Dr. Arnold Wilson and Domes: Past, Present and Future

Dr. Arnold Wilson, S.E.

Dr. Arnold Wilson is a licensed structural engineer, a retired professor at Brigham Young University, and the engineer of record for hundreds of Monolithic Dome structures.

Brigham Young University

Dr. Arnold Wilson doesn’t credit human ingenuity for the invention of a dome—he credits the egg. Wilson, who retired after completing a 40-year career as Civil Engineering Professor at Brigham Young University, says, “The egg has always fascinated me. You can see that it’s the shape and structure of the shell that gives it its strength. Much the same is true for a dome, and I think we borrowed from nature when we began building domes.”

Wilson sees that inherent strength of a dome as one of its greatest advantages, particularly in the future. He says, “Domes are just too good of a thing not to gain in popularity. They can withstand just about any force, and they are economical to build and maintain. What more can you ask?”

Explosion Relief

He reinforces his point about a dome’s strength by recounting a 1988 incident involving a fire inside a Monolithic Dome in Alabama, capable of holding one million bushels of grain. This dome, 150 feet in diameter and 75 feet in height, had a hopper that sloped toward its bottom, making its center 20 feet deeper. A tunnel and conveyor system at the base of the hopper removed grain from the dome.

Aftermath of Grain Explosion.

A fire burned inside the one million bushel grain storage in Alabama for 60 days, ending in a large explosion. The dome’s top was completely destroyed. A grain explosion in a conventional silo will scatter concrete debris up to a half mile away and will often cause fatalities. When the dome top opened, it released the explosion upward and sucked the debris back inside. No injuries, deaths, or other damage occurred.

Grain Storage Before the Explosion.

The grain storage dome before the explosion.

“The fire apparently started in the tunnel where gases built up, as the grain deteriorated or fermented, but were not properly eliminated,” Wilson says. “I was called to help determine where holes could be cut into the dome, so the fire could be fought more effectively. At that point, the dome contained 300,000 bushels of grain. The fire had been going for 60 days, one semi-truck load of carbon dioxide had already been injected into the dome to extinguish the fire.”

“Before the cutting decision could be made,” Wilson continues, “they had an explosion. The dome’s top, acting like a relief valve, blew off, creating a skylight of about 100 feet in diameter. The sound of the explosion woke people as far as four miles away. But here’s the wonderful part about this whole incident: the dome contained the explosion. Escaping gas sucked the debris back into the dome so that lives were not lost and other property was not damaged.”

The incident also proved a principle once demonstrated in a class Wilson attended at Brigham Young University. “The professor covered the hole in one end of a spool of thread with a scrap of paper,” Wilson recalls. “Then he blew through the other hole; the paper stayed in place. To our amazement, the harder he blew, the tighter the paper clung to the spool, because the air going around the paper sucked it down. That same principle accounts for the dome containing the explosion.”

Load Test on Wilson's First Concrete Thin Shell.

A live load test was performed on this dome in Provo, Utah, using an incredible 360,000 pounds of concrete block. The test showed no measurable deflection of the dome’s surface. This was Dr. Wilson’s first dome, an earth-formed, affined transformation of an ellipse that was 160′ × 240′ × 40′ in size.

Wilson’s First Dome

As a student at BYU, Wilson got to know Harry Hodson, a professor of engineering, who gave Wilson some articles on thin shell domes. “I was immediately absorbed and fascinated,” he remembers, “and eventually asked Professor Hodson if I could do my master’s thesis on thin shell domes, and he said "yes.” That really marked the start of my working with domes.“

In 1961, Wilson became involved in the construction of a giant ice skating rink in Provo, Utah. He describes it as, "a tri-axial elliptical dome, constructed using an earth form. It is 240 feet long, 160 feet wide, and 40 feet high at its center, but it’s only 3.5 inches thick.”

“And it’s still in use today,” Wilson adds, “not as a skating rink, but as a supermarket. The owners recently asked me to evaluate the structure, and I found it in great shape.”

[Editor’s Note: Sadly it was razed on February 11, 2006.]

Monolithic Introduction

Wilson continued experimenting with small domes, some using earth forms, some using rebar cages. His goal: finding an affordable method for constructing domes.

By 1975, Wilson had patented a form, much like a collapsible umbrella, over which a dome could be built. “But then,” Wilson says, “I met David and Barry South and they had a better idea and patent than mine, the Airform.”

That meeting marked the beginning of a continuing relationship for Wilson as Senior Consulting Engineer with Monolithic.

Like parents who may love their children equally but remember their first-born with more excitement and in greater detail, Wilson still thinks of one of his first, air-formed dome projects as the most challenging and exciting. He says, “I was the structural engineer for an ongoing project that involved building three huge domes in three different States. They would all be used for the storing of coal and limestone, that eventually would be burned to generate electricity.

