Nonlinear Active Wave Modulation Approach for Evaluating Bond Conditions between Adhesively Bonded FRP Sheet/Concrete Substrate

摘要

Many recent studies have indicated that externally bonded Fiber Reinforced Plastic (FRP) composite sheets can be used effectively to strengthen concrete structures. Composite action suggests that the individual parts of a composite work together as one. Stresses must be transferred from one constituent to the other through some interface. If there is little or no bond at the interface then there is little or no transfer of stress and therefore poor composite action. In this study, we intend to develop a NDE tool for evaluating such interfacial bond conditions. An innovative active modulation approach, Nonlinear Active Wave Modulation Spectroscopy (NAWMS), is adopted in our study. In this procedure, a probe wave will be passed through the system. Simultaneously, a second, modulating wave will be applied to the system. Using three-inch thick concrete slabs we have prepared several FRP laminated samples with artificial flaws (one-inch square) designed into the interface. The sender is on one side of the flaw and the receiver on the other. Maintaining the separation of this pair of transducers, we progressively move them away from the flaw location. The resulting frequency modulations will be analyzed, and will be correlated to the presence of the flaws.