Leonhardt, Andrä und Partner Beratende Ingenieure VBI AG
Tiefbauamt Kanton St. Gallen
Bad Ragaz, Canton St. Gallen, Switzerland
This is undoubtedly an outstanding engineering solution, and the judges were impressed by the elegance, clarity and economy of the design. The judges noted the efficiency of the structural system, as well as the beautiful way that the design integrates with its spectacular surroundings. This is a concrete arch design in the best traditions of Christian Menn and Robert Maillart, and the engineers have produced a world class and graceful design.
The judges liked the way that the open spandrel prop supports are inclined in a radial fan arrangement, and the high degree of transparency that has been achieved, with an attractive rhythm for the spans of the deck girder. This transparency is accentuated by the slenderness of the thin inclined props which is achieved by the use of meticulously detailed concrete hinges.
The two end props, which spring from the ends of the arch, imposing both physical and visual weight at these points to good effect, work as part of an integral framing system with the slightly deeper end spans of the girder. These spans can therefore be longer, thus avoiding the need for additional foundations at the sensitive upper slopes of the valley. So the bridge stands on just four foundations, reducing construction uncertainty and maximising the economy of the scheme.