Look-Out Tower on Rügen Island, Germany
Structural Analysis and Timber Construction of Tower
Office for Structural Analysis
Ing.-Büro Wolf GmbH
Architect Josef Stöger
Erlebnis Akademie AG
Bad Kötzing, Germany
In May 2013, the German Chancellor Dr. Angela Merkel inaugurated the natural heritage center of Rügen in the Prora beach resort.
The highlight of the center with an area of 1,900 hectares on the Baltic Sea island is the ‘nest tower’ which is 40 m high and the third tree tower that has been constructed by the WIEHAG company. The tower was built on a hill lying more than 40 m above sea level, offering visitors a breathtaking panorama over the landscape at a height of about 80 m.
Construction of Tree Tower
The tower structure consists of an external ring made of 12 vertical glued‑laminated beams. They are arranged with rotational symmetry and set up with an angle difference of 30° each, thus forming a polygonal, spatial structure.
The columns are supported by means of steel girders on single foundations. The tree tower is stabilized by a close meshed net of diagonal steel members as well as horizontal ring components.
Twelve arcs consisting of glued‑laminated timber have been added to the upper third of the tower to make the top look like an eagle eyrie. The arcs' top ends are attached to the cantilevering steel platform and the bottom ends to the glued‑laminated timber columns. The outside diameter of the timber tower is approximately 24 m, on the "eyrie" level it is approximately 36 m.
Visitors can access the tower by using the tree-top walk connected to the look-out tower, having a length of 1,250 m winding through the treetops in a height of 4 - 17 m. The path is also the entrance to the tower. To reach the viewing platform on the tower top, visitors must tread the spiral structure with a length of 600 m in the tower interior.
The platform itself consists of cantilevered steel beams connected to the timber columns where longitudinal timber girders with planks are lying in between.
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Programs Used for Structural Analysis
The structural engineering software for design of frame, beam and truss structures, performing linear and nonlinear calculations of internal forces, deformations, and support reactions
Timber design according to Eurocode 5, SIA 265 and/or DIN 1052