Rottendorf

Rothof viaduct

New viaduct for the A7 motorway upgrade

The A7 motorway connects the north and south of Germany and is being extended and modernised in sections. As part of these works, the Rothof bridge was also rebuilt. The new bridge consists of two separate superstructures, each 410 metres long. For the planned six-lane extension of the motorway, the width of each carriageway is 14.50 metres. Even before vehicles could travel across the new bridge, the foundations, piers and superstructures were constructed step by step along the route.

410-metre bridge on large-diameter bored piles

The Rothof viaduct rests on two abutments and seven pier axes. The largest span lengths are 60 m, whilst the pier heights range from around 12.5 m to 25.5 m. The foundations were laid using large bored piles with a diameter of 1.50 m and lengths of up to 22 m. These form the basis for transferring the structure’s load into the subsoil. The pile foundations thus created the conditions for the subsequent construction of the substructures and superstructures.

Segmental pushing method over the valley

The two superstructures were constructed using the segmental pushing method. Advance beams approximately 36 m long were used for this purpose. In a total of 15 stages, the bridge structures – each with a maximum individual length of 30 m – were advanced. This is how the two prestressed concrete box girders were created, which today support the carriageways of the A7. The incremental launching method enabled the superstructures to be constructed in sections, whilst railway lines and transport routes continued to operate beneath them.

Transverse sliding of a 17,760-tonne superstructure

A distinctive feature of the project was the traffic management during the runtime. To maintain traffic flow on the A7, the carriageway in the direction of Fulda was initially constructed on a temporary bypass alongside the existing structure. Following the dismantling of the old bridge, the final abutments and piers for both carriageways were constructed. The second superstructure for the Würzburg-bound carriageway was then built. Finally, the previously constructed superstructure for the Fulda-bound carriageway was transversely shifted. Weighing approximately 17,760 tonnes, the superstructure was moved 19.75 metres into its final position.

Construction between the motorway, railway lines as well as existing structures

The works took place in the immediate vicinity of a heavily trafficked motorway as well as several railway lines. Construction sequences, traffic management and bridge construction were co-ordinated section by section. Step by step, the new Rothof viaduct took shape amidst existing infrastructure, temporary traffic diversions and new structures.

Foundation for the new crossing

The completion of the bridge paved the way for the further modernisation and expansion of the A7 motorway in the Würzburg area. Even before traffic could be routed over the new superstructures, large-diameter bored piles, piers and prestressed concrete box girders were constructed to form the foundation of the new structure. Between the railway lines, the valley and the motorway, a further section of the transport infrastructure along the A7 was thus created.