Guys, this is a REALLY interesting and educational thread, and the technology
is something I had questioned for a few years. (Here comes the "brother-in-law"
story...)
A few years ago he and I were talking about concrete and anchors. His company
installs and maintains the rides and safety railings at the large amusement
park in Shakopee, MN. He told me he uses epoxied fasteners to anchor all the
steel work! Ever since that discussion, I have wondered about this new
technology.
My question came up because I was thinking of changing brands of self
supporting towers. I was questioning him how this could be accomplished. My
first thought was to fabricate thick steel plates to accommodate the
dimensional transition. He quickly cast that idea aside and said he would
simply drill and epoxy new fasteners into the existing foundation!
I have to admit, my "gut feeling" is "that just couldn't be strong enough". I
guess I've had enough super glue failures to taint my opinion! But he went on
to explain this was a new "space age" technology and the holding resistance
would be greater than the imbedded steel.
Okay, so here's my REAL question... Universal Tower concrete base stubs are
about 2.5" square 3/8" wall steel tubes that are 6 feet long. These legs go all
the way to the bottom of the concrete foundation. What size and what depth
would epoxied fasteners need to go to be equivalent or better? This is a tip
over base which has two 1/2" grade 8 bolts holding each leg to the steel base
coupling. I would suspect the two windward bolts would be the tension limiting
factor on this base.
Actually, I had 90' a tower failure and the aluminum legs are what sheered off
at the steel/aluminum transition. So in a real-world situation, the grade 8
bolts were not the weakest link.
My non-engineering, "gut feeling" would be to install 2.5" threaded steel rod
for each leg. But the remaining question is how deep a hole would provide the
appropriate tension resistance?
This is a hypothetical question now because I have already replaced the tower
with the same manufacturer so this was not an issue.
73 de Bob - K0RC
* * * * * * * * * * * * * * * *
Message: 5
Date: Fri, 3 Feb 2006 13:51:28 EST
From: HFDXJUNKIE@aol.com
Subject: Re: [TowerTalk] Epoxied bolts
To: thinair@thinair.cc, jimlux@earthlink.net, aa6dx@arrl.net,
towertalk@contesting.com
Message-ID: <2e5.1a62d9a.31150030@aol.com>
Content-Type: text/plain; charset="US-ASCII"
Yup, Always a big problem of trying to teach old dogs new tricks...building
codes change and so does material . Being in the building trades...I have seen
ornamental ironworkers using epoxy for railings plenty of times in which
people would eventually leaning on these that would be the only thing from
keeping them falling 200 ft ! I asked how safe is that stuff, the epoxy...they
called it hydraulic cement. I was told the building would prob fall before
anything went wrong with the epoxy. Engineers really know their stuff, just
watch
Modern Marvels !
73 Pete NA2P
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