"They were huge, 260 feet in diameter and 130 feet in height. It was my job, as structural engineer,” Wilson continues, “to determine how much concrete and steel were needed and where it had to be placed. Many people had their doubts. Some were absolutely sure a dome that size would never work. I always expected it to work—and it did!”

Crenosphere Test Inflation at BYU.

Dr. Wilson and two students examine the Crenosphere test model. A Monolithic Dome built without cables may be built to 296′ in diameter. This test showed that a cable restrained dome may achieve domes up to 1000′ in diameter.

The Crenosphere

Asked to define small and large domes, Wilson chuckles, “The answer to that depends on whom you ask and when. In 1975, a dome with a diameter of 100 feet was considered large. Today, that dome is small.

"Today we define domes with diameters of 300 feet or more as large. The future will probably see 300 feet diameter domes as small. It’s large to us, right now, because the largest one built, to date, is 260 feet by 130 feet.”

Wilson says that in 1975 David South asked him, “How big can we go?” and he answered, “I’m thinking 800 feet diameter.”

According to Wilson, when building a Crenosphere Dome, a cable net placed over the outside of the Airform prevents these gigantic expanses of fabric from tearing, and concrete ribs on the inside of the Crenosphere make its increased diameter possible.

He explains, “A Crenosphere differs from a Monolithic Dome in two important ways, one on the outside and one on the inside. On the outside, a steel cable net is secured to the dome’s foundation, over the Airform, before inflating begins. When the Airform is inflated, the fabric pillows out between the cables, forming a series of connected smaller domes—like a spherical quilt.”

On the inside, the Crenosphere is first sprayed with foam, then crisscrossed with rebar ribs, and sprayed with concrete. “Those ribs,” Wilson says, “give the Crenosphere more depth, but not weight, and create row upon row of small domes—thus eliminating the problem of snap-through buckling.”

The Future

Wilson predicts an exciting future for domes. For example, he sees them as a practical means for providing low-income housing and says, “Housing for the poor is a big problem, and it’s here now. Domes can definitely be the housing-answer for the masses, particularly in less developed countries. People can be taught to build their own small, thin shell domes using an Airform or a pre-cast segment.

"Either of these could be used repeatedly or become a permanent part of the structure. Local materials could be used that would make the domes strong and fireproof. The domes could be 16’ in diameter and provide 200 square feet of living space—that’s a luxurious area in many parts of the world. Dome building makes an ideal do-it-yourself project, and the best way to go when you want to help someone. It’s better to teach people how to do for themselves than to just do for them.”

Wilson thinks domes may play a role in the closed communities that futurists describe as closed complexes within which people will live, work, shop and socialize. He says, “Economically speaking, Monolithic Domes would be ideal for such a complex. But before that happens, we have to get people to accept the roundness. If, for instance, they could see the roundness of the structures as a visual that psychologically promotes a feeling of communal togetherness, they would be more accepting of these new architectural shapes. Then circular shapes could be a big selling point.”

Asked if weather changes and increasing violence within our society might promote dome building, Wilson says, “People are definitely concerned about safety. I think they would be interested in Monolithic Domes if they knew about them. We have to get the information out. I think the way to go is to get the architect groups informed and interested. They are very influential.

"Unfortunately, growing violence is another change that could stimulate popular interest in domes,” Wilson adds. “People living in cities are experiencing drive-by shootings. Think how scary that is for someone living in a wood frame house that a bullet can easily penetrate. Masonry might stop a bullet. It might. A Monolithic Dome would stop it.”

Wilson predicts domes in outer space as well, and says, “We will build spheres on the moon and probably other planets. Air-formed domes will make ideal space stations. They’re strong, can use local materials, and are the least expensive to construct. Inflating the Airform would be easy because in a vacuum it takes very little to do the inflating. So you can just use a pressure cylinder to inflate the Airform. The problems that have to be solved have to do with constructing in a different gravity.”

But while Wilson sees all these advances as “very exciting and challenging,” he is most excited and challenged by the Crenosphere. “For the first time, we can actually, affordably construct huge domes using concrete—the ideal building material,” he says. “It’s virtually indestructible and fireproof; steel cannot claim that; steel falls down or melts in temperatures of 800 or 1000 degrees.”

His list of additional advantages of a Crenosphere includes:

  • Superior insulation with a R60 value—an automatic result of the foam layer sandwiched between the Airform and the concrete. Such layering eliminates sudden changes or peaks in the Crenosphere’s interior temperature and greatly reduces heating and cooling costs.
  • Reduced construction time: Since much of the constructing can be done inside the Crenosphere, time and weather do not decide work schedules. By using crews divided into three shifts, construction can continue without interruption.
  • Easy availability of concrete and other building materials.

“The Crenosphere Dome is a most exciting advance,” Wilson concludes. “It’s ideal for athletic events, and economically it’s just the wisest choice. We just have to do one of these arenas, and they’ll begin going like hot cakes.”

Reprinted from the Fall 1998 issue of the Roundup: Journal of the Monolithic Dome Institute.