Papers by Author: Robert Phillips

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Authors: Ivan Bartoli, Salvatore Salamone, Robert Phillips, Francesco Lanza di Scalea, Stefano Coccia, Charles S. Sikorsky
Abstract: Researchers at UCSD are investigating, in collaboration with Caltrans, 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, 15.2-mm diameter twisted strands typically used in post-tensioned concrete structures. A semianalytical finite element analysis is used to predict forced wave solutions as a function of the applied prestress level. A feature shown sensitive to load levels is the inter-wire energy leakage. In order to monitor such feature, piezoelectric sensors were experimentally employed to probe the individual, 5-mm wires comprising the strand. Results of load monitoring in embedded strands during laboratory tests will be presented and a statistical approach will be used to enhance the evaluation of prestress loss in the strands.
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Authors: Claudio Nucera, Robert Phillips, Francesco Lanza di Scalea
Abstract: Among structural concerns for the safety of rail transportation are internal flaws and thermal stresses, both of which can cause disruption of service and even derailments. Ultrasonic guided waves lend themselves to addressing both of these problems. This paper reports on two inspection systems for rails being developed at UCSD under the auspices of the US Federal Railroad Administration. Both systems utilize ultrasonic guided waves as the main probing mechanism, for the two different applications of flaw detection and thermal stress detection.
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