Lookout Tower on Rügen Island, Germany
In May 2013, German Chancellor Angela Merkel inaugurated the natural heritage center Rügen in Prora. The highlight of the 1,900-hectare natural heritage area on the Baltic Sea island of Rügen is the 131-feet-high "Nest Tower". It is already the third tree tower that WIEHAG GmbH has built.The tower stands at a height of more than 131 feet above sea level. Visitors are thus provided with a breathtaking view of the landscape at a height of over 262 feet.
Structural Analysis and Timber Tower
Structural Engineering Office
Ing.-Büro Wolf GmbH, Passau, Germany
Architect Josef Stöger, Schönberg, Germany
Erlebnis-Akademie AG, Bad Kötzing, Germany
Construction of Tree Tower
The structure of the tower consists of an outer ring made of 12 vertical glulam 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 structures.
The upper third of the tower was fitted with 12 glulam arcs to make it look like an eyrie. The arcs are fastened to the cantilevered steel platform at the top and to the glulam columns at the bottom. The outer diameter of the timber tower is approximately 79 feet, in the area of the "eyrie" it is about 118 feet.
Connected to the observation tower is a 1,367-yard-long walkable treetop path that winds through the treetops at a height of 13 to 56 feet. The path is also the entrance to the tower. In order to reach the viewing platform at the top of the tower, visitors have to enter the 656-yard-long spiral structure inside the tower.
The platform consists of steel cantilevers protruding outwards that connect to the timber columns, and between them longitudinal timber beams with planking.
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When designing many members in one design case, it is sometimes difficult to recognize the governing designs. To improve the overview and to display the relevant designs in a compact way, you can use the filter options under the result tables. These are included in all design modules of steel, aluminum and timber structures in RFEM and RSTAB.
The cross-section resistance design analyzes tension and compression along the grain, bending, bending and tension/compression as well as the strength in shear due to shear force.
The design of structural components at risk of buckling or lateral-torsional buckling is performed according to the Equivalent Member Method and considers the systematic axial compression, bending with and without compressive force as well as bending and tension. Deflection of inner spans and cantilevers is compared to the maximal allowable deflection.
Separate design cases allow for a flexible and stability analysis of members, sets of members, and loads.
Design-relevant parameters such as the stability analysis type, member slendernesses, and limit deflections can be freely adjusted.
- In RF-/TIMBER AWC and RF-/TIMBER CSA, I receive the error that says torsion limit exceeded. How do I bypass this error message?
- Why is the strength always reduced by the kmod value of 0.6 during the calculation in the RF‑LAMINATE add‑on module, although I have load combinations with variable loads?
- Can I consider a reduction of the stiffness according to the German regulation NCI NA.5.9 in TIMBER Pro?
- I have selected all available members for design in RF-/TIMBER Pro. Why are tapered members not designed?
- When performing the fire resistance design with TIMBER Pro, I get the error 10001. How can I fix the error?
- Is it possible to set user-defined values when viewing solid stress results?
- How are the signs for the release results of a line release and line hinges interpreted?
- How can I create a curved or arched section?
- Is it possible to design the support pressure or the compression perpendicular to the grain in RX‑TIMBER?
- After the design with RF‑/TIMBER Pro, I optimized a cross-section. Why is the utilization of the optimized cross-section exceeded now?
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