[P2] Case Study Archive

INSTITUT FÜR LEICHTE FLÄCHENTRAGWERKE Frei Otto 1968 Maya Koch Brahms, Anna Katrine Tan, Alex Hartway, Iben Enevoldsen

INSTITUT FÜR LEICHTE FLÄCHENTRAGWERKE - Frei Paul Otto

Frei Otto is a german architect - but works also as an engineer and a mathematician with a speciel interest in structures and membranes.

He was an airpilot in the second world war - and the lack of materials in the war-time made him interested in tents as a shelter. Because of the world war, the first architecture he designed was cemiteries and barracks which - when he was released of the war - lead him to do architecture that was both human and natural, but could also easily be destroyed - just as nature. Therefore, he was very inspired by organic structures, which is stressed in his pavillions that are made out of cablenets and membrane structures. It was important for Frei Otto that nature was not the goal or a role model, but a way to understand natural structures.

He kept asking questions and making experiments out of different materials “How must we live in the future? - We must think, research, develop, invent and venture more to allow all people to live a peaceful life in a nature which they themselves protect.”1 - Its questions like this that makes him a world leading authority in light weight structures today. He used familiar childhoodmaterials - soap-bubbles, sand, stones, thread, cloth, chains, plaster and plastic film. Trough these experiments and the following thoroughly systematic analysis, the light weight structures began to take form. Tensile nets and cable structures made it possible to put into practise.  Institut für Leichte Flächentragwerke was one of the first tent stuctures and a prototype to test the construction of the German pavilion for the world Expo 1967 in Montreal. It is a symbol today of modern architecture. This was Frei Ottos first, worldwide acknowledgement in lightweight structures which makes him a world leading authority in that expertise today. 2

http://www.uni-stuttgart.de/print?http://www.uni-stuttgart.de/impulse/imp/alles.php?id=6&lang=en, accessed: 24.09.13 http://www.uni-stuttgart.de/ilek/index.php?id=21&L=1, accessed: 24.09.13 Photo: ILEK, Universität Stuttgart, Institut für Leichte Flächentragwerke, http://www.kuenstlerhaus.de/en/archive/oscar-tuazon-against-nature-institut-fur-leichte-flachentragwerke_special-tour_5680, accessed: 27.09.2013 1 2

SHANGHAI EXPO BOULEVARD - SBA GmbH Shanghai/Stuttgart architects

The Expo Boulevard is the main part of the expo with its 35 meters of height, 100 meters width and one kilometers lenght. The idea with the boulevard was to make all the public facillities united, just as in the ancient Rome. It required therefore a compact structure to comprimise both postoffice, shops, securitygates, restaurants, cafes, etc.

The covering is one of the worlds largest membrane roofs. 6 funnel-like structures called Sun Valley. These so called sun valleys direct natural light into the basements and the lower floors.

The main load is carried by nine mega columns comprimising a glass and steel framework, while the edge of the roof is supported by rows of slim pillars - 19 interior masts and 31 exterior masts. The membrane roof/structure is in the tradition of Stuttgarts light weight structures - where Frei Otto is a leading authority.

The structure is taking static demands1 into consideration when using large scale triangles - and the fact that it stands on its apex makes the structure seem lightweighted and is the exact opposite of “Institut für Leichte Flächentragwerke” where the triangle is standig on one of the sides insted of the spike. Both structures are light weight structures, but where “Institut für Leichte Flächentragwerke” is using the structure as a covering, the Sun Valley is reaching towards the sky - as the opposite reaction of a covering. This could be a reaction on the different weatherconditions that are to be found in the North vs. Asia.

