Load testing — Load 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 a fascination. The egg shows us that a relatively soft and weak material can be used to create a very strong structural shape. A simple demonstration illustrating the strength of an egg was made using 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 a time, for a total of 376 pounds or 188 pounds on one egg. The shell did not crack! Such is the strength of some domes.
The cost of forming dome structures, until recently, has always been a major problem. Through the use of air-supported forms, such as the Airforms used in Monolithic Dome construction, 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 enclosed by walls, and serving as a dwelling, storehouse, factory, shelter for animals, or other useful structure.”
The buildings we are considering more specifically will include houses, schools, churches, storage facilities, industrial and commercial buildings and stadiums for athletic events such as football, hockey, basketball and baseball. These structures usually have some basic requirements such as the following:
- Economy – Structure should be economical to build and maintain.
- Safety – Buildings should resist elements such as fire, wind, seismic, vandalism and deterioration.
- Aesthetics and Comfort – Requirements for a storage facility or a horse barn would be much different than for a house or church.
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 in many locations. However, it takes a lot of energy to produce Portland Cement used to produce concrete. So, if we use concrete, we should use a type of building that requires a minimum amount of material, that, in turn, requires the minimum amount of energy for producing the material to build the building.
Recently, at the semi-annual convention of the American Concrete Institute, in Dallas, Texas, the famed P. Kumar Mehta, professor emeritus in the Civil Engineering Department at the University of California, Berkeley, was a keynote speaker, talking about “Reducing the Environmental Impact of Concrete.” He said, “The world’s yearly cement production of 1.6 billion tons accounts for about seven percent of the global loading of carbon dioxide into the atmosphere. Portland Cement, the principle hydraulic cement in use today, is not only one of the most energy-intensive materials of construction but also is responsible for a large amount of greenhouse gases.”
If we build concrete thin shell buildings, such as domes, a much smaller volume of building materials will be utilized. This will result in a very efficient use of building materials and hence reduce energy use and pollution.
As buildings are utilized, the amount of energy used in heating and air conditioning can be very significant. Suppose an economically constructed building could be built in such a manner as to reduce the average energy utilized in heating and air conditioning by 50% or more. An example of such a building is a concrete Monolithic Dome, built using an Airform, with urethane foam between 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. The Wilson 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-inch thick concrete dome with 2 inches of urethane foam provided pleasant summer living without air conditioning. When compared to a more conventional masonry house of the same size, with a wood truss roof, a new 98% efficient gas furnace, R30 insulation in the roof, and located in the same area, the average gas bill was double that of the dome home. The smaller surface area and less volume of the dome house, in addition to the increased R-value of approximately R60 including the mass effect of the concrete inside of the urethane foam insulation, results in very significant energy savings throughout the building’s life. Maintenance and upkeep of a concrete building is generally much less than that of a more conventional wood frame building.
Buildings should be capable of providing safety from the elements without excessive costs. If you live in a conventional wood framed house, with 1/2-inch sheet rock on the inside, 1/2-inch plywood on the outside of wood studs and siding or plaster on the outside, you live in a building that will protect you from some wind, rain, snow and sun. Heat and air conditioning costs twice as much as energy used by most concrete dome homes. An inside fire will penetrate the 1/2-inch sheet rock in about 20 minutes. A recent example of a two-story frame house as described above had a fire from a wood-burning stove, in the middle of the night, and its occupants literally ran for their lives. The fire department was at the house in less than 20 minutes to put out the fire that caused extensive damage to the interior. House and contents would have been completely destroyed in another 20 minutes.
Many people don’t realize how fast fire destroys. Several years back in Georgia, four units of an apartment complex and some 25 automobiles in a nearby parking lot disappeared in just a few minutes. Someone accidentally tipped over a red hot barbecue. Fire spread over the grass and within seconds attacked the vinyl siding that covered the buildings. Five fire fighting units arrived within seven minutes, but they could not save the four structures or the cars. Radiant heat from the burning buildings even melted the vinyl siding on two buildings 80 feet away. A fire chief later said that had the fire fighters been sitting on the spot, they could not have stopped that fire.
In 1967 Chicago’s famous McCormick Place Building — steel construction throughout — succumbed to fire. Steel is noncombustible, but it’s probably one of the worst materials there is in case of fire. The heat of a fire stresses steel so it’s unable to carry a load. It doesn’t pop or crack; it just falls down. Chicago replaced its original steel building with a reinforced concrete structure.
