Bond behavior of steel deformed bars embedded in concrete confined by FRP wire jackets

This study provides experimental results of bond tests for concrete confined by FRP wire jackets and investigates bond behavior. The used FRP wire jackets are newly introduced and found to be more effective in wrapping around concrete members than conventional FRP sheet jackets. Bond–slip tests were conducted by push-out tests using concrete cylinders with an embedded rebar at the center of the cylinders. Two parameters of concrete strength and amount of confinement were chosen. Bond strength and radial strain of concrete are discussed with the stiffness ratio of confinement. A method to estimate the increment of bond strength due to confinement is suggested. The bond strength of confined concrete shows a logarithmic relationship to the stiffness ratio of confinement and, thus, there is a limit on how to increase the bond strength by external confinement. It is found that radial strain at bond strength or the corresponding lateral confining pressure is a critical factor to increase bond strength.