Hamburg Central Station

1. Task given by the client

The listed Hamburg Central Station was built in 1906 and is one of the most impressive long-distance train stations in the Federal Republic of Germany. The station concourse is one of the most impressive pieces of architecture in the Hanseatic city with its historic roof structure spanning over 70 m.

The particular challenge lay in the refurbishment during ongoing operations, especially as the station is the busiest station in Germany with 450,000 visitors per day.

As a result of regular inspections of the supporting structure and the building shell of the station halls, considerable damage was identified, which was renovated and reconstructed in accordance with the preservation order:

• Repair/replacement of parts of the steel supporting structure in the main hall and side halls
• Renewal of the glass façades of the main hall (approx. 3,500 m²)
• Renewal of the skylight glazing (approx. 1,500 sqm)
• Replacement of over 4,000 panes of glass in the side halls
• Repair of the south façade
• Renewal of the maintenance facilities
• Renewal of the roof waterproofing, skylight domes and drainage facilities
• Refurbishment of more than 300 defects from the building logbook distributed across the entire construction project

The task was therefore to make the existing listed structure stable, safe for traffic and rainproof for the next 50 years while maintaining traffic, and to make it attractive for visitors thanks to the new transparency.

2. Description of the main supporting structure

The station roof is made up of riveted steel main trusses with a span of 73 m and a ridge height of 32 m, which were designed as double-hinged trusses at a distance of approx. 15.5 m from each other. Lattice girders are mounted between the main trusses to absorb and transfer the loads from the roof cladding and the façades. Truss girder frames are attached to the sides, which absorb the horizontal shear from the main frames and in turn serve as supports for the barrel roofs of the side halls on both sides of the main hall. The horizontal shear is absorbed on the sides by granite bearing stones. The south façade is formed by a steel structure suspended from the 1 main truss.

3. Choice of building materials

Due to the requirements of the monument protection authorities, the choice of building materials and the color scheme had to be carried out in close coordination with the monument protection authorities. The defective steel structures were replaced with new profiles. The glass façades were designed with a steel add-on construction and glazed with 8 mm VSG glass, consisting of 2 x 4 mm TVG with PVB film in between.

In the south façade of the side halls, several granite block infill panels weighing several tons were removed to replace the steel structure and reinstalled after reconditioning. In the central section, existing reinforced concrete blocks with an exposed aggregate concrete structure were replaced with cast stone made from refined precast concrete elements using different textured formliners and aggregates from Italian granite. The production of these prefabricated reinforced concrete elements modeled on the granite was supervised by the Office for Monument Protection. Approval for the use of Italian aggregates for the DIN-compliant production of the precast elements had to be obtained separately.

4. Explanation of the design

The special requirement for the design was the faithful reconstruction of the components. For example, the supporting profiles of the skylight glazing in the side halls could not be replaced with new ones, but the old profiles were dismantled individually, numbered and refurbished in the corrosion protection plant. These profiles were then reinstalled in exactly the same position. This faithful reconstruction meant that the glazing could only be created using previously created templates. In general, particular emphasis was placed on preserving the overall urban impression during the design process.

5. special engineering services

The special engineering achievement lies in the complexity of the construction task.

A wide range of refurbishment and renewal measures had to be carried out throughout the entire main station while operations continued, taking into account a wide variety of boundary conditions. During the planning phase, a major handicap was initially the very narrow time window granted by the railroad for breaks in operations, during which extensive temporary structures were to be erected.

The only rudimentary existing structural analysis of the structure from 1904 also made it necessary to carry out extensive surveys of the load-bearing steel structure, which had already been rebuilt several times, particularly in the area of the south apron and the south footbridge. Initially, large-volume room scaffolding was planned as free-standing scaffolding in the main and side halls of the station, which would also serve as protective and working scaffolding for the work on the supporting structure, the glass façades and roof riders as well as the skylight domes. By changing the assembly technologies, these scaffolds were replaced in cooperation with the client by more delicate, easier and faster to assemble and dismantle protective net constructions inside the main hall on the glass façades and under the ridge and, on the other hand, by suspended scaffolding on the main trusses, under the roof riders and scaffolding on the roofs. Extensive structural calculations were required for these scaffolding structures on the roofs, some of which were also heavy and could be erected outside of the closed periods, in order to verify their stability using the existing load reserves of the existing structure.

A positive side effect of these technological changes for the temporary structures was a barely noticeable disruption to rail and passenger traffic, as the main and side halls as well as the rows of stores could be kept free of disruptive scaffolding. The refurbishment of the entire south apron, which directly adjoins the Steintordamm bridge belonging to the City of Hamburg, was also carried out without disrupting car and pedestrian traffic. The necessary scaffolding was erected as special constructions in sections with partial overbuilding of the pedestrian lane. In this case, the scaffolding loads and loads from lifting equipment for dismantling and installing the granite block infills had to be factored into the bridge construction. The load reserves were also very low here, as the bridge was found to be damaged by piers that were no longer load-bearing and the load-bearing capacity of the bridge was considerably reduced.

In general, special attention was paid to the various intermediate construction conditions during the steel construction work, whether in the hall when replacing dilapidated beams, hinged plates or entire frames or on the south apron when dismantling and reassembling the load-bearing hangers and façade beams. Extensive structural verifications were required, which had to be reconstructed by analyzing the existing structure due to the lack of structural analysis. During the renovation of various damages from the building book, more extensive damage was found in some areas after uncovering the areas, so that planning and structural analysis was required during construction.

Numerous material tests were also carried out to assess the material quality in terms of strength and weldability. Wherever possible, standardized solutions were found for the replacement of the profiles, which could be reproduced as required. The principle was to intervene as little as necessary, but to do so permanently and comprehensively. These interventions were always carried out taking into account the interests of monument protection, e.g. to reproduce existing rivet patterns or profiles.

6. What positive effects does the special engineering work have?

The already impressive station concourse is now flooded with light thanks to the renovation of the glass façades and invites you to linger with its diverse range of stores. The renovation work has not only made Hamburg's main station fit for the next 50 years, but has also made it much more attractive.

Explanatory report by Eiffel Deutschland Stahltechnologie GmbH for submission to the Ingenieurbau-Preis 2013