48′ Dome Panel Load Test
load of almost four tons of sand & bags of Portland Cement on panel
The above photo shows the additional 40 bags of Portland cement that were set on top the sand loaded panel, bringing the total weight on the panel to almost four tons. The center deflection increased to less than 3/8 inch. The grand total deflection of less than 3/8 inch with almost four tons of weight was astonishing to us. Our panel withstood 170 lbs. per sq. ft. of load.
Q: Do you have an engineering statement about your dome panels that can be submitted to my building department?
A: Yes, to view the statement click on Engineering.
In October 2000 Ai performed a load test on one of its 48′ triangular shaped building kit panels. The test was performed on Ai’s largest panel using the standard 7″ thick E.P.S. insulation, ¾” thick concrete exterior reinforced with galvanized steel mesh and a fiber reinforced plaster on the interior. The strength of the component panel can best be determined by measuring the deflection of the panel as a load (weight) is applied in increments. The panel was placed horizontal. Its weight and the weight of everything placed on it was only supported along the outer edge of the panel. The loading of the panel was done by adding sand in 470 lb. increments. Plywood sides were attached to the panel edges so sand could be spread evenly, providing a uniform load.
The deflection was measured in the center and six other locations. At all measured points a steel ruler was attached to the panel extending high enough to be visible when the panel was fully loaded with sand. A surveyor’s transit allowed the engineer to measure the deflection.
After 3,783 lbs. of sand was dumped on the panel its center had deflected less than 1/16 inch. Three days later, the deflections had only increased to 3/32 inch. Our own amazement at the strength made us even braver; so we cut through the interior plaster on the bottom of the panel. Even then the deflection was less than 3/16 inch.
Ai had not expected this exceptional strength. We could not mound the sand any higher so we set a pallet of 40 cement bags on top of the sand thinking, “This could do the panel in.” That doubled the weight and the center deflection increased to less than 3/16 inch.
The grand total deflection of less than 3/8 inch with almost four tons of weight was astonishing to us.
A 120-mph wind will exert a pressure of 30 lbs. per sq. ft. on a vertical wall and a snow load exceeding 90 lbs. per sq. ft. is rare. Typically snow loads are 20 to 50lbs. per sq.ft. American Ingenuity’s triangular shaped 48′ component panel withstood 170 lbs. per sq. ft.
This picture was taken after Ai had loaded 3,783 lbs. of sand onto our 48′ dome panel. After the sand was dumped on the panel its center had deflected less than 1/16 inch. Three days later, the deflections had only increased to 3/32 inch. Our own amazement at the strength made us even braver; so we cut through the interior plaster on the bottom of the panel. Even then the deflection was less than 3/16 inch.
The men in the photo from left to right are:
- Michael Busick, inventor of American Ingenuity’s building panel and building method
- Luke Miorelli, mechanical engineer
- An engineer that was an independent observer
- Leo Cherbano, American Ingenuity’s plant manager
I would like to completely bury the dome. Is this possible?
- No we do not recommend this. What do you want to accomplish by covering the dome with earth? There may be a better way than covering with dirt.
- A dome like an arch, increases its effectiveness as it is compressed so it will support partial earth berming or any snow load. We have fortified our reinforced concrete with space-age fibers and special admixtures, as well as galvanized steel. As the panels of the dome are assembled, the beveled seams between them are concreted, creating a network of interlocking arches of structural beams.
- Our dome lends itself very well to earth berming because of the strength of the dome shape and the totally concrete exterior wall, with no materials to rot. Ai’s domes have been bermed with as much as 4 feet of backfill. However, if you earth berm your dome, we recommend a drain system to draw water away from the foundation. Plans for this drain system are included with our basement plans.
- The Ai Dome could be bermed higher or even buried, but we do not recommend it because the additional expense of labor and extra concrete would probably not be worth the gain. A dome or a structure that is not buried would never have to withstand loads greater than 100 lbs. per sq.ft. If a structure is buried the earth could put loads in excess of 500 lbs. per sq.ft. and we do not design our standard dome to for those extreme conditions that would normally never occur.
- Four feet is the maximum height of back fill that can go back against the dome. Back fill higher than this would cause more expense and complications than is likely to be worth while. Consider landscaping with plants to enhance the appearance that you want. Ai has never had one of its domes buried with dirt.