Abstract— Pneumatic structure is basically a constructed form that derives its rigidity from captured pressurized gas. The technique has evolved during different periods starting from the 50s and 60s. This paper aims at understanding the history and principles of pneumatic structures as well as their revival and applications in the modern era.

Index Terms— Pneumatics,

I. INTRODUCTIONPneumatic structures are basically membrane structures that are stabilized by the pressure of compressed air. First posited in the 1960s, the idea of pneumatic structures as a progressive and lightweight alternative to ‘normal construction has renewed relevance to the current re-evaluation of energy use and new forms of climatically responsive envelopes. In pneumatic constructions, the pressure differences between the enclosed space and the exterior are responsible for giving the building its shape and also for stabilizing the hull. This system of using membranes for construction evolved from practical applications in other fields such the helium dirigible and hot air balloons. The fabric is pre-tensioned by an internal overpressure of the air. The load developed is from the tensile stresses. Its stabilization is done by pre-stressing the membrane either by:-

A) Applying an external force which pulls the membrane

B) Internal pressurizing if the membrane is volume enclosing.

II. HISTORY OF PNEUMATIC STRUCTURES

A. Hot Air Balloons and Airships

The first experiments with pneumatic structures were undertaken during the development of hot-air balloons. An effective start for the development of balloons just occurred at the end of the 18th century.These balloons were made by linen and paper.

At the same year, Jaques A. C. Charles built the first hydrogen balloon a derigible called the zepellin.

The idea of transposing the dirigibles technology to architecture tracks back to the English engineer F. W. Lanchester. His patent of a pneumatic system for campaign hospitals was approved in England, in 1918, but was never

actually constructed, due to the lack of adequate membrane materials or appeal to possible clients..

B. World War II and the U.S. Army

During the Word War II and after the invention of nylon, pneumatics started to be used in military operations, as emergency shelters and decoys. At the end of the War, the increase in the number of military air operations demanded implementation of a large and sophisticated network of radars over the American territory. In order to protect these radars from extreme weather conditions, the American Army sponsored the development of thin non-metallic shelters, avoiding interference with the radar signals. These were called ‘radomes’.

Jeson, SEM VI student, KMEA College of Architecture

PNEUMATIC STRUCTURES

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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 fiberglass fabric.

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.

C. Utopian Ideas

Frei Otto was the first to undertake academic investigations, especially about the process of form finding. Through various publications, Otto broadened the landscape, not only of pneumatics, but of tension structures in general. Pneumatics were also part of the repertoire of Richard Buckminster Fuller. His proposal of a pneumatic dome to cover New York (1962, Figure 6) is a famous example of Utopian pneumatic architecture. Realization of this project would require a radical environmental transformation, a sterilized enclosure without dust, pollution, exhaust gases and so.

III. PRINCIPLE OF PNEUMATIC STRUCTURES

Air-inflated and air-supported structures represent a special area of membrane construction. In pneumatic constructions, pressure differences between the enclosed space and the exterior are responsible for giving the building its shape and also for stabilizing the hull. Fabric is pre-tensioned by an

internal overpressure of the air. While this might seem at first to be uncomfortable to the occupants of the structure, the pressure differential is no greater than that of ordinary barometric fluctuations.

Pneumatic structures are a combination of two componentsWith very different properties: an airtight membrane and Compressed air. Air is a gas, essentially composed of nitrogen, oxygen and carbon dioxide, and its properties are merely defined by its composition, the temperature, the pressure and the volume. The membrane is in a solid state and its properties are defined by the material properties and geometry of the constituents, as well as by the way materials are used for its construction, such as the chemical composition and the elastic modulus of the yarn, the mass density of the coating, the type of weaving and so on. The compressed air pretensions the membrane and forms the volume of the structure defined by the membrane-cutting pattern. Such a pre-stressed membrane can support both tension and compression and thus can withstand bending moments. Obviously, the pre-stress in the membrane is a function of the air pressure.

IV General Characteristics

A. LIGHT WEIGHT:- The weight of the structure as compared to the area it

covers is very less The weight of the membrane roof , even when it is stiffened

by cables, is very small Low air pressure is sufficient to balance it Even with spans of more than 100mts, the weight of the

structure does not exceed 3kg/square meter

B. SPAN Another advantage over other structures is that, for

pneumatic membrane, there is no theoretical maximum span as determined by strength, elasticity, specific weight or any other property.

It is hardly possible to span a distance of over 36km. With a steel cables as they would fail because of their inability to sustain their own weight. But with pneumatics, such spans are quiet possible.

C. QUICK ERECTION AND DISMANTLING Suitable for temporary constructions because they are as

easy to dismantle as to establish. 1 sq.Km. Of an area can be brought down in 6 hours. And

establish in less than 10 hours. The 4 hours difference is due to establishment of pegs etc.

D. ECONOMYIt is not expensive where it is used for shifting structures. For permanent structures, it is very expensive. Otherwise

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the cost per square foot of air supported structures is among the lowest for large span roofs.

E. GOOD NATURAL LIGHTGives good natural light as translucent/transparent plastic sheets are typically used to form the membrane. Daylight can be brought in efficiently. There is a lot of flexibility in getting sun light (50%-80%).

IV. CONCLUSION

Pneumatic structure is an efficient system having wide applications in not only the architectural field but various others as well. The possibilities of these structures can be broadened with the advancement of technology and can be incorporated for varied uses and scenarios.

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