Published Online: 15 SEP 2009
Copyright © 2009 John Wiley & Sons, Ltd. All rights reserved.
Encyclopedia of Structural Health Monitoring
How to Cite
di Scalea, F. L., Bartoli, I., Rizzo, P., Marzani, A., Sorrivi, E. and Viola, E. 2009. Multiwire Strands. Encyclopedia of Structural Health Monitoring. .
- Published Online: 15 SEP 2009
Multiwire strands are used in civil structures as prestressing members of posttensioned concrete systems, and tendons of cable-stayed and suspension bridges. This article discusses the use of ultrasonic guided waves for providing both defect detection and stress monitoring capabilities in the common seven-wire, 15.34-mm (0.6-in.) steel strands using embedded transducers. The semianalytical finite element method is first used to model the multimode and dispersive vibrational behavior of the strand waveguide. Experimentally, magnetostrictive transducers probing the strand as a whole are shown to be sensitive to small notch-like defects in reflection-based measurements, which are aided by robust feature extraction and statistical defect classification. Small piezoelectric transducers probing the individual wires comprising the strand are, instead, shown to be suitable to monitor the level of stress applied to the strand. In particular, the ultrasonic transmission between the peripheral wire and the central wire, quantified in terms of ultrasonic energy and frequency, is found to be highly sensitive to the level of stress. The method discussed is currently under laboratory development, and its effectiveness in the field remains to be demonstrated.
- prestressing strands;
- ultrasonic guided waves;
- feature extraction;
- semianalytical finite element method