EFFECT OF CONCRETE STRENGTH AND GROOVE DIMENSION ON PERFORMANCE OF GROOVING METHOD TO POSTPONE DEBONDING OF FRP SHEETS IN STRENGTHENED CONCRETE BEAMS

Abstract

A major obstacle in using FRP sheets for flexural and shear strengthening has beendebonding failure, which leads to premature and noneconomic failure of the strengthened element.Surface preparation of concrete member has been widely used to provide good bonding of thecomposite sheet onto concrete surface; however, it is found to be only partially effective indelaying debonding. Recently, Grooving Method (GM) has been introduced as a novel substitutefor conventional surface preparation in Externally Bonded Reinforcement (EBR) strengthening ofconcrete beams. Although the previous experiments have shown that grooving method canpostpone or even eliminate the debonding of FRP sheets from concrete substrate, the method isstill in its early stages of development and awaits further research for maturation. The presentstudy is an attempt to examine the effectiveness of grooving method for beams with differentconcrete compressive strength; also, to investigate the effects of groove depth and width oncontrolling FRP debonding for concrete specimens with different compression strengths.The experimental specimens included 44 concrete beams, which with three samples per beamresulted in a total of 132 specimens. Initially, two grooves of varying widths and depths were madein each specimen. The grooves were then filled with an appropriate epoxy resin and the FRP sheetswere bonded onto the concrete surface. After the resin had hardened, the specimens were subjectedto the four-point flexural test. The experimental results showed the superiority of grooving methodon conventional surface preparation for all four experimental categories with different compressivestrength of concrete. The results also showed that a depth of 10 mm may be the optimum groovedepth for all four experimental categories.