Situated on the northern edge of Seestadt Aspern, the Aspern Nord underground station will in future serve as a joint station for the Austrian Federal Railways and Wiener Linien. Its exceptional architecture reflects its significance as a transport infrastructure project, while its design language and integrated art projects establish links to its historic surroundings. The transparent structural fire protection system enables an exceptionally airy and bright design whilst taking complex fire scenarios into account.
As part of the U2 project, a 120-metre-long central platform has been created for the underground. The station building comprises not only the track superstructure and passageway, but also a spacious entrance hall with an access area, and is arranged at right angles to the tracks. The main entrance, characterised by a dynamically cantilevered canopy, is located on the south side of the station. Adjoining this in the outdoor area are a bus station and a park-and-ride zone. These connecting facilities aim to shift private transport from the “Spange Flugfeld Aspern” motorway feeder road of the Vienna Outer Ring Expressway (S1) to public transport in future. As a metro station, this transport hub is part of the fourth phase of expansion of the Vienna Metro and was built as part of the U2 line extension from Aspernstraße to Seestadt Aspern.
Contemporary transport architecture
Katzberger and Moßburger, the architectural practices collaborating on the U2 project, have already established themselves as specialists in sophisticated transport infrastructure. They have worked on a wide range of projects, including new builds and refurbishments of underground stations, exhibition centre car parks, tunnel portals, and outdoor facilities in public spaces. Their preferred design repertoire includes openness, clarity, functionality and light, alongside minimalist building materials such as glass, steel, aluminium and concrete. Artistic concepts have also been incorporated into the functional architecture of their buildings on several occasions. At the Wien Aspern Nord station, for example, the design is clearly inspired by the dynamic, light-filled architecture of modern airport terminals, which is an allusion to the historic Aspern airfield. This impression is reinforced by the design's openness, but above all by its consistent use of modern, functional building materials.
Art commemorates a site steeped in history
The Aspern Nord underground station, which is located in an area steeped in history, has been the focus of particular attention for two reasons. Firstly, as part of the U2 line extension into the ‘Seestadt’ urban development area, it is a significant infrastructure project connecting this up-and-coming location on the outskirts of Vienna. Secondly, the site's significant history demanded an extraordinary design. Aspern has seen two important moments in world history. In 1809, Archduke Charles defeated Napoleon Bonaparte there, and in 1912, Aspern Airfield – the largest and most modern airport in Europe at the time – opened. Drawing on these events, Bavarian artist Stephan Huber designed two 10 m by 6 m murals mounted behind glass and positioned at either end of the platform. The mural Aspern Affairs (1809) on the western wall is based on a map of the Greater Vienna area which has been surrealistically distorted and supplemented, collage-style, with countless true, false and ironic details. The right-hand section of the mural depicts the Battle of Aspern. The mural Aspern Affairs (1912) on the eastern end wall, in the same style, deals with Aspern Airfield and the history of Vienna during this period.
Coloured life lines
Further artistic references to the location characterise the appearance of the transparent platform canopy, which is a delicate, inclined, steel-and-glass façade structure. Stephan Huber's installation, Lebenslinien (Life Lines), has been applied to the glass surfaces. Colourful, labelled stripes depict the lifetimes of several prominent figures, arranged on a long timeline to show their historical relationships. The coloured lines were meticulously applied to the glass surfaces using a baked-on enamel process to ensure long-lasting colourfastness and protection against abrasion caused by cleaning and weathering. This approach also took bird strike protection into account.
Fire Safety Plan for Special-Purpose Buildings
As with German building regulations, the fire safety requirements for special structures such as the Aspern Nord underground station are not adequately covered by Austria's applicable building or special regulations. As part of the approval process, the relevant building authorities therefore required a presentation of solutions to potential fire scenarios, based on expert assessments, recognised technical standards, and special tests. This process was primarily carried out by the Vienna University of Technology (TU Wien), in cooperation with the Institute for Fire Protection in Linz (IBS). The U2/15 planning consortium managed the project, with support from SFL Technologies, a key contractor specialising in façades.
