Why Build a Concrete Dome

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Why build a concrete dome?

Dr. Arnold Wilson November 06, 2009, 1:24 p.m.Engineering Blogs

Load testingLoad testing a small thin-shell dome at the BYU laboratories.

The concrete dome is similar in shape and structure to an egg which has always been afascination. The egg shows us that a relatively soft and weak material can be used to create a
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very strong structural shape. A simple demonstration illustrating the strength of an egg was madeusing a 2 10 wood plank, supported on one end by a rigid support and on the other end by one

hard boiled egg. Four bags of Portland Cement were placed on the plank, at center span, one at atime, for a total of 376 pounds or 188 pounds on one egg. The shell did not crack! Such is thestrength of some domes.

The cost of forming dome structures, until recently, has always been a major problem. Throughthe use of air-supported forms, such as the Airforms used inMonolithic Domeconstruction,superb structures can now be built economically.

Webster defines a building as, a constructed edifice designed to stand more or less

permanently, covering a space of land, covered by a roof and more or less completely enclosedby walls, and serving as a dwelling, storehouse, factory, shelter for animals, or other useful

structure.

The buildings we are considering more specifically will includehouses,schools,churches,

storage facilities,industrial and commercial buildingsandstadiums for athletic events such asfootball, hockey, basketball and baseball. These structures usually have some basic requirementssuch as the following:

1. EconomyStructure should be economical to build and maintain.2. SafetyBuildings should resist elements such as fire, wind, seismic, vandalism and

deterioration.3. Aesthetics and ComfortRequirements for a storage facility or a horse barn would be

much different than for a house or church.

1. Economy

Concrete is the most common building material used throughout the world, followed by wood,steel and a number of miscellaneous materials. It has proven to be available and economical inmany locations. However, it takes a lot of energy to produce Portland Cement used to produceconcrete. So, if we use concrete, we should use a type of building that requires a minimumamount of material, that, in turn, requires the minimum amount of energy for producing thematerial to build the building.

Recently, at the semi-annual convention of the American Concrete Institute, in Dallas, Texas, thefamed P. Kumar Mehta, professor emeritus in the Civil Engineering Department at theUniversity of California, Berkeley, was a keynote speaker, talking about Reducing the

Environmental Impact of Concrete. He said, The worlds yearly cement production of 1.6billion tons accounts for about seven percent of the global loading of carbon dioxide into theatmosphere. Portland Cement, the principle hydraulic cement in use today, is not only one of themost energy-intensive materials of construction but also is responsible for a large amount ofgreenhouse gases.

If we build concrete thin shell buildings, such as domes, a much smaller volume of buildingmaterials will be utilized. This will result in a very efficient use of building materials and hencereduce energy use and pollution.
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As buildings are utilized, the amount ofenergy used in heating and air conditioningcan be verysignificant. Suppose an economically constructed building could be built in such a manner as toreduce the average energy utilized in heating and air conditioning by 50% or more. An exampleof such a building is a concrete Monolithic Dome, built using anAirform, with urethane foambetween the Airform and the concrete.

A specific example of a dome house 40 feet in diameter, 19 feet high, consisting of two stories,with a total floor area of more than 2000 square feet, was built in 1986 in Springville, Utah. TheWilson dome used natural gas for heating, cooking and hot water with a gas bill for January,February and March in 1987 of $40, $35, $30 respectively. The natural efficiency of the 2-inchthick concrete dome with 2 inches of urethane foam provided pleasant summer living without airconditioning. When compared to a more conventional masonry house of the same size, with awood truss roof, a new 98% efficient gas furnace, R30 insulation in the roof, and located in thesame area, the average gas bill was double that of the dome home. The smaller surface area andless volume of the dome house, in addition to the increased R-value of approximately R60including the mass effect of the concrete inside of the urethane foam insulation, results in very

significant energy savings throughout the buildings life. Maintenance and upkeep of a concretebuilding is generally much less than that of a more conventional wood frame building.

