Roof over Parking Area in Montreux

“Tensairity” is the epigrammatic expression coined to describe a new lightweight structural concept. The membrane roof over the parking area at Montreux station near Lake Geneva is an example of this system. The development not only complements a two-storey, underground parking space dating from 1997; a further aim was to create a contrast to the solid forms of construction in the surrounding area. The structural principle seems familiar: steel compression and tension chords are supported on rigidly fixed columns. The innovative feature lies in the fact that the membrane, filled with compressed air, does not bear the actual roof loads, but serves to prestress – and thus stabilize – the steel elements. This enabled the cross-sectional dimensions of the structure to be reduced and the weight to be roughly halved in comparison with conventional forms of construction. The patented trusses span a width of 28 metres and are laid out at 5.80-metre centres. Raking columns transmit the loads to the foundation slab of the parking block and brace the structure in the lateral direction. The long facades are formed by a metal mesh that allows natural lighting and ventilation. The lightweight quality of the construction is underlined by the handling of light. The membrane allows diffuse daylight to fall on the parking spaces, while at night the pneumatic structure can be illuminated in various colours, thus becoming a salient point in the area. The technical and design effects were possible only through a close collaboration between all planners involved in the scheme. Initial reservations towards the new girder concept were overcome by a feasibility study. In a preliminary project, it was demonstrated that the structure could compete with conventional forms of construction even in terms of costs. Stability is guaranteed by a system based on telephone and Internet links that immediately report any loss of air pressure. Should this system fail, the trusses are laid out in such a way that they are capable of bearing their own weight plus ten centimetres of snow, even without compressed air.