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RE: Braced Steel Frame System Question

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I am not sure where you are located or what seismic zone you are in but if
you are in a zone 3 or 4 I would recommend the following:

1. The condition you describe in question 1 is a weak story.  This condition
is not allowed in buildings over two stories in height and when it is
allowed it is with some special rules. However, these types of structures
have performed very poorly in past seismic events and if this is a new
building I would not design this type of structure. 

2.In regards to flat bars I believe the code criteria of 720/Sqrt(Fy)is a
requirement for all bracing.  Personally I would not use flat bar bracing. I
have seen this bracing fail in much smaller lighter structures and do not
feel it would be appropriate for a three story structure of this size, and
as Daryl said installation in a tension state is critical to its
performance.  




Mark Harper SE
HDR Architecture