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Proceedings Paper

Application of electromagnetic waves in damage detection of concrete structures
Author(s): Maria Qing Feng; Franco De Flaviis; Yoo Jin Kim; Rodolfo E. Diaz
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Paper Abstract

Jacketing technology using fiber reinforced polymer (FRP) composites is being applied for seismic retrofit of reinforced concrete (RC) columns designed and constructed under older specifications. In this study, the authors develop an electromagnetic (EM) imaging technology for detecting voids and debonding between the jacket and the column, which may significantly weaken the structural performance of the column otherwise attainable by jacketing. This technology is based on the reflection analysis of a continuous EM wave sent toward and reflected from layered FRP-adhesive-concrete medium: Poor bonding conditions including voids and debonding will generate air gaps which produce additional reflections of the EM wave. In this study, dielectric properties of various materials involved in the FRP-jacketed RC column were first measured. Second, the measured properties were used for a computer simulation of the proposed EM imaging technology. The simulation demonstrated the difficulty in detecting imperfect bonding conditions by using plane waves, as the scattering contribution from the voids and debonding is very small compared to that from the jacketed column. Third, in order to alleviate this difficulty, a special dielectric lens was designed and fabricated to focus the EM wave on the bonding interface. Furthermore, the time gating technique is used in order to reduce the noise resulting from various uncertainties associated with the jacketed columns. Finally, three concrete columns were constructed and wrapped with glass-FRP jackets with various voids and debonding condition artificially introduced in the bonding interface. Using the proposed EM imaging technology with the lens especially designed and installed, these voids and debonding condition were successfully detected.

Paper Details

Date Published: 20 April 2000
PDF: 9 pages
Proc. SPIE 3988, Smart Structures and Materials 2000: Smart Systems for Bridges, Structures, and Highways, (20 April 2000); doi: 10.1117/12.383132
Show Author Affiliations
Maria Qing Feng, Univ. of California/Irvine (United States)
Franco De Flaviis, Univ. of California/Irvine (United States)
Yoo Jin Kim, Univ. of California/Irvine (United States)
Rodolfo E. Diaz, Arizona State Univ. (United States)

Published in SPIE Proceedings Vol. 3988:
Smart Structures and Materials 2000: Smart Systems for Bridges, Structures, and Highways
S.-C. Liu, Editor(s)

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