BEHAVIOUR OF EXTERNALLY REINFORCED R.C. BEAMS STRENGTHENED IN SHEAR WITH VARYING PLATE THICKNESSES

Abstract

The strengthening of R.C. members by externally bonded steel plate is becoming increasingly popular in recent years due to its cost effectiveness and versatility. This is a relatively new approach and considered as an effective and convenient method for improving their performance under service loads and also increasing their ultimate strength. Another advantage of this technique is that changes in the member dimensions are negligible. The present investigation deals with the effect of varying plate thicknesses of 1.5, 3.0 and 6.0mm with a constant glue thickness of 1.5mm, on the shear strength of R.C. beams. Studies were carried out on simply supported reinforced concrete beams which were tested to failure in shear. Control beams were tested in shear and failed in shear. The control beams were strengthened by externally epoxy bonded steel plates with, different thicknesses to the sides of the beams. The experimental cracking load of the strengthened beams is increased by 18.7 to 31.3 per cent. The strengthened beams with varying plate thicknesses showed 25.63 to 34.13 per cent increase in strength over the control beams. Also the mid span deflection of beams with different plate thicknesses was 6.33 to 20.11 per cent less than control beams. The study showed that the addition of steel plates to the concrete beams can substantially increase their stiffness, reduce deflection, cracking and structural deformations at all load levels. Provided the adhesive is chosen carefully and proper glueing techniques are used, the plated beams show beam action and composite behaviour right upto failure. This technique can be advantageously used for strengthening of existing concerete members, thereby increasing their life span.