Experimental Study on Bond-Slip Behavior of Longitudinal Bars in Reinforced Concrete Beams Confined with Fiber Reinforced Polymer Sheets

Twenty cantilever type specimens and four beam specimens were tested to evaluate the bond behavior in reinforced concrete members confined with carbon or aramid FRP sheets. The main test variables were the vertical depth, the diameter and the number of longitudinal bars, and the type and the amount of FRP sheets. The test results showed that the confined specimens had higher bond strength, larger peak load slip displacement and lesser bond degradation after the peak than their unconfined prototype counterparts. Based on the test results, an equation was developed to predict the increase in bond strength due to the FRP sheet confinement. That increase was expressed similarly to that due to transverse steel reinforcement except that the elastic modulus of the FRP sheet was validated using results of column specimens tested in other research institutes and by cantilever and beam specimens test by authors. It was proved that as long as the bond strength of an unconfined prototype specimen is evaluated properly, the total bond strength of confined specimens can be predicted accurately using the proposed equation although the limitations of the proposed equation still need to be clarified.