B+S
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Description
The Döllbachtal Bridge is located on the A7 motorway, approximately 15 km south of Fulda. The structure spans the Döllbachtal valley, which is approximately 50 m deep and partially designated as a protected landscape or FFH area. Due to various damages, the structure will be replaced by a new replacement at the same location.
The use of a launching gantry was planned for the dismantling of the superstructures. Due to the specified construction sequence during dismantling, a launching gantry with a relatively short, longitudinally movable demolition platform was used. During the dismantling process, the demolition platform was gradually moved under the superstructure to catch the demolition material. For this purpose, the superstructure had to cantilever at the demolition edge. A separation of the respective dismantling section from the remaining superstructure was therefore not possible. In order to absorb the unavoidable relative displacements between the superstructure and the launching gantry during dismantling, presses had to be arranged between the superstructure and the launching gantry. During the dismantling of each field, the press forces had to be adjusted several times. For individual dismantling conditions, the superstructure had to be reinforced in order to be able to absorb the stresses occurring during dismantling with sufficient safety (shear force reinforcements, reinforcement of the bending load-bearing capacity).
The superstructures of the new building were manufactured as a 12-field prestressed concrete hollow box girder bridge in composite construction using the incremental launching method. The first superstructure was launched downhill with a 1.4% longitudinal slope, the second superstructure uphill with the same longitudinal slope. For the new building, the auxiliary pier already used for dismantling was provided with a correspondingly adapted pier head. The auxiliary pier was moved transversely after the construction of the first superstructure and reused for the dismantling and new construction of the second superstructure.
Special features
Dismantling:
- Worldwide first-time dismantling of a valley bridge of this size using a launching gantry
- Dismantling without cutting the superstructure, i.e. consideration of the interaction between the launching gantry and the superstructure in all dismantling conditions
- Complex press control to compensate for relative displacements between the launching gantry and the superstructure
- Use of the same auxiliary pier both for the dismantling of the existing superstructure and subsequently for the incremental launching of the new superstructure
- Creation of an auxiliary crossbeam to introduce the loads from the auxiliary pier into the field center of the existing superstructure
- Planning of shear force reinforcements of the superstructure to absorb the load from the auxiliary pier in the area with low stirrup reinforcement
- Anchoring of the longitudinal tendons via bond; for this purpose, development of a multi-stage concept for checking the grouting condition and the anchoring of the tendons
- Cutting off the cantilevers over the entire length of the transversely prestressed superstructure with control of the residual load-bearing capacity of the transverse tendons
New construction:
- New construction of the abutments above the remaining old abutments
- Launching of one superstructure downhill with a 1.4% longitudinal slope and the other uphill with a 1.4% longitudinal slope
- Arrangement of a precast pier head for the use of the dismantling auxiliary pier also for the new construction, afterwards
- Transverse displacement of the 46.40 m high auxiliary pier both for the dismantling and for the replacement new construction of the second directional lane
Publications
Lingemann, J.; Sonnabend, S.:
Dismantling of the Döllbachtal Bridge on the BAB A7 – First-time dismantling of a valley crossing with a launching gantry.
In: Bridge Construction – Construction & Engineering, Issue 1/2 2012, pp. 90-96
Lingemann, J.; Sonnabend, S.:
Dismantling of the Döllbachtal Bridge on the BAB A7 – First-time dismantling of a valley crossing with a launching gantry.
In: Proceedings of the 11th Munich Solid Construction Seminar 2011
Lingemann, J.; Däbritz, M., Wagner, P.; Ranft, A.:
Dismantling of the Döllbachtal Bridge on the BAB A7 – from design to execution.
In: Proceedings of the 1st Bridge Colloquium of the Technische Akademie Esslingen, 2014
Other
Award of the dismantling of the Döllbachtal Bridge in the Manufacturing Technology category on February 11, 2020 on the occasion of “20 Years Symposium Bridge Construction in Leipzig” (Execution planning by Büchting + Streit)
