Neckar viaduct: Two bridges are better than one
The longest motorway bridge in Baden-Wuerttemberg will be completely replaced by 2022 – yet another mammoth project for MEVA in the truest sense of the word
Data & Facts
- New Neckar viaduct BAB 6 at Heilbronn
- ViA6West GmbH & Co. KG
- Hochtief PPP Solutions, DIF, BUNTE
- MEVA systems
- Engineering and support
- MEVA Schalungs-Systeme,Munich office
Major role for MEVA systems
The Neckar viaduct on the A6 motorway at Heilbronn is 1,326 metres long, was renovated at a cost of €17 million as recently as 2003, and is nevertheless no longer able to cope with 100,000 vehicles a day. Within the scope of the A6 expansion project between the Weinberger junction and Wiesloch/Rauenberg, the bridge is to be completely renewed by 2022.
When the extension of the 25 km section of motorway for an estimated €1.3 billion was announced at the turn of the year 2016/2017, it was immediately clear what the greatest challenge would be: construction of the new six-lane bridge over the Neckar. The project company ViA6West, a public-private partnership, is responsible for the planning, construction and operation as well as maintenance until the end of 2046.
In actual fact, two bridges will be built over the Neckar valley: a temporary parallel construction for the ongoing traffic and after the old bridge has been dismantled, the new bridge.The temporary construction is currently being erected next to the old bridge in two steps: the foreland bridge with launching girder and the section over the Neckar using the incremental launching method. The two sections will meet and be connected shortly before the Neckar island. The entire superstructure with the travel lanes and noise barriers is already complete. Subsequently, the old bridge will be demolished and the final foundations and piers erected. The highlight of the project is then planned for 2022: the lateral displacement of the two bridge sections by up to 20 m onto the end piers and hence the completion of the structure. 40 hydraulic cylinders will be used to position the bridge sections precisely to the nearest millimetre using a computer- and camera-controlled system. The task will be completed within just a few days and the bridge sections and connections will be completed. A deadline has already been set in concrete: the National Garden Show in Heilbronn, which opens its doors on 17 April 2019. By then the traffic should be rolling over the temporary bridge.
A lot of work for a stopgap
When using special formwork, it is normal that wooden constructions in particular are designed to be used only once. That the concrete bridge piers and foundations are only temporary structures that will be dismantled when the actual main bridge is complete is the exception rather than the rule. Gerald Hauke, the press officer at ViA6West, gave the following explanation: “There are two reasons for this complex process: Firstly, the state owns the land. A change to the route taken by the motorway and thus an overlap of old and new parts in the area of the abutments and connecting structures would involve immense extra costs.” Thus a complete new structure is being built next to the old bridge from the 1960s to keep the traffic flowing. The exciting phase of the construction project is when the structure is pushed into its final position.
Major role for MEVA systems
Andreas Scherzl, who is supervising the project for the branch office in Munich, is impressed by the size of the construction project: “Building a bridge of this size parallel to the old bridge, i.e. to one side, and then moving it laterally into position, is literally a mammoth task.” It is thus clear which MEVA systems are being used. The foundations for the abutments and the bridge piers are being poured using the Mammut 350 formwork system – as are the bridge piers themselves. The KLK 230 climbing platform and the Space shoring tower ensure that formwork can be erected safely. The launching beams on the piers of the temporary bridge also play a key role to ensure that the entire construction can be manoeuvred laterally into its final position after completion of the superstructure complete with travel lanes and noise barriers.
More than just bridge piers
For the round pier columns and the special pier heads in the area of the steel-reinforced concrete bridge directly above the Neckar the know-how of MEVA’s special-design department was required. Alexander Schmid is supervising the project in Haiterbach: “The tricky thing about this construction was the concurrent bending and twisting in the four formwork panels. At the customer's request the formwork panel had to have a wooden surface.” But not only the panel version poses a challenge. The planning of the demanding form also required the expertise of the MEVA specialists: “We created the plans for the special formwork using a 3D program, allowing precise and efficient implementation.”