Palais de l’Atlantique
The Parc des Expositions de Bordeaux, or Bordeaux Exhibition Center, has been equipped with a new Hall of 14,000 square meters, Hall 2 Palais de l’Atlantique. In order to create a proper front entrance, facing the tram stop, the facade of the new Hall features a cantilever canopy of 24 meter, rising above the entrance square. A single layer of ETFE film supported by cables was installed on the underside of this large awning. Summum Engineering provided the structural analysis for this cladding system.
The ETFE cladding and tensioned cables, delivered and constructed by Highpoint Structures and Buitink Technology, is part of the eye-catching front canopy of the new Hall of the Bordeaux Exhibition Center. LAH/AT Architects and BLP Architects designed the entire complex, and ensured that it worked within the constraints of the existing site. The canopy is 78 m in length, with a 24 m cantilever. Its soffit is divided into eleven panels, fitted with tension cables every meter. The total surface area for the ETFE panels is 1.450 square meter. According to the client, the decision to use ETFE was due to the material’s self-cleaning property, its durability and extremely low-weight.
Summum Engineering performed the structural analysis of the canopy’s ETFE soffit, subject to self-weight, pretension and wind loads, and according to recommendations from Tensinet and prospects for a future Eurocode. Loads were derived from wind tunnel testing. The results showed wind suction to be of primary concern, and higher than would have been found from code, especially at the outer edges of the canopy. This meant that 6 or 8 mm tension cables had to be placed inside the ETFE along sleeves, with higher tension at the outer panels. The wind loads were conservative as they are determined on the basis of a rigid model, whereas in reality the flexibility of the ETFE can reduce the effects of wind. Furthermore, the possible cooling effect of the wind on the ETFE can reduce the temperature meaning the material’s resistance increases. The final design used 0.300 mm thick ETFE throughout for visual coherence, and a cable prestress of no more than 9 kN. Although the ETFE has very low weight, the benefit for a single layer system is somewhat offset by this pretension, which is required to keep it flat and taut, but avoid plastic deformation.