Passing the Bullet Test
The strength and durability of Monolithic Domes
July 1, 2004
by David B. South
As they say on TV, "Don't try this at home." Don't shoot holes in your home with a 30-06 caliber rifle. In the photograph on the left Gary Clark is firing on one of our 32-foot Monolithic Dome storage buildings. He is firing from very close range, nearly perpendicular to the dome. He shot one shell into each of two of our 32-foot diameter shops. The first shell entered through the Airfrom leaving a hole in it about the size of a pencil. The bullet disintegrated inside that hole. We dug out the bullet later, and it was totally flat. The bullet fired from a 30-06 was a 180 grain hunting bullet with a full copper jacket. This is the type of shell that was used in World War II in the Garand Rifle. It is far more powerful than today's modern M-16 bullets.
The second dome when hit with the 30-06 rifle had a small piece of concrete approximately the size of a fist fall off the wall, but the bullet did not penetrate. This experiment shows that the Monolithic Dome can withstand a substantial amount of rifle fire. Certainly, it would withstand any pistol fire or anything smaller than a heavy duty 30-06 at a point blank range, and perpendicular.
Rifle Fire vs. Projectiles
Any projectile fired at a surface will dramatically loose its effect at an angle. Obviously a Dome presents a far smaller area perpendicular to the plane of any projectile than any other structure.
On the other hand, rifle fire is not the same as a two by four doing a hundred miles an hour. The mass of the two by four is extraordinary. Nevertheless, a four-inch reinforced concrete wall will stop that two by four. Very few Monolithic Domes have less than four inches of concrete in the wall section. The urethane foam on the outside will also mitigate the impact of a projectile, be it large or small. The foam will also absorb a large amount of the energy, especially off a projectile with a large surface such as the two by four.
The fact that the urethane is applied over the concrete and the concrete of a Monolithic Dome is stronger than normal concrete, the chances of penetration become extremely small. Now, add that to the fact that the dome is curved. A curved surface, especially curved in two dimensions as the dome is, changes the dynamics of a force impinging on the dome dramatically. The force immediately is directed around the dome rather than concentrated at the point of impact. This is most especially true of something like a two by four -- less true with something like a rifle bullet. So, not only do we have the other things going for us, the compound curve adds a huge amount of value in repelling a projectile. In fact, the projectile really doesn't become a problem at all to a Monolithic Dome except at the doors and the windows.
Experts have tried to calculate what would happen if an eighteen wheeler flew through the air and landed on a Monolithic Dome. The consensus has been that if you can you can get the truck airborne, a Monolithic Dome might crack but would certainly not cave in. A more likely scenario would be a car. An automobile does not have enough mass or energy from a tornado to be a serious factor when and if it landed on a Monolithic Dome.
If you are lying in a bed in your bedroom and you hear the onset of the tornado, it's a good idea to roll out of the bed and move up against the dome wall away from what could be flying glass if it shatters. The dome can handle tornado pressure both inside and outside so the loss of one window just means there is some air blowing around outside. If you lose windows on both sides of the house the wind can blow through the house and you may lose some of your possessions, but if you will stay up against the concrete wall you will be as safe as reasonably feasible.
There is peace of mind that comes from being in a Monolithic Dome during a storm. You quickly realize you might lose the dog house, the trampoline, the carport, and even the porch, but at least the dome you are in will survive. It's also comforting to know that you don't have to stay up all night watching television to make sure the tornado watch is cancelled before going to bed. The risk is definitely minimized within a Monolithic Dome.
Each person has to decide what is an acceptable risk for themselves. In the past, conventional construction did not offer much in the way of tornado protection without spending a lot of money for a separate structure for the sole purpose of providing protection. On the other hand, the Monolithic Dome provides near-absolute protection, in most cases, without spending any extra money. In fact, it generally will save the cost of the structure in energy savings.
Again, do not try this at home.
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