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RE: Minimum area of steel in concrete column

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Mark -

I agree completely with the first two parts of your question.  Long live
decent logic!  I'm curious what other list-ers think.  I don't know about
caissons.

Eli Grassley
PSM Engineers
Seattle


-----Original Message-----
From: Mark L. Puccio [mailto:mpuccio(--nospam--at)ramaker.com] 
Sent: Friday, October 15, 2004 12:13 PM
To: Seaint List (E-mail)
Subject: Minimum area of steel in concrete column

I have a 3part question to settle some differences of opinion in our office
regarding the minimum area of steel required for a concrete column that is
not in a high seismic region. 

Section 10.9.1 states that the area of longitudinal reinforcement shall be
not less than 1% of the gross area. Section 10.8.4 states it shall be
permitted to base the minimum reinforcement and strength on a reduced
effective area not less than one-half the total area. 

My interpretation is that you can design a column with a minimum area of
steel of 1% and if (and only if) that works you can increase the total area
of concrete up to twice the "design" area without adding anymore area of
steel. So if 1% doesn't work (for the original design area) you have to
increase the steel even if using that area and increasing your d gives you
the strength required. My argument here is that you can't simply design a
column based on 0.5% steel.  Correct?

The second part of this question is with regard to the commentary for
10.8.4, it states ...simply add concrete around the designed section... I
would say it is okay to put the steel you designed for the smaller column
out toward the larger column perimeter. Do you all agree?

Third question do all of these requirements apply to caissons.

Thanks in advance

Mark L. Puccio P.E.,S.E.


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