2015-08 Frei Otto.pdf

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August 2015 Frei Otto

IntroductionFrei Otto’s many projects, built and unbuilt, were often a magic of invention, complexity and practicality, worked out with the team through his meticulous physical modelling, where every detail was worked out in his mind through 1:1 modelling but at a small scale. This methodology allowed all players on the team to join in the vision – and in particular the engineers to bring their knowledge and problem-solving abilities into play – of particular importance as his intuition was often in advance of the current engineering techniques for solution1.

Otto was born in Saxony, the son of a sculptor. He started his architectural training

Synopsis

Following the death earlier this year of Frei Otto, the celebrated German architect and Honorary Fellow of The Institution of Structural Engineers, Michael Dickson, a long-time collaborator with Otto, looks back at his inspirational career and ground-breaking projects with a host of leading structural engineers. Part 1 of this two-part article examines Otto’s philosophy and early work, while Part 2 will focus on his later years and legacy.

Dickson worked on a number of projects with Otto while at Ove Arup (1968–76) and latterly at BuroHappold. He was also a member of the Wolfson Air Supported Structures Research Group (1980–86) at the University of Bath, which corresponded with Otto’s research group in Stuttgart on the development of air-supported lightweight structures.

Frei Otto – inspired inventor, researcher and designer (part 1)Michael Dickson CBE, FREng, BA, MS, DEng, CEng, FIStructE, FICE, HonFRIBA, Founding Partner, BuroHappold; Visiting Professor of Engineering Design, Bath University; Past President of The Institution of Structural Engineers

� Figure 1Frei Otto, Ted

Happold and Walter Bird at Sonderforschungsbereich (SFB) 64 conference in Stuttgart

before WW2 and returned to architectural school at the Technical University, Berlin in 1948. His parents were both members of the Deutscher Werkbund, a group of forward-looking artists and designers, under whose infl uence he grew up. From 1945 he spent two years as a prisoner of war in France, where his latent skills as a designer of shelters with ‘more from less’ fi rst emerged. Later, he encountered the work of Fred Severud, the US structural engineer, during an exchange visit to the USA in 1950–51; and the book based on his doctoral thesis, Das Hangende Dach (The suspended roof)2, shows the infl uence of Matthew Nowicki’s roof for the Dorton Arena, Raleigh and that

of the net structures of Russian structural engineer, Vladimir Shukhov.

In 1952 Otto married Ingrid Stolla and established his studio in Berlin. In 1968 he moved with his family to Stuttgart to set up their home there, and to start the Atelier in Warmbronn and the Institute of Lightweight Structures (Institut für

Leichte Flächentragwerke or IL) at Stuttgart University (Figure 1). In 1986, as an international authority on lightweight structures, he was awarded an Honorary Fellowship by The Institution of Structural Engineers.

Philosophy of sustainabilityMuch of Otto’s work was directed at creating the maximum from the minimum – now referred to as the search for sustainability. Beauty of architecture, effi ciency of structural form and appropriateness of material use were fundamental to his thoughts and designs. His enclosures house and enhance the activities of society and endeavour to do this without drawing upon unnecessary construction materials or excessive quantities of non-renewable energy. To quote Otto: “… the use of large spans is not just a game to make the Guinness Book of Records, but a search for real solutions for mankind. To know about large spans also opens the opportunity for advances for shorter spans”. This inspiration led to a whole series of fascinating projects – tents, cable nets, gridshells and compression vaults, air-supported and masonry structures – often with unusual but stimulating aesthetics and almost always pushing at the boundaries of current engineering knowledge and techniques. All themes were pursued by inquiry, observation, discourse with colleagues, research and measurement.

Otto’s many inspired ideas and innovations were often corralled into an organised architecture with the help of distinguished architectural collaborators – Rolf Gutbrod (Mecca Conference Centre),

Part 1

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"Much of Otto’s work was directed at creating the maximum from the minimum"

Günter Behnisch (Munich Olympics), Carlfried Mutschler (Mannheim), Jörg Gribl (GrossVoliere, Munich Zoo), Omrania (Casa Tuwaiq, Riyadh), Richard Burton (Hooke Park Workshop), Bodo Rasch (Medina Umbrellas), Shigeru Ban (Japanese Paper Pavilion, Hanover Expo 2000) and many others. Necessarily, these advances were coupled to much skill, eff ort and courage from collaborating engineers – Fritz Leonhardt (1975 Institution Gold Medallist) of Leonhardt und Andrä, Jörg Schlaich (1990 Institution Gold Medallist) of Schlaich Bergerman und Partner, Ove Arup and Partners, Ted Happold (1991 Institution Gold Medallist), Ian Liddell (1999 Institution Gold Medallist) and others of us at BuroHappold and elsewhere3.

