Page 1 of 8 EXPERIMENTAL STUDY ON THE EFFECTIVENESS OF EBROG METHOD FOR FLEXURAL STRENGTHENING OF RC BEAMS Davood MOSTOFINEJAD Professor Department of Civil Engineering, Isfahan University of Technology (IUT) Isfahan, Iran dmostofi@cc.iut.ac.ir Seyed Masoud SHAMELI Graduate Student Department of Civil Engineering, Isfahan University of Technology (IUT) Isfahan, Iran sm.shameli@cv.iut.ac.ir Ardalan HOSSEINI Graduate Student Department of Civil Engineering, Isfahan University of Technology (IUT) Isfahan, Iran a.hosseini@cv.iut.ac.ir * Abstract The structural behaviour of RC beams which were flexurally strengthened with FRP composites using a new method made by bonding FRP sheets on the pre-cut surface grooves named Externally Bonded Reinforcement On Grooves (EBROG), was investigated in this paper. The main points focused in the paper are: (i) the flexural behaviour of RC beams strengthened with EBROG method in terms of ultimate loads and displacements, (ii) the effect of using double FRP layers on the beams ultimate limits and (iii) the effect of strengthening method and the number of FRP layers on the beams failure mode. To perform the experimental program, five RC beam specimens with the dimensions of 120×140×1000 mm, strengthened with one and two FRP layers with EBR and EBROG methods, were tested. The performances of EBR and EBROG techniques were found to be very close when one layer of FRP was used; however, experimental results showed that when two FRP layers are used, EBROG method performs much more effective than EBR technique. Keywords: Debonding, EBR, Externally Bonded Reinforcement On Grooves (EBROG), Fiber Reinforced Polymer (FRP), Longitudinal Grooves, Strengthening. 1. Introduction Strengthening and retrofitting of existing RC structures with externally bonded FRP composite materials have gained a worldwide attention in the past two decades. High tensile strength, ease of application, light weight and corrosion resistance are among the main advantages of the method. In some situations, FRP composites are the only plausible material that could be used for strengthening, especially in places where heavy machinery cannot gain access [1]. One of the most common techniques for flexural strengthening of concrete beams with FRP materials is the Externally Bonded Reinforcement (EBR). Nevertheless, the main problem that has greatly hampered the use of EBR method is the premature debonding of FRP laminate from the beam substrate. Experimental researches have shown that debonding is the most common failure mode in concrete structures strengthened with externally bonded FRPs