Safety upgrading of the S37

Situation

On the S37 Klagenfurt motorway, which connects the cities of Klagenfurt and St. Veit in Carinthia, serious traffic accidents occurred time and again due to the high volume of traffic and a lack of structural separation. To improve road safety, a 6 km section of road was widened by 5 m in the St. Veit area as part of the 2023-2025 safety upgrade. The aim of the measure was to avoid dangerous oncoming traffic areas by structurally separating the lanes. To maintain traffic on the S37, temporary bridges had to be erected during the construction period, which were to be completely dismantled again after completion of the new bridge structures.

Solution

As a simple and cost-effective solution, it was decided to construct the bridge abutments of the temporary bridges from geosynthetic reinforced earth (KBE). The first existing bridge was demolished between March and April 2023. Parallel to the existing bridge, overhanging, steep earth embankments were built to the west and east of the motorway using the KBE construction method with a layer spacing of 60 cm. Fortrac® 55T geogrid reinforcement was installed across the dam axis and Fortrac® 110T at the face of the dam ends and across the dam axis in the area of the concrete foundations. Fortrac® geogrids not only have the required tensile strength and sufficient tensile stiffness, but also very good bond flexibility, which is an essential prerequisite for efficient force transmission between the installed geosynthetic reinforcement and the fill soil.

At both ends of the dam, concrete beams for the foundation of the temporary steel bridge were installed approx. 2.2 m below the dam crest at right angles to the dam axis. In total, the bridge comprised an approx. 4.2 m wide carriageway for single-lane traffic with traffic lights and a 1.1 m wide footpath for pedestrian traffic. The span between the concrete foundations was 45.7 m. After completion of the KBE, the pre-assembled temporary steel bridge over the S37 was installed in just one night and the existing bridge was demolished. After the debris had been removed and the carriageway cleaned, it was open for traffic at 6.00am as planned.

Advantages

• Simple and safe construction
• Shorter construction time and lower construction costs compared to conventional solutions
• Temporary structures can be dismantled quickly and easily
• Easy integration into existing structures and simple adaptation to topographical conditions
• Resource-saving construction