One of the most memorable projects to emerge from the early days of collaboration between Happold and Otto was the timber gridshells for the 1975 Mannheim Garden Show with Mutschler and his partners Winfried and Joachim Langner (Figure 2). Who, apart from Otto, could contemplate that an accurate, hanging, free-form

model made of jewellers chains could be upturned into a compressive shell of a double layer of thin hemlock laths braced by the occasional diagonal wire rope? As so often, this concept of the gridshell was considerably in advance of the engineering knowledge of the day and required the problem-solving skills of Happold, Liddell and Dr Chris Williams and the team at Ove Arup, working with engineer Heribert Speigh of Mannheim, who designed the foundations and supporting structures4.

The Mannheim gridshell is the forerunner

of many subsequent advanced timber structures, e.g. the 2003 gridshell structure for the Weald and Downland Open Air Museum by Edward Cullinan Architects and engineers BuroHappold, constructed by Green Oak Carpentry at Singleton in Sussex. It was the fi rst permanent gridshell construction in the UK and won the Wood Awards Gold Award in 2003 as well as being shortlisted for the RIBA Stirling Prize. Subsequent buildings include the Visitor Centre for Savill Garden, Windsor, by architect Glenn Howells with engineers HRW. This was constructed once again by Green Oak Carpentry, with analysis and design by BuroHappold. The project was also shortlisted for the Stirling Prize and received the Wood Awards Gold Award in 2008.

Early tents and nets with StromeyerAn early wave-form tent had three parallel spans of 15m and was patterned by overlapping cotton canvas to create the enclosure for a fl ying priest, Pater Schulte. It doubled as a translucent place of worship by day and a small aircraft hangar by night (Figure 3).

In 1957, in consultation with Peter Stromeyer, the famous maker from Konstanz of circus and other tents, Otto used geometrical patterning from form models to produce the 36m diameter wave tent for a dance stage at Cologne (Figure 4). Its sprightly form with six externally guyed, exceptionally slim batten masts is now a listed structure and has been re-covered in a patterned PVC polyester membrane. The 1996 version of the same generic form for the Venice Biennale used an A-frame to transfer loads to foundations that are shared with the tie-downs for increased effi ciency5.

These early experiences led to the cotton canvas and cable-net, sail-like buildings for Lausanne Expo 64 (Figure 5) and on to the German Pavilion for Montreal Expo 67 with architect and friend, Gutbrod. This project stretched even the engineering techniques of Leonhardt. But Otto’s reality modelling of those spectacular masts, cable-net forms and underhung membranes, the construction of a prototype, together with some basic statical calculations from Leonhardt, enabled Stromeyer’s fi rm to deliver this outstanding pavilion (Figure 6). The team solved the problem of geometrical tolerances between the cable net of 12mm cables at 500mm with forged cross-clamps at 500mm centres and its covering by underhanging the translucent, white, PVC-coated polyester membrane on springy steel ‘bretzels’.

N Figure 2Main hall at

Mannheim Garden Show

W Figure 3First wave-form tent

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Origins of Institute of Lightweight StructuresThe prototype for the construction at Montreal became the IL, where Otto tested out the teardrop cable connection to the mast top with his soap bubble modelling of minimal surfaces (Figure 7). The Montreal project brought about a paradigm shift in cable-net technology that was ably followed up by the research arising from the later construction of the Munich Olympic roofs in 19726.

This prototype building, which is still in use in 2015 as the IL, became a base from which Otto worked with research teams over the next 30 years or so, on a whole range of basic architectural, form and material studies. The output resulted in many IL publications (1–42), including Minimal Netz, City in the Arctic, Grid Shells,

Natural Building and Bamboo among others7.

Roofs for 1972 Munich OlympicsThe IL was also the focus for Sonderforschungsbereich 64 (SFB 64), which was set up by Leonhardt, Argyris and Otto to pull together the basic research on architectural, engineering and construction themes that was stimulated by the design and construction of the spectacular cable net roofs for the 1972 Olympics in Munich, with architect Behnisch. Jörg Schlaich was the structural engineer from Leonhardt und Andrä. The roofs of the Olympic Stadia used a net of double 16mm cables with cross-clamps at 750mm centres to form a doubly curved cable-net roof, with fl ying masts to improve curvatures and supporting a roof deck of 1.5m Perspex® sheets separated by rubber gaskets (Figure 8). Because of the nature of loadings on this large-scale arena, relatively high levels of prestress were employed to limit defl ections, which resulted in some substantial and ingenious large casting connections between principle cable elements8.

