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fema 356 v. SEAOC Blue Book re: CBF effective length

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Hello,

Where were the proponents of the SEAOC Blue Book position 
during the FEMA 356 committee discussions that led to the 
requirement that "for common cross bracing configurations where 
both braces cross at their midpoints and attach to a common 
gusset plate, the effective length of each brace shall be taken as 
0.5 times the total length of the brace **for both axes** of 
buckling."  (FEMA 356 paragraph 5.6.2.3.2)

This FEMA requirement is at odds with the Blue Book position 
described on page 237, wherein it is suggested that, for out-of-
plane buckling, the total length of the continuous brace be used 
when checking lower bound capacity vs. the max compression 
demand.    (The half-length is to be used to determine upper bound 
strength, as for connection design.)

Two questions: 

1. Why did the "use-the-half-length-for-out-of-plane buckling" 
position prevail in the presumably-state-of-the-art FEMA 356?  

2. As the Blue Book notes, there are many studies on the out-of-
plane behaviour of x-bracing with two flexurally continuous braces, 
and I have a nice collection of them, but can anyone provide 
references to literature that    specifically   addresses out-of-plane 
effective lengths of x-bracing with one continuous brace and one 
flexurally-discontinuous brace,  connected by a common gusset at 
the bracing mid-point?

Thanks,

Dave Evans, P.E.
TNH, Inc.  

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