The Sun Valley has been transformed into a permanent green space for Shanghai and is now a permanent structure and a part of a new urban Shanghai2. http://www.e-architect.co.uk/shanghai/expo_shanghai_2010_megastructure.htm, accessed: 24.09.13 http://inhabitat.com/shanghais-stunning-sun-valley-pavilion-boasts-the-worlds-largest-membrane-roof/, accessed: 24.09.13 Photo: Helbig, Knippers, Shanghai 2010 Boulevard, http://www.archdaily.com/57749/shanghai-2010-boulevard-knippers-helbig/003_expo_knippershelbig_72dpi/, accessed 27.09.2013 1 2

STRUCTURAL ANAYSIS

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The Institut für Leichte Flächentragwerke is a tension on tension structure, which is what creates the double curvature of the surface of the roof. This structure is visible from both the inside and the outside. The centrally placed pillar functions as a compression component and the cable net of the roof as tension on tension leading down to the compression elements placed at the ground. The building was developed through analogue model, because the computer technology was not available at the time of construction so to optimise the surface area the institute was modelled with tulled stretched out as the cable net.3 The conical shape of the Institut für Leichte Flächentragwerke is turned upside down in the Shanghai Expo Boulevard and by this the central pillar becomes a tension point instead of a compression component as the case in the institute. The structural compossion consists of wires joined in the tension point at the bottom and canvas stretched over the wire structure, which is fastened further on with wires over a compression pillar.

In the the Shanghai Expo Boulevard the conical shape is part of a repeated sequence in spatial relation to each other, which creates the atmosphere of a space for movement whereas the Institut für Leichte Flächentragwerke is a unique enclosed structure, which invites to stay and shelter for the weatherconditions outside.

Drawing: Bahamón, Alejandro, 2004, The Magic of Tents Transforming Space, Harper Design International and LOFT Publishers, p.: 13 Helbig, Knippers, Shanghai 2010 Boulevard, http://www.archdaily.com/57749/shanghai-2010-boulevard-knippers-helbig/elevation-33/, accessed: 27.09.13 3 Bahamón, Alejandro (2004) The Magic of Tents Transforming Space, Harper Design International and LOFT Publishers, p.10 1 2

Compression

Tension

STRUCTURAL ANALYSIS - model

The investigation of this model was to try out what was the consequence and effect of turning a tension structure upside down. Some fabric was attached to a wooden frame functioning as the tension structure. Then the fabric was covered with plaster to stiffen the textile surface. Afterwards the model was turned upside down and functioned as a selfsupported compression structure.

The spatial change, which was created by the turning upside down raised interesting questions in order to how the change of one single factor can create a completely different situation.

COVERING

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Institut für Leichte Flächentragwerke The roof of Otto’s IL acts as the primary membrane between outdoor elements and interior space.

Constructed in layers, it is composed from the inside out by:

• • • •

Cable structure formed by 50cm squares Thin strips of timber panels, acting as the primary acoustic insulation Thermal insulation Asbestos cement slate tiles, acting as the primary exterior cladding4

It is interesting to note how the seemingly stretched, flexible membrane is actually a rigid substrate for the cladding it supports. When the membrane is fully tensioned, it becomes a stiff entity that is fully capable of supporting roofing elements.

The individual components of the roof structure, however, are perceived as a single tensile membrane, such as a soap film—a covering draped from the central mast to the outer edges of the space.

Sets of cables are drawn out from base points of this membrane, stretching the “fabric” from the mast and toward the earth and creating a medium that is durable enough to maintain conditions in the covered space despite the outdoor elements. The central glazing affects the sense of a hole in the membrane, one that selectively allows in natural light but still protects from harsher elements.

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The full-height glazing encircling the base of the roof acts as a different type of membrane, one that is operable and that provides constant visual contact and connection with the external environment and landscape. It is subtle enough to preserve the prominence of the tension membrane above.

Slate tile cladding the outside of the roof ensures adequate insulation and weatherproofing, more so than simply a lightweight fabric would.5 This protection element makes the IL more of a sheltered destination space than an open, transitive pavilion, as is the case at the Shanghai Expo.

