The University of Luxembourg, in collaboration with the Administration des Ponts et Chaussées, carried out a large test bridge on 13 September 2018 in Altrier, Luxembourg. By taking pictures along the bridge with drones and by applying the principles of photogrammetry, the researchers measured the deflection line of the bridge with high precision in order to allow in the future early damage detection by applying a new developed algorithm.
In the frame of a research project entitled “Condition assessment of bridge structures by analytical and numerical methods”, engineers of the Laboratory of Solid Structures from the Research Unit in Engineering Sciences (RUES) at the University of Luxembourg have developed an algorithm to better analyse the condition of bridge structures.
“The algorithm, which is able to identify damage based on the measurement of the deflection line under static load, showed very promising results, not only in theoretical examples but also in laboratory experiments. Thus, we decided to go further with an in situ load deflection experiment on a real bridge structure by using the latest measurement techniques such as laser scanner and photogrammetry”, explain Professor Danièle Waldmann and PhD student Dolgion Erdenebat who have been working on this project since Mai 2015.
With the help of the Administration des Ponts et Chaussées, the research team selected the bridge in Altrier due to its configuration, access and space. PhD Erdenebat was really involved in this choice: “First of all, we selected beam bridges instead of arch, truss, suspension or cable-stayed bridges because they have usually a continuous cross-section. Then, we took into account environmental conditions to facilitate the access of trucks, the flight of drones, the traffic flow and the workspace”.
After 8 hours of measurements divided in three steps: before loading, during loading and after loading, the experiment was a real success. The researchers were very satisfied with the results obtained: “These measurements enable us to include to our algorithm the impact of large-scale dimensions and environmental conditions”, comments Prof. Waldmann.
Researchers will now continue to develop the method, based on the collected valuable information, and optimize the researched algorithm and measurement techniques as a contribution to the safe and economic preservation of our infrastructure.
The experiment was carried out by a team composed of technicians and researchers from the Institute of Civil and Environmental Engineering (INCEEN) and the Interdisciplinary Centre for Security, Reliability and Trust (SnT).