An air-supported (or air-inflated) structure is any building that derives its structural integrity from the use of internal pressurized air to inflate a pliable material (i.e. structural fabric)

envelope An envelope is a common packaging item, usually made of thin, flat material. It is designed to contain a flat object, such as a letter or card. Traditional envelopes are made from sheets of paper cut to one of three shapes: a rhombus, a ...

, so that air is the main support of the structure, and where access is via airlocks. The first air-supported structure built in history was the radome manufactured at the Cornell Aeronautical Laboratory in 1948 by Walter Bird. The concept was implemented on a large scale by David H. Geiger with the United States pavilion at

Expo '70 The or Expo 70 was a world's fair held in Suita, Osaka Prefecture, Japan between March 15 and September 13, 1970. Its theme was "Progress and Harmony for Mankind." In Japanese, Expo '70 is often referred to as . It was the first world's fai ...

in Osaka, Japan in 1970. It is usually dome-shaped, since this shape creates the greatest

volume Volume is a measure of occupied three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch). ...

for the least amount of material. To maintain structural integrity, the structure must be pressurized such that the internal

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country a ...

equals or exceeds any external pressure being applied to the structure (i.e.

wind Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few ...

pressure). The structure does not have to be airtight to retain structural integrity—as long as the pressurization system that supplies internal pressure replaces any air leakage, the structure will remain stable. All access to the structure interior must be equipped with some form of airlock—typically either two sets of parallel doors or a

revolving door A revolving door typically consists of three or four doors that hang on a central shaft and rotate around a vertical axis within a cylindrical enclosure. Revolving doors are energy efficient as they, acting as an airlock, prevent drafts, thus de ...

or both. Air-supported structures are secured by heavy weights on the ground, ground anchors, attachment to a foundation, or a combination of these. Among its many uses are: sports and recreation facilities, warehousing, temporary shelters, and radomes. 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 a structure with only an air-supported roof can be built as a permanent building.

Design

Shape

The shape of an air-supported structure is limited by the need to have the whole envelope surface evenly

pressurized {{Wiktionary Pressurization or pressurisation is the application of pressure in a given situation or environment. Industrial Industrial equipment is often maintained at pressures above or below atmospheric. Atmospheric This is the process b ...

. 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 practice, 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 against the air-supported envelope are internal air pressure, wind, or weight from snow build-up. To compensate against wind force and snow load, the structure's inflation is adjusted accordingly. Modern structures have computer controlled mechanical systems that monitor dynamic loads and automatically compensate the inflation for it. The better the quality of the structure, the higher forces and weight it can endure. The best quality structures can withstand winds up to and snow weight to 40 pounds per square yard (21.7 kilograms per square meter). Tokyo Dome 2015-5-12

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 to the substructure in a roof-only design). For wide span structures cables are required for anchoring and stabilization. Anchoring requires ballast (weights). Early anchoring designs incorporated sand bags, concrete blocks, bricks, or the like, typically placed around the perimeter on the seal skirt. Most modern design structures use proprietary anchoring systems. The danger of sudden collapse is nearly negligible, because the structure will gradually deform or sag when subject to a heavy load or force (snow or wind). 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. A common misconception is that these structures are not meant to be permanent facilities, however all major corporations participating in this industry conform to some form of The International Building Codes. To be a permanent facility these domes have to be engineered to the same building codes as a traditional structure. Air-supported structures or domes are also commonly known as "bubbles".

Material

The materials used for air-supported structures are similar to those used in tensile structures, namely synthetic fabrics such as fibreglass and polyester. In order to prevent deterioration from moisture and

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation ...

radiation, these materials are coated with polymers such as PVC and Teflon. Depending on use and location, the structure may have inner linings made of lighter materials for insulation or acoustics. Materials used in modern air supported structures are usually translucent, therefore the use of lighting system inside the structure is not required during the daytime.

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. Internal pressure is commonly measured in inches of water, inAq, and varies fractionally from 0.3 inAq for minimal inflation to 3 inAq for maximum, with 1 inAq being a standard pressurization level for normal operating conditions. In terms of the more common pounds per square inch, 1 inAq equates to a mere 0.037 psi (2.54 mBar, 254 Pa).

Notable air-supported domes

In operation

* Bennett Indoor Athletic Complex, Toms River, New Jersey, United States * Dalplex (athletics complex), Halifax,

Nova Scotia Nova Scotia ( ; ; ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. Nova Scotia is Latin for "New Scotland". Most of the population are native Eng ...

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by to ...

Olympic Training Center Velodrome The Olympic Training Center Velodrome, also known as the 7-11 Velodrome, is a velodrome in Colorado Springs, Colorado Colorado Springs is a home rule municipality in, and the county seat of, El Paso County, Colorado, United States. It is the ...

, Colorado Springs,

Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of the ...

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

* Edmonton Soccer Dome,

Edmonton Edmonton ( ) is the capital city of the Canadian province of Alberta. Edmonton is situated on the North Saskatchewan River and is the centre of the Edmonton Metropolitan Region, which is surrounded by Alberta's central region. The city an ...

Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest T ...

* Harry Jerome Sports Center, Burnaby, British Columbia, Canada. * Krenzler Field, Cleveland State University, Cleveland, Ohio, United States * Tokyo Dome,

Tokyo Tokyo (; ja, 東京, , ), officially the Tokyo Metropolis ( ja, 東京都, label=none, ), is the capital and largest city of Japan. Formerly known as Edo, its metropolitan area () is the most populous in the world, with an estimated 37.46 ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...

Former notable domes

* BC Place,

Vancouver Vancouver ( ) is a major city in western Canada, located in the Lower Mainland region of British Columbia. As the most populous city in the province, the 2021 Canadian census recorded 662,248 people in the city, up from 631,486 in 2016. ...

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, for ...

(Formerly the largest air-supported stadium in the world. The roof was changed to a retractable roof in 2011) * Greater Binghamton Sports Complex, Binghamton, New York, United States. (Roof collapsed in December 2020) * Burswood Dome,

Perth, Western Australia Perth is the capital and largest city of the Australian state of Western Australia. It is the fourth most populous city in Australia and Oceania, with a population of 2.1 million (80% of the state) living in Greater Perth in 2020. Perth is ...

(Demolition commenced June 2013) *

Carrier Dome The JMA Wireless Dome, originally the Carrier Dome (1980–2022) and colloquially called "The Dome," or more recently "The JMA Dome," is a domed sports stadium in Syracuse, New York. Located on the campus of Syracuse University in the Universit ...

Syracuse, New York Syracuse ( ) is a city in and the county seat of Onondaga County, New York, United States. It is the fifth-most populous city in the state of New York following New York City, Buffalo, Yonkers, and Rochester. At the 2020 census, the city' ...

, United States (air-supported roof was deflated for the final time on March 16, 2020, with a steel frame-supported roof installed that September) * DakotaDome, Vermillion, South Dakota,

(air-supported roof was replaced by a steel frame domed roof in 2001) * Donald N. Dedmon Center, Radford, Virginia,

(air-supported roof was replaced by a steel truss and fabric roof in 2009) *

Hubert H. Humphrey Metrodome The Hubert H. Humphrey Metrodome (commonly called the Metrodome) was a domed sports stadium located in downtown Minneapolis, Minnesota. It opened in 1982 as a replacement for Metropolitan Stadium, the former home of the National Football League' ...

, Minneapolis, Minnesota, United States (Roof deflated January 18, 2014, demolished in February 2014) * O'Connell Center, Gainesville, Florida,

(air-supported roof was replaced by a steel frame-supported roof in 1998) * RCA Dome,

Indianapolis, Indiana Indianapolis (), colloquially known as Indy, is the state capital and most populous city of the U.S. state of Indiana and the seat of Marion County. According to the U.S. Census Bureau, the consolidated population of Indianapolis and Mar ...

(demolished in December 2008) * Pontiac Silverdome, Pontiac, Michigan,

(deflated in early January 2013; demolished December 2017) * St. Louis Science Center Exploradome, St. Louis, Missouri,

(Demolished in 2013) *

UNI-Dome UNI-Dome (pronounced "YOU-nih-dome") is a multi-purpose stadium, on the campus of the University of Northern Iowa, in Cedar Falls, Iowa, United States. It opened in 1976, as the home of the UNI Panthers basketball and football teams. The facilit ...

, Cedar Falls, Iowa,

(air-supported Teflon/Fiberglass roof was replaced with a steel frame-supported stainless steel/fiberglass roof in 1998) * Yuengling Center (originally USF Sun Dome), Tampa, Florida, United States (air-supported Teflon/Fiberglass roof was replaced with a steel frame-supported roof in 2012)

Similar concepts

Blimps A blimp, or non-rigid airship, is an airship (dirigible) without an internal structural framework or a keel. Unlike semi-rigid and rigid airships (e.g. Zeppelins), blimps rely on the pressure of the lifting gas (usually helium, rather than hyd ...

, the application of this technique to airships, using the pressure differential between their

lifting gas A lifting gas or lighter-than-air gas is a gas that has a density lower than normal atmospheric gases and rises above them as a result. It is required for aerostats to create buoyancy, particularly in lighter-than-air aircraft, which include free ...

and the outside atmosphere to provide structural integrity. *

Balloon tank A balloon tank is a style of propellant tank used in the SM-65 Atlas intercontinental ballistic missile (ICBM) and Centaur upper stage that does not use an internal framework, but instead relies on a positive internal pressurization to keep i ...

s, the application of this technique to rockets, using tank pressurization for rigidity.

References

External links

Tension Structures

DESIGN MANUAL FOR GROUND-MOUNTED AIR-SUPPORTED STRUCTURES
{cbignore, bot=medic
GUIDE FOR ESTIMATING MAXIMUM ANCHOR LOADS ON AIR-SUPPORTED STRUCTURES
Buildings and structures by type Tensile architecture Tensile membrane structures