High up in northern Germany, on the A7 highway from Hamburg to Denmark, Implenia is working on the replacement of the Rader High Bridge. From 2030, this bridge will carry six lanes for 1.5 km across Lake Borgstedt, Rader Island and the Kiel Canal, the world's busiest artificial sea route. The first of two planned bridges is scheduled for completion at the end of 2026. This will make this element of Germany's highway infrastructure fit for the needs of the next century.
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It has been ten years since serious damage was discovered on the Rader High Bridge, which opened in 1972. In view of the massive increase in traffic - 63,000 vehicles a day are expected on this section of road by 2035 - the old bridge with two lanes in each direction is to be replaced by two new bridges by 2030. These will each have three lanes in each direction and a hard shoulder.
Since DEGES awarded the contract for the first of the two bridges in December 2022, all parties involved have been working hard to achieve the ambitious target of completion by November 30, 2026. Despite an extremely tight preparation and planning period, the first work began shortly after the contract was awarded - an achievement that was only possible thanks to the close partnership between the client and the inspector.
Innovative idea shortens execution time
The hydraulic engineering site in Lake Borgstedt, a branch of the Kiel Canal, presents particular challenges. Here, three piers have to be erected in the water, which requires the installation of 40-meter-deep bored piles from the water. Thanks to an innovative proposal from the Implenia team, the construction time can be reduced by using fewer and larger bored piles per pier.
The poor subsoil poses a further challenge, as load-bearing sands are only available in deeper layers. In the water and in the area of the mudslide, 31-metre-long cladding pipes with internal reinforcement are therefore inserted into the ground. Total weight of the bored pile reinforcement: around 22 tons.
Logistically challenging hydraulic engineering site
Implenia is providing all the water logistics for the work on the hydraulic construction site, including a construction site ferry, a push boat and various pontoons, barges and two jack-up platforms, which have a deck load of 250 and 400 tons respectively. The technical coordination and equipment of the jack-up platforms required intensive work preparation. The jack-up platforms were equipped with modular legs to enable them to pass over high-voltage power lines with a maximum clearance height of 23 meters. Numerous feasibility studies were carried out to optimize the configuration of the cranes, the logistics plans with the watercraft and the mooring options. Detailed deck plans for each jack-up platform ensure stability during floating and working conditions and provide the basis for the smooth operation of the heavy-duty machines.
The Rader High Bridge project
Under the technical leadership of Implenia, a consortium is constructing the replacement of the Rader Hochbrücke / BAB A7 highway bridge on behalf of DEGES. The new highway bridge is 1,500 m long and 42 m high and carries the A7 east of Rendsburg, Schleswig-Holstein, over the Kiel Canal and the Borgstedter Enge. The bridge is a steel composite construction and plays an important role for traffic to and from Denmark and Scandinavia.
Location: Borgstedt, Germany
Construction volume (Implenia services). CHF 103.608 million
Start of construction: January 2023
Completion: December 2026
Client: DEGES (Deutsche Einheit Fernstrassenplanungs und -bau GmbH)
In addition to the hydraulic construction site, the team has other exciting and technically demanding tasks ahead of it in the near future, including the construction of the hybrid piers to be built alternately on the Kiel Canal. These piers are unique in this dimension, with a height of 50 meters and 40-meter-long concrete haunches projecting out to the sides. Their load-bearing function is realized in combination with the steel cross-section above, which is pushed over the piers using the incremental launching method.
Sönke von Fintel, Head of the Hamburg office and Project Manager of ARGE RHB, is very proud of the team's performance: "Thanks to the excellent partnership and cooperation, we are well on schedule to complete the new bridge by the end of 2026. Through innovative approaches, we are ensuring that the disruption to shipping in the important Kiel Canal traffic artery is minimized."