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RE: Pier and grade beam foundation systems

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Reference ACI 21.2.2.3 and the commentary.  If you are resisting lateral earthquake forces by the lateral bearing pressure of the drilled piers, chapter 21 is applicable.  If you have dissipated the lateral forces between the soil and the grade beam or by some other means and are relying on the drilled piers for gravity loads only, Chapter 21 provisions do not necessarily need to be applied.

Harold Sprague
Krawinkler, Luth & Assoc.
4412 W. Eisenhower Blvd.
Loveland, CO 80537
Voice: 970 667-2426
Fax: 970 667-2493
Email: hsprague(--nospam--at)klaalov.com



-----Original Message-----
From:	John Buchanan [SMTP:jjb(--nospam--at)scruznet.com]
Sent:	Tuesday, April 07, 1998 5:41 PM
To:	seaoc(--nospam--at)seaoc.org
Subject:	Pier and grade beam foundation systems

To all:
I have a general question regarding a foundation system for residential wood structures founded on a pier and grade beam foundation system.
A college of mine has received a plan check comment from a locale building official stating that the pier and grade beam system should be considered a reinforced concrete frame structure and designed per the requirements of section 1921 of the 1994 Uniform Building Code. 
The standard of care for the area has always been to use an 8" x 18" or 24" deep concrete grade beam with #3 ties and 2 #5 bars top and bottom. The beam reinforcing varies per the vertical load. Typically the piers are spaced at eight to twelve feet on center.
The grade beams are tied to the piers with four #5 bars from the grade beam to the top of the pier.
The piers are reinforced with six number five bars and #3 ties at 10" o.c.  with 4 #3 ties at two inches o.c. at the top of the pier.
So the question is should the pier and grade beam system be considered a frame system a be detailed per the requirements of chapter 21?
If the consensus is no, how does one confront the building official? (There is a board of appeals)
My college has called the ICBO and they do not offer any help.  Calls to ACI have been relatively unresponsive and they try to defer the question to others.
(makes you want to be a member Ha!!!!)
Have a call into EERI to discuss the project but no return phone calls as of yet.


So does any one have any comments?\
John Buchanan




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