24 March 2010

Knight & Helbig win at Margaretengürtel

A competition to design a 380m long footbridge at Margaretengürtel in Vienna has been won by Knight Architects and Knippers Helbig. The bridge will link recreational parkland to Bruno-Kreitsky Park, carrying pedestrians over a busy highway. The designers beat 36 other entrants [PDF, German], and win a share of a 70,000 euro prize fund.

The design proposes a startling intrusion into the historic Vienna cityscape, with its organic folds and curves oddly reminiscent of a crinkly pringle. It also makes me think of the Termite Pavilion at London Zoo, a sculptural environment built from contoured timber strata.

I’m not entirely sure that I understand the bridge’s structural concept. The larger spans are supported from concrete plinths (resisting highway vehicle impact loads), from which the timber deck appears to grow upwards like a dust cloud. Away from the highway, the supports are extremely slender steel stilts. The deck has a core of layered glulam timber (spruce), which appears to be clad with the contoured outer layer (larch). The timber is reinforced with steel rods inserted between the various layers.

It is intended to be built as a series of pre-assembled sections up to 20m long, stitched together on site. In total, there’s an estimated 960 cubic metres of timber involved. The designers state that the choice of material is far more environmentally friendly than any steel or concrete alternative, and it’s undoubtedly the case that timber is under-exploited as a material for modern bridges. In large part this is due to nervousness on the part of public bodies regarding its long-term durability, and its resistance to vandalism.

The bridge’s S-shaped curvature in plan is complemented by the creation of high, curved edge upstands. These provide a convenient space for bench seating, but have the unfortunate effect of increasing the bridge’s visual mass. They also obscure views off the structure (although they are above the highway so it’s unclear whether the view is of much interest). They also seem to offer a fantastic inclined surface for skateboarders and cyclists to try and negotiate, not unlike the banked surface of a velodrome track.

The parapets appear to be illustrated as simple stainless steel frames with an infill mesh, with a relatively transparent quality allowing the visual focus to remain on the laminated timber. The visualisations suggest a highly unusual structure with the potential to be quite gorgeous if the simple, smooth detailing can be successfully carried through into construction. Timber lends itself to the forming of such irregular surfaces, which would be far less economic in steel or concrete. As a result, the engineering, while clearly unconventional, is probably less forced in service of the architectural concept than is the case for much other modern blobitechture.

2nd prize in the contest was awarded to Luggin with Martin Kohlbauer (see Luggin website for images). 3rd place was taken by PCD ZT with Zeininger Architects (see Competitionline for images).

Updated 29 March: details of prize money corrected.

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