I have to add my two cents worth:
A manufacturers' base design is usually based on "standard soil conditions",
which is something like 2000 lbs/sq ft if memory serves. If the local
conditions are lower than that, then the design must be modified accordingly,
and only a PE is allowed to do that.
A base can take on at least two forms: A column which is relatively narrow
and deep. This type depends a lot on the soil to prevent over-turning.
Usually traffic lights are mounted on this type, since real estate is
limited.
Another type is called a slab which is relatively wide, square and not very
deep, and heavily re-inforced. This type can sit on the parking lot and
support the tower without turning over. These are usually used for large
structures that have high overturning moments (earth station antennas). Both
types are still dependent on the soil compression strength.
73s
Bob, W5LT
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