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[FSRahbar(--nospam--at)aol.com]

I am checking a Metal-Structure building. It is similar to a Butler Building 
where there are no bearing walls and beams and columns support the entire 
roof.

The building is long and narrow, therefore, the seismic loads in the narrow 
direction is somewhat comparable with wind loads. The lateral resisting 
elements in narrow direction are two sets of 3/4" diameter rod cross bracing. 
Obviously the rods only work in tension and not compression. The engineer for 
the building has used a "R" Value of 5.6 to determine the seismic loads. This 
"R" value is taken from Table 16-N, Building Frame System, Item 4, Ordinary 
Braced Frames with Steel.

My questions are: Is "R" Value of 5.6 correct for this steel rod cross 
bracing? Is the ordinary Brace Frame consist vertical truss and the members 
can take both tension and compression?

It was my opinion that since the rod cross bracing system is not really 
defined in Table 16-N, the closest system would be item 1-3 with tension only 
brace with "R" Value of 2.8.

I appreciate it someone can try to clear this.

F. S. Rahbar SE