[TowerTalk] Anchor bolts?

[Jim Thomson]

Date: Sat, 24 Mar 2018 11:51:44 -0700
From: "Steve Jones" <n6sj at earthlink.net>
To: "'Hans Hammarquist'" <hanslg at aol.com>
Cc: <towertalk at contesting.com>
Subject: Re: [TowerTalk] Achor bolts?
Message-ID: <002701d3c3a1$27fd50a0$77f7f1e0$@earthlink.net>
Content-Type: text/plain; charset="us-ascii"



<My 89' US Tower crankup has 2 anchor bolts at each leg, a total of 6 bolts.
<Each bolt is 1 -1/8" diameter and 27" long of ASTM grade 36 steel.

<I think I'd trust US Tower's licensed PE wet-stamped drawing before
<Facebook!

<73,
<Steve
<N6SJ

##  I have the  5000 lb, old style UST  HDX-689   89’ tall tower.   It uses  12 x anchor bolts,  4 per  corner. 
Each group of  4 x rods are in a square config, aprx 5.25 inches  C to C. 
Each anchor rod is  1.125 inch diam x 60 inches long.  Each rod has a 6 inch thread on each end. Anchor rods
come in 3 x different astm strengths.... and each top is color coded.   The 36 ksi are blue.  The  57 ksi are green,
and the 103 ksi are red.  I used the  red / 103 ksi versions.   You require a full 6 inches of threaded rod  sticking 
out of the concrete  for the mating 640 lb steel base..which is  1 inch thick.  The new version of the same 89 ft
tower uses  W bracing, weighs less, at only 3250 lbs,  but uses even bigger diam anchors....  1.25 inch diameter. 

##  UST specified  36 ksi rods that are only 36 inches long.... which leaves only 30 inches embedded in the concrete. 
The finished  concrete top  can be any where from flush to the lawn, to a max of 8 inches above the lawn. If the finished 
concrete is  8 inches above the lawn, the bottoms of each anchor rod are only  22 inches below the lawn. 

## My base is 6.9 ft x 6.9 ft x 9 ft deep.  Aprx 5.5 inches above the lawn,  17 yards in total. 
5075 psi concrete used.   Seems silly to me to have a base thats 9 ft deep, with anchor rods that are only   22-30 in  below
lawn level. So I had portland bolt  custom make the anchor rods longer, 60 inches, and also had em turn a 6 inch thread on 
each end of each rod. Then had them use the 103 ksi material. Then had the local metal shop fabricate 3 x identical plates for me. 
Each plate is  9 inches square by .375 inches thick, with 4 x holes punched out.   One plate at the bottom of each 4 x rod assy. 
1 13/16 wrench +  deep impact socket used to tighten the  8 x nuts that hold each plate in place.   The  9x9 plate increases the
pull out capacity through the roof, compared to using either nothing, or perhaps a stack of washers. 

##  Per the engineers I talked to, if the rods are not embedded deep enough, and the base lets go,  you end up with whats called...
base blow out.  Looks like a real shallow angled  funnel, no deeper than the embedded rod depth and aprx the same dimensions 
as the top of the finished  concrete.  

##  I also re-designed the  rebar cage, used  50 %  more vert rebars, 9 inches inside to inside, around the perimeter.  24 x 1 inch rebars in total. 
A lot more 15mm one piece horizontals used, since there is a horizontal for every 6 inchs of  embedded anchor rod, then its  every 12 inches after that. 
Also installed a horizontal grid of re-bars, one just below the lawn level..and a 2nd grid, just below the  three  9 x 9 plates.    

##  UST towers are not ICE rated, nor is the tower, nor the oem UST  base, seismic rated.  Being in a residential area, typ postage stamp sized lot,  87 x 115,  the concrete 
base install is a one shot deal.   You dont get a 2nd chance to do it right.  With the  .375 thick chromolly mast on top, + ants, prop pitch, cabling, 2 x bearing plates, mast steps,
etc, etc, the total weight is aprx 5500 lbs.   The ONLY thing connecting the  5500 lb tower to the 70,000 lb concrete  base is the anchor rods !!   And some idiot  on face book
wants to use  $3.00   home depot anchor rods, wtf?   Anchor rods are the LAST place  you want to cut corners.....and...save money. 

##  IF you are on acreage,  and the tower falls over..and knocks over a few bails of hay, go for it. 

Later....  Jim   VE7RF