Footbridges in Lourdes
Construction of three footbridges, part of the refurbishment of the Domain of Our Lady of Lourdes, taking pilgrims across the Gave de Pau river and providing safety of the structure in the event of flooding.
The water level of the Gave de Pau fluctuates greatly and so the footbridges have to be liftable. In addition to fully raising the footbridges in large floods, the lifting mechanism provides an intermediate position at 50 cm. In this position, the bridges can still be used once the access ramps have been raised.
The footbridges share the same simplified construction comprising a grid of steel girders, 40 cm thick and with a span of 40 m.
The stainless steel plating, with a heavily sanded finish and random perforation pattern, forms the upper surface of the beams. De useful width of those bridges is respectively 10 m, 6 m and 4 m for a total width of 11 m, 7 m and 5 m.
There is a dual statics diagram: simply supported under constant loads and embedded under variable loads. The latter arrangement consists of a double support for the deck on each abutment, comprised of a 3.4 m extension of the structure into the abutment. The end is locked by a bolt providing rear support.
Bureau Greisch, in a joint venture with Eiffage construction Midi Pyrénées (FR) and Beterem Ingénierie (FR), has provided the architecture and stability studies for these three footbridges.
Complete stability and architecture mission