As part of the safety extension of the S31 to Weppersdorf, the valley crossings at Sieggraben will be widened or newly constructed. The four new bridge structures are intended for the Oberpullendorf directional carriageway, while the Eisenstadt directional carriageway will be routed over the existing bridges.

Harald Mayer, project manager at ASFINAG Bau Management GmbH, gave an introduction to the project. Thomas Veselsky and Rudolf Füsselberger then continued the tour and explained the construction methods and designs in detail.

Key data of the project:

• Total length: 3.4 kilometers
• Planned total costs: approx. 72.29 million euros
• Planned start of construction: March 6, 2023
• Planned opening to traffic: end of 2026

Most of the bridge sections will be built using the incremental launching method, a technique that poses a challenge even for experienced experts. "Although it is a tried-and-tested system, it is always challenging. Put simply, bridge sections are concreted in front of the valley and connected with cables. We then push the existing piers out with the help of hydraulic pumps. We repeat this process until the bridge has reached the other end of the valley,” explains project manager Harald Mayer.

Widening the old roadway was not possible for structural reasons. Therefore, traffic heading towards Oberpullendorf will be routed over the new bridges in future, while traffic heading towards Eisenstadt will continue to use the existing valley crossings, each with two lanes. The S31 safety expansion project, in particular the construction of the new bridges, is not only a technical masterpiece due to the challenging terrain topography, but also an example of sustainable construction. The rocky excavation pit and the concrete demolition of the auxiliary structures will be recycled on site to minimize the environmental impact. An additional focus is on the innovative pilot project of the ASFINAG alliance contract, which aims to share risks and allow the contractual partners to participate in the success of the project, which is particularly important for high-risk projects.