[TowerTalk] Pad and Pier Foundations

[Jim Lux]

At 12:13 PM 7/5/2005, JC Smith wrote:
>Hi Gene,
>
>As you know, I'm planning on this type of tower.  I've been looking at the
>foundation options and I really don't want a 9' x 9' (or even an 8' x 8')
>concrete pad under the tower (the Solid Block option) but I don't like the
>idea of forming and compacting either.  Seems to me that if you do two pours
>y

You might want to talk to a local engineer about the idea of drilling a 
deep round hole and setting a caisson type base. I hesitate to speculate 
about sizes, but about a year ago, they were installing some traffic lights 
on a 6 lane wide road near my house. It had to support a canteliever all 
the way out over the left turn pocket, 30-40 feet away from the main 
pole).  Huge bending moment load, especially when you add the required 
seismic (0.6g, I think) and wind loads.  Those traffic lights aren't 
lightweight, nor are the signs, etc.

They basically drilled a 2 or 3 foot diameter hole some 15-20 feet deep 
(with a big truck mounted auger), lowered a big rebar cage into it, and 
filled it with concrete.  It ain't necessarily cheap, but the surface 
disruption is small: they jackhammered out about 6 feet of sidewalk on the 
corner and did it in the rectangular hole that was about 4x6 ft, then 
poured a new sidewalk slab around it.  A 8x8x8 foot cube of concrete isn't 
going to be cheap either.

Jim.