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Proceedings Paper

Load monitoring in multiwire strands by interwire ultrasonic measurements
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Paper Abstract

Nearly 90% of the bridges in California are post-tensioned box-girders. Prestressing (PS) 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 and on the presence of structural defects (e.g. corrosion and broken wires) in the PS tendons. In collaboration with Caltrans, UCSD is investigating the combination of ultrasonic guided waves and embedded sensors as an approach to provide both prestress level monitoring and defect detection capabilities in concrete-embedded PS tendons. This paper will focus on the prestress level monitoring by first discussing the behavior of ultrasonic guided waves propagating in seven-wire, 0.6-in diameter twisted strands typically used in post-tensioned concrete structures. A semi-analytical finite element analysis is used to predict modal and forced wave solutions as a function of the applied prestress level. This analysis accounts for the changing inter-wire contact as a function of applied loads. A feature shown sensitive to load levels is the inter-wire energy leakage. In order to monitor such feature, the method uses low-profile piezoelectric sensors able to probe the individual, 0.2-in wires comprising the strand. Results of load monitoring in free and embedded strands during laboratory tests will be presented.

Paper Details

Date Published: 8 April 2008
PDF: 12 pages
Proc. SPIE 6932, Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2008, 693209 (8 April 2008); doi: 10.1117/12.775934
Show Author Affiliations
Ivan Bartoli, 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)
Salvatore Salamone, Univ. of California/San Diego (United States)
Stefano Coccia, Univ. of California/San Diego (United States)
Charles S. Sikorsky, California State Department of Transportation (United States)

Published in SPIE Proceedings Vol. 6932:
Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2008
Masayoshi Tomizuka, Editor(s)

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