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Proceedings Paper

Nonlinear ultrasonic guided waves for stress monitoring in prestressing tendons for post-tensioned concrete structures
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Paper Abstract

Many bridges, including 90% of the California inventory, are post-tensioned box-girders concrete structures. Prestressing tendons are the main load-carrying components of these and other post-tensioned structures. Despite their criticality, much research is needed to develop and deploy techniques able to provide real-time information on the level of prestress in order to detect dangerous stress losses. In collaboration with Caltrans, UCSD is investigating the combination of ultrasonic guided waves and embedded sensors to provide both prestress level monitoring and defect detection capabilities in concrete-embedded PS tendons. This paper presents a technique based on nonlinear ultrasonic guided waves in the 100 kHz - 2 MHz range for monitoring prestress levels in 7-wire PS tendons. The technique relies on the fact that an axial stress on the tendon generates a proportional radial stress between adjacent wires (interwire stress). In turn, the interwire stress modulates nonlinear effects in ultrasonic wave propagation through both the presence of finite strains and the interwire contact. The nonlinear ultrasonic behavior of the tendon under changing levels of prestress is monitored by tracking higher-order harmonics at (nω) arising under a fundamental guided-wave excitation at (ω). Experimental results will be presented to identify (a) ranges of fundamental excitations at (ω) producing maximum nonlinear response, and (b) optimum lay-out of the transmitting and the receiving transducers within the test tendons. Compared to alternative methods based on linear ultrasonic features, the proposed nonlinear ultrasonic technique appears more sensitive to prestress levels and more robust against changing excitation power at the transmitting transducer or changing transducer/tendon bond conditions.

Paper Details

Date Published: 30 March 2009
PDF: 11 pages
Proc. SPIE 7292, Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2009, 729220 (30 March 2009); doi: 10.1117/12.815614
Show Author Affiliations
Ivan Bartoli, Univ. of California, San Diego (United States)
Claudio Nucera, Univ. of California, San Diego (United States)
Ankit Srivastava, Univ. of California, San Diego (United States)
Salvatore Salamone, Univ. of California, San Diego (United States)
Robert Phillips, Univ. of California, San Diego (United States)
Francesco Lanza di Scalea, Univ. of California, San Diego (United States)
Stefano Coccia, Univ. of California, San Diego (United States)
Charles S. Sikorsky, California State Dept. of Transportation (United States)


Published in SPIE Proceedings Vol. 7292:
Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2009
Masayoshi Tomizuka, Editor(s)

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