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Re: R value for the design of braced frame in a plywood shear wall building

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Depends on your brace configuration.
 
You do not have a "dual" system.  Transitioning to a single frame line somewhere in a structure does not qualify as a dual system.  If the building is essentially a wood bearing wall / shearwall system, the appropriate R factor would be 5.5 (less than three stories).  If the braced frame element is not configured in such a way that the braces carry gravity load, the same 5.5 factor would apply for the braced frame per 1630.4.2, 1630.4.3, and 1630.4.4.
 
If the bracing does in fact carry gravity load, then the R value of 4.4 would apply to the entire structure, including the wood shear walls under the same code sections.
 
 
----- Original Message -----
Sent: Tuesday, August 13, 2002 8:03 AM
Subject: R value for the design of braced frame in a plywood shear wall building

Hi,
 
Should I be using R of 4.4 for an X- braced frame at the first story and for all of the plywood shear walls in the direction of the braced frame including the ply shear wall above the braced frame?
 
I originally used R=5.6 (item 2.4.a of table 16N of the UBC) because braces are not designed to support gravity loads.  The plan checker commented that the use of R=4.4 is appropriate per item 1.4.a because this is a bearing wall building.  In fact I believe that this is a dual system building where part of it is a bearing wall and other part is a building frame system (steel columns and beams at the line where the brace frame occurs).
 
Any thoughts?
 
Regards,

Alexander (Sasha) Itsekson, SE
Enginious Structures
Oakland, CA
tel. 510.601.1646
fax  510.420.8110