Efficiency of near surface mounted technique using fiber reinforced polymers for the flexural strengthening of RC beams

• This paper investigates the use of FRPs for the flexural strengthening of RC beams.
• All strengthened beams showed a capacity increase ranging between 31 and 133%.
• The CFRP strengthened beams gave greater capacities than the GFRP strengthened ones.
• The GFRP strengthened beam, however, showed much better ductile behavior.
• The ACI 440-2R gave reasonable predictions of the ultimate capacities of the beams.

This paper presents the test results of an experimental study that investigates the behavior of reinforced concrete (RC) beams strengthened in flexure with near surface mounted (NSM) technique using glass and carbon fiber reinforced polymers (GFRP & CFRP). A total of 10 full scale reinforced concrete beams were constructed and strengthened in flexure with FRPs. This study included four parameters; technique used (NSM or Hybrid), type of FRP used (carbon or glass), amount of FRP used, and steel reinforcement ratio. All beams were tested under four point bending set-up. The test results included ultimate capacity, deflection, cracking, strains and mode of failure. All strengthened beams showed an increase in the capacity ranging between 31 and 133% compared with the reference beams. The NSM-CFRP strengthened beams showed greater ultimate capacities than the NSM-GFRP beams but they showed less ductile behavior. The NSM-GFRP strengthened beam, however, showed good ductile behavior with high deflection values at ultimate load. This gave ample warning before failure and can be considered as an advantage of strengthening RC beams with NSM-GFRP system. The measured ultimate capacities of all strengthened beams were compared with the design provisions provided by ACI440-2R guidelines, which showed very reasonable and conservative predictions for all strengthened beams.