Just for information only, I seem to recall that the pull-out improvement is
not a linear function of the area under the nut (plate, washer, etc) because
the principle stresses in the footing develop at an angle to the direction
of the bolt tension...
In any event - you should be fine with the 2x2 block, or even heavy washers
for that matter... again have yet to hear of a pull-out failure on a UST
installation.
Hope all goes smoothly with your tower project.
73
Matt
KM5VI
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Mike
Fahmie
Sent: Sunday, November 03, 2013 1:44 PM
To: Matt; 'reflector -tower'
Subject: Re: [TowerTalk] FW: Base Anchor Bolts
Thanks for all of the feedback on my anchor question.
My HDX-572 was manufactured around 2001 but never erected. I bought it from
an SK's estate without doc's. Evidently this was before their anchor design
became more conservative since the 6 provided anchor bolts are type C
(welded nut, no washer/plate). The SAR that UST sent me (dated Aug 2009)
was also calculated with just a welded nut. My bolts are 1"x27" for about
21" of embedment.
The added surface area of the nut (nut minus bolt) calculates out to about
1.16" sq., that doesn't seem all that substantial. A 2"x2" 1/2" thick plate
welded to the existing nut would almost quadruple that. I think that will be
my plan.
-Mike-
WA6ZTY
>________________________________
> From: Matt <km5vi@flukey.cc>
>To: 'reflector -tower' <towertalk@contesting.com>
>Sent: Saturday, November 2, 2013 11:13 PM
>Subject: [TowerTalk] FW: Base Anchor Bolts
>
>
>The link below shows some diagrams of different anchor bolt types.
>Which ones do you have? The last HDX572 design calculations I have
>from UST specify (6) 1" by 27" ASTM F1554, grade 55 (55,000 psi yield),
>with type E block arrangement using a 2" square x 5/8" thick A-36
>(36,000 psi yield) steel block welded to the top die of the nut. Min
>embedment was 21". This arrangement with a 5.5' x 5.5' x 7.5' footing
>was rated at 55,000 ft lbs overturning moment in 100 psf soil.
>
>http://stanley-sales.com/media/e5b0d8a7677e8f11ffff89b7ffffe904.jpg
>
>I know that the ASCE revised the their standards a few years back
>resulting in more conservative designs for anchor bolt pull-out
>strength. We routinely run computer analysis for anchor pull-out
>these days considering not only the embedment but also the overall
>geometry of the footing, The last two shipments of grade 55 anchor
>bolts I purchased from my anchor supplier were fabricated to the new
>ASTM F1554 standard and were Type F with the heavy square block
>sandwiched between two welded nuts. FYI - bolts I received from UST
>under the old design standards were ASTM A36
>(36,000 psi) with Type D washer & nut welded to the base.
>
>I have never heard of an anchor bolt pull-put failure on a UST. I
>would be curious if anyone on the reflector has?
>
>Hope this helps,
>
>Matt
>KM5VI
>
>-----Original Message-----
>From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
>Mike Fahmie
>Sent: Saturday, November 02, 2013 8:49 AM
>To: towertalk@contesting.com
>Subject: [TowerTalk] Base Anchor Bolts
>
>My HDX-572MDPL came with 1" anchor bolts with a welded nut at the
>bottom. The nut diameter is only slightly larger than the shaft so I am
>considering the addition of a heavy washer wired against the nut to
>increase the 'grab'. Is this a good idea?
>
>How does the welded nut approach compare with 'L' shaped anchor rods?
>
>-Mike-
>WA6ZTY
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