ASCE 7 Seismic Calcuations

[SteelPE]

Attached you will find a simplified sketch of what my question is:

I’m trying to figure out what I would use for W in equation 12.8-1 of a two story building (ASCE7-05). Case 1 has the foundation wall on 3 of the 4 sides. Case 2 has the foundation wall on 2 of the 4 sides. I am trying to figure out if I am supposed to add the W of the floor into the overall calculation for the building.

H=the average roof height of the structure with respect to the base.
Base = the level at which the horizontal seismic ground motions are considered to be imparted to the structure.

So would I consider the floor W in the calculation of V for both case 1 and 2? It almost appears as if I would not include the W load for case 1 but would need to for Case 2, but I am not sure.

 

[pete600]

W = weight is total seismic weight of the building including floors & interior/exterior walls

ASCE 7-5 provides the following definitions:

BASE: The level at which the horizontal seismic ground motions are considered to be imparted to the structure.

BASE SHEAR: Total design lateral force or shear at the base.

V = C_s W = Base Shear

Based on these definitions, I would consider the base the lowest exterior grade (Each direction can be considered separately).

If the floor is at or below grade on a direction, then you should be able to ignore it.

If the floor above grade on a direction, then it must be considered.

Note:
snow load, equipment, and storage loads may also need to be considered as per 12.7.2.

 

[SteelPE]

I was leaning the same way you are.

My floor load is 250 psf so there is going to be a huge increase in W for this load (need to take 25% of this plus the weight of the slab). I plan to have steel bracing on the open sides and I want to make sure I design this bracing (and the foundation under the bracing) properly.

 

[pete600]

250 psf is significant dead load.

What about the seismic weight of the soil on the high side of the structure when one side is higher then the other?

Should this be included in the base shear as well?