Seismic Response Modification Factor - 2-story wood home w/daylight basement

[CBSE]

Just out of curiosity, what do most people use for the R-value for the situations where you have (2) stories of wood walls above concrete retaining walls on (3) sides and wood on the front of the daylight basement?

 

[CBSE]

Bump:

I'm debating with a friend over this issue and the argument is whether or not to use R=6.5 or R=4.0. Just want an opinion from this forum as there is usually a lot of help here.

Thanks.

 

[manstrom]

6.5

Don't penalize the wood. If you really want to, you could do a two stage analysis.

 

[KootK]

If you've got a daylight basement, then two of the concrete sides have steeply sloping grades, right? If so, I'd take your seismic base to be the basement floor elevation and treat your building as a three story structure. You're probably already doing this.

Because of the stiffness difference between the wood and concrete shear walls, I'd be concerned that the basement will tend to act as a three sided system. Consequently, I vote for the use of a conservative R value.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[racookpe1978]

Poured concrete retaining walls with rebar and cross-ties at the two corners?
Or CME that is not strongly linked together at the corners with anything but the mortar?

reason I ask is the " full height" of the front wall and the two side walls are actually two stories, right?

 

[CBSE]

I'm treating it as 3 stories: 2 wood framed stories above a daylight basement. Basement has 3 sides that are full height concrete and the front is wood.

I'm torn between 6.5 and 4 at this point.