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RE: Rho, Rho, Rho your boat (foundation)

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I'm not sure your interpretation is correct.  I agree that seems contradictory - I think that it should state "except as defined in".  I believe the intent is that, for example, drift and P-delta effects are calculated without the rho factor even in Seismic Design Categories D through F.
Bill Sherman

From: Jules [mailto:JulesG(--nospam--at)]
Sent: Wednesday, August 20, 2008 10:11 AM
To: seaint(--nospam--at)
Subject: Re: Rho, Rho, Rho your boat (foundation)

I think the wording of the ASCE Section Is not very good. The intent is that ALL conditions should be met for rho =1. Otherwise Section would be contradictory.
----- Original Message -----
Sent: Tuesday, August 19, 2008 9:36 AM
Subject: RE: Rho, Rho, Rho your boat (foundation)

Section 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


From: Garner, Robert [mailto:rgarner(--nospam--at)]
Sent: Tuesday, August 19, 2008 9:22 AM
To: seaint(--nospam--at)
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(--nospam--at)