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Re: ASCE 7-05 Section 12.2.3.2

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The second part is addressing each line of resistance, not the entire building.




-----Original Message-----
From: Jason Christensen <jason(--nospam--at)wcaeng.com>
To: seaint <seaint(--nospam--at)seaint.org>
Sent: Tue, Sep 13, 2011 2:57 pm
Subject: ASCE 7-05 Section 12.2.3.2

Can anyone expand on the second sentence in this section?  It seems to mean 
nothing, considering the requirement of the first sentence.

12.2.3.2 R, Cd , and Ω0 Values for Horizontal Combinations.
Where a combination of different structural systems is utilized to
resist lateral forces in the same direction, the value of R used for
design in that direction shall not be greater than the least value
of R for any of the systems utilized in that direction. Resisting
elements are permitted to be designed using the least value of R for
the different structural systems found in each independent line of
resistance if the following three conditions are met: (1) Occupancy
Category I or II building, (2) two stories or less in height, and (3)
use of light-frame construction or flexible diaphragms. The value
of R used for design of diaphragms in such structures shall not be
greater than the least value for any of the systems utilized in that
same direction.

Maybe I am missing something, but it seems to say in the first sentence that you 
have to use the least R values (which makes sense), but the second sentence 
seems to be giving an exception if the three criteria are met, however it still 
states that the least R values is to be used. 

Any thoughts would be helpful.

Jason

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