Adaptation of bridges: increasing durability and optimizing stiffness

In Germany, there is a great need for renovation and new construction of highway and railroad bridges. Due to decades of increasing loading, the bridges often only have a short service life.

Due to the increasing loads caused by new generations of trains, such as the ICE 4, stresses and deformations of railroad bridges are rising. The high requirements on the deformation limits pose a particular problem. In cooperation with DB InfraGO AG, it is being investigated how retrofitting the tied-arch bridge with active elements can counteract this. Particular attention is being paid to active vibration damping for this bridge. The hangers are replaced with actuators. In this feasibility study, various actuation strategies are applied to the bridge and investigated.

In preliminary work on the Stuttgart Träger and the demonstrator high-rise building D1244, it was shown that more efficient results can be achieved by directly considering the actuation during the design and optimization of the structure than with subsequent actuation of optimal passive structures. It is plausible that this also applies to bridge structures and that different and new bridge typologies are therefore required for adaptive bridges. This allows limit values for deformations and stresses to be actively adhered to, so that cross-sectional dimensions can be reduced, resources saved and emissions avoided. The holistic inclusion of actuation from the outset also keeps actuation costs as low as possible.

For example, the External Adaptive Tensioning System (EAT) is one such new type of bridge. This is an adaptive underslung tensioning system. As the cables run eccentrically to the neutral axis of the bridge, a bending moment is applied when tensioning the lower deck cables due to the change in length of the actuators, which counteracts the effect of the external loads. This can reduce the mass by up to 30 percent compared to a conventional bridge structure.

Other new bridge typologies are also being considered as part of this research project. For example, a Gerber beam with switchable joints would be conceivable.

Project title: 
Teilprojekt C07 - Adaption von Brücken: Erhöhung der Dauerhaftigkeit und Optimierung der Steifigkeit
project webpage
Funding:
German Research Foundation (DFG), Collaborative Research Centre SFB 1244 "Adaptive Hüllen und Strukturen für die gebaute Umwelt von morgen", GEPRIS project number 324661605
Project partner:
Institute for Lightweight Structures and Conceptual Design (ILEK), University of Stuttgart
Researchers:
Axel Trautwein