2. SafetyBuildings should be capable of providing safety from the elements without excessive costs. Ifyou live in a conventional wood framed house, with 1/2-inch sheet rock on the inside, 1/2-inchplywood on the outside of wood studs and siding or plaster on the outside, you live in a buildingthat will protect you from some wind, rain, snow and sun. Heat and air conditioning costs twiceas much as energy used by most concrete dome homes. An inside fire will penetrate the 1/2-inchsheet rock in about 20 minutes. A recent example of a two-story frame house as described abovehad a fire from a wood-burning stove, in the middle of the night, and its occupants literally ranfor their lives. The fire department was at the house in less than 20 minutes to put out the firethat caused extensive damage to the interior. House and contents would have been completelydestroyed in another 20 minutes.

Many people dont realize how fast fire destroys. Several years back in Georgia, four units of anapartment complex and some 25 automobiles in a nearby parking lot disappeared in just a fewminutes. Someone accidentally tipped over a red hot barbecue. Fire spread over the grass andwithin seconds attacked the vinyl siding that covered the buildings. Five fire fighting unitsarrived within seven minutes, but they could not save the four structures or the cars. Radiant heatfrom the burning buildings even melted the vinyl siding on two buildings 80 feet away. A firechief later said that had the fire fighters been sitting on the spot, they could not have stopped thatfire.

In 1967 Chicagos famous McCormick Place Building steel construction throughoutsuccumbed to fire. Steel is noncombustible, but its probably one of the worst materials there isin case of fire. The heat of a fire stresses steel so its unable to carry a load. It doesnt pop orcrack; it just falls down. Chicago replaced its original steel building with a reinforced concretestructure.
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Price, Utah has a municipal complexof four Monolithic Domes: a 90 30, three-story officefacility and three other domes that each measure 130 43. If fire happened in the office

building, what would happen to the other three domes? Nothing! The fire would be contained; itwould never get outside. The fire might destroy whatever was inside, but the shell would survive.

If afire attacked the outside of a Monolithic Dome, it might melt the foam, but the concretewould still be there.

Winds cause extensive damage to buildings on a regular basis. Hurricanes, such as Andrew inFlorida in 1992 that completely destroyed more than 6,000 homes and other buildings at a cost of25 to 30 billion dollars, are not uncommon. Earthquakes such as the Northridge, Californiaearthquake of 1994 caused an estimated financial loss of over 20 billion dollars. It is interestingto note that the duration of the strong motion at most locations only lasted between 10 and 15seconds. On January 17, 1995 an earthquake in Kobe, Japan caused great destruction and loss oflife. The collapse of residential housing was the single biggest factor in the quakes heavy

casualty toll: 5373 dead; 34,568 injured; 320,298 homeless. Overall, 82,105 buildings totally

collapsed, another 98,892 buildings partially collapsed. Damage estimates exceeded 100 billionU.S. dollars. We are reminded each year of the destructive nature of tornadoes. The U.S.Government has sponsored considerable research and made publications available on techniquesthat can be used to build a safe room inside your house, that may save your life if a tornadoimpacted your home. These safe rooms are usually built with reinforced concrete walls androofs, or reinforced masonry, or sheets of steel combined with heavy plywood, or combinationsof these anchored in such a manner as to remain in place even if the house is destroyed.

Tornadoes are extreme conditions that affect a small number of buildings and people, but arevery devastating to those involved. Tornadoes are placed in several categories, with the worstbeing EF4 and EF5.

EF4 Devastating: Well-constructed houses are destroyed; some structures are lifted fromfoundations and blown some distance; cars are blown some distance; large debris becomesairborne.

EF5 Incredible: Strong frame houses are lifted from foundations; reinforced concrete structuresare damaged; automobile-sized missiles become airborne; trees are completely debarked.

Most reinforced concrete Monolithic Domes are easilydesigned to withstand earthquakes,hurricanes and even the strongest tornadoesand remain standing in the same location. It becomeseasier and more economical to build a safe, reinforced concrete house that provides safety for allthese conditions by utilizing a Monolithic Dome building than any other type of structure.

