and chemicals and the easiness to adapt to the shape of the structural member. Experimental and theoretical investigations show that good improvements in the strength and stiffness of r.c. beams can be obtained, although in the presence of a limited ductile behaviour. This is also connected to the failure mode of the beams. In this context, the paper presents the main results of an experimental campaign aimed at studying the behaviour, in service and at collapse, of r.c. beams strengthened with mono-directional carbon fibre reinforced polymer (C-FRP) sheets.