The importance of wind ratings:
The footing design for a fabric structures are determined by the wind ratings designated for your area. Dome shaped buildings, at the apex, have a profile similar to an aircraft wing. When strong winds pass over the curved section it creates lift. The stronger the winds the more lift.
This lift is substantial, even using the lowest “Region A” wind ratings, 41m/sec or 148kph (90mph). For a 16m (54′) wide shelter you require 510kg (1,100lb)/linear metre of container each side, so just over 6 tons of ballast in each container to hold it down in a severe wind. For a 12m (40″) wide structure in the same conditions you need 958kg (2,107lb)/linear metre of ballast. The smaller shelter needs almost double the ballast because the curve of the roof produces a very much higher lift.
If you are within 10km of the coast, on a hill top, or in the bottom of a valley the winds will be higher than the regions average. Increasing the strength of your structure to the next higher wind rating is a very cheap insurance policy. Always check with your local building authorities as to the wind ratings used for your area. To enlarge the map below click here Australian Wind Ratings Regions.