Bell Tower in Bleibach, Germany
An extraordinary bell tower has been built in Bleibach in the Southern Black Forest Nature Park, Germany. The structure, with a height of approximately 111.5 ft, has a triangular floor plan and consists mainly of cross-laminated timber (CLT).
Röm.-kath. Kirchengemeinde Mittleres Elz- und Simonswäldertal
Pfarrei St. Georg - Bleibach, Germany
|Object and Structural Design||
Wirth Haker PartmbB
Holzbau Baumer GmbH
There is a viewing platform at a height of about 46 ft. Upon request, you can look out over the surrounding valleys and the peaks of the Black Forest mountains.
The engineering office of Wirth Haker PartmbB from Freiburg, Germany, was responsible for the structural analysis of the tower structure. The engineers used RFEM and the RF‑LAMINATE and RF‑DYNAM Pro - Natural Vibrations add-on modules for the structural analysis and design.
The tower shaft, the bell chamber, and the spire form the three main components of the tower. The ground plan forms an equilateral triangle with side lengths of about 22 ft. The side walls consist of cross-laminated timber elements with a thickness of 7 7/8 in., made of silver fir. They rest on a reinforced concrete ring foundation with about 11-foot-high foundation walls and an 18-in.-thick floor slab. The walls are anchored in the foundation by means of cast-in steel rod anchors as well as slotted plates and dowels.
You can reach the viewing platform (at a height of approximately 46 ft) by climbing 60 steps and crossing twelve intermediate landings. The level of the viewing platform is at a height of about 9 ft. Above this, the belfry extends over two levels (2 x 9.5 ft). The upper end is the spire in the shape of a three-sided pyramid with a height of 36 ft.
The triangular shape of the tower and the wall elements made of CLT with their glued longitudinal and transverse layers ensure high stiffness and dimensional stability of the structure. In addition to the static loads, the dynamic loads due to the swinging bells are absorbed well.
For fire protection, fire resistance class F30 was required. This was used in the fire resistance design of all structural components, including the steps. The vertically arranged façade formwork made of Accoya wood ensures the construction timber protection. This wood, chemically modified with acetic anhydride (acetylation), is particularly resistant to wood-destroying fungi and insects as well as weather conditions.
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Compared to the RF‑/TIMBER Pro add-on module (RFEM 5 / RSTAB 8), the following new features have been added to the Timber Design add-on for RFEM 6 / RSTAB 9:
- In addition to Eurocode 5, other international standards are integrated (SIA 265, ANSI/AWC NDS, CSA 086, GB 50005)
- Design of compression perpendicular to grain (support pressure)
- Implementation of eigenvalue solver for determining the critical moment for lateral-torsional buckling (EC 5 only)
- Definition of different effective lengths for design at normal temperature and fire resistance design
- Evaluation of stresses via unit stresses (FEA)
- Optimized stability analyses for tapered members
- Unification of the materials for all national annexes (only one "EN" standard is now available in the material library for a better overview)
- Display of cross-section weakenings directly in the rendering
- Output of the used design check formulas (including a reference to the used equation from the standard)
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