An experimental study on the flexural bonding characteristic of a concrete beam reinforced with a GFRP rebar

This study was conducted to examine the bond strength of a beam reinforced with a GFRP (Glass Fiber Reinforced Polymer) rebar through a four-point bending test, adopting the British standard. The variables were made to have a bonding length 5 times (5 db), 10 times (10 db), and 15 times (15 db) that of the nominal diameter of a GFRP rebar. This was done to analyze the relationship between the bonding strength and the slip. The results of the test reveal that pull-out failure was dominant in the 5 db and 10db specimens. Both patterns of the pull-out failure and concrete-splitting failure appeared in the 10 db specimen. On the other hand, the 15db specimen showed only concrete-splitting failure at the end of its bonding length. Therefore, it was proven in this study that the available bonding length of GFRP rebar under a bending condition in a static test is over 15 db. Further research should be conducted on this subject, though, particularly a fatigue bending test and an FEM (Finite Element Method) parameter study, and a bonding model must be developed.