Structural response monitoring and damage detection using an embedded ETDR distributed sensor

The application of an on-line structural health monitoring system can provide important information regarding real time structural response and the state of structural integrity condition. Early detection of structural damage can prompt needed repair and reinforcement to prevent ultimate catastrophic failure of the structures, which could lead to costly reconstruction, loss of use, and even loss of life. Electrical time domain reflectometry (ETDR) sensors possess great potential for the application of online health monitoring of large concrete structures. They are capable of capturing deflection profiles of the structure and detecting crack damages in early stages. In this thesis, laboratory scale concrete specimens with embedded ETDR sensors coated with interfacial adhesives were fabricated and tested under 3-point bending load. The ETDR signal from the embedded sensors was calibrated to obtain the distributed strain in the specimens. The deflection profiles of the specimens were then determined based on the distributed strain measurements of the ETDR sensors and compared with the beam deflections measured at discrete locations of the beam using LVDT displacement sensors. Comparison between ETDR and LVDT sensor measurements for the specimen response below yielding were in good agreement. In addition, the embedded ETDR sensor was also able to detect the presence of crack damages and pinpoint their locations in the specimens. It was also seen that the application of interfacial adhesives significantly increased the signal response of the embedded sensor.