08 November 2014

French Bridges: 4. TGV Viaduct, Avignon

There are many impressive bridges in this part of France, but the twin TGV viaducts spanning the River Rhone are particularly spectacular.

They were built between 1996 and 1999, to a design conceived by Michel Virlogeux with Jean-François Blassel, and developed by RFR. Built as part of a TGV route extension, they were reportedly the first viaducts of their type to be built by the French railway body, SNCF.

The viaducts are each 1500m long, comprising a number of 100m main spans and 50m approach spans. They are post-tensioned concrete box girders, built in precast segments and erected using giant launching gantries. Both internal and external prestressing are incorporated.

A special white concrete was used in recognition of the visual sensitivity of the site, and taking into account distant views of the highly historic Palais des Papes in Avignon.

The most interesting feature of the bridge, visually, is the relationship between the concrete girders and the support piers. Tapering circular piers are topped with chiselled caps, widening out sufficiently to carry the bridge bearings. The lower face of the concrete girders dips down towards these points, while also widening out. This looks okay from some angles, but decidedly odd from others. In some views, it creates a pronounced and unwelcome visual kink.

As Britain develops plans for its second high-speed rail line, HS2, it will be interesting to see whether designers can match the high quality of structures such as the Avignon TGV viaduct. British designers are being challenged to develop repetitive, modular designs which can be largely pre-fabricated off site, and there will be a tension between the need to provide a consistent visual identity for the project against the need to consider the context of different sites through which it passes.

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