One R for the entire structure? 1

[Adamian]

I need an advise on using one R for the roof level, another for north and south directions.
Is there a provision about this? I am designing a two story light frame building that has a 40' long steel beam providing the required turning space in the garage. If R=3 is used for the entire structure, there are not enough shearwalls at the roof level. Can I use R=6.5 for the roof level only? How about using different Rs for each level and direction?
Project site is in Los Angeles area. Any help is appreciated!

 

[JAE]

For a static analysis, in any one direction, you must use a single R for the entire height of the building unless you use the two-stage method prescribed in the IBC (or CBC as applicable).

 

[Adamian]

Thank you JAE!
I see it in ASCE 7-06 12.2.3.1 EXEPTIONS:
Section 12.2.3 Combination of Framing Systems in the Same Direction. answers other part of my questions.