Modeling Stress State Dependency of Bond Behavior of Fiber Reinforced Polymer Tendons

The bond behavior of carbon FRP tendons for concrete is characterized with an interface model. In particular tendons with a surface structure that produce significant mechanical interlocking with the adjacent concrete are considered. This type of mechanical interaction can produce damage in the adjacent concrete and within the surface structure of the reinforcing element. The combination of these mechanisms is characterized with an elastoplasticity model that fully couples the longitudinal and radial response; the model calibration is based upon a series of bond tests under differing stress states. The model does not provide a detailed description of the underlying mechanics associated with the progressive bond failure, and it will generally require recalibration when applied for a GFRP bar, the model gives acceptable estimates of the bond strength of several tests of a particular CFRP tendon, even though the specimens have significantly different attributes. Additional validation tests (using data with measures of the experimental scatter) are needed to define the predictive limits of the model; nonetheless the transfer length problem further demonstrates the potential application of the model to help predict and understand the behavior of FRP-reinforced structural components.