The SFB 64 group held a series of great conferences within the IL building at which the fundamental research on long-span structures resulting from the Munich Olympics was disseminated across the world9–11.

Pneumatics and research into air-supported structuresAir-supported structures are stabilised by the diff erence in air pressure between the interior and exterior environments, which is generally created using fans. The higher the internal pressure, the more stable the

W Figure 4Cologne dance tent

W Figure 5Lausanne Expo sails

W Figure 6Montreal Expo

cable net and underhung membrane

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structure is likely to be under extreme wind loads or snow loading – but the higher will be the losses through leakage and thus the cost of infl ation from fans.

Low-cost air-supported structures have existed for storage or coverage of tennis courts for a number of years. They followed in the footsteps of a number of high-value Radomes constructed by Walter Bird of Birdair – often in remote locations and often operating at relatively high internal pressures. However, the fi rst long-span air-supported structure was really that for the US Pavilion at Osaka Expo 72 by US engineer, David Geiger, with construction by Bird. It was a PVC-coated membrane restrained by low-profi le steel cables arranged on the diagonal and anchored to a super-elliptical concrete edge beam. A low profi le avoids the diffi culties caused by the pressure of wind gusts by maintaining the dome in a zone of suction.

Following extensive studies on ‘Pneu’ at the IL, examining alternative fundamental forms through a range of plaster models within fl exible membranes, Otto followed the Osaka precedent with a proposal for ‘A City in the Arctic’ with Peter Rice of Arup. Here, the diagonal cables restraining an unspecifi ed transparent membrane had the elasticity which resulted from being made of polyester (Figure 9).

Both Otto and Happold subscribed to the rigour of looking at the whole picture and both believed that research drives invention, which in turn inspires the creation of innovative answers for our natural and built environment. So, when Happold moved to the University of Bath to become Professor of Building Engineering in 1976, he set up the Wolfson Air Supported Structures Research Group at the Department of Building Engineering (with Professor Mike Barnes, Williams and others), which corresponded with Otto, Bird and the SFB 64 group to investigate air-supported structures as an archetypal form of lightweight structure. This research was documented in two international conferences at the University of Bath in 1980 and 1984 sponsored by The Institution of Structural Engineers.

Studies included a thorough investigation of interior environments, form fi nding and the cause of air house failures, material properties of enclosing membranes and foils, fan power and stability, and much else. Out of this research came the proposal with architects, Arni Fullerton and Dennis

E Figure 7Institute of

Lightweight Structures under construction

E Figure 8Munich Olympic

Stadium roofs

E Figure 9City in the Arctic



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Wilkinson, for a 600 × 300m elliptical, air-supported dome at latitude 58°N to cover a township of some 2000 people (Figure 10).

The primary cables run north to south and were to be anchored to a tall ring glazed on the south side to admit low-angle winter sun. In order to moderate the severe winter climate and to keep out the black fl y in the summer, and to enhance permanent occupation by providing views of the sky through the long winters, the cable net was to support a series of ETFE air-infl ated foil cushions. These are now widely accepted for use as lightweight but translucent roof coverings, providing a degree of insulation. They are used for swimming pool and sports hall coverings and indeed airport and railway station halls, as well as – most spectacularly – for the biodomes of the Eden Project in Cornwall, by architect Grimshaw Associates with engineers Antony Hunt and Associates.

Collaboration with HappoldIn 1966 Gutbrod and Otto won a competition for the Conference Centre at Mecca, originally conceived as a cable net but developed subsequently with engineers Ove Arup (Happold, Rice, Ting Au and Lennart Grut) into a series of deadweight hanging roofs covered in refl ective aluminium sheeting. Uplift from desert storms is prevented by a combination of the deadweight and damping of the thick insulation layers over the interior wooden plank ceiling and

interior air volume (Figure 11).Following the successful outcome of

these deadweight hanging roofs in 1972, Happold started a Lightweight Structures Laboratory at Arup to collaborate with Otto. An early built project was the 80 × 40m ‘humped tent’ sewn from 900mm wide strips of cotton-polyester fi re-proofed fabric and stressed into doubly curved surfaces to resist wind and the snows of Aberdeen, Scotland (Figure 12). It was a descendant of his 40 × 30m Berlin Exhibition entrance canopy, built in 1957 of cotton canvas deformed over a series of mushroom supports and tied down to anchorages around the edges. Without the need for complex patterning, the tent at Dyce (Aberdeen) was designed and constructed for BP in fewer than 10 weeks

to celebrate – in the presence of HM The Queen, Prime Minister Harold Wilson and a 1000-person audience – the arrival of oil onshore in 1975. It subsequently was re-erected in Hyde Park, London, in 1977 for the celebrations of the Queen’s Silver Jubilee.

