Fly over junction of AKN-Line A1 and city railways (S-Bahn)
in Hamburg-Eidelstedt

Cross section Client: AKN Eisenbahn AG, Germany Construction Costs: approx. 20 million Euro Services: Conceptual and detailed engineering design, provision of all documents for the official approval, tendering, awarding, construction supervision Period: 2002 - 2006 Cooperation: ICB Hamburg GmbH

The one-track line A1 of the northern German railway transportation company AKN between Hamburg-Eidelstedt and Kaltenkirchen is being expanded to two tracks. The existing grade intersection with the Hamburg city lines (S-Bahn) in Eidelstedt will be reconstructed to a fly over intersection to further enlargen the capacity of both AKN and S-Bahn. The construction area is located within a residential quarter of Hamburg-Eidelstedt. Due to the consequent lack of space the fly over construction itself consists of only one AKN track, see fig.1.

Sellhorn heads all planning processes of this project. Paramount part of the fly over junction is the general and detailed design of the necessary tunnels, retaining walls and a bridge expansion with regard to the undisturbed operation of all railway tracks and lines:

• A northern expansion of a highly skew railway bridge and tunnel with three openings and a crossing angle of approx. 21°.
  Parts of the existing structure have to be torn down to integrate the remaining reinforced concrete walls and slabs into the expansion. The foundation of the existing structure is shallow, the extended part is founded on bored piles.
• A junction structure of approx. 65 m length with six adjoining retaining walls, partly anchored, partly combined as a cofferdam. The junction structure and the retaining walls consist of reinforced concrete walls founded on overlapping bored piles, also supporting the concrete superstructure of the junction to form a rigid framework. The railways of AKN (down) and S-Bahn (up) cross at an angle of approx. 20°. The retaining walls support level differences of up to 12 m.
• A closed rigid framework bridge for an AKN railway fly over intersection with a footpath.

The area of construction consists of about 900 m alongside the AKN track and about 700 m alongside the S-Bahn tracks. All works are executed in various steps and phases to guarantee a widely undisturbed operation of all railway tracks and lines. Planning and realisation take place in close cooperation with the S-Bahn Hamburg GmbH and the Deutsche Bahn AG (DB), owning the existing infrastructure and future owner of the junction structures.

The most difficult part with regard to work next to, above and beneath operational railway tracks is the northern extension of the highly skew railway bridge and tunnel, since all railway tracks have to be kept operational throughout the demolition and construction process, with only very few interruptions of service.

The documents for the official approval include various appendixes regarding:

• Compensatory and substitute measures (landscape conservation plan, study of environmental compatibility),
• Expertise of noise protection ,
• Expertise of vibration protection incl. comparing measurements,
• Expert’s report on soil properties and foundations,
• Layout of lines (AKN, S-Bahn and DB) during construction and for the final state and
• High voltage and overhead contact lines

which were supplied by third parties and coordinated resp. integrated into the document by Sellhorn.

Sellhorn prepared two tender documents to award the works in two main contract sections. Both sections meanwhile have been awarded to major construction companies. Works on the first section started in February 2005 and on the second section in July 2005, both have been finished in time before the kick-off of the soccer world championships 2006 in Germany.