Photos: Bahamón, Alejandro, 2004, The Magic of Tents Transforming Space, Harper Design International and LOFT Publishers, pp.: 10, 15 Photo:Ott, Thomas, Shanghai Boulevard 2010, http://www.e-architect.co.uk/images/jpgs/shanghai/expo_shanghai_2010_k310310_2.jpg, accessed: 27.09.2013 4 Ratscheck Schiefer, http://www.rathscheck.de/Moderne-Architektur/Dach/ILEK-Stuttgart/and, accessed: 24.09.10 5 uni-stuttgart, 2008, http://www.uni-stuttgart.de/hi/gnt/campus/Stationen/vaihingen/nord/info_station_r2.html, accessed: 24.09.10 1,2 3

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COVERING

Shanghai Expo Boulevard The covering canopies at Shanghai Expo Boulevard have a totally different perception than the roof at the IL. These canopies are, in most places, a double layer of translucent canvas. They allow plenty of light in but still shade from harsher direct light. Tension cables securing the edges of the canopies to support masts keep the roof from moving in the wind, though some air is still allowed to pass through and around the fabric. Most of the rainfall is also shed off of the outer layer of canvas and directed to drainage, though the moistened fabric increases the relative humidity of the space below.

This membrane has no thermal insulation or cladding, and is therefore not perceived as a “sheltered� space in the same sense that the IL is. The open, airy pavilion directs occupants to pass through and around and treat the space as transitive versus destination.

There is no glazing or structure present on the outer faces of the exposition space, indicating free movement through and around for pedestrians as well as allowing breezes and rainfall to enter horizontally. There is less of a sense of security here, but a greater connection to the environment and city fabric than there is at the IL.

FINAL MODEL #1

The purpose of the investigations in the final models was to question: what if? As we started out in our initial investigations, we questioned what happens if the conical shape is turned upside down in relation to the tension and compression forces as well as how there is a change in the spatial experience. To take this a step further we turned the use of materials upside down as well in the sense that the materials of the Institut für Leichte Flächentragwerke are originally solid and opaque to protect from climatic conditions, whereas the material of the Shanghai Expo Boulevard is translucent canvas to screen from direct sunlight but keeping the lightness of a pavilion in a temperate climate. To investigate this, we switched the materials so that the membrane of the Institut für Leichte Flächentragwerke is made of tulle covered in wax to obtain the translucency. The Shanghai Expo Boulevard is made in tulle and plaster to get an opaque surface. In both models a structure of piano string hold the membranes.

We have looked into three factors which affect the spatial experince: the conical shape, the material of the membrane and the fact that the Institut für Leichte Flächentragwerke is one unique shape and the Shanghai Expo Boulevard is a system of repeated cones. When the envelope materiality of the two structures are switched, there is a change in the perception of space. As documented below, the membrane of the Institut für Leichte Flächentragwerke becomes translucent, almost glowing, and thereby the atmosphere is lighter and not as enclosed and shelter-like as with its original heavy opaque covering. The Shanghai Expo Boulevard (see next), when switched, then gains a heavier impression with the opaque plaster and seems more enclosed than the original situation where there was some connection to the sky by the light passing through the membrane. However, the shape is still opening outwards towards the sky and in that sense it is still not as enclosed as the Institut für Leichte Flächentragwerke. This creates an ambiguous experience, because of the mixing of the contrasting factors as open/closed and opaque/translucent.

FINAL MODEL #2

It was interesting to use plaster in such a fashion for our “what if� analysis on the Shanghai Expo canopies, as it is not usually applied to free-formed, double curved canvas shapes. Through this, we began to understand the underlying structural reprecussions of applying a compression-oriented material onto a tension membrane. Spacially, the Shanghai model with the plaster appears more dense and impermeable than it would have with a more translucent wax membrane that we applied to the IL roof. It also loses the gentle glow that canvas creates, which is now more prevalent in the IL roof model.

With further investigation using more coats of plaster, we could create an even more opaque membrane that would be totally impervious to light and elements, beginning to construct an envelope that would be more suitible for the climate phenomena found in the harsher Northern locale of the IL. Vise versa, trying to use a thinner coat of wax for the IL roof would make it seem more open and permeable and then suitible for the conditions in Shanghai. In this way, we have begun to explore how membrane not only affects space and light, but how it can change environmental context as well.