[TowerTalk] Base Anchor Bolts
Roger (K8RI) on TT
K8RI-on-TowerTalk at tm.net
Sun Nov 3 05:21:48 EST 2013
On 11/3/2013 3:57 AM, Bryan Swadener wrote:
> The anchors I ordered from UST for my TX472 were Type-F.
> IIRC, they were 1-1/8" diameter x 27" L. Yes, I could've
> researched them and saved some money by buying them
> from someone else. However, the cost from UST didn't
> break the bank, and they were a phone call away.
"I think" the new design comes from design calculations
that will give a pull out strength that matches the
breaking strength of the concrete with a minimum of material.
OTOH, Be they J-bolt, welded nut and washer, or the new block between nuts,
all are more than sufficient, if the concrete is strong enough.
I have a minor in mathematics, but my math is far too old
(meaning I haven't used it in so long, I don't trust my figures)
to really prove it. I couldn't do a derivative
or integral if my life depended on it, so like many other things at this
I place my faith in others. <:-))
I "remember doing" lots of calcs to come up with minimum materials for
volume or strength.
Based on "rough" calcs (these are my opinions). I come up with the
over kill, but producing an asymmetrical load.
The welded nut and washer being symmetrical but a bit under maximum
while the new approach produces a symmetrical load, near optimum
strength, with a
minimum of material.
The loads are near symmetrical on each bolt with the up wind side being
a pull and the
down wind side a push.
As I said, with my rusty math skills, these are my "opinions"
Like other things, math belongs in the "Use it or lose it" category.
> vy 73,
> Bryan WA7PRC
> Date: Sun, 3 Nov 2013 01:13:53 -0500
> From: Matt KM5VI
> 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.
> 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,
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