An experimental study on flexural performance of RC beams strengthened by NSM technique using GFRP strips for a resilient infrastructure system

Abstract

Near surface mounted method (NSM) is an emerging technique with wider scope in repair and rehabilitation. In this method as lesser repair material is used and as FRP is placed inside grooves it offers higher serviceability, resistance to corrosion, higher impact damage resistance and fire resistance there by providing higher long-term economy. This method of strengthening avoids adverse environmental impacts, interruptions to service therefore considerable savings in time and cost. Hence, NSM technique helps in building resilience into infrastructure system. This paper is to present the experimental work on enhancing flexural performance of reinforced concrete beams by implementing NSM method. The side near-surface mounted (S-NSM) is an alternative method used for applying fibre reinforced polymer (FRP) flexural strengthening on reinforced concrete (RC) beams as in practical case the bottom face of the beam may be some times inaccessible. The S-NSM method places the FRP grooves at the sides of the beam on either side, rather than at the bottom in the normal near surface mounted (NSM) method. The present study is carried out on the use of NSM for strengthening of RC deficient beam designed for 30kN with NSM composite material namely glass fibre reinforced polymer (GFRP) strips as reinforcement. The experimental work included control specimen and strengthened beams at different locations and orientations of GFRP that is both bottom NSM and side NSM method (both horizontal and vertical orientation of strips) are studied and these beams are subjected to two point bending flexural test. The effect of groove location, crack pattern, deflection at midspan and quarter span and also different modes of failure are the characteristics studied based on results obtained.