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RE: R value UBC97

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You do not have to assume the bracing carries gravity load.  As long as the beams and columns can carry all the gravity load without the braces in place, then you are not utilizing a frame where the braces carry gravity load.  Even if there is some load in the braces due to gravity load, it is only 4.4 if the braces have to be there for the gravity system to work.


From: Jeff Smith [mailto:jeffsmith7(--nospam--at)]
Sent: Monday, December 03, 2007 10:57 AM
To: seaint(--nospam--at)
Subject: RE: R value UBC97




I have spoke with another engineer who thinks R would be 5.6 under building frame system item 4a.


Do you mind clarifying R=4.4. Why would I assume the diagonal brace takes gravity loads?




From: David Topete [mailto:d.topete73(--nospam--at)]
Sent: Thursday, November 29, 2007 1:56 PM
To: seaint(--nospam--at)
Subject: Re: R value UBC97

Assume the diagonal does carry gravity load, and use R=4.4 (bearing wall system, 4a) in the direction of the brace frame.  5.5 for the other direction (wood shear walls).

On Nov 29, 2007 11:16 AM, Jeff Smith < jeffsmith7(--nospam--at)> wrote:

I searched the archives and I am still unclear. I have a new wood framed residence that needs one story braced frames in one direction, mainly due to OT uplift requirements. The 2 vertical columns will take gravity load, but the top chord and single strut diagonal chord will not. What R should I use? We are submitting this in California before the end of the year.





David Topete, SE