Retractable Membrane Roof for inner-city shopping street

Description

Context
It is always the desire of retail and catering to make shopping streets more attractive. So far only suburban shopping malls manage to provide protection from all weather conditions. In Buchs, Switzerland (Canton St. Gallen), an inner-city shopping street has now been designed as an exceptional meeting place with adaptable weather protection.
Project description
A retractable membrane roof covers the 50m long Metzgergasse in the heart of the city and can be opened and closed within 5 minutes, at the touch of a button. The street area is completely covered by the 525m² fabric roof and provides protection from rain and sun. The pedestrian zone is significantly valorised through the design and functionality of this project. The adaptive roofing provides the site with significant economic benefits, since even in bad weather, the public space is fully available and can be used for a variety of events.
The convertible roof is opened and closed longitudinally along 4 parallel rails. When open, it takes on a very spatial wave geometry. The textile fabric is stretched between curved ridge and valley belts thereby forming a sequence of dynamic elements with an average height of 6.50m above street level. The folded membrane is 'parked' at the north end under a canopy between the buildings forming a gateway to the Metzgergasse. During deployment, the membrane is transversely pre-stressed to provide optimal stability for wind loads.
A particular challenge in the foothills of the Alps is always the strong foehn winds, which are typical in the Swiss-Austrian Rhine Valley. Therefore, the relevant wind loads for the roof construction were determined though precise experiments in the wind tunnel.
The selected membrane made of polytetrafluoroethylene (Teflon) is chemically inert, UV-resistant and non-fading, the natural color is white.
With an interdisciplinary planning team of architects from Nikolia Kugel arch22 and the engineers from str.ucture, this project continues the unique Stuttgart lightweight tradition. The planning team has been consistently developing the technology of retractable membrane structures to advance structural optimisation and functional design of such unique lightweight structures. This enables a highly efficient use of resources and leads to the inherent elegance of lightweight design.

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Description of the environmental conditions