Tree Tower in Bavarian Forest, Germany
Project, Structural Analysis and Construction
Erlebnis Akademie AG
Bad Kötzting, Germany
The path leading through forest tree-tops has a total length of 1,300 m and is the longest tree-top walk worldwide. It was built in 2009 in the Bavarian Forest National Park in Germany. The walk's principal magnet of tourism is the walkable tree tower with a height of 44 m. It consists of a spiral structure with a length of 520 m, directly connected to the 780 m long tree-top walk.
Architecture and Structural Analysis
The egg-shaped tree tower was built around three trees with a height of up to 38 m, growing on a rock formation.
In this way, the visitors are able to follow the trees' individual steps of growth. Reaching the two story steel platform at the tower top, they can enjoy the view across the national park.
The tower's principal supporting structure, mainly built of timber, consists of 16 larch glulam beams which are curved and arranged in rotational symmetry. The upper part of the tower was stiffened by a close mesh of diagonal steel members. The lower part was stiffened by four compression-resistant and tension proof crosses consisting of steel hollow sections anchored with the timber archs. The spiral timber construction is attached to the timber arches by steel suspensions and secondary steel beams.
The structural system was calculated according to the second-order analysis. The calculation resulted in a compression force of 1,160 kN within the timber arches and a maximum horizontal tower deformation of 15.7 cm.
Ralf Kolm, engineer at the WIEHAG company and responsible for the structural analysis, says:
“The egg-shape of the structure required the use of a program that is able to calculate spatial frameworks. We decided to work with the Dlubal program RSTAB, which is best suited for such a challenge.”
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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
Stress analysis of steel members
Stability analysis according to the eigenvalue method
Dynamic analysis of natural frequencies and mode shapes of member models
Dynamic and seismic analysis including time history analysis and multi-modal response spectrum analysis
Seismic and static load analysis using the multi-modal response spectrum analysis