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Work Package

Objectives

In field applications however, the environmental conditions can affect the performance of the method, as observed during the continuous monitoring of 5 pairs of ultrasonic transducers embedded into the concrete ceiling of the Rogier Tunnel in Brussels where we see that the environmental conditions strongly impact the measured ultrasonic signals, even in the absence of damage. 

Such an influence is at least of the same order of magnitude or even greater than the expected changes due to the damage to be detected, which can lead the monitoring system to trigger repeated false alarms if these effects are not filtered out. 
The objective of this PhD project is therefore to develop innovative methods to filter out such effects and improve the robustness of damage monitoring systems to changing environmental and/or operational conditions.

The strategy is based on two different steps :  (1) studying new methods to extract damage indicators that are less sensitive to environmental and/or operational changes (including the possibility of using non-linear ultrasonic measurements),  and (2) using statistical approaches to identify a subspace of variations from the aforementioned data and develop techniques to detect changes outside of this subspace (taking into account the correlations between transducers pairs on the same structure). 
The robustness and efficiency of the proposed techniques will be tested on the continuously monitored data from the Rogier Tunnel for which data for the last 3 years is available, as well as new monitoring data from the Woluwé tunnel which is currently being installed.

Planned intersectoral, interdisciplinary and international secondments

• Isamgeo, Alessandro Brovelli, 2 months, M11-M12: Filtering of confounding effects for seismic measurements collected by Isamgeo.
• Vallen, Horst Trattnig, 2 months, M18-M19: Work on filtering of confounding effects for active ultrasonic monitoring of concrete.
• UEiffel, Odile Abraham, 2 months, M28-M29: Work on non-linear ultrasound as a means of added robust ness to environmental effects.