Damage Assessment of FRP-Encased Concrete Using Ultrasonic Pulse Velocity

Abstract

Since concrete members with fiber-reinforced polymer (FRP) reinforcement are not as ductile as conventional structures, and since concrete in retrofitted members is often covered and not readily available for visual inspection, development of nonintrusive and nondestructive damage assessment tools is essential. Ultrasonic pulse velocity (UPV) can provide such an assessment tool, and help quantify the extent and progression of damage in concrete. Continuous UPV monitoring of a number of concrete cylinders and concrete-filled FRP tubes showed the concrete-filled tubes to have higher sensitivity at lower stress ratios as compared to plain concrete. When compared with the axial strain energy, the UPV damage index has a much better resolution for stress ratios up to about 50% of ultimate strength. This ratio depends on the thickness of the jacket. It was also shown that the UPV has a strong correlation with volumetric strains after confinement is activated. Therefore, at high levels of axial loads when the con...