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
age,
I place my faith in others. <:-))
I "remember doing" lots of calcs to come up with minimum materials for
maximum
volume or strength.
Based on "rough" calcs (these are my opinions). I come up with the
J-bolt being
over kill, but producing an asymmetrical load.
The welded nut and washer being symmetrical but a bit under maximum
holding strength.
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.
73,
Roger (K8RI)
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.
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
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