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Re: Braced Frame Question

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Chris Palmateer Wrote:

>I'm curious how others are designing the connections for their chevron 
>braced frames.  Specifically, with regard to UBC Section 2211.8.3.1, I would 
>be curious at how other engineers interpret item 3.  I have always designed 
>these connections for item 2 and another engineer in our office is trying to 
>convince me that this is too conservative.  His position is that per 
>2211.8.4.1 the brace itself is only designed for 1.5 times the *seismic* 
>forces (gravity loads not included), so this is the maximum force that can 
>be transferred to the system.  Well, how does everyone else read/interpret 
>the code?
>Chris Palmateer

The method that your co-worker is using to design the brace connection is 
incorrect.  His assumption that the maximum force the brace can take is only 
1.5 times the code level force is incorrect. The braces can usually take much 
more (and usually will have to) force than 1.5 * code level force.  The 1.5 
factor is intended to account for the unbalanced load sharing between the 
tension and compression brace in the chevron configuration.  Most engineers I 
know use method #2.  Be careful in determining what the maximum force that can 
be delivered to the system for method # 3.

Good Luck!
Lanny Flynn