Knies Magician's Hat in Rapperswil, Switzerland

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Shell Structure Made of Timber Elements

The new building in the children's zoo of the Knie Circus in Rapperswil brings a breath of fresh air to the site. The former sea lion arena has become obsolete, creating space for an event hall for concerts, banquets, events, and circus performances. The new building is impressive due to its unique architecture.

Dlubal customer PIRMIN JUNG was responsible for the structural design, structural design checks, and fire protection. They utilized RSTAB for the structural analysis and design.

Structure

The folded timber structure, designed by PIRMIN JUNG structural engineers, is held together by timber compression rings at heights of 36 and 59 ft and a concrete ring at the bottom. The compression rings give the roof structure a high degree of stability. Under the roof is the circus arena with a diameter of 104 ft, with a free span.

The structure is rotationally symmetrical and consists of twelve equal and twelve mirrored timber elements, each curved twice. Two of each element make a pair that forms one of the twelve V-shaped roof elements. They rest on the concrete tension ring at the low points of the collar roof. The "hat" forms the upper end of the roof structure.

The ribs and transverse ribs are made of glued-laminated timber. On top of this lies a double diagonal formwork made of local spruce, which is 0.94 inches thick and bent and nailed manually. The roof elements, including the roof sheathing and shingles, were prefabricated from galvanized sheet metal at the factory. As a result, they weighed up to 4.41 tons; the "hat" itself weighed almost 22.05 tons. Due to the high level of prefabrication, the assembly time on the construction site could be kept short. Thus, the noise pollution to residents and the animals in the Knies children's zoo was reduced to a minimum.