[TowerTalk] Epoxied bolts
k0rc at citlink.net
Fri Feb 3 17:04:33 EST 2006
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
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Date: Fri, 3 Feb 2006 13:51:28 EST
From: HFDXJUNKIE at aol.com
Subject: Re: [TowerTalk] Epoxied bolts
To: thinair at thinair.cc, jimlux at earthlink.net, aa6dx at arrl.net,
towertalk at contesting.com
Message-ID: <2e5.1a62d9a.31150030 at 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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