The working mechanism and the measurement principle of topology-based crack sensors made of coaxial cables are briefly reviewed. The sensitivity, spatial resolution, and ruggedness of two coaxial cable sensors, respectively made of rubber and Teflon dielectric materials, were compared and validated with laboratory testing of a 4/5-scale, T-shaped, reinforced concrete beam-column specimen. Two Teflon sensors were installed on one of the solid decks of a three-span continuous highway bridge to investigate their durability and measurement repeatability. Laboratory tests indicated that both types of sensors have high sensitivity, but the Teflon sensor has a higher spatial resolution and a negligible spillover effect of any significant cracks. At a 90-degree bend, however, the Teflon sensor is more susceptible than the rubber sensor to the rubbing action of the outer conductor of a coaxial cable against its dielectric layer. No cracks were observed during the field load tests of the instrumented bridge. Both sensors indicated high durability in realworld application but a certain variation of waveforms was measured over a period of 5 years because of the use of different instruments. Future research is directed to develop an online calibration of crack sensors with a small portion of built-in standard cable at the end of the cable sensor.


Civil, Architectural and Environmental Engineering

Second Department

Electrical and Computer Engineering

Keywords and Phrases

90-Degree Bend; Coaxial Cable Sensors; Crack Sensors; Detectability; Dielectric Layer; High Durability; High Sensitivity; Laboratory Testing; Load Test; Measurement Principle; Measurement Repeatability; On-Line Calibration; Real-World Application; Reinforced Concrete Beams; Rubber Sensors; Spatial Resolution; Spillover Effects; Wave Forms; Working Mechanisms; Cable Stayed Bridges; Polytetrafluoroethylenes; Rubber Testing; Telecommunication Cables

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version

Final Version

File Type





© 2010 National Research Council (U.S.), All rights reserved.

Publication Date

01 Jan 2010