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A Corrosion Monitoring System for Post-Tensioned Structures by Guided Ultrasonic Waves

This study presents a corrosion diagnosis technique for steel strands using guided ultrasonic waves. Steel strands are one of the main components in constructing prestressed concrete structures, cable-stay bridges, and re-centering systems. Guided waves have been used in the past for monitoring corrosion in reinforced and prestressed concrete structures. However, its application for corrosion interrogation in multiwire strands is limited given that the existing approaches often need a reference baseline to which the signal energy is compared. In this study, a reference-free algorithm based on the group velocity of ultrasonic waves at tuned frequencies is proposed through which the extent of corrosion is quantified by estimating the cross section loss. The frequency of excitation was tuned for frequencies at which the velocity was more sensitive to cross-section loss. The statistical features of the ultrasonic waves were extracted using a continuous wavelet transform. The proposed method is validated experimentally.

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