Flexural strengthening of R.C. beams using epoxy bonded CFRP laminates : plate separation & anchorage systems

Abstract

Existing reinforced concrete structures may, for variety of reasons, be found to be unsatisfactory. In such circumstances, there are two possible solutions, either to demolish and rebuild, or to carry out a strengthening program. In recent years, plate bonding using Carbon Fibre Reinforced Plastics has gained considerable importance as a strengthening technique, and extensive research has been carried out showing significant improvements in structural performance. However, investigations have also shown that premature failures occur because of stress concentrations at the ends of the laminates, resulting in debonding by ripping off of the concrete cover at the level of the internal steel reinforcement. This study investigates the behaviour of reinforced concrete beams strengthened in flexure using epoxy bonded CFRP laminates, their associated failure by plate separation, and some possible methods for the prevention or attenuation of this failure mode. Various types of anchor bolts and adhesively bonded angle plates were used to try to alleviate this problem of plate separation. Both anchorage systems proved effective in increasing the flexural capacity by a maximum of 27.2% over the unanchored plated beam, and also resulted significant improvements in ductility. An outline of some alternative repair and strengthening techniques is also given, together with some guidelines on the selection, installation, and maintenance of plate bonding systems in general. The experimental results obtained, are also used in the validation of a numerical model developed during other research in this field, which was used to predict the behaviour of the tested beams yielding very satisfactory results.