Experimental investigation into bond behavior of CFRP sheets attached to concrete using EBR and EBROG techniques

Abstract

Over the last decade, an extreme increase in the application of fiber reinforced polymers (FRPs) for strengthening of reinforced concrete (RC) structures has been observed. The most common technique for strengthening of RC members utilizing FRP reinforcements is externally bonded reinforcement (EBR) technique. Despite certain benefits of the technique such as simple and rapid installation, the main problem which has greatly hampered the use of EBR method is premature debonding of FRP composite from concrete substrate. Recently, grooving method (GM) has been introduced as an alternative to conventional EBR technique. Grooving with the special technique of externally bonded reinforcement on grooves (EBROG) has yielded promising results in postponing or, in some cases, completely elimination of undesirable debonding failure in flexural/shear strengthened RC beams. Consequently, the main intention of the current study is to make a comparison between FRP-to-concrete bond behavior of EBR and EBROG techniques by means of single-shear bond tests. To do so, CFRP sheets were adhered to 16 concrete prism specimens using EBR and EBROG techniques. The specimens were then subjected to single-shear bond test and the results were compared. A non-contact, full field deformation measurement technique, i.e. particle image velocimetry (PIV) was utilized to investigate the bond behavior of the strengthened specimens. Successive digital images were taken from each specimen undergoing deformation during the test process. Images were then analyzed utilizing PIV method and load–slip behavior as well as slip and strain profiles along the strengthening CFRP strips were reported. Experimental results of the current study strongly verify the capability of GM for strengthening RC members to completely eliminate the debonding failure.