31. March 2023

New research group on the deformation of structures and infrastructure New research group on the deformation of structures and infrastructure

Roads, bridges and dams age. How long can such structures still bear the weight? The new research group “Deformation Analysis with Terrestrial Laser Scanner Measurements (TLS-Defo)” at the University of Bonn wants to make a step forward in answering these questions. The German Research Foundation (DFG) will fund the group with around 2.4 million euros over the next four years.

The Brucher Dam serves as one of the test objects in the new research group.
The Brucher Dam serves as one of the test objects in the new research group. © AG Kuhlmann
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“A terrestrial laser scanner is a geodetic measuring instrument that can be used for the contactless measuring of object surfaces,” says the spokesman for the new research group, Professor Dr.-Ing. Heiner Kuhlmann from the Institute of Geodesy and Geoinformation at the University of Bonn. The measuring instrument emits a laser beam that is reflected by the object and then picked up again. From this, the distance can be determined. Since the laser is movable, the beams can be emitted in different directions. The surface of objects can be “scanned” using a large number of these measurements.

“Defo” stands for “deformation analysis.” This involves determining and evaluating geometric changes to objects. The members of the new research group are particularly interested in bridges and dams. “Both groups of objects are relevant because we are talking about ageing infrastructure,” says the geodesist, who is also spokesperson for the PhenoRob Cluster of Excellence and on the steering committee of the Transdisciplinary Research Area “Sustainable Futures.” Media reports frequently mention the A1 highway and the Leverkusen Rhine Bridge and the A45 highway with the Rahmedetal Bridge. Kuhlmann: “However, it’s believed that there are about 5,000 ‘critical’ bridges in Germany and about 50,000 ‘critical’ dams worldwide.”

Small deformations in advance

Before dams and bridges collapse, small deformations appear. “So if we succeed in detecting these small geometric changes very early on, it’s possible to initiate repair measures in time to avoid closures or total failure,” says the researcher. These “changes” take place in the range of a few millimeters or sometimes even well below that. The deformation analysis therefore evaluates whether these are really changes in the object or a measurement inaccuracy.

“Herein lies the novelty of the research group: For the first time, complete modeling of the measurement uncertainties of the terrestrial laser scanner is performed for use in deformation analysis,” says Kuhlmann. This would provide an objective and efficient measurement method for deformation analysis. “That would certainly be beneficial given the challenges of aging infrastructure.”

In addition to the University of Bonn, the University of Hanover, the Technical University of Vienna, the Technical University of Munich and the Karlsruhe Institute of Technology (KIT) are involved in the project.

Contact:

Prof. Dr.-Ing. Heiner Kuhlmann
Institute of Geodesy and Geoinformation
University of Bonn
Telephone: +49 (0)228 73-2620
E-mail: heiner.kuhlmann@uni-bonn.de

You can see a deformation in the middle of the wall (blue color) of 6 to 8 mm. This deformation results from the varying water level in the reservoir, which causes the pressure on the wall to vary.
You can see a deformation in the middle of the wall (blue color) of 6 to 8 mm. This deformation results from the varying water level in the reservoir, which causes the pressure on the wall to vary. © Figure from Holst et.al.: Using point cloud comparisons for revealing deformations of natural and artificial objects. 7th International Conference on Engineering Surveying (INGEO), October 2017, Lisbon, Portugal.

In addition, the research group “Sacred Space Transformation. Function and Use of Religious Places in Germany” was extended by the German Research Foundation for another four years. The speaker is Prof. Dr. Albert Gerhards from the Faculty of Catholic Theology at the University of Bonn. Further information: https://www.transara.uni-bonn.de/de/allgemein/for-2733

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