| Air-supported Structure |
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Among its many uses are: sports and recreation facilities, warehousing, temporary shelters, Radome s. The structure can be either wholly, partial, or roof-only air supported. A fully air-supported structure can be intended to be a temporary or semi-temporary facility or permanent, whereas roof-only air-supported structures can be built as permanent buildings. DESIGN Shape The shape of an air-supported structure is limited by the need to have the whole envelope surface evenly pressurized. If this is not the case, the structure will be unevenly supported, creating wrinkles and stress points in the pliable envelope which in turn may cause it to fail. In practise, any inflated surface involves a double curvature. Therefore the most common shapes for air-supported structures are hemispheres, ovals, and half cylinders. Structure The main loads acting on the air-supported envelope are the internal air pressure, wind, and snow loads. In order to cope with the varying loads of wind and snow, the inflation of the structure must be adjusted accordingly. Modern structures have computer controlled mechanical systems that can sense the dynamic loads and compensate the inflation for it. The highest quality ones are able to withstand winds up to 120 mph (190 km/h), and snowloads up to 40 lbs. Of course, the air pressure on the envelope is equal to the air pressure exerted on the inside ground, pushing the whole structure up. Therefore it needs to be securely anchored to the ground (or substructure in the case of roof-only). For wide span structures, cables are required for anchoring and stabilization. All forms of anchoring require some form of ballast. Earlier designs used to use sand bags, concrete blocks, bricks, or the like, placed all around the perimeter on the seal skirt. Nowadays most manufactures have proprietary anchoring systems. Danger of sudden collapse is nearly negligible, since the structure will deform or sag in case a heavy load (snow or wind) is exerted on it. Only if these warning signs are ignored or not noticed, then the build-up of an extreme load may rupture the envelope, leading to a sudden deflation and collapse. Material The materials used for air-supported structures are similar to those used in Tensile Structure s, namely synthetic fabrics such as Fibreglass and Polyester . In order to prevent deterioration from moisture and Ultraviolet radiation, these materials are coated with Vinyls such as PVC and Teflon . Depending on use and location, the structure may have inner linings made of lighter materials for insulation or acoustics. AIR PRESSURE The interior air pressure required for air-supported structures is not as much as most people expect and certainly not discernible when inside. The amount of pressure required is a function of the weight of the material - and the building systems suspended on it (lighting, ventilation, etc.) - and wind pressure. Yet it only amounts to a small fraction of Atmospheric Pressure . ADVANTAGES AND DISADVANTAGES with its large air-supported roof.]] There are some advantages and disadvantages as compared to conventional buildings of similar size and application. Advantages:
Disadvantages:
AIR-SUPPORTED DOMES IN OPERATION
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