Structural Health Monitoringof Large Concrete Structures

Patrik FröjdEngineering Geology, Lund University

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Non‐Destructive Testing (NDT)

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Structural Health Monitoring (SHM)

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Ultrasonic waves

• Velocity• Attenuation• Nonlinearity

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Coda waves

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Continuous waves

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Continuous waves ‐ Lock‐In amplifier

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Signal Recovery 7210 Multi‐channel lock‐in

• ”Locks in” on a referencesignal

• Measures amplitude and phase relative to reference signal

• Samples signals withextremely low SNR

Pulsed vs Continuous waves

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Pulsed vs Continuous waves

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[40 dB = 100x]

dB

dB dB dB

dB dB

dB

Transducer network

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Transducer network

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Transducer network

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Transducer network

13Deviation from baseline (std)

Transducer network

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Deviation from baseline (std)

Deviation from baseline (std)

Conclusions

• Diffuse wave fields suitable for SHM of concrete.• Continuous wave transmission potential for greater distances or higher frequencies at given distance.

• ”Small” damage (~cm) detected over ”long” distance (>8 m).• 50 kHz waves can be used for localization through tomography .

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Thank you!Patrik Fröjdpatrik.frojd@tg.lth.se

Hoover Dam – Colorado River, USA16