Corrosion and fire protection for Hamburg's public transport system

(Feb. 2020/OM) - The steel structures at Hamburg's new "Elbbrücken" stop and transfer point for subway and commuter rail passengers are protected against corrosion and fire for the long term with coating systems. A novelty in this construction project is the additional use of a fire protection system, which not only increases the fire resistance of the load-bearing components but also meets the high requirements for corrosion protection in a maritime environment.

Hamburg's HafenCity is the most important urban expansion area in the metropolitan region. In the east, the new "Elbbrücken" quarter is currently being built there with residential space, offices and Hamburg's first skyscraper. In the future, the new subway and S-Bahn station will be used by up to 20,000 passengers a day. These will include not only Hamburg residents but also numerous tourists. The functional and architectural demands placed on the construction of the new transportation infrastructure are correspondingly high. For the last few meters, the subway runs above ground. From the elevated glass station as well as at the transportation hub itself, passengers are offered impressive views of Hamburg's landmarks such as the Elbe Philharmonic Hall, the Michel and the Elbe.

The construction of the platform roof for both the subway and the suburban train station consists of an external, curved supporting structure made of steel. The suspended glazing of the hall roof runs underneath. The steel arches span the stops diagonally and are twisted curved. The executing steel construction company SEH Engineering GmbH developed special bending and assembly jigs for this purpose in order to precisely realize the profile course of the welded, double-T-shaped and twisted arch trusses. At the 2018 Steel Innovation Award ceremony of the German Steel Federation, SEH Engineering GmbH was awarded 1st prize in the steel in construction category for the design of the steel roof.

There are three levels in the subway station hall. There, passengers have access to the trains and opportunities to safely cross the tracks. A pedestrian bridge, the so-called "Skywalk", connects the subway station with the future S-Bahn stop. Deutsche Bahn is the operator of the S-Bahn line and opened the new stop in December 2019.

The entire steel superstructure of the suburban and subway railroad station is protected against corrosion with a coating system from Sika Deutschland GmbH in accordance with TL/TP-KOR-Stahlbauten, Sheet 87. This consists of the primer coating SikaCor Zinc R, the edge protection SikaCor EG Phosphate and the intermediate coating SikaCor EG-1. The final top coat SikaCor EG-4 was applied in the color DB 702.

The soffits of the track superstructure and the tree supports at the subway stop were coated with a 2-component fire protection system from Sika: Sika Unitherm Platinum intumescent was applied to the SikaCor Zinc R primer coating and SikaCor EG Phosphate edge protection to increase the fire resistance of the load-bearing components. As a final top coat, SikaCor EG-4 in color DB 703 according to Sheet 87 was also used here.

The steel superstructure of the "Elbbrücken" subway terminus in Hamburg is thus one of the first steel structures to be completely equipped with a Sika corrosion protection system according to Sheet 87 in combination with a Sika fire protection system. Both of the manufacturer's systems are compatible with each other and thus unique on the market in this combination capability. The result is considerable time savings during fabrication in the factory and on the construction site, as there is no need to use different primer and top coats.

The top coat was applied with a highly crosslinked, UV-stable 2K polyurethane topcoat: Proguard 169(37) was also applied to corners and edges by brush, then applied wet-on-wet by airless spraying in two coats with a total thickness of 80 µm.

The factory precoating of the steel elements was carried out by Surface Protection GmbH, a subsidiary of SEH Engineering GmbH. Special craftsmanship was required for the coating work on the round tree supports of the skywalk in order to achieve a uniform layer thickness of the material.

The welded joints were brought up to the level of the factory coating on site in accordance with the specifications of ZTV-ING, Part 4, Section 3 - Corrosion Protection of Steel Components with the primer coating, edge protection and intermediate coating. Finally, the entire steel structure was coated with the top coat SikaCor EG-4 in color DB 702.

The coating of the topsides of the cover plates in the area of the track crossing and the pedestrian bridges was carried out in accordance with ZTV-ING, Part 7, Section 4 - Bridge Coverings on Steel Surfaces. Sika Ergodur 500 S was applied twice as a primer. This was followed by waterproofing by means of a bitumen welding membrane. In total, approx. 12,000 m² of the steel structures at the new "Elbbrücken" stops are protected with systems from Sika Deutschland GmbH.

The technical consultants of Sika Deutschland GmbH were already involved in the corrosion and fire protection planning of the construction project and supported the planners and fabricators with their knowledge. The coating work in the factory and on the construction site was accompanied by Sika application technicians.

The services around the construction project - from planning to execution in the plant and on the construction site - were highly appreciated by the client, the contractor and their applicators during the realization of the new Elbbrücken stops in Hamburg.

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