DC08 Jitendra Sharma - ULB
Throughout the world, a large part of the civil infrastructure made of concrete was built in the 1960's and 70's and has reached the end of its theoretical lifetime of 50 years. Many of these structures made of concrete present today important pathologies and need heavy repair, often causing major disruption of traffic. Inspection and maintenance of concrete infrastructure is therefore currently a major concern for all infrastructure management services all around the world.
In Brussels, the current strategy for inspection and repair of tunnels and bridges is based on a two phase procedure. In the first phase, visual inspection is performed to identify the zones of potential damage to the concrete. This requires removing all panels and equipment covering the concrete, and is very long and labor intensive. In the second phase, and based on the results of the first inspection, concrete core samples are extracted at different locations in the tunnel and subjected to different mechanical and chemical tests in the laboratory to determine properties such as concrete strength or depth of the carbonation front. The results of the second phase serve as a basis to decide on the repair actions that will be taken to restore the structural integrity of the concrete infrastructure.
AT ULB, in the BATir department, the research team of Prof Arnaud Deraemaeker has been developing a novel strategy for automated real-time monitoring of concrete infrastructure. The aim of this permanent on-line monitoring is to detect damage as early as possible. This early detection allows to reduce the costs and the time needed for the repairs, therefore also allowing to reduce traffic disruption.
The monitoring system is based on ultrasonic transducers directly embedded in the concrete. The transducers allow to monitor continuously the state of concrete without any need of removal of concrete panels or equipment, or any human intervention. This method has been successfully applied to several laboratory tests with constant temperature and humidity conditions.
Keywords: Monitoring, damage detection, concrete, ultrasonic testing, non-destructive testing, statistics
Research field: Civil engineering
Click here to watch Jitendra introduce himself as well as his PhD subject.
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.
1. Development of novel damage indicators based on linear and non-linear ultrasonic measurements obtained with using ultrasonic transducers embedded in concrete.
2. Development of statistical methods to filter out environmental and operational conditions, applicable to ultrasonic measurements in concrete as well as features extracted from other types of transducers for infrastructure monitoring
- 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 effect
- C. Dumoulin and A. Deraemaeker. All-season monitoring of concrete repair in an urban tunnel in Brussels using embedded ultrasonic transducers with emphasis on robustness to environmental variations. Journal of Civil Structural Health Monitoring, 2021. https://dipot.ulb.ac.be/dspace/bitstream/2013/324943/3/CSHM_Rogier2021…
- A. Deraemaeker and C. Dumoulin. Embedding ultrasonic transducers in concrete: A lifelong monitoring technology. Construction and Building Materials, 194:42–50, 2019. https://dipot.ulb.ac.be/dspace/bitstream/2013/278194/5/Elsevier_261821…
- A. Deraemaeker and K. Worden. A comparison of linear approaches to filter out environmental effects in structural health monitoring. Mechanical Systems and Signal Processing, 105:1–15, 2018. https://dipot.ulb.ac.be/dspace/bitstream/2013/267088/6/doi_250715.pdf
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DC08 Jitendra Kumar Sharma
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Local academic supervisor Arnaud Deraemaeker
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Industrial co-supervisor Alessandro Brovelli
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PhD supervisor Arnaud Deraemaeker