Forty cantilever type specimens were tested with and without fiber reinforced polymer (FRP) sheet confinement in order to study the improvement in bond-slip behaviors of longitudinal reinforcing bars. The FRP sheets used were carbon and aramid with the elastic modulus of 230 GPa and 118 GPa, respectively. Other variables were the amount of FRP sheet (up to 0.32%), the number (2 or 4 bars) and the diameter (19 mm or 25 mm) of longitudinal bars, and the cover depth (40mm, 57 mm, or 72 mm). Concrete strength used in the test was under 30 MPa so that the test results can be applied when retrofitting existing ordinary structures. In previous work which used the test results of twenty cantilever type specimens conducted in 1998, it was shown that the confinement greatly enhanced the bond strength and ductility, and the bond strength contribution from FRP sheet increased linearly with the elastic modulus of FRP sheet. Based on these findings, an equation was proposed to predict the bond strength for members confined with FRP sheet. Test results of additional twenty specimens in 1999 showed that effectiveness of the confinement on the bond strength did not stay constant but decreased as the amount of FRP sheet increased. To take into account this new finding, a previously proposed equation was modified to make a better prediction for the bond strength. The proposed equation was validated using test results of beam and column specimens.
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