Price, Utah has a municipal complex of four Monolithic Domes: a 90′ × 30′, three-story office facility 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; it would never get outside. The fire might destroy whatever was inside, but the shell would survive.
If a fire attacked the outside of a Monolithic Dome, it might melt the foam, but the concrete would still be there.
Winds cause extensive damage to buildings on a regular basis. Hurricanes, such as Andrew in Florida in 1992 that completely destroyed more than 6,000 homes and other buildings at a cost of 25 to 30 billion dollars, are not uncommon. Earthquakes such as the Northridge, California earthquake of 1994 caused an estimated financial loss of over 20 billion dollars. It is interesting to note that the duration of the strong motion at most locations only lasted between 10 and 15 seconds. On January 17, 1995 an earthquake in Kobe, Japan caused great destruction and loss of life. The collapse of residential housing was the single biggest factor in the quake’s 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 billion U.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 techniques that can be used to build a safe room inside your house, that may save your life if a tornado impacted your home. These safe rooms are usually built with reinforced concrete walls and roofs, or reinforced masonry, or sheets of steel combined with heavy plywood, or combinations of 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 are very devastating to those involved. Tornadoes are placed in several categories, with the worst being EF4 and EF5.
EF4 Devastating: Well-constructed houses are destroyed; some structures are lifted from foundations and blown some distance; cars are blown some distance; large debris becomes airborne.
EF5 Incredible: Strong frame houses are lifted from foundations; reinforced concrete structures are damaged; automobile-sized missiles become airborne; trees are completely debarked.
Most reinforced concrete Monolithic Domes are easily designed to withstand earthquakes, hurricanes and even the strongest tornadoes and remain standing in the same location. It becomes easier and more economical to build a safe, reinforced concrete house that provides safety for all these 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 small dome 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 wasn’t interested in keeping the dome, so he hired a local contractor to remove it. After inspecting the dome, the contractor said that he could remove it in less than one day. He considered using a large front-end loader to lift the dome on the side opposite its wide entrance. This, he thought, would cause the dome to collapse, and the concrete could then be broken up and hauled away. But when he actually tried this, it didn’t work. His heavy equipment would not lift one side of the dome. The contractor then brought up his crane with a large steel wrecking ball meant to knock down the dome in short order. That did not work. Hours of pounding 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 from natural forces, you feel comfortable and at ease when the wind blows. If you live in an area where a few human beings are ruthless, mean, and inclined to rob, steal and shoot holes in houses as they drive down the road, then a reinforced concrete barrier can also bring peace to your soul. David South took a 30-06 rifle and fired into the side of a 2-inch thick Monolithic Dome and there was no penetration.
Most of the houses in this country are of wood frame type construction with plywood on the outside 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 a battery-powered cut-out tool or a battery-powered skill saw with the intent of entering a house through the outside wall. I estimate that with either of these simple tools a hole large enough to enter could be cut in less than one minute. In areas where human elements are a threat to the safety of your house, several locks and bolts on your door are not sufficient to protect your property. The old statement that locks are only for honest people is still true, but it would take a lot longer with much more effort to enter through two inches or more of reinforced concrete.
3. Comfort and Aesthetics
Comfort is the homey, intimate term which implies the imparting of cheer, hope and strength as well 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 was economical. They did not worry about storms or heavy snow or outside noise. It was very comfortable.
A house hidden in the hills or in the back country may be rather plain but very aesthetic to the owner, partly because it is comfortable and economical. The same house located at the center of attention in a high-density, residential area, consisting of more conventional construction, may be considered undesirable or even ugly. Aesthetics usually consider the type of building and how it associates with its surrounding conditions. Comfort and aesthetics need not greatly increase costs. A beautiful and functional concrete dome building can provide the economy, safety and comfort 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 large flying saucer. A circular ring was installed around the form and held out in its final position by a series of cables attached to the ground. The Airform arrived at the job site and was attached to the foundation and inflated. But it took all day before this dome was ready for foam, rebar and concrete. So the crew decided to wait till morning to start foaming. They left for the night, not realizing that lights were still on inside this dome, sitting above the town. The next morning, just as the crew started construction, police arrived followed by a long line of townspeople. Through the night the locals had been watching this shining dome that looked like a flying saucer, but no one 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 serious injuries. Concrete dome buildings succeed in providing safety to their occupants better than most other buildings.