The 1980 multi-masted GrossVoliere aviary for Munich Zoo (Figure 13), with Otto as consultant and BuroHappold as engineer, was also originally conceived by the engineers as a humped tent; a model of the desired form was constructed in the Atelier Warmbronn to the planning constraints of the site and the ornithological patterns and breeding requirements for an aviary defi ned by the zoo’s architect, Gribl. This visually inconspicuous construction used a close 63mm structural mesh of 3.2mm, crimpled, 304 low-carbon, stainless steel wires supported over nine tubular masts and with one tie-down to improve curvatures. The mast tops and tie-down are confi gured as a series of zigzag stainless steel pantographs, a system conceived by Otto to enable erection of the mesh around an existing listed ash tree.

Following a full set of statical hand calculations to size the masts and anchorages and verify the mesh capacities, the erection of the entire structure was numerically simulated and the form for construction, which had been established initially by Otto’s model, was analysed under 100kg/m2 of ultimate snow loading

"The GrossVoliere received its full design loading shortly after completion and is now 35 years old"

E Figure 12Dyce humped tent

W Figure 11Interior of Mecca

Conference Centre

S Figure 10Southern elevation

of proposed air-supported dome at 58°N

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(equivalent to a three-day storm) using the dynamic relaxation techniques of Barnes at Bath University. Metallurgists at Bath University also helped defi ne the tungsten inert gas (TIG) processes needed to weld the many crimped wires together, fi rst into 15m wide rolls in the factory using clamps adapted from Mole grips, and then into the entire oblong 90 × 40m shape when laid out fl at on the ground. Advances in dynamic relaxation techniques, with zoom capability into individual masthead zones, established the detailed geometry for construction and forces under snow for all the masthead pantographs and cable arrays.

For the sceptics among us, the GrossVoliere received its full design loading shortly after completion and is now 35 years old and a listed building (Denkmalschutz).

The engineering profession owes much to Barnes and his development of the technique of dynamic relaxation as a powerful tool to investigate the nonlinearity of large deformation structures, as well as subsequent elasto-plastic performance towards ultimate failure – stimulated as so often by the pressures of solving the engineering design and construction of a Frei Otto structure.

IllustrationsMost of the illustrations for this article have kindly been provided by Christine Kanstinger Otto of Atelier Frei Otto unless attributed otherwise.

E 1 Drew P. (1976) Frei Otto: Form and structure, London, UK: Crosby Lockwood Staples

E 2 Otto F. (1990) Das Hängende Dach [in German], Dresden, Germany, Verlag der Kunst

E 3 Dickson M. (2005) ‘Frei Otto’s life’s work: an inspiration for all’, The Structural Engineer,

83 (10), pp. 23–29

E 4 Happold E. and Liddell W. I. (1975) ‘Timber lattice roof for the Mannheim

Bundesgartenschau’, The Structural Engineer, 53 (3), pp. 99–135

E 5 Stromeyer P. (1973) Textiles Bauen: ein Begriff für leichte Flächentragwerke [in German]

Konstanz, Germany: Stromeyer and Co.

E 6 Happold E. and Dickson M. (1974) ‘The story of Munich: Zodiac 21’, Architectural Design,

44 (6), pp. 339–344

E 7 Association for the Advancement of Lightweight Structures (2015) List of IL

Publications [Online] Available at: www.leichtbauverein.de/en/publications/list-prices/

index.htm (Accessed: June 2015)

E 8 Leonhardt F. and Otto F. (1976) Prestressed cable net construction – the Munich

Olympic roof [translated from German], Stuttgart, Germany: SFB 64

E 9 SFB 64 (1976) International Symposium on Wide Span Surface Structures, Stuttgart,

Germany, V1-3/1


Germany, V1-2/2


Germany, 3 V1-2

References

� Figure 13GrossVoliere aviary at Munich Zoo

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2015-08 Frei Otto.pdf

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