BEHAVIOUR OF R.C. BEAMS REHABILITATED WITH EXTERNAL REINFORCEMENT

Abstract

Rehabilitation of in-situ concerete beam elements by bonding steel plates using epoxies on the concrete surfaces is now considered as an effective and convenient method of improving the performance of concrete member. The ultimate strength capacity of the reinforced concrete beams can be increased considerably with a negligible change in the member dimensions by using this technique. In the present study, simply supported reinforced concrete beams were tested to failure in flexure and shear. The beams tested in flexure were repaired with epoxy and then strengthened by bonding steel plates to the tension face of the beam with adhesives. The repaired beams showed a 24 percent increase in strength over the original beams, when subjected to the same loading pattern. All the repaired beams failed in flexure and showed a 28 percent reduction in deflection as compared to the original beams. Control beams, externally reinforced before loading showed a 31 percent increase in strength and failed in flexure. The beams tested in shear were repaired and strengthened esternally in shear by bonding steel plates to the sides of the beam. The strengthened beams showed a 20 percent increase in strength over the the original beams. Also the deflection of the strengthened beams was 20 percent less then the original beams. Whereas, the beams repaired with epoxy but not strengthened with iv external steel plates showed a 7 percent increase in strength over the original beams and 13 percent reduction in deflection as compared to the original beams. All the repaired beams failed in shear. Control beams, externally reihforced in shear before loading showed a 37 percent increase in strength and failed in shear. The study showed that the addition of steel plates to concrete beams can substantially increase there stiffness, reduce deflection, cracking and structural deformations at all load levels. Provided the adhesive is chosen carefully and proper glueing techniques are followed, the plated beams show beam action and comosite behaviour right upto failure. The, technique can be advantageously used for strengthening of existing concrete members.