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RE: Conc. Bond to plain steel

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The last code to allow bond to plain steel was the ACI 318-63.  It went away because there were studies indicating huge variablilty in the bond that could be developed and no one wanted to either write an elaborate prep requirement nor did they want to agree to an arbitrary lower bound. 
 
In the tower industry, guy cables are anchored with steel bars embedded into concrete.  However, they weld angles on the embed that resist the pull out in bearing.  How much trouble would it be to weld some sort of lug onto the embedded column?
 
Another option (to avoid welding) is to drill holes into the TS, hook rebar into the holes, and embed the whole thing.  You can calculate that. 
 
Intuitively, I would find it difficult to see a TS pull out, but I like to have something more definitive. 

Regards,
Harold Sprague



From: lrhauer(--nospam--at)hotmail.com
To: seaint(--nospam--at)seaint.org
Subject: Conc. Bond to plain steel
Date: Wed, 12 Mar 2008 12:09:01 -0700

I am designing some "flag pole" type footings for a prefabricated building which is supported by 4" sq. tubes embedded in the concrete footings. The uplift is about 4,000# and I am concerned if it is actually possible for the tube columns to "lift" out of the footings if the bond is broken between the concrete and surface of the tube columns due to concrete shrinkage. The contractor would rather not weld anything to the TS columns, (base plate, dowels, etc.), since it is a prefabricated structure, (greenhouse), with the pieces already fabricated. Is there some type of bond value I can use between the concrete and steel surface? Am I paranoid thinking the columns can actually lift out of a 6 foot deep flag pole type footing?
 
Thanks in advance,
 
Larry Hauer S.E.


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