[TowerTalk] Pad and Pier for ROHN SSV. Pad and Pier Foundations

Sat Jul 9 10:42:44 EDT 2005

Of couse like everyone else here on this list that puts up thier own tower I am trying to save money.  But also trying to stay safe.   The property I am putting this on was originally part of a piece of land that was hopeful that the city would get a large business to be on.  So for that reason they did core samples of the property.  So I am going to try to acquire a copy of the results of those core samples to see what they say.   So my question is I don't see in Rohn's book a spot for "if XXX sandy conditions then modify piers by doing this or that"  or "if XXX compactness with clay then modify piers by doing this or that".     Once I get that where do I look for those modifications.  Also I tried when I bought this tower to get engineering drawings from ROHN but after MANY calls was unsuccessful.  Does anyone have any new experience with new radian / rohn and think my ability to get those drawings would be better?  Better question is it seems all the information is in the Rohn Catalog and I am wondering what I will get off of those drawings that is not in the catalog (since the drawings will probable be for the original owners Soil conditions).?

thanks terry

  ----- Original Message ----- 
  From: Bob Gates 
  To: isp at bnjcomp.com 
  Sent: Saturday, July 09, 2005 2:04 AM
  Subject: Re: [TowerTalk] Pad and Pier for ROHN SSV. Pad and Pier Foundations

  Terry,

  Well, you've forced me to go look at my Rohn catalog, and I see where the problem is.  The foundation dimensions for section 14 "assume" you have the other 13 sections on top of it.  That's why such a massive footing design.  Since you're only using 8 sections (7-14 I think your original note said), the footing requirements are much less.  However, you can't use the dimensions for section 8 either because you have more weight and mass involved than if you were using sections 1-8.  

  Now I gather you don't need a permit for this, otherwise you wouldn't be asking.  But I would make a compromise between the section 8 dimensions and the section 14 dimensions.  Install a square footing using the "Drill and Bell" option basic numbers.  The dimensions would be about 12' deep and 5' square (the numbers for section 11).  Forget the bell portion, just a square hole.  Having said that, it might be difficult to keep the hole only 5' square while digging down 12', so you may wind up with a slightly larger hole, which is also okay.  Just dig the hole, use the trackhole to drop in a modified  expanded rebar cage, and fill it with concrete.  Don't forget to keep the rebar cage off the bottom of the hole to prevent rusting over time.

  Hope this helps and GL,

  73, Bob W7BJ
    ----- Original Message ----- 
    From: isp at bnjcomp.com 
    To: towertalk 
    Sent: Friday, July 08, 2005 10:03 PM
    Subject: Re: [TowerTalk] Pad and Pier for ROHN SSV. Pad and Pier Foundations

    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 at 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

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