Innovations in materials and design are opening up new uses for air-inflated structures.
By Jonathan Kalstrom
Editor’s note: This article appeared in the May/June 1997 issue of Fabric Architecture (then called Fabrics & Architecture).
The design, applications and mechanical systems of air structures have continued to evolve. Among the noteworthy recent developments in the industry are enormous clearspan air-supported structures and mobile air-inflated structures, both products of innovative designs. Efficient mechanical control systems that automatically respond to environmental conditions provide reduced energy costs, as do double-wall fabrics. And, among the applications are indoor golf driving ranges, multi-purpose sports facilities, industrial warehouses, construction-site enclosures and exhibition halls.
One such air structure, an exhibition hall, was unveiled in October 1996. Designed by Festo AG & Co. KG, Esslingen, Germany, it is the first building in the world to be constructed with a cubic interior comprised of supporting structures built with air-inflated chambers. “The basic idea is to use it for mobile exhibition purposes,” says structural engineer Hans-Joachim Schock of Festo. He notes that the inflatable structure can be packed into one 4.25m container.
The load-bearing structure of the hall, which includes 40 Y-shaped columns and 36 wall components along both longitudinal sides, offers a variety of new features: double-wall fabric that acts as a load-bearing element, flame-inhibiting elastomer coatings and a new, translucent ethylene-vinyl acetate coating. “We have used some materials which have never been used before in this context,” says Schock, including EVA-coated fabric, which provides high translucency in the roof structure.
This air-inflated structure responds to environmental forces so the pressures in the different elements are increased in the cases of high wind or snowfall, Schock explains. Columns, arranged in the shape of a saw-tooth pattern, along with pairs of wall components, carry vertical and horizontal loads, such as snow. The horizontal wind load is carried by the frame and by elastic tension elements or “muscles.” When wind hits a side wall, the muscle elements contract. The computer-controlled muscle-elements, an innovation of Festo, are made of polyamide fabric with an internal silicone base. The horizontal girders, or air beams, contribute to the stability of the structure.
The structure requires a small, but continuous amount of energy that is provided by a pressure supply system, according to Schock. One advantage of this type of structure, he notes, is its thermal insulation.
The ability to provide an R-12 or better insulating value in air structures is an important development at Yeadon Fabric Domes Inc., St. Paul, Minn. “Typically an air structure has an R of 2 [or] 2.2 maybe,” says Yeadon’s technical services manager Milosh Nadvornik. “With our system, we can enhance that to an R-12.” The advantage of having higher R values is that it keeps warm air inside in the winter and cool air inside in the summer, resulting in lower energy costs, Nadvornik explains.
“It’s the biggest thing, most likely, that’s hit this whole industry in 20 years,” says Peter Donoghue, general manager and secretary treasurer of Yeadon. “The insulation just brings the energy costs down to something very reasonable.” Yeadon manufactures both permanent and seasonal air-supported structures for such sports applications as tennis, golf, football and hockey. Yeadon, for example, constructed a 110m multiple-sports structure in St. Paul, Minnesota, that covers a city park in the winter and is taken down in the spring.
“The market has required bigger, larger, wider structures which has caused us to look at and come up with new designs, new cabling and new ways of doing them,” says Donoghue. “The concern about energy costs has allowed us to come up with mechanical systems—inflation and heating and air conditioning—and the controls to run them that are state-of-the-art at the present time.” Yeadon has developed an integrated system that houses everything from backup blowers and air conditioning coils to the heating component in one box, Nadvornik says. Automatic controls for inflation and pressurization of the dome present energy savings. “You used to have to adjust manually any time the wind came up, you had a snow condition or a storm approaching,” Nadvornik says.
The increased size of the enclosures is another development in the industry. “We’ve gone from the little tennis bubble or swimming pool enclosures to the huge complexes that encapsulate the activities, whether its soccer, football, lacrosse, running track and so on,” says Jan Ligas, technical sales manager for Air Structures American Technologies Inc. (ASATI), Rye Brook, N.Y. The transition in the industry to the golf dome and multi-sport arena started in about 1990, according to Ligas. In the early 1980s, company CEO Dan Fraioli develop his first trapezoidal-shaped, multi-height air structures for indoor golf driving ranges. “We were pretty much 10 years ahead of the market with the demand—golf really started to take off in the late ’80s and early ’90s,” says Ligas. He adds his company’s golf domes have been “a tremendous success, and it’s created a boom to our industry.”
A typical golf dome is about seven to eight stories high and has a driving distance of roughly 90m, according to Ligas. He notes that his company makes efficient use of space in the golf domes because as the ball travels, the building tapers. “So, if you were 76m wide at the area where you’re driving from, the building actually becomes 38m wide at the far end,” Ligas explains. One reason the company became involved in this niche, he says, is that in certain geographical areas the weather limits golfing to only three or four months a year.
Golf domes are just one type of structure that ASATI has focused on. It is also involved in multi-sports facilities, as well as industrial applications such as warehouses and multi-acre construction-site enclosures. Because of the popularity of soccer in particular, most large facilities are becoming multi-functional for such sports as soccer, golf and softball.
Because ASATI has developed a patented cable-stress release system, it can erect clearspan buildings ranging from several hundred square meters up to 6 or 8 hectares [15–20 acres], if necessary. For example, ASATI constructed a facility for a chemical company in Corpus Christi, Texas, considered the world’s largest ground-mounted air structure at about 2.36 hectares [5.9 acres] clearspan. As a result of the cable-stress release system, the fabric does not recognize the size of building to which it is attached. Whether it’s a small 450m2 building or a 45,000m2 building, the loads on the fabric are relatively the same, Ligas explains.
The future for the air structure industry looks bright. Ligas says that the air-structure applications he described will become even more popular in the future. “It’s just the beginning,” he says.