In the municipality of Häselgehr, located in the scenic Lechtal valley in Austria, an important infrastructure project is underway – the renovation of the bridge and road connection in the hamlet of Grießau. Due to the aging bridge and challenges related to traffic safety and flood risks, a comprehensive solution is being prepared, incorporating modern construction and engineering approaches.
The Plateia software played a key role in the planning process, as it allowed for detailed modeling of the road infrastructure. Advanced digital planning helped analyze possible solutions more accurately and reduced the risk of problems in later construction stages.
Challenge: How to Ensure a Safe and Sustainable Connection?
The existing bridge over the Lech River no longer meets modern standards. During high water levels, it can cause dangerous river blockages, increasing the risk of floods and negatively affecting traffic flow and safety. Additionally, the limited space for road expansion requires smart engineering solutions.
The main goals of the project focus on creating a stable and flood-resistant bridge, optimizing the connection to road B198, and providing safe paths for pedestrians and cyclists. The new infrastructure must also be sustainable and visually harmonized with the natural surroundings to blend seamlessly into the local landscape.
Image: View from below the existing Grießau bridge.
To achieve these goals, the designers used advanced digital planning to carefully evaluate different bridge construction and traffic management options. Through simulations, they were able to minimize potential construction challenges early in the process and ensure the optimal solution.
Selected Solutions: New Bridge Structure and Traffic Arrangement
After a detailed analysis of several possible solutions, two bridge designs and two different traffic arrangements were selected as the most suitable. Both designs were modeled in a 3D environment, allowing for precise simulation of their behavior under real traffic and weather conditions.
Bridge Design
1.1 Frame Bridge with Composite Construction
The frame bridge in composite construction is designed with an exceptionally thin profile, significantly reducing the need for embankments and extensive construction work. This design is particularly suitable for areas with limited space, as it requires a smaller footprint and better adapts to the existing terrain.
Additionally, the slim structure allows the bridge to blend harmoniously into the surrounding environment, enhancing the visual coherence of the entire road infrastructure. With its lightweight construction and technical efficiency, the bridge combines high load capacity with an aesthetically pleasing design.
Image: Frame Bridge Variant.
1.2. Bridge with Reinforced Concrete Girders
The bridge with reinforced concrete girders (Zügelgurtbrücke) is a modern version of a suspension bridge, where concrete supports replace traditional steel cables. This solution enables a slim yet stable structure that efficiently distributes loads and ensures long-term durability.
The inclination of the pylon in this design is adjusted to improve road visibility and enhance the bridge’s aesthetic appeal, while also providing greater stability under heavy traffic conditions.
Image: Bridge with Reinforced Concrete Girders (Zügelgurtbrücke).
Both variants underwent thorough testing to assess their load capacity, resistance to stress, and necessary adjustments to ensure flood safety.
2.Traffic Arrangement: Two Possible Solutions
In addition to the bridge design, the connection to road B198 also needed optimization. Two different solutions were analysed.
2.1. Solution 1: Additional Lane for Left Turns
This solution includes an extra lane for vehicles turning left, which improves traffic flow and safety. By organizing vehicle movements better, it reduces the chance of traffic jams. It also features a pedestrian crossing, a bike path, and bus stops, enhancing safety and accessibility for everyone. Due to limited space, careful planning of road elements was necessary.
Image: Plan of the First Solution.
Image: Cross-section of solution 1.
In Solution 1, the bridge is designed as a semi-frame structure with steel beams along the edges of the roadway to carry the main loads. Between these beams, a concrete slab will be placed to support the roadway. The pedestrian walkway and bicycle path will be attached to the eastern beam. On the left side, the upper structure will be separated from the abutment to prevent stress from temperature changes. The steel beams will rest on elastomeric bearings, which allow for movement and flexibility.
Image: Visualization of solution 1.
2.2. Solution 2: Without Left-Turn Lane
The second option does not include a left-turn lane but offers an alternative with a safe underpass for pedestrians and cyclists. This design maintains smooth traffic flow while ensuring safe crossing of the road. The underpass separates pedestrians and cyclists from motor traffic, significantly increasing safety and reducing the risk of accidents. This solution also provides more space for the bridge foundations and greater construction flexibility.
Image: Plan of the second solution without left-turn lane.
Image: Cross-section of solution 2.
In Solution 2, the bridge is designed as a “Zügelgurtbrücke”, where the tension elements are constructed as reinforced concrete walls, providing continuous support along the edges of the roadway. Due to the widening of the structure in certain areas, significant torsional moments arise, which are managed by two pylons connected with load-bearing planes. Additionally, the pylons are anchored into the abutment on the Grießau side. The bridge is supported by two abutments: the abutment on the B198 side consists of a load-bearing wall and a chamber wall, while the abutment on the Grießau side includes a vertical wall and foundations with anchored pylons.
Image: Visualization of solution 2.
Both versions were carefully analyzed in terms of flow, safety, and cost-effectiveness to ensure optimal traffic management.
What’s next?
The project is in the final planning stage, with the ultimate decision on the variant to be made in collaboration between the Häselgehr municipal administration and the Reutte District Construction Office. The chosen solution must consider traffic needs, financial capabilities, and environmental constraints.
The renovation of the bridge and road connection in Grießau will provide safer, more modern, and more reliable infrastructure, benefiting residents and visitors to the region. Advanced digital planning, as facilitated by Plateia, ensures that the project is carefully analyzed and optimized from the design phase, reducing risks during implementation and providing an efficient traffic connection for future generations.