Eect of Rebar Geometries on Ultrasonic Waves Propagation in Reinforced Concrete Structures using Finite Element Method

摘要

Corrosion of steel rebar in reinforced concrete (RC) structures introduces internal stress at the interface betweenrebar and concrete, ultimately leading to the failure of structures. Detection of early-stage corrosion of steel rebarcan significantly reduce maintenance cost and risks. An active photoacoustic fiber optic sensor system had beenproposed for early-stage corrosion detection of steel rebars by generating and receiving surface ultrasonic waves.However, the implementation of a corrosion detection method requires knowledge of surface ultrasonic wavespropagating at rebar-concrete interface. The objective of this study is to investigate the interaction of surfaceultrasonic waves with local geometries (of a number four rebar) and concrete covers using the finite elementmethod (FEM). In this study, seven three- dimensional finite element models were created to simulate surfaceultrasonic waves propagating in three different cross-sections of a steel rebar with different concrete cover. Threelug locations and three types of concrete (differed by Youngs modulus) were considered. The pitch-catch modewas adopted, in which one source and one receiver were deployed at each rib of the rebar. 1 MHz sinusoidal pulsewas introduced at the source while time domain radial displacements were collected at the sensor. Short-timeFourier transform was used to analyze collected time domain radial displacements. From our simulation results,it was found that high frequencies of ultrasonic waves were affected by lugs more than lower frequencies. Presenceof concrete cover suppresses the amplitude of surface ultrasonic waves.