Experimental and analytical study on flexural strengthening of RC beams via prestressed EBROG CFRP plates

The present manuscript reports results obtained from both experimental and analytical studies on the behavior of reinforced concrete (RC) beams strengthened in flexure using prestressed carbon-fiber-reinforced polymer (CFRP) plates via the externally bonded reinforcement on grooves (EBROG) method. A major concern in strengthening beams with prestressed FRP plates is the proper transfer of prestressing force to the beam. The present study pioneers the use of EBROG technique in prestressed CFRP plates considering the proven superiority of the bond efficiency created by the EBROG technique over that by the EBR. For the purposes of this study, seven RC beams with cross-sections of 200 x 300 mm and lengths of 2600 mm were subjected to the four-point loading test in order to investigate the effects of different parameters including prestressing level, using anchorage system, and the strengthening technique employed. Experimental results indicated that the EBROG technique, in the absence of any end anchorage, was well capable of transferring the prestressing stresses to the beam, which obviously led to significant reductions in strengthening costs. Compared to the specimens strengthened through the EBR technique, those strengthened via the EBROG technique exhibited an enhanced flexural behavior as evidenced by their increased load carrying capacity, ductility, and CFRP debonding strain that were higher by 18, 53, and 36%, respectively. It was also observed that prestressing CFRP plates attached via EBROG method was able to postpone the debonding and increase the strength efficiency of the FRP plates. A maximum enhancement of 20% in ultimate load-carrying capacity was measured in prestressed beams strengthened via the EBROG technique relative to the non-prestressed ones.