PSI - Issue 64

Chongjie Kang et al. / Procedia Structural Integrity 64 (2024) 1232–1239 Chongjie Kang, Maria Walker, Steffen Marx / Structural Integrity Procedia 00 (2019) 000 – 000

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The primary objective of this bridge DT is to extend the service life of the Nibelungen Bridge in Worms, which is the physical entity. First, we collected and investigated the inventory data, including the technical drawings, the calculation and recalculation reports, the examination and survey reports, photos, etc. Both the physical bridge and the inventory data form the basis for the development of a bridge DT. To create a precise 3D geometry presentation of the current bridge, a laser scanning survey was performed. As a result, a BIM-model with a LoD300 of the pilot area was created based on the obtained point clouds. This BIM-model is used as the central digital representation of the DT. Meanwhile, to monitor the global behaviour of the pilot area and to facilitate data-driven methods to detect damages, an initial SHM system was established. In this scope, 20 sensors, including radiation, humidity, temperature, inclination, linear variable differential transformer (LVDT), and acceleration sensors, have already been installed on the bridge. The measurement rate of the sensors is between 10 Hz and 200 Hz, depending on the sensor type. All data is automatically transferred from the on-site measuring system to a local server, then copied to cloud storage, and forms the basis for comprehensive multi-stage processing. The processed data will be structured in a database. Afterwards, a web-based visualisation platform is developed to show the monitoring results in a relatively real-time manner; more specifically, the measured results will be updated every three hours on the web-based platform. Besides, through the investigation of the bridge and inventory data, two critical issues were identified in relation to norms and bridge history development in Germany. The first issue is the corrosion of both prestressing tendons and reinforcements, which is a result of historical construction methods that were not well developed and insufficient concrete cover. To assess the corrosion state, a thorough investigation of the historical maintenance history of the bridge will be carried out. Besides, structural diagnostic investigations using non-destructive testing methods, such as potential field measurements, will be conducted. As a result, a specific corrosion condition indicator (CI) will be developed. The second critical issue is the weak shear capacity due to the absence of stirrups. In the 1960s, shear resistance was not correctly considered in the design of bridge constructions. To evaluate its remaining shear capacity precisely, sophisticated finite-element modelling with solid elements should be performed, taking into account the non-linear material properties of the components. This will help identify critical positions on the bridge. Based on this, goal-oriented measurements should be applied to develop a shear capacity CI. Besides, according to the German norm DIN 1076, a simple and a major examination must be carried out on bridge constructions every three and six years, respectively. Besides, additional exanimations and inspections shall be carried out under certain circumstances. These inspection results are commonly systematically managed in a software named SIB-Bauwerke, which is developed and owned by the federal and state road construction administrations. Using the as-maintained BIM-model as the central digital entity of the DT. In the end, a front-end web-based platform is developed to host all this heterogeneous information. Hence, users can access all the results and developed CIs through this front end, directly or indirectly. Currently, the Bridge DT aims to extend the service life of the Nibelungen Bridge, which is still in development. An extension of this system to the entire bridge, including a functional expansion, is currently being planned. By incorporating the latest working methods and techniques into the digital twin, the aim is to demonstrate how the digitalisation of maintenance can extend the service life of infrastructure structures. In the future, the Nibelungen Bridge will continue to serve its purpose as an icon of digital transformation. 5. Discussion and outlook The DT is a new and high-potential digital method for bridge maintenance. It is currently dynamically investigated and requires contributions from interdisciplinary domains, including civil engineers, data scientists, computer engineers, etc. On the one hand, new technologies are necessary to monitor and record the behaviour of bridges, and data-driven methods are necessary in developing analysis models. On the other hand, new data management approaches are demanded to achieve interactive and interoperative data flows. In regard to the digital entity of DTs, different models, including the information model (commonly BIM), the data-driven surrogate model, the analysis model, the 3D surface model, and the federated model, have been utilized. These different models have different advantages, however, and are also limited to different conditions. BIM is nowadays more commonly used due to its advantages in linking and hosting heterogeneous data. Further investigations shall be continuously carried out in order to find the optimal solutions for modelling the digital entity of DTs.