Linking up the west part of the Parisian financial district La Defense with Nanterre via the Tour Granite, this 90 m long footbridge winding through a dense architectural tissue is a modern urban promenade based on an ambitious structural concept.
Starting off behind the Grande Arche as a ramp in continuation with a street, the generous circumscription of the office building of the Société Générale Bank - visible in the plan - asked for a specific solution. The bridge keeps a large distance with the building and the supporting structure has been transferred to the exterior curve. This allows for a maximum of natural light to reach the offices and cafeteria. The bridge attains/reaches/ the Tour Granite on the first floor. Escalators and stairs link up with the ground level. The main structural elements are the girders accentuating the bridge every 10 m like “vertebras”. The “spine” of the bridge consists of steel sheet box girders. The radiating “vertebras” are interconnected by pre-stressing “tendons”. A system of cantilevers takes on the vertical forces.Very good resistance against torsion is assured by the deck and a band below interlinking the pre-stressed in the circumferential direction. Glass banisters are fixed at the exterior curve so that the pedestrian may contemplate the cityscape. At night the illumination of the masts emphasizes the rhythmic structure of the promenade.