带肋 FRP 筋与混凝土的粘结强度预测方法

Until now, there has been limited research on the bonding behavior of ribbed fiber-reinforced polymer (FRP) bars. In this paper, bond test data of the spirally-glued FRP bar and mechanically-grooved FRP bar were collected to investigate the test parameters on the bond behavior. The results show that the macroscopic failure mode for the two types of ribbed FRP bars is pullout failure. More specifically, spirally-glued FRP bars mainly exhibit shearing off of FRP bar ribs, while slight damage occurs in concrete. Most grooved FRP bars show shearing off of concrete ribs, and the bond strength increases with the increase of concrete strength for both FRP bars. Spirally-glued FRP bars show higher bond strength by increasing concrete cover which contributes to better confinement to FRP bars, but this seems to have no effect on grooved FRP bars. The bond strength of spirally-glued FRP bars can be improved by increasing relative rib height h_rd and FRP bar rib width ratio F_R. While grooved FRP bars are almost unaffected by h_rd, and are mainly influenced by concrete rib width ratio C_R, having higher bond strength by increasing C_R. The calculated results by the proposed equations are in good agreement with the test results with greater accuracy than the design codes. This is because the effect of rib forming process and geometrical features of ribbed FRP bars on bond strength is accurately accounted in the proposed equations.