Your Project Technical data of the project Project title: A periscope in Fochteloërveen. Physical Location: Fochteloërveen on the border of Province of Friesland & Drenthe. Site owner: Stichting Natuurmonumenten Architect: ir. D. de Haan Engineering office: ABT Adviesbureau voor Bouwtechniek te Velp. General contractor: Bouwbedrijf Doornenbal & Louwes te Appelscha. Location: Fochteloërveen on the border of Province of Friesland and Drenthe. Total weight of the steel structure: +/- 23000 kg. Building costs: +/- 230000 Euro. Highest point: +/- 17,5 meter. Building period: April 2000 - June 2000. Short description of the project Architectural design In 1997 the foundation Natuurmonumenten decided to bring back the marshland of Fochterloo to its original state. The result is that the marsh is no longer accessible to visitors, so you can only look at it from the edge. For this reason one decided to build a tower. In 1998 architect Dick de Haan († 1998) designed a tower with the shape of a big "7". A big periscope looking over the marsh. The lower part of the tower leans backwards to accentuate the shape of the trees. The upper part is like a telescope coming out of the woods. The bend in the leg turns over 90 degrees halfway, so it was necessary to place two large columns under the structure. To accentuate the periscope effect, the tower has been closed from the outside by wooden panels (Western Europe Softwood). And when you reach the top, the front of the periscope has a wall of glass to give the highest transparency. The highest point of the tower is about 17,5 meter. Not higher because the tower may not dominate the trees. When you are at the highest level, it gives you the feeling of looking over the marshland of Fochterloo like a hawk. Structural aspects. The idea was to build a structure with large prefabricated parts to avoid too much damage to the woods. For that reason the material that has been chosen is steel. So after making a concrete foundation, the tower can be build by placing big steel three-dimensional elements on top of each other. The wall has been built up with large wooden prefabricated panels, which can be attached to the steel structure after the erection. As mentioned the structure has been placed on a large concrete foundation block, which is supported by four prefabricated concrete piles. The problem of this structure is the deformation. It is not only the horizontal and vertical deformation, but also the rotation, which is important, because of the slope of the median. That mainly was the reason to use ESA-Prima Win for three-dimensional structures. After the module "3D frame" the module "Steel Code Check (NEN 6770/6771)" was used, so it was easy to find out if the unity checks were OK. After calculating the steel structure, the foundation block was calculated by using the module "2D plates" and the module "Analyse betonnen 2D elementen (NEN 6720)" to calculate the reinforcement. So it was easy to find out if and where a basic reinforcement was not enough. To get a feeling on the deformation and rotations, different loading combinations were calculated. To calculate the rotations it was important to put the different levels of wind loads on different parts of the structure. Because the structure is like a hollow section, and torsion is a very big issue for the deformations, it was very important to design stiff frames on the most sensitive places of the structure. Using ESA-Prima Win gives us the opportunity to analyze the structure to find these sensitive places and after that to optimize the frames which are places in these locations. Use of ESA-Prima Win Description of the technical questions to be solved with ESA-Prima Win: The structure is like a hollow section, and torsion is a very big issue for the deformations. So it was very important to design stiff frames on the most sensitive places of the structure. A description of our experience with ESA-Prima Win when realising the project: Using ESA-Prima Win gives us the opportunity to analyze the structure to find these sensitive places and after that to optimize the frames which are places in these locations. Modules used: 3D frame Steel Code Check (NEN 6770/6771) 2D plates Reinforcement Design 2D elementen (NEN 6720) 11 SCIA User Contest Catalog
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