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- Concrete (2)
- Bridge (1)
- Coda Wave Interferometry (CWI) (1)
- Coda wave interferometry (1)
- Monitoring (1)
- NDT (1)
- Structural health monitoring (1)
- Structural health monitoring (SHM) (1)
- Ultrasonic (1)
- Ultrasonic testing (1)
Organisationseinheit der BAM
Ultrasonic coda wave interferometry can detect small changes in scattering materials like concrete. We embedded ultrasonic transducers in the Gänstorbrücke Ulm, a monitored road bridge in Germany, to test the methodology. Since fall 2020, we've been monitoring parts of the bridge and comparing the results to commercial monitoring systems. We calculate signal and volumetric velocity changes using coda waves, and long-term measurements show that the influence of temperature on strains and ultrasound velocity changes can be monitored. Velocity change maps indicate that different parts of the bridge react differently to environmental temperature changes, revealing local material property differences. A load experiment with trucks allows calibration to improve detectability of possibly damaging events. Our work focuses on measurement reliability, potential use of and distinction from temperature effects, combination with complementary sensing systems, and converting measured values to information for damage and life cycle assessment.
Active ultrasonic monitoring with coda wave interferometry has demonstrated its potential for structural Health monitoring in concrete structures. This study investigates its application using ultrasonic transducers embedded in the ceiling of a subway station in Munich, Germany. We evaluate the impact of environmental conditions, specifically electromagnetic interference and temperature, on data quality, as well as the influence of regular loading from passing trams. Results indicate that electromagnetic interference significantly affects measurements, while temperature effects remain minimal due to the station’s stable thermal environment. Long-term measurements and a controlled load test show that both dynamic and static loading from trams induce ultrasonic velocity changes of only 0.01%–0.06%. Although the experiment demonstrates the capacity to detect structural responses and supports the feasibility of long-term monitoring, improved electromagnetic shielding and Hardware reliability are required for successful future applications.
Efficient maintenance of infrastructure relies on monitoring and assessment of its condition. New technologies and methods thereby enable a deeper understanding of the materials used and of the structures built. Coda Wave Interferometry (CWI) is currently explored for continuous monitoring of reinforced concrete structures as well as material testing. This ultrasound-based method is sensitive to even small material alterations and therefore suitable for the detection of initial damage stages. Herein, a step-by-step procedure for the evaluation of ultrasonic signals with CWI methods is presented. The described procedure is proposed for ultrasonic signals collected with embedded ultrasonic transducers with a center frequency of 50 kHz to 70 kHz from prism-shaped concrete specimen with dimensions of 400 mm x 100 mm x 100 mm. The raw ultrasonic signal, preprocessing and CWI analysis are described and influences of parameters within the analysis are discussed. The presented procedure allows systematic and comparable analysis of ultrasonic signals generated with similar conditions and therefore contributes to the application of CWI methods for structural health monitoring and material testing.