Realistic fire scenarios
In terms of its fire loads and the structural features provided as escape and rescue routes, the station itself is not considered to pose a risk. However, the specific requirements for the building were derived from a 'worst-case' fire scenario involving a burning train entering the station. In this case, swift and safe evacuation via the staircases and passageway to the outside must be guaranteed, even for large, intermittent flows of passengers. The design is therefore based on evacuation via the staircases from the platforms to the passageway. These staircases have been converted into 'fire-resistant escape tunnels' by enclosing them in a transparent fire protection system with a fire resistance class of EI 30. This protects the escape route from fire and radiant heat. In line with this scenario, smoke extraction via generously sized vents has also been taken into account. The glass escape tunnels do not feature fire-resistant closures in order to prevent the formation of upper and lower fire compartments, as such door systems could significantly hinder or even prevent a rapid escape to open air in the event of a sudden influx of people.
Passageway and platform glazing
The passageway, which serves as the main fire escape, is fitted with EI 30 glazing. Fire-rated door and partition systems effectively separate the shops located along the passageway from the escape route. The enclosure around the tracks, i.e. the external platform façades featuring the coloured lifelines, was also required to have fire protection properties. However, additional protection against the passage of radiant heat was not required in this case, so the E 30 requirement was applied instead, which involves maintaining compartment integrity for 30 minutes. The fire safety concept for Aspern Nord underground station was developed in a highly tailored manner in line with specific requirements through various combinations of fire-resistant glass. Three different fire resistance classes, adapted to the respective installation situations, form the core requirements: E 30 for the platform enclosure, EI 30 for the staircases and passageways, and EI 60 for the glazing of the smoke extraction shaft. Additional requirements included fire-resistant insulating glazing for extra thermal insulation and colour-printed fire-resistant glass. Thanks to the in-depth consultation and ongoing support provided by Pilkington Austria GmbH and the international sales department and product management team at the Gelsenkirchen production site, all specific requirements were met using tested and approved types of Pilkington fire-resistant glass. Around two-thirds of the G(E) 30 platform glazing (740 m²) was fitted with Pilkington Pyroclear®, while 230 m² was realised using 14 mm Pilkington Pyrodur® monolithic laminated safety glass due to increased safety requirements. The EI 30 glazing for the stairwell enclosures and passageways uses Pilkington Pyrostop®, and varies in construction while maintaining the same basic form. Depending on the installation situation, glass types with and without integrated safety films were used, as well as monolithic and double-glazed types.
Special testing of colour-printed glass SFL
Technologies, the fabricator and façade contractor, also undertook the specific task of having the Pilkington Pyroclear® E 30 glazing, much of which was printed with coloured ribbons, tested for fire safety compliance. Standardised fire tests carried out at the Institute for Fire Protection (IBS) in Linz confirmed that the coloured design did not affect the fire safety properties of Pilkington Pyroclear®. This meant that both the fabricator and the client could obtain all fire-rated glass specifications from a single source.
A crucial additional criterion
A key requirement of this contract for the Vienna underground station was that the fire-resistant laminated safety glass should maintain consistent visual quality at low outside temperatures. A temperature range of down to -20°C was considered an extreme case and was therefore imposed on the fire-resistant glass. Pilkington Pyrostop® and Pilkington Pyrodur® fire-resistant glazing met this requirement easily. Fire-resistant glazing in fire resistance classes EI and, in some cases, EW/E provides thermal insulation and reduces heat transfer in addition to its fire-compartmentalising effect. This glazing is made up of laminated safety units with intermediate fire-resistant layers. However, at extremely low temperatures, these intermediate layers can 'freeze' and cause irreversible damage, significantly impairing the glass's optical properties. In internal tests, Pilkington Deutschland AG subjected its fire-resistant glass to sustained temperature stresses ranging from -40°C to +50°C and found no adverse effects. This proves that the products maintain constant optical properties over the specified temperature range. This means that Pilkington Pyrostop® and Pilkington Pyrodur® can safely be used in façades exposed to extreme cold. Another advantage of this 'cold resistance' is that transport, delivery, on-site storage and installation can take place in severe winter temperatures. This optimises site logistics, as installation of the fire protection structures can take place at any time, not just once the building has been 'sealed'.