Novel coaxial cable sensors that feature high sensitivity and high spatial resolution are developed for health monitoring of concrete structures using a time-domain reflectometry (TDR). The new sensor was designed based on the topology change of its outer conductor, which was fabricated with tightly wrapped commercial tin-plated steel spiral covered with solder. The cracks that developed within concrete structures will lead to out-of-contact of local steel spirals. This topology change results in a large impedance discontinuity that can be measured with a TDR. A simplified equivalent transmission line model and numerical full-wave simulations using finite-difference time-domain techniques were used to optimize the sensor design. The sensors under test demonstrated high sensitivity and the capability of multiple-crack detection. A plasma-sprayed coating technique was employed to improve sensor uniformity. Engineering implementation issues, e.g., signal loss, signal postprocessing, and sensor design optimization, were also addressed.


Electrical and Computer Engineering

Second Department

Civil, Architectural and Environmental Engineering

Keywords and Phrases

Coaxial Cable; Crack/Strain Sensor; Plasma Spray; Sensitivity; Signal Loss; Spatial Resolution; Time-Domain Reflectometry

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version

Final Version

File Type





© 2009 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.

Publication Date

01 Aug 2009