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# Re: Definition of Pier in ACI 530-02

• To: seaint(--nospam--at)seaint.org
• Subject: Re: Definition of Pier in ACI 530-02
• From: "Gerard Madden, SE" <gmse4603(--nospam--at)gmail.com>
• Date: Thu, 3 Aug 2006 14:16:22 -0700

Piers are generally for thin elements like walls of concrete or cmu. THis is more of a column with the dimensions in both directions being fairly close. See UBC/CBC section 1921 for the wording they use. The oddball part of your thing is the length is only 30" high, therefore its a pedestal. If it were taller, then it would just be a column.

If it's less than 3x it's thickness, it's a column
If it's greater than 6x it's thickness, it's a shearwall
If it's height is greater than 5x it's length, then its a column again.

Think of a 4 foot stretch of a wall that's 6-8" thick, that's a pier or "Wall Pier" in this case

-gm

On 8/3/06, Joe Grill <jgrill(--nospam--at)swiaz.com> wrote:

I can't quite get my pea brain around the definition of a pier in the ACI 530-02 document.  It states:

"An isolated vertical member whose horizontal dimension measured at right angles to its thickness is not less than 3 times its thickness nor greater than 6 times its thickness and whose height is less than 5 times its length."

I have a "pier" that is 24"x28"x 30" high.

I see the thickness=24", L=28", h=30"

3 x thickness = 72"

6 x thickness = 144"

5 x L = 140"

The horizontal dimension measured at right angles to its thickness = 28" which is less than 72" therefore the way I read this this is not a pier.

What am I not getting here?  I see a "pier" as being the same as a "pedestal" in ACI 318-02, but the definition of a pedestal is clear.

Thanks,

Joe

Joseph R. Grill, P.E. (Structural)

Shephard - Wesnitzer, Inc.

Civil Engineering and Surveying

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-gm