Flexural behaviour of RC beams strengthened With externally bonded (EB) FRP sheets or Near Surface Mounted (NSM) FRP rods method

Strengthening is a process of upgrading to increase the strength of structural components to carry additional loads. Strengthening methods include externally bonded (EB) Fiber Reinforced Polymer (FRP) plates, (or wet laid-up fabrics) and Near Surface Mounted (NSM) FRP rods. The present investigation study the enhancement in flexural performance of un-cracked RC beams strengthened with either a single ply or a 2-ply wet laid-up carbon fiber reinforced polymer (CFRP) fabric(s) or NSM glass fiber reinforced polymer (GFRP) rods. An identical RC beam in its un-strengthened form is used as the control. A series of RC beams of dimensions 170 mm width × 270 mm depth × 2325 mm length were tested to destruction under four point bending. The variables are the number of carbon plies in a wet laid-up scheme and the number of GFRP rods in a NSM scheme. The RC beams were designed to have excess reinforcement in shear to allow the beams to fail in bending. The flexural performance was assessed in terms of the enhancement in the ultimate load carrying capacity, load-deflection characteristic up to and beyond peak, initial stiffness, and strain development in the RC beams, due to the attached carbon fiber reinforced polymer (CFRP) sheets and GFRP rods. Test results show that the RC beams strengthened with two (2) NSM GFRP rods recorded the highest of about 88% increase in strength capacity over the control beam and 34% increase corresponding to those of strengthened with a GFRP rod. The strength capacity of the beam specimens strengthened with a rod and two (2) rods of NSM GFRP recorded an ultimate load of about 62% higher and 29% respectively than those beams strengthened with a layer and two (2) layers of EB CFRP sheets. The higher performance enhancing ability of the NSM strengthening scheme is therefore evident compared to that of the conventional and industry preferred wet laid up.