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Re: Conc. Bond to plain steel

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It depends on whether concrete cracks when it shrinks. If it does than the ring gear analogy doesn't work (unless you expect the ring gear to fracture, in which case it is appropriate).

Why not drill a hole 6" from the bottom of the tubes and slip a bar through it?

Garner, Robert wrote:

That old dilemna: when a concrete ring shrinks, does the hole get bigger or smaller?  (Think of how they install ring gears on flywheels for the answer).  Will you put any hoop reinforcement in the footing to keep it from cracking away from the post?


Bob Garner, S.E.


From: Larry Hauer [mailto:lrhauer(--nospam--at)]
Sent: Wednesday, March 12, 2008 12:09 PM
To: seaint(--nospam--at)
Subject: Conc. Bond to plain steel


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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