Butterfly meadow, Graz

Description

Introduction
Even the name for the project “butterfly meadow” has been selected and implemented faithfully. The whole open space that was designed new, covers an area of about 6000m² and should give a park-like character. The main structure, a single-layer, trussed ETFE foil and steel roofing is located in the eastern part of the square.
Project
In the plan view, the shape is reminiscent of two interlocking eggs - perhaps the earliest development stage of a butterfly? The two ellipses are set to a total of eight, slightly inward, to each oval centre, inclined columns. In its longest dimension, one oval amounts to about 17m and in its short dimension to about 9m. The covered area of the whole roofing amounts to about 220m².
Each oval consists of a steel sheet and three respectively four also elliptical cutouts for the ETFE foil, a total of seven ETFE openings. The cutouts are covered with a transparent and printed ETFE foils. The domed shape is obtained by pressing thrust plates by means of trussed cables upwards against the foil. One difficulty was to find a way that allows to transfer the right-angled grid of cables to the thrust plates without lose much space between the cables, so that foil and cables run as close as possible to each other. Furthermore, a concept had to be worked out that the top pressure points are free from creases and will not get a problem with punching.
On the inside of the ETFE cutouts several spotlights are foreseen, they intensify the harmonious design of steel, ropes and ETFE foils. Harmonious, structured and elegant appears the construction also through the relatively thin cross sections of the columns with internal drainage, the small cable diameters and the thrust plates which allows an additional possibility of adjustment to tension the foil and the cables.
This project was carried out with great attention to detail and the result shows - it is worthwhile! [Tensinews 30 - 2016]

Description of the environmental conditions