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Air Apparent: Pneumatic Structures

First posited in the 1960s, the idea of pneumatic structures as a progressive and lightweight alternative to ‘normalʼ construction has renewed relevance to the current re-evaluation of energy use and new forms of climatically responsive envelopes

Pneumatics is the forming process of all living things’ Graham Stevens, Desert Cloud (1974)

It is approaching 50 years since the 1st International Colloquium on Pneumatic Structures took place at the University of Stuttgart in 1967. Organised by the International Association for Shell and Spatial Structures (IASS), the event hosted an outstanding grouping of the leaders of this rapidly evolving technological art − Walter Bird, Victor Lundy, Heinz Isler, Dante Bini, Nikolaus Laing, Cedric Price, and hosted by Frei Otto.

Walter Bird presented an overview of the field titled The Development of Pneumatic Structures, Past, Present and Future. Bird is an acknowledged pioneer in the use of tensile fabric and pneumatic structures, which began with his air-supported radome prototype for the US Air Force in 1946 made from neoprene-coated fibreglass fabric. In 1955 he established Birdair Structures and produced pneumatic ‘bubble’ enclosures such as tennis court and swimming pool covers, which attracted much media attention. Birdair subsequently produced large-scale pneumatic structures (notably with architect Victor Lundy) and the largest fabric roof ever produced for the Hajj Terminal in 1980, with Skidmore, Owings and Merrill and structural engineer Fazlur Khan. Bird’s colloquium paper documents his enthusiasm for the potential of pneumatic structures, although he notes the problems of technical descriptions and names for this new field, which include ‘single wall’, ‘air-supported’, ‘air structure’, or ‘air-inflated’.

Bird concluded by noting the unique and outstanding features of the air structure: ‘The air structure is the most efficient structural form available to date … no other type of structure has the potential of providing free-span coverage for so large an area … as the air structure is constructed of lightweight, flexible materials, it can be made easily portable and lends itself readily to the design of demountable or removable structures.’ Cedric Price, commending the works of Bird and Lundy, introduced a note of ‘constructive pessimism’ and was concerned that pneumatic techniques were being used to solve ‘normal structural and shelter problems’ and as such could result in actions detrimental to the development of pneumatic technology.

Bubble1

An early prototype for a Standard Pneumatic Environment, 1968. Stevens says he quickly realised that air and fabric were a very quick, lightweight and inexpensive means to create structures and environments

Price also drew attention to the semantic distinctions between air-supported and air-inflated structures, seeking a general agreement on the terminology, while listing his interests in the technology as an architect. These interests span the material properties and potentials of multi-membrane enclosure to moderate light, sound and air movement as well as the deployment and movement of structures using air and the re-classification of mechanical plant (pumps, blowers etc) as structural elements.

Price concludes with a cautionary note about the use of pneumatics stagnating unless ‘design and development work, can enable air structures to contribute to a higher degree of sensitivity in society’s continuous control of the physical environment’.

An attendee of the colloquium was the artist Graham Stevens who was particularly interested in the structure and science of these new forms. Stevens is an artist, however he works across the domain of architecture and the acquisition of his early drawings by the Centre Pompidou is under the auspices of ‘experimental architecture’. Stevens first met Cedric Price at this event and subsequently took regular counsel with Price and engineer Frank Newby as his own pneumatic structures grew in size and complexity. Stevens began working with air structures and plastic membranes to produce single colour surfaces to explore a saturated (colour) environment as an inhabited artwork. The structure formed by the air, the colour by the fabric. The success of these early prototypes encouraged Stevens to purchase his own high-frequency welding machine to join the plastic membranes, and his studio in (the then semi-derelict) St Katharine Docks in east London became the site (or his playground) for a series of extraordinary large-scale air sculptures, brilliantly captured on film by photographer Andrew Tweedie.

StKatherineDocks

Graham Stevens’ ‘Atmosfields’ in 1970 transformed St Katherine’s Docks into a playground of inflatable sculptures

An extraordinary set of pneumatic artworks saw Graham Stevens walking on water in a polythene cube (http://ssa.nls.uk/film/T0829/74959364) and traverse land, water (and underwater) in his Hovertube (Pontube) project. Hovertube is an inflated transparent polythene tube, which allows you to literally walk on water, and deployed on land can bridge rough terrain with the aid of pneumatic integrity. As well as the beautiful image created by the quarter-mile-long prototype in Cornwall (1970) and captured as a part of the Atmosfields film, this human transportation tube would seem to have any number of practical applications as well as its sensory delights as documented by and described by the artist. Stevens had also seen the physicist Nikolaus Laing talk at the pneumatics colloquium and was interested in his work, which connected the two disciplines of air structures and solar energy. Stevens also cites Farrington Daniels’ influential book (recommended to him by Price) Direct Use of the Sun’s Energy (Yale University Press, 1964).

