Bob,
Please rember that I don;'t know or have access to a belling machine. Makes me
kind of paranoid to think about getting 10-12' in a hole and hand belling out
hole. Are you suggesting a big square hole (have easy access to 70' trackhole
but would have to hire someone out (like a well boring person in our area) if I
wanted a "round" hole) that is size of recomended rohn pad at bottom of pier?
IN my rohn bible book on page SSV-3 is where I am getting my specs. For a 14N
section:
1. pier pad combo is 12' down with a 2' X 2' X 2' pad at bottom. 18 yards of
concrete
2. drill and bell is 14' down with a 6' bell 16.7 yards of concrete
3. drill is 25' down 27 yards of concrete.
I am also thinking that all of these specs "assume" that you will have sections
6n - 1w which I don't so that should give me some relief.
my concrete/tower guy wants to go 10' and put a massive pad at bottom of piers
to give it weight.
I am going to ask my trackhole person how much of a "bell" he can put at bottom
of 14' with his trackhole. I mean the main hole is 3' right so that gives him
room to go down and then scrap out 2' all way around right? Guys am I way off
here?
I only get to do this once so am looking for good input from this list.
thanks terry
----- Original Message -----
From: Bob Gates
To: isp@bnjcomp.com
Sent: Friday, July 08, 2005 1:39 AM
Subject: Re: [TowerTalk] Pad and Pier for ROHN SSV. Pad and Pier Foundations
Terry,
Pardon the expression, but that is a hell of a lot of digging and concrete.
Spent 30 years with a major oil company, most in Marketing Engineering. I was
a region manager when the company was going through a cost cutting exercise,
and the next thing I knew the drawings for our large canopies were revised to
show these spread footings. I'm talking structures that were 48'x105'++.
There were two columns every 25' lengthwise. Upon asking why the change, I was
advised that the bell footings used less concrete, ergo less cost. When I
pointed out that digging the bell, and forming out the rest of the hole so
someone couldn't get buried if a wall fell in, actually increased the cost.
The design was quickly changed back to a rectangular footing. BTW, the
canopies had a wind rating of 110mph. Would suggest the same in your case.
Either dig a rectangular hole the size of the bottom of the bell, or auger a
hole the same diameter as the bottom. Spend a few dollars more on co
ncrete and save significant man hours. Net is a lower cost, and just as safe.
If you feel uneasy about this, ask a registered engineer in your area. GL.
73, Bob W7BJ
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|