Berliner Straße railroad overpass
Client
Niedersachsen Ports GmbH & Co. KGBrommystrasse 2
26919 Brake
Services
Road construction | Civil and hydraulic engineeringPlanner
Eriksen and Partner GmbHProject volume
approx. € 6.3 millionDas Projekt
Building site:
In order to achieve the height difference of approx. 8 meters from the existing road level to the new bridge structure, ramps were poured on both sides according to the specified gradient. Due to the poor ground conditions, the two ramps had to be backfilled before the bridge was built. This backfill then had to rest for a period of approx. 8 months in order to consolidate the soil. Only after this time and approx. 1.5 meters of settlement of the ramps could the excess material be removed (total soil mass approx. 100,000m³ of sand) and bridge construction could begin.
Building geometry:
The official design originally envisaged a single-span bridge. However, the client allowed secondary bids in the invitation to tender in an effort to allow access to existing lines. The commissioned secondary offer now provided for a 3-span bridge, which met the client’s wish to maintain accessibility. As the gradient anchored in the planning approval decision could not be adapted to the 3 span bridge, this resulted in an unusual structure geometry. In addition to widening and twisting, this structure geometry also provides for a constant change of gradient in the edge fields. This geometry not only pushes the planners to their limits, but also us in the execution. The amount of formwork required is exceptionally high as no dimension is constant in length, width and height throughout the bridge structure. Furthermore, at the client’s request, the geometry of the piers, originally planned as simple slabs, was significantly altered, so that the construction of the approx. 9-meter-high piers also turned out to be a special feature.
Cables as a disruptive factor and safety risk:
The bridge will be built underneath an EON overhead line, above a DB overhead line and next to buried high-pressure dirty water and gas pipes. These cables extremely restrict the design options. For example, the prefabricated driven piles intended as deep foundations in axis 20 (pillar) had to be driven with a special device which, with its total construction height, can work just below the EON overhead line. This “old” pile driver (Baunut) had to be specially delivered from Denmark by our NU (Aarsleff). An “older” tower crane also had to be used as lifting equipment below the EON overhead line, as newer, commercially available equipment significantly exceeds the required installation height. For all work for which no exact height limit can be defined (concrete pump, mobile crane for laying tendons and shoring work), the overhead line is switched off on one side in agreement with Avacon in order to ensure safe working conditions.
Besonderer Geräteeinsatz
Fushun crawler crane, slewing crane with defined working height, piling rig with limited working height.
Besondere Leistungen
The installation of the 5 precast prestressed concrete elements over the tracks was a special event. The 80-tonne prefabricated prestressed concrete elements were laid in a single night using a crawler crane from our own company (Fushun) in the course of the requested closure breaks. The date of the closure break had to be set and applied for approx. 6 months before the actual execution.
In addition to the tight time frame, the special feature of the execution was primarily the boundary conditions of the building environment. When developing the installation concept, factors such as poor subsoil with regard to the stability of the lifting device, heights and positions of the freely suspended cables and interfering edges of the surrounding building stock had to be taken into account. As can be seen in the photo, the prefabricated parts weighing several tons had to be manoeuvred to within a few centimetres of the DB overhead line and the Avacon overhead line.
Successful implementation is the result of detailed work preparation, critical self-monitoring and professional execution by everyone involved.
