flexural performance of rc continuous beams strengthening by cfrp with grooves

Externally bonded reinforcement (ebr) is the most common technique used to strengthen the rc members with carbon fiber reinforced polymer (cfrp) sheets. recently, a new proposed technique was named externally bonded reinforcement on grooves (ebrog) has been presented as an alternative method to avoid or eliminate the undesirable de-bonging failure mode that is accompanying to ebr method. this paper is devoted to investigating the effect of the strengthening techniques on the flexural behavior of rc continuous beams externally strengthened with cfrp sheets in both hogging and sagging zones, by testing twelve beam specimens. all beams have the same cross-section (200×130) mm and 2300 mm length. the parameters of this study include strengthening methods, length and layers number of cfrp sheet and number, length and direction of grooves, in addition to the effect of presence of steel fiber in the hogging zone. the results are introduced in terms of ultimate load, ultimate deflection, ductility index and mode of failure. the test results showed that the ebrog strengthening method has highly effective in improving the ultimate load of strengthened beams. the specimens strengthened by one and two layers of cfrp using ebrog with three longitudinal grooves have a rising in the ultimate load by about (24.4 and 52.6) % respectively, in comparison with the same beams but strengthened by ebr. also, the mode of failure was changed from cfrp debonding in case of ebr beams to cfrp rupture, or to concrete cover separation in ebrog beams. finally, the strengthened beams with cfrp sheets presented a more brittle behavior at failure than the unstrengthening specimen.