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RE: Concrete Seismic Detailing - Piers

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Hi,
 
Perhaps you can use 0.005Ag for piers. But can you also reduce the spirals ? This is quite significant when you go to larger diameter stuff. IMHO the ACI codes are too conservative on piers, and the one on piers in siesmic regions, unnecessarily so.
 
Syed Masroor
Karachi, Pakistan
 

Subject: Concrete Seismic Detailing - Piers
Date: Thu, 3 Feb 2011 21:23:53 -0600
From: mpuccio(--nospam--at)mpsqrd.com
To: seaint(--nospam--at)seaint.org

Hello,

 

Working on a one story SDC C building.  

 

Question one is for typical column piers, which in this case are mostly 2-ft  but as long as 14’ (to get footings deep enough to not effect adjacent basement). Do piers need to have ties detailed per ACI 21.11.2.2 OR would this only apply to columns (not surrounded by soil)? Code is not specific – so I assume it applies to piers as well.

 

Also, ACI 10.8.4 allows for area of steel in compression member to be .005Ag if only half the area of concrete is required for strength.  Is there anything in ACI restricting this for SDC C? I was planning to use .01Ag for the real columns but for piers this is just seems wrong.

 

Thanks for your insights-

 

M

 

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