Seismic Force Resisting System to determine "R"

[Deadblow]

All,

Per ASCE 7-05, Table 12.2-1, how would you classify the seismic force resisting system of this wood framed building? I am trying to determine the response modification coefficient, R, to calculate the seismic response coefficient. FYI, wind will probably control my lateral analysis for the location of this site.

The posts are 4.25"x5.25" at 4'-0" o.c. and are braced with 2x6s on the interior and 2x4 girts on the exterior. The girts are fully sheathed with 1/2" APA rated plywood.

Thanks for your input. Please see the attachment in my next post.

EIT

 

[Deadblow]

Here is the attachment for the previous post.

EIT

 

[JAE]

H.

You don't have a bearing wall braced with sheathing, shear panels, or flat strap bracing (i.e. metal straps).



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[JAE]

Forgot to say - with H you have R = 3

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[Deadblow]

JAE,

Thank you for such a quick response. Doesn't "H" only apply to "steel systems"?

EIT

 

[JAE]

Well, technically yes - the only thing I see otherwise would be this language found in that section:

I'm not aware of any "analytical and test data" for pole barns, though.



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[Wallache]

I would use R=1.5, from cantilever columns systems - timber frames.

 

[JAE]

Otherwise - perhaps the building gets designed elastically (R=1)? I'm not sure here what I'd do with that kind of building.

If you look at the AWC SDPWS 2015, section 4.3.7.6, they refer to "Shear Walls: Diagonally Sheathed with Single-Layer of Lumber..."
So in the SDPWS, the term "sheathed" can mean either a panel (i.e. plywood or OSB) or in this 4.3.7.6 section - a single lumber of 1" thick minimum.

So with that - you could then perhaps argue that you could enter the ASCE 7-05 table 12.2-1 using A.13 with an R = 6.5. I'd have to research that a bit to make sure I wouldn't have to use A.14 with R = 2.



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[JAE]

Read the commentary to the SDPWS - C4.3 as well as they discuss the use and stiffness of walls with diagonal "sheathing".

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