Monolithic Domes provide great strength. Some years ago, a group in Colorado built a smalldome about 60 in diameter, 30 high and 2" thick. It had windows, a door, and a large opening,

about 40 wide, on one side. After several years of use, the owners decided to sell the property.

But the new owner wasnt interested in keeping the dome, so he hired a local contractor toremove it. After inspecting the dome, the contractor said that he could remove it in less than oneday. He considered using a large front-end loader to lift the dome on the side opposite its wide
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entrance. This, he thought, would cause the dome to collapse, and the concrete could then bebroken up and hauled away. But when he actually tried this, it didnt work. His heavy equipment

would not lift one side of the dome. The contractor then brought up his crane with a large steelwrecking ball meant to knock down the dome in short order. That did not work. Hours ofpounding on the dome just made it look like a giant piece of Swiss cheese. It took the contractor

more than a week to remove the dome.

Safety and peace of mind go hand-in-hand. When you live in a building that protects you fromnatural forces, you feel comfortable and at ease when the wind blows. If you live in an areawhere a few human beings are ruthless, mean, and inclined to rob, steal and shoot holes inhouses as they drive down the road, then a reinforced concrete barrier can also bring peace toyour soul. David South took a 30-06 rifle and fired into the side of a 2-inch thick MonolithicDome and there was no penetration.

Most of the houses in this country are of wood frame type construction with plywood on theoutside of wood studs and sheet rock on the inside. Some walls are veneered with brick, but most

are covered with plaster or sheeting. Consider going to the local hardware store and purchasing abattery-powered cut-out tool or a battery-powered skill saw with the intent of entering a housethrough the outside wall. I estimate that with either of these simple tools a hole large enough toenter could be cut in less than one minute. In areas where human elements are a threat to thesafety of your house, several locks and bolts on your door are not sufficient to protect yourproperty. The old statement that locks are only for honest people is still true, but it would take alot longer with much more effort to enter through two inches or more of reinforced concrete.

3. Comfort and AestheticsComfort is the homey, intimate term which implies the imparting of cheer, hope and strength aswell as the lessening of pain.

People who have lived in Monolithic Domes have indicated that it was very comfortable,meaning there were no drafts, the temperature was very consistent and the fuel consumption waseconomical. They did not worry about storms or heavy snow or outside noise. It was verycomfortable.

A house hidden in the hills or in the back country may be rather plain but very aesthetic to theowner, partly because it is comfortable and economical. The same house located at the center ofattention in a high-density, residential area, consisting of more conventional construction, maybe considered undesirable or even ugly. Aesthetics usually consider the type of building and howit associates with its surrounding conditions. Comfort and aesthetics need not greatly increasecosts. A beautiful and functional concrete dome building can provide the economy, safety andcomfort desired easier than any other building system for some locations.

Airforms can create unusual, unique shapes, such as a dome in Colorado built to look like a largeflying saucer. A circular ring was installed around the form and held out in its final position by aseries of cables attached to the ground. The Airform arrived at the job site and was attached tothe foundation and inflated. But it took all day before this dome was ready for foam, rebar andconcrete. So the crew decided to wait till morning to start foaming. They left for the night, not


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realizing that lights were still on inside this dome, sitting above the town. The next morning, justas the crew started construction, police arrived followed by a long line of townspeople. Throughthe night the locals had been watching this shining dome that looked like a flying saucer, but noone had the courage to investigate until daylight.

Buildings are built as permitted by local building codes for the welfare and safety of the public,and we should remember that building codes are not designed to prevent damage to buildings.That is unrealistic given the magnitude of possible earthquakes, hurricanes and tornadoes.Rather, the aim is for buildings to resist catastrophic damage and thus prevent deaths and seriousinjuries. Concrete dome buildings succeed in providing safety to their occupants better than mostother buildings.

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Why Build a Concrete Dome