This paper proposes a guided wave-based approach for monitoring stress redistribution in prestressing strands under corrosion. The stress dependence of wave velocity is leveraged for stress measurement, while targeting advantageous frequencies of higher-order wave modes to eliminate the geometric effects of corrosion. For practical longterm monitoring scenarios, where sensor reattachment/replacement may introduce artificial noise, a technique for eliminating such effects (called modal modulation) is also proposed. To demonstrate the approach, accelerated corrosion testing was carried out on a strand while actively generating and receiving higher-order modes. The strand was subjected to 29 cycles of accelerated corrosion (reaching 45% mass loss), with the 29th cycle terminated at the simultaneous fracture of three peripheral wires. The measurements from several higherorder modes were processed into a single estimate using a data fusion approach. The data fusion estimate showed good agreement with the measured stress values even under significant surface roughness (up to 20% mass loss), and especially under a large stress increase due to fracture. To evaluate the modal modulation technique, stress estimations obtained without applying the technique were also shown, which yielded incoherent results.
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