Section 12.3.4.1 of ASCE 7 specifies the conditions where Rho can be assumed to equal 1.0. Foundation is not one of them.
Ben Yousefi, SE, CBO
Chief Building Official
City of Mountain View, CA
(650) 526-7007
ben.yousefi@mountainview.gov
From: Garner, Robert [mailto:rgarner@moffattnichol.com]
Sent: Tuesday, August 19, 2008 9:22 AM
To: seaint@seaint.org
Subject: Rho, Rho, Rho your boat (foundation)
I'm designing a steel framed structure in Seismic Category D. For the steel framing, Rho will be 1.3. For the foundation (a concrete mat foundation), we are using a Rho of 1.0 - our reasoning being that the purpose of Rho is to assure that no single seismic force resisting element above the foundation (the building frames) will likely fail in an earthquake. Nowhere in the Codes can I find a statement that Rho is to be applied to the foundation. Can anyone challenge me on this with a Code quote or logical argument?
Thanks for any help you can offer.
Bob Garner, S.E.
R. Garner
Moffatt & Nichol
Tel.: (619) 220-6050
Fax.: (619) 220-6055
e-mail: rgarner@moffattnichol.com