A student of Otto explains how she teaches the basics.
By Mark Zeh
More than in any other branch of architecture, the creation of cables and membrane structures requires coöperative work and a blurring of roles between engineers and architects. Recently I talked with Prof Dr. –Ing. Rosemarie Wagner of the Department of Architecture at Fochhochschule Munich about why this is, and her philosophy and techniques in teaching people how to build with lightweight materials.
Mark Zeh: It appears that membrane and cable architecture is a sort of unconscious indigenous architecture for Germany—
Rosemarie Wagner: (laughing) That’s because it all came from Frei Otto! The spread of the idea of building modern structure from membranes and cables is still traceable to people and projects he worked on all over the world. Nothing is really a “secret” anymore, though— Germany still leads in membrane and cable architecture, since it essentially got started on it first, has more experience and has developed more materials— and not all of the literature is translated into other languages, yet! I was recently in China, working on a modelling project there, when this became evident—
M.Z.: —the ideas started with Frei Otto?
R. W.: Most of it came from him. He was really influenced by the Raleigh Arena in the U.S. (J.S. Dorton Arena, Raleigh, North Carolina, 1952, Matthew Nowicki and William Henley Deitrich, Fred Severud.) That arena is one of the first examples of cable architecture. Frei Otto collaborated with and taught many great architects and engineers all over the world.
M.Z.: This is still a relatively “young” field of architecture. Most tent-like structures have been temporary. Architecture and engineering with rigid materials have thousands of years of precedent to build on.
R. W.: That’s true. There are a lot of non-linear relationships in designing tension structures. The focus of our research work has been understanding and creating predictive models for the behavior of membrane structures with mathematical tools. A great example is that Frei Otto used to tell us that the total included fiber angle between two adjacent pieces of woven fabric could not be more than six degrees. He didn’t offer an explanation or a proof, but had discovered this somehow. Now we finally know how this works and understand better how to predictively model the right amount of slip in the fibers and the distribution of tension through woven membranes.
M.Z.: What other unresolved or difficult-to-resolve problems still exist?
R. W.: There is still the problem of the relationship between the cutting patterns of the membrane elements and the desired final shape of the structure. This isn’t so simple to resolve, since there are complex changes in dimensions across the membranes due to tension and consistency of material behavior to consider—
M.Z.: It seems that the materials are still developing—
R. W.: And we’re still experiencing some unexpected results. A good recent example is the roof of the building for the Agency of Waste Control at the Munich Olympia Park. This membrane structure was designed with a large safety factor and conservative consideration of loads from the climate. It failed in an unexpected way that is complicated to predict or understand. It seems to have been a result of cracking in the layers of coating protecting the glass-fiber material. The cracks allowed water to be in constant contact with the glass. The polar nature of water changed the properties of the glass over time, leading to failure. The problem is that materials are sometimes used in ways that haven’t been anticipated by the developers, or sometimes a supplier will make changes to a material that preserve the apparent structural properties, but lead to an unexpected result—
M.Z.: An area of emphasis for you has been inflatable structures. The pneumatic house you developed for Festo of Esslingen, Germany is well known and things like the Allianz Arena in Munich and the Tensairity roof structure at the rail station in Montreux (Luscher Architectes, Airlight Ltd, 2003) are unexpected uses of membranes. These structures have a lot of appeal, from materials use, energy use and acoustic attenuation—
R. W.: My interest in membrane architecture has been an attraction to the aesthetic of things that can be guided by movement and that change form when you touch them. Most of the architects and engineers working in membrane and cable architecture come from similar backgrounds: the idea of these structures started with something that was for temporary use. Therefore, membrane structures are still “just a cover” to most architects and engineers. Most structural and acoustical engineers don’t know yet how to think about a vertical surface that isn’t either a window or a hard, structural wall. To structural engineers, inflatable structures are a new kind of problem. Suddenly they find themselves having to incorporate some complicated thermodynamics into their thinking about structures. The “green” angle is still new and not yet a big part of the thinking or teaching.
M.Z.: How do students at your school learn how to design with membranes and cables?
R. W.: First, I have to explain that a Fachhochschule is a sort of technical school, where the emphasis is on practical applications and working in industry. The universities in Germany are more theoretical and more for people who want to go into teaching. My students have all finished a special kind of high school degree (Fachoberschule Abitur) and have worked in industry for two years before coming here—
M.Z.: How old are they when they arrive?
R. W.: They’re generally between 20 and 25 years old. I teach two courses: one for architects, and one for engineers. The topics are the same, but the emphases are different. I believe that we can divide the field up into six areas. I lecture for a week, the following week the students do applied exercises in that area, then we go on to the next theme.
M.Z.: What are the six areas?
R. W.: We start with lectures on the main problem in membrane and cable architecture: the shape of equilibrium. The other themes are: structures and structural behavior; cutting patterns and manufacture of membranes; materials; construction elements and components; and finally detailing. For architects, the important learnings are: not all geometries are possible; the relationships between curvature and stress; and how to bring a structure to tension on site. For engineers, we emphasize: rules of design; the behavior of materials; and mathematical relationships within these structures.
Prof Dr.-Ing.Rosemarie Wagner has been a professor at Fachhochschule München in the department of Architecture since 1997. She studied under Frei Otto at the Universität Stuttgart from 1980-82. She is also a founding partner of LEICHT in Rosenheim, Germany (www.leichtonline.com).
Mark Zeh is a frequent contributor to Fabric Architecture. His piece on the Ohel Jakob synagog in Munich appeared in the Jul/Aug 2007 issue.
Prof. Dr. –Ing. Rosemarie Wagner, Leibnitz Business Office of the Bavarian Academie of Science faculty information: www.lrz-muenchen.de/~architektur/fachbereich/Professoren/wagner/d_wagner.htm
J. S. Dorton Arena, North Carolina Department of Agriculture and Consumer Services, N.C. State Fair Division: www.ncstatefair.org/dorton.htm
The Frei Otto exhibit information at the Pinakotech der Moderne in Munich: www.freiotto-architekturmuseum.de/index2.html
Frei Otto biography: www.uni-stuttgart.de/impulse/imp/biographie.php?bid=8&lang=en
Project documentation for the roof of the Munich Department of Waste Removal, CBP Consulting Engineers: www.cbp.de/fileadmin/cbp/PDs/PM/Amt_fuer_Abfallwirtschaft.pdf
Bauen mit Membranen: Der innovative Werkstoff in der Architektur, Klaus-Michael Koch, Prestel 2004, ISBN 978-3-7913-3048-8
“Tensairity-Patent— Eine pneumatische Tenso-Struktur,” Mauro Pedretti, Rudolf Luscher, Der Stahlbau Mai 2007, No. 5, pp 314–319.