Students of the Master's program in Civil Engineering at the Technische Hochschule Mittelhessen (THM) are allowed to learn on real infrastructure projects, regularly supported by Hessen Mobil: This summer semester, the focus was on modern methods of structural diagnostics, structural digitization and condition assessment at the Lahn bridge of the B429 at Eselswiese southwest of Giessen .
The bridge, currently undergoing repairs, is of great importance to the region's transportation infrastructure. According to plans by the Federal Ministry for Digital Affairs and Transport, the structure is to be replaced by a new bridge by 2044. Reinforcement work already completed, among other measures, ensures safe operation until then. For the students in the elective module "Bridge Construction," the bridge thus provided a vivid practical example of the design planning for a potential replacement structure.
The excursion was accompanied by Prof. Dr.-Ing. Bertram Kühn, Prof. Dr.-Ing. Walter Sharmak, Kerstin Lenz and Thomas Berkenkamp from the Department of Civil Engineering, as well as Dr.-Ing. Timm Wetzel from Hessen Mobil. The aim was to provide students with practical experience in current methods of structural inspection and to apply these methods directly to an existing engineering structure.
Various measurement and testing methods, typically used in bridge condition assessments, were employed. For example, the students used a Ferroscan to examine the position and arrangement of the reinforcement in the reinforced concrete. They also conducted phenolphthalein tests to determine the carbonation depth of the concrete. This test investigates the extent to which the material's protective alkalinity has already been reduced – an important indicator of potential corrosion risks to the reinforcement.
Furthermore, the students took samples of drill cuttings, which were subsequently analyzed in the laboratory for their chloride content. Such investigations provide important insights into corrosion-promoting influences and the general condition of the structure. In addition, dynamic probing was used to investigate the soil conditions in the vicinity of the bridge in order to establish initial geotechnical boundary conditions.
Also participating in the site visit was the international course “M23 – ICT for Construction Projects and BIM” from the field of digitalization in construction. This master's program, offered jointly by the University of Porto, the University of Santander, and the host university THM provides sustainable and digital perspectives on buildings, infrastructure, and urban spaces.
The international students undertook tasks including drone photography and mobile laser scans to digitally capture the bridge's geometry. Based on the collected data, a virtual space is being created that will be accessible using virtual reality technologies. This will allow further analyses and explorations of the structure to be carried out in a digital real-world laboratory in the future.
The joint site visit highlighted the close collaboration between different disciplines within civil engineering. By combining traditional structural investigations with modern digital data acquisition and visualization technologies, the students gained practical insights into current developments in structural diagnostics and digitalization in the construction industry. The direct application of testing and measurement methods to a real bridge structure complemented the academic instruction with important practical experience in the areas of structural inspection, structural maintenance, and design planning.