Shear Transfer at stacking wood structural panel shear walls

[andr3w44]

Hello
I'm checking capacities of floor diaphragms and at a point where I have some stacking shear walls I'm wondering if the shear loads from the upper shear wall would transfer to the lower wall through nailing and blocking (SEE DETAILS 1 AND 4 OFF ATTACHED,) or would I still need to account for those loads acting on the diaphragm? I figured i would definitely need to for shear transfer at offsetting and cantilevered walls. If regardless I account for these loads on the diaphragm, would I used the load values from the upper wall or the lower wall(which are higher)?

Another quick side question, for shear walls attached to the foundation(stem wall), would the stem wall need to maintain the same height throughout the length of the shear wall? Or could it step up at some point within the length of the shear wall? Would this then turn it into two separate shear walls?
Thanks for the help and any input.

 

[jayrod12]

Nailing and blocking camp for me. Provided the connections between walls above, blocking, and walls below are adequate. That being said, I never let them splice the sheathing at the floor plate. Some guys call me difficult but to me, it's a significantly better detail to have the splice at least 12" above the bottom plate or 12" below the top plates.

When I have a stepped stem wall I treat each step like a separate segment.

 

[Mjkkb2]

It will transfer via nails and blocking. If you design for the whole shear load to transfer then no need to include the diaphragm. You would only have the diaphragm load from this floor that would need to get into the shear wall below (again via blocking). In real life the shear from above will be split in some fashion between the blocking and the diaphragm. A portion of it will "leave" into the diaphragm and distribute to other shear walls based on stiffness of the plywood and shear walls panels (length, height, location) etc...AS long as you provide an adequate load path then 'keeping' the shear from the stacked wall in the wall is the simplest way to take it down to foundation.