Hillside base level diaphragm

[HofOblivion]

I have a project where hillside ordinance is applied. One side of the building is fully day-lighted (T.O. soil and T.O.S. at the same elevation) and the other side is retaining soil up to 8'-0" height. I cannot determine if the I have to assume the base level diaphragm at the roof level (at 10'-0" above the T.O.S.) or at the slab as the building cuts into the (E) soil. Which is the correct way to design this building?

 

[msquared48]

As you probably have concrete walls on three sides, I would take the base at the 8 foot high floor diaphragm level for forces normal to the slope.

In the other direction parallel to the slope, I would take the base at the slab. You will need wood shear walls at the day lighted wall of the basement.

Mike McCann, PE, SE (WA)