New roof tops off Foster + Partners-designed restoration of German train station
Buro Happold has provided the engineering design for the spectacular fabric roof of the refurbished Dresden Main Station, which opens today (10 November).
A collaboration between the practice’s London and Berlin offices, Buro Happold engineers worked closely with the architects at Foster + Partners and the engineers for the overall refurbishment, Schmitt Stumpf Fruhauf and Partners of Munich.
The challenge for the Buro Happold team was to introduce a fabric roof over the restored steel arches of the 155-year-old station without transferring excessive load to the original structure.
A replacement for the previous opaque cladding, the translucent 30,000m² PTFE-coated, glass fibre fabric roof has transformed the vast spaces of the station, filling the station hall with light. Also, as the membrane roof is much lighter than the original, or a conventional replacement, it permitted reuse of the original steel arches.
The station covers an area of 240m by 120m, but the roof is divided into three areas, covering: the entrance building and middle hall (59m across with a roof height of 30m), flanked by two side halls (the north hall is 32m wide; the south hall slightly narrower – both with a ceiling height of 22m), each covered by barrel-vaulted fabric sections.
Buro Happold partner and the project principal, Mike Cook, said: “A key part of the restoration is letting more light into this great 19th century station, through replacing the roof. Realising this dramatic design in fabric while working with such a venerable support structure created significant challenges for the engineers, solved through a process of physical modelling, form-finding and computer analysis using our own, in-house software, called Tensyl.
“The use of fabric created some significant extra work for the contractors, largely to contain all the stresses of the stretched material. This saw the addition of temporary supports during construction to resist the stresses of the membrane, while preventing excessive loading on the original arches. Only once the last panel of the membrane was installed and pre-stressed could these temporary struts be removed.”
Material testing of the original steelwork found massive structural weaknesses, partly due to damage inflicted during World War Two, so the major issue for Buro Happold was to transfer load from the fabric membrane through the repaired steelwork and into the foundations. This was achieved by building a secondary structure to transfer loads from the membrane to the top chord of the old steel arches. These fragile arches have little resistance to horizontal forces and so any longitudinal stresses have to be transferred to the braced end bays. These act as 10m wide trusses as part of the transfer structure.
To allow for catastrophic loads (eg: in the event of partial or total membrane failure), additional cables underneath the fabric have been introduced to make sure overall stability is maintained.
The full refurbishment work saw the complete strip down of the roof, repair of existing steelwork arches and foundations, the erection of the new roof steelwork with additional secondary steelwork, and installation of roof lights, drainage pipes and lightning protection.
The official opening ceremony is being attended by the German Transport Minister, local politicians and dignitaries.
The project team
Client: Deutsche Bahn Station&Service AG
Regionalbüro für Großprojekte Dresden
Architect: Foster + Partners, London and Berlin
Project Manager: Homola AYH AG, Dresden
General planner and structural engineer
for the steelwork and concrete works: Schmitt Stumpf Frühauf und Partner, Munich
Structural engineer for the membrane roof: Buro Happold, London and Berlin (Happold Ingenieurbüro GmbH)
Building Services: Schmidt Reuter und Partner, Dresden
General contractor: ARGE Dywidag und Heitkamp, Dresden
Sub contractor membrane roof: Skyspan (Europe) GmbH, Rimsting
