The video shows the first of four piers and its associated longituindal girders being installed using what is known as the balanced lowering method.
The technique was developed by Johann Kollegger, professor at the Technical University of Vienna's Institute for Supporting Structures, and involves mounting the girders in a vertical position on both sides of a concrete pier and then unfolding them into their final positions like an umbrella. “The two girders are connected to each other at the top, directly above the pier,” Johann Kollegger explains. “With hydraulic systems, this joint is then slowly lowered, and the girders unfold to both sides.”
The girders are thin-walled prefabricated elements with steel reinforcement which are filled with concrete once in their final position. “Erecting bridges using scaffolding usually takes months. The elements for the balanced lowering method on the other hand, can be set up in two to three days, and the lowering process takes around three hours,” says Johann Kollegger.
The first large-scale tests of the technology were carried out in 2010, and the method was fine-tuned through to its first application on the Fürstenfeld Highway.
The 116m-long bridge was unfolded on 27 February 2020.