Flexural strengthening of RC beams with NSM-GFRP technique incorporating innovative anchoring system

Abstract

Reinforced concrete (RC) beams may require flexural strengthening due to the corrosion of reinforcing bars or changes in the design load. The near surface mounted (NSM) and externally bonded (EB) techniques, using either glass or carbon fibre-reinforced polymer (GFRP or CFRP) composites, are used for strengthening deficient RC beams. However, RC beams strengthened with both techniques are susceptible to the debonding failure of the FRP composites. This paper proposes an innovative anchoring system for NSM strengthening of the RC beams, which comprises an L-shaped GFRP bar anchor (L-anchor), U-shaped CFRP strips (U-strips) and double plate (DP-anchor). The developed strengthening technique is termed as NLUD technique. Seven RC beams were cast and tested under four-point bending. The experimental results showed that RC beams strengthened with the NLUD technique achieved significantly higher flexural load. The NLUD technique prevented the debonding failure of GFRP bars of the strengthened RC beams.