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- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: The Most Ridiculous Item of the Day (with apologies to Bill O'Reilly)
- From: "Stuart, Matthew" <mstuart(--nospam--at)schoordepalma.com>
- Date: Wed, 11 Jan 2006 12:23:03 -0500
Per ACI 10.8.4: Oversized members can be reinforced with .5% Ag
The point is that what you are making is so oversized for the applied loads that I would tend to agree with Rich that you don't need steel at all.
Ideally I would have made a 8 to 12" dia column (depending on the anchor bolt requirements) with a spread 8 to 10" thick footing & so no controversy would have taken place :-)
----- Original Message -----
From: Bill Allen
Sent: Wednesday, January 11, 2006 9:09 PM
Subject: The Most Ridiculous Item of the Day (with apologies to Bill O'Reilly)
Now I know I have finally made it to the Big Time ™. I have recently been retained to design a light standard foundation. The light standard is 5” square and 25 feet tall with a light fixture at the top. The footing projects 2’-6” above grade and is 2’-0” in diameter. The installation is in Southern California (BTW, it’s going to get to 70o F today) which means I have designed this “structure” to the 1997 UBC / 2001 CBC.
The “project” was plan checked by an outside consultant who shall remain unnamed. The plan checker is an SE and his number is only about 400 higher than mine. At a passing rate of 100/year, that means he probably passed in 1987-1988 or so. So, it’s not like he’s a neophyte.
I’ve got a plan check list consisting of six items, four of which are structural.
I’ll limit my post to The Ridiculous Item of the Day. Since the top of the footing projects 2’-6” above grade, he is requesting that the footing be designed as a concrete column with a minimum reinforcing of 1%. He is citing CBC section 1910.16.8.6 but I believe he really means 19.10.1 since the footing is not a composite section. For a 2’-6” diameter section, this means I need to provide (don’t laugh) 9-#8 bars!
Now, I can find a few references to reinforce (sorry for the pun) my argument that this section is not a column (Pu<0.10f’cAg, d/L>3, tension controlled section, etc.), but I seem to recall a section of the code where it was very clear that, if Pu<0.10f’cAg, then the section can be considered a beam and not a column. Unfortunately, I can no longer find that specific section in the code.
Is this still applicable? Am I dreaming that there is an exception in the code?
T. William (Bill) Allen, S.E.
Consulting Structural Engineers
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