The word pneumatic is derived from the Greek word “pneuma”, meaning breath of air, as members get mainly supported by air. Although this kind of lightweight structures has been used been known for thousands of years, it was introduced to the building technology only a few decades ago.
Lightweight: there is no maximum span as determined by strength, elasticity, specific weight as with other materials, thus allowing for great lengths.
Safety: while the plastics used by the pneumatics can fire quickly and totally, their light weight prevents accidents, making them safer than other materials. Also the human body can resist the pressure needed to sustain pneumatic structures; therefore, no health concerns are presented.
Benefits: this type of structures is very easy to fabricate erect and dismantle, as well a very economical, making them a choice material for temporary constructions.
Types of pneumatic structures.
Air inflated- pressurized air is supplied and contained in the volume
Air supported- a single member supported by a small internal pressure difference. Difference. Internal air must be supplied constantly and kept at a pressure higher than atmospheric. This type of structures can be further divided into positive pressure difference which makes the structure curve outward or negative pressure, where the membrane curves inwards
Isotropic: – these show the same strength and stretch in all directions.
– Plastic films: these are primarily produced from pvc, poly ethylene, polyester, polyamide etc.Fabrics: these may be made of glass fibers or synthetic fibers which are coated in pvc, polyester or polyurethane film.Rubber membrane: they are the lightest and most flexible.
– Metal foils: they possess a very high gas diffusion resistance and high tensile strength. One of the major problems in the use of metal foils is in need to produce very exact cutting patterns
Anisotropic materials: – these do not show the same strength and stretch ability in all directions. They have direction oriented properties.
– Woven fabrics: they have two main direction of weave.
They can be made of:
Organic fibers – wool, cotton or silk.
Mineral fibers: glass fibers.
Metal fibers: thin steel wires.
Synthetic fibers: polyamide, polyester and polyvinyl.
– Gridded fabric: these are coarse-weave made of:
Organic mineral or synthetic fibers or metallic networks. They are particularly used where maximum light. Transmission and high strength is required.
– Synthetic rubbers: combination of plastic and rubber. They can take better wear and tear. They are latest and are more resistant to elongation.
– Plastics: like woven fabrics. Its advantage is that they have more of tensile strength than normally manufactured plastic sheets.
Uses throughout history
The technology behind pneumatic structures has been long known to us. One common instance of this technique is balloons and airships which acquired great importance and were used for military missions as shown in Figure 1. During world war pneumatic structures played a key role as emergency shelters and decoys were introduced. Figure2 shows an inflatable tank used for distraction of the enemy. But even after it was increasingly used in a variety of aspect, Frei Otto was the first to investigate the possibilities and strengths of this form. He broadened the landscape, not only of pneumatics, but also tension structures.Figure3 Architects have progressively embraced the ideas of inflatable forms to challenge traditional ideas of construction. The portability of pneumatic structures gave rise to their use on exhibitions such as the Atoms for Peace Pavilion in 1966 by victor Lundy in Figure 4. More recent examples include a wide variety of exhibits that go from small installations such as the one in Figure 5 by Onishi Yasuaki, interactive traveling exhibits of Architects of Air in Figure 6 or that grand scale projects such as The Yorkshire Diamond Pavilion by Various Architects shown in Figure 7.
Pneumatic structure: is a membrane structure that is stabilized by the pressure of compressed air. Theses structures are the most cost effective type of building for long spans.
Air supported structures: is a supported structure that is supported by internal air pressure. A network of cables stiffens the fabric, and the assembly is supported by a rigid ring at the edge
Air inflated structures: are supported by pressurized air within inflated building elements that are shaped to carry loads in a traditional manner.
Air Pressure: within the bubble structure the air pressure is increased slightly above normal atmospheric pressure and maintained by compressors of fans.
Air locks: these are entrances to prevent loss of the internal air pressure.
The shape of a pneumatic structure is usually round because it creates the greatest volume for the least amount of material. The whole envelope surface has to be evenly pressurized for its best stability. There are two types of pneumatic structures, air supported structures and air inflated structures. Pneumatic structures can be used to create a whole structure as an entity or part of another system. They can be used for permanent and temporary structures for a variety of purposes. The initial and operating costs are lower than that of a conventional building because of its simplicity; a lot of these structures are completely prefabricated and they can be assembled fast. Because of the light weight, pneumatic structures can be easily relocated. Many of the typical shapes that are categorized with the pneumatic structure are a hemispheres, ovals, and half cylinder. Any inflated surface involves a double curvature.
Successfully design and construct inflatable objects based on basic platonic shapes that include the square, circle, triangle, rectangle, diamond, rhombus, pentagon, and hexagon.
Pneumatic systems in fixed installations use compressed air because a sustainable supply can be made by compressing atmospheric air. In order to construct a successful pneumatic structure we must construct tight seams that will prevent air leakage.
Air compressor, Iron, Metal straight edge, 2 mm. Plastic, Scissors, Wax paper
First, we identified our dimensions. We chose to design our pneumatic objects within a 2 X 2 frame. In future experiments we will increase the dimensions of our objects in relation to the 2:2 Ratio. We cut two pieces of 2 millimeter plastic in the shape of a square. Then, we proceeded to overlay the two pieces of plastic one on top of the other. We placed the wax paper on top of both pieces of plastic. Next, we placed the metal straight edge along the edges of the square in an effort to create clean, tight seams. Once we had all our pieces overlaid, we ironed over the wax paper, all the while keeping the metal straight edge aligned with the edges. We ensured that we left a small opening at the corner of our object to allow room to insert the tip of the air compressor. Then, we flipped the plastic inside out, to hide the seams inside the square. Finally, we aired up the square inflatable. We repeated this process for the circle, triangle, rectangle, diamond, rhombus, pentagon, and hexagon.
The first few pneumatic objects that we constructed held the air fairly well. The excess plastic beyond the seams was close to 1 inch in our first few models. After testing the objects and after observation, we constructed the remaining models with tighter seams that were closer to a ¼” and we flipped the object inside out to conceal the seams. After inflating these objects, we observed that these held the air better with a tighter resistance. In conclusion, tighter seams hold the compressed air successfully. This will allow us to explore more shapes and their relationship to one another when we begin to combine them when we create more elaborate structures. Furthermore, we will test different materials of different textures and elasticity and record the effects inflating has on them.