It's a big bridge, some 30m and 400m long in total, and it's perhaps surprising to see a winner which is an essentially entirely new type of bridge. Essentially, it's a steel cantilever bridge along the lines of the Forth Railway Bridge, but with a number of unusual features.
The cantilever trusses are curved rather than comprised of straight pieces, requiring significant quantities of additional steel to resist the local bending induced in the steelwork. Very limited support is provided to the deck, which therefore has to be excessively deep.
The oddest feature, however, is the fact that the cantilevers sit on single lines of bearings, so that under uneven loading, the only stability is provided by the connection between adjacent cantilevers. Those short connection pieces don't really look stiff enough to provide that stability, and I wonder quite how the engineer has persuaded the design to work.
Of the other designs, the 4th prize entry is the most ambitious, with what appears to be a 250m span network arch bridge (just shy of the existing longest span of this type), a very challenging and complex structure to build.
Winner - Marc Mimram
2nd Prize - Öhlinger+Partner ZT GesmbH, Ponting Consulting Engineers and Zeininger Architects
3rd Prize - Gruppe VCE Vienna Consulting Engineers ZT GmbH, FCP Fritsch, Chiari&Partner ZT GmbH and Quist Wintermans Architects
4th Prize - SSF Ingenieure AG, ISP ZT GmbH and Knights Architects
So they are definitely demolishing the old railway bridge? Not understanding German, it's hard to find information about this. Has this design been chosen because it was the only one of the entries to evoke the three arches of the old bridge?
ReplyDeleteIch spreche kein Deutsch.
ReplyDeleteTo Jonathan:
ReplyDeleteThe press release linked at the beginning of the post states that this design competition was aimed at reconstructing the railway bridge / building a new one. "Neubau der Eisenbahnbrücke" in German, which means that the old railway bridge will be affected and a new one will be built in its place, but it does not strictly mean reconstruction. From the context it seems that the new bridge will carry tram, car and pedestrian traffic.
The comments of the jury do not definitely say that the resemblance to the old bridge was decisive. Instead they say: "Das Projekt besticht durch seine Leichtigkeit – das Bogenmotiv stellt sich als subtile Transformation einer „echten Bogenbrücke“ dar." - in English: The design appeals through its lightness - the arch motif presents itself as a transformation of a "true arch".
Yes, let's transform an arch by taking something that isn't an arch at all and faking it so that it looks a bit like an arch.
ReplyDeleteAnd "lightness" in this context appears to mean "making it really heavy, but having only a smaller number of heavy bits".