In a further development of his work with pneumatic membrane structures, Stevens developed what were to be some of his most ambitious projects, which conflated air-filled and temperature dependent ‘buoyancy’ and a composite mix of membranes. Stevens’ film of 1974, Desert Cloud, is a wonderful documentary montage of these new forms. A transparent cellular mattress is subdivided by black membrane webs and lined on the underside with a silver reflective fabric. This specific arrangement captures the radiation of the sun through the transparent layer, shortens the wavelength with the black internal panels, which superheats the air inside to create a buoyant structure (or cloud), the reflective underside providing much needed desert shade. Graham demonstrated also how the structure could condense (or capture) water on its surface and he even managed to create ice from a clear desert sky.

Pontube

The 1970 Hovertube Project - shown here as a quarter-mile-long prototype - allowed Stevens to literally walk on water

With the recent rediscovery of the energy crisis and the re-evaluation of energy systems, the simultaneous rethinking of the climatic envelope (or physical enclosure) might usefully employ (or re-explore) some of the ideas and thinking that Stevens was exploring. The inexpensive power and utility of air to create both structure and environmental moderation might suggest new modes and means of climatic envelopes and a redefinition of the physical interaction between the architecture, the environment and human beings.

A more recent development of the pneumatic membrane as a building skin is the ETFE cushion. The air-filled pillows of Vector Foiltec’s ethylene tetra fluoro ethylene (ETFE) are a disruptive technology socialised into the construction industry by architect Ben Morris. In big roof and cladding projects, glazed elements can be replaced with large air-filled ETFE cushions at a fraction of the weight and with attendant structural economies. Perhaps even more interesting is the redefinition of the notional climatic enclosure as with the roof of the Chelsea and Westminster Hospital, which reclassified courtyard spaces as external while providing a new kind of climatic skin. If you extend this thinking across a large-scale housing development, you re-order priorities for thermal insulation and heating systems and return to Buckminster Fuller’s ideas of domed-over cities. In 1950, Fuller proposed a two-mile diameter dome or ‘bubble’ over mid-Manhattan to obviate expensive heating and cooling across the city and that, he claimed, would have paid for itself in 10 years.

LaingDiagram1

Detail of wall element with pneumatically operated folding film K inside the air chamber L, on the left in ‘transmission’ position T, on the right in ‘reflection’ position R. Yellow shading indicates transparent film; green is reflecting metal coating; red arrows indicate solar radiation; dotted arrows show ground radiation.

LaingDiagram2

Detail of electrostatically controlled wall design. A is a transparent conductive outer layer; B is an insulating, transparent support layer; C is a metallised folding layer. If A and C are equally charged electrically then C assumes a vertical position (thus realising full transparency). If the charge is opposite, C will cling to B (thus realising complete reflection). Diagrams from ‘The Use of Solar and Sky Radiation for Air Conditioning of Pneumatic Structures’, Nikolaus Laing, 1967

ETFE is mostly (if not exclusively) used as multi-layered inflated cushions with low air pressure used to resist the natural creep of the material and structurally stiffen the panels. The layering of the cushion can create active (deployable) internal surfaces for controllable opacity or responsive thermal performance. The layers are typically clamped together in edge frames, which are fixed back to structural frames. Some of Ben Morris’s most interesting work replaces the structural frame with a cable system, such as the uniaxial cable-net roof of the Hampshire Tennis Club (with Euan Borland Architects) where the cushions and tensile wire rope work together to create an incredibly strong and lightweight structural system.

In the same family of structures we might also include Luchsinger and Pedretti’s Tensairity structures. They have taken the structural efficiency of Buckminster Fuller’s tensegrity principle (separating the compressive and tensile elements) and created a compressive component from an air beam, which is in turn resisted and reinforced by a coaxial winding of steel (tensile) cable. These new lightweight composite beams have been proposed as bridge structures, temporary enclosures and wide-span roofs. In Luchsinger and Pedretti’s paper outlining Tensairity’s structural principles and the field of pressure-induced stability, the technology is said to be capable of the loadbearing of a steel beam, with substantial weight reduction. This new form of air-beam develops the innovations of inventors such as Keith Stewart with improved resistance to buckling, while the cabling provides useful anchor points and physical connections to more conventional engineering elements.

People

Some 300kg of researchers on a Tensairity beam, courtesy Airlight

The designer Nick Crosbie (Inflate) has been working with inflatable structures for 20 years. At a recent lecture at the University of Westminster, he demonstrated the utility and portable qualities of the genre by inflating a changing room from a backpack in less than a minute. Inflate work at a range of scales from their celebrated inflatable eggcup to large-scale temporary ‘event’ buildings, which can be inflated and deflated in hours with a medium that provides continuous structural support across a surface (even at low pressure) as opposed to the more roughly calibrated, but ubiquitous support of beams and columns. The immediacy of these structures and the economy of their principal structural component still seems anathema to the architect who could usefully embrace ‘air’ as a structural material or at least a useful additive in countering the doggedly heavyweight business of construction.

Legs2

Nick Crosbie, Legs II, Inflate, 2007, extends the lineage of pneumatic invention

About the author:

Will McLean is head of technical studies at Westminster University with Peter Silver, with whom he has co-authoured three books

 

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