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Free Roll, 1998

Design, planning and structural calculation Students of the Augsburg University
Production Students of the Augsburg University
Installation Students of the Augsburg University
Research Prof. Alexander Furche, Prof. Dr. Robert Off (Initiators and direction)
First Membrane of the world built with a "free roll"

 

Starting point was a 10 day workshop (August 1998) at the University Augsburg.

Initiators and directors: Prof. Alexander Furche and Dr. Robert Off 

Participants: 15 students of Augsburg University supported by Jürgen Hennicke (Institute for light weight structures IL, University Stuttgart)


The Idea and Basic Reflections

Task of the workshop was to create a membrane as a cover for outdoor activities at the University to be continued through light rain. Different solutions to install the membrane between the surrounding  buildings were analysed.

Obviously, the existing solid structure was not able to resist the additional forces occurring by fixing the membrane to the buildings. Some medium sized to major sized changes and additional reinforcements of the existing  building structures would have been necessary. Therefore the realization of the project would have been doubted right from the beginning, due to complications expected by the administration of the Augsburg University.

After a lot of research, the favored solution was a freestanding membrane.

 

Form Finding, Calculation and Patterning

To convert the design and idea into a real construction it was absolutely necessary to go on working on the project and do further research.

At the University Augsburg the subject of membrane structures was established and lectured by Dr. Robert Off.
Students of the following semesters tried using the method of models to develop patterning and steel details.

Due to its complexity, the free roll required a type of patterning inconceivable by employment of physical models alone. The only solution was to find a method of computational modelling.

For form finding, calculation of membrane forces, and patterning the if-group Germany with Dipl.Ing. Horst Dürr and Dipl.Ing. Reiner Essrich was given full professional support.

After several discussions and trials it was possible to generate the free roll as a computational model. At that moment calculation of the actual forces was possible.

Sponsor Companies and Institutions

The whole project was done without any public finances. All involved companies, institutions and individuals donated their activities and materials to this challenging task.Without this extraordinary sponsoring the project would have never been realized.

Start of work ceremony

The works started in spring 2001. The mayor of Augsburg, Mrs. Margarete Rohrhirsch-Schmid headed the start of work ceremony. It was a great pleasure to celebrate together with the companies involved and the students just before completion of the project.

 

Project Realization and Construction

The survey calculations and the actual survey of the construction was done by: Prof. Dr. Weber University Augsburg together with his students.
Planning and detailing of the steel structure and the steel-membrane connections, as well as the overall management, was done by the independent Institute of Membrane and Shell Technologies e.V. (I.M.S.)

For fixing the membrane at the sharp ends at both sides of the roll, three-dimensional clamping details had to be developed and designed.

The steel structure consists of three masts. Each of them is built with three bent tubular pipes using metal discs as spacers between. The difference in height was compensated by the foundations. The maximum compression in the mast  under snow load reaches 308 kN. The maximum tension forces in one of the twin cables of the mast reaches 124 kN. The masts are anchored at 4 points, Therefore the masts are fixed even without the membrane, and their position is exactly defined.

Three reinforced concrete compression foundations sized 2,0 m * 2,0 m * 1,5 m performed by company Dywidag.
Edge cables: 16mm galvanized steel spiral cable guy cables: 20mm spiral cable clevises, threads, turn buckles, bolts were chosen from the international catalogue of Augsburger Drahtseilfabrik (AUDRA).

For the tensional forces up to 9 m long GEWI – piles from Fa. PST Spezialtiefbau were used.

Drilling and executing the piles in the correct direction and inclination was possible due to the detailed survey of Prof. Weber. In some areas the piles are under the existing buildings.

The design and construction of all membrane tension foundations and guy cable foundations of the masts are identical.

As biggest hindrance of the whole project, two small trees were in the way. Only after a signed declaration that the trees were not be cut but transplanted, permission for building the membrane sculpture was granted.

The local company Garten König not only transplanted the two trees but also performed all the pavement, plantation including bamboo and all related landscape works.

Erection of the Mast Structures and the Membrane

At each head the plates welded to provide the connection of the membrane cables are different in location and size. Base plates are fixed to the threaded rods of the foundation. The direction and declination of the masts and guying are now already finally determined and fixed.

The steel structure had to be designed for in case that the membrane is not working for example due to severe damage. The result was the design and construction of a safety cable and a connection of all masts by a tie knot. A cable was adjusted to each mast and the tie knot. This construction we called “safety cable“.

At the head of each mast the cable is connected to the mast by a hole (drilling) and a bolt fixed to the cable is screwed into this hole by a nut. The safety cable had to be positioned above to highest level of the membrane fabric. Then it was also possible to erect the masts without the membrane.

The material chosen was a PVC – polyester Type III of the French company Ferrari. Inside the “free roll“ the material had to be doubled in order to take the high forces. Confectioning was taken over by the German company CenoTec.

Pattering according to the computational model created problems again. For this task the membrane had to be divided into different sections and a seam had to be introduced in the symmetry axes of the “free roll“. Due to the calculated forces in weft and warp direction, stripes were now directed to the “free roll“. In consequence, the patterns of both sides of the membrane sculpture had to meet with identical width in the centre in order not to disturb the optical appearance of the membrane. Connecting the membrane to the steel structure required the development of anchor elements and clamping.

Opening ceremony

On the occasion of the opening ceremony, the membrane was given the name Romeo and Juliet. It is supposed to reflect form, use and usefulness. The ceremony offered all persons involved exquisite food and drink and gorgeous music. Thereby the successful completion of the project was highly appreciated by all parties.


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