Lateral loads for walk out basement

[jeffhed]

I am working on a 2 story 45'x28'detached garage with basement walls with full retaining on 3 of the 4 sides. The upper floor is living space and the lower floor is garage. Wing walls are running off of each side so that the 'walkout' 4th side can have the garage doors. In the past on walk out structures, I usually only have retaining around the back and partway down each side. In those instances the lateral loads obviously need to be figured as a 2 story structure at the walkout portion. However, on this particular project, since the full retaining is on three sides, do I just have to transfer the upper story shear down through the first story, like a full basement, or should I still calculate lateral loads as if it is a 2 story structure? With this being the face of the building where the garage doors are located, the load calculation is critical since there is very limited wall segments that can be utilized for shear walls.

 

[csd72]

I would expect that you would have soil pressures that need to be taken care of down to basement level.

 

[jeffhed]

Yes. The soil load will be there from the reaction at the top of the basement wall, but there will not be any lateral load (wind or seismic) that must be transferred down besides the lateral loads from the top story. (No lateral loads from the floor level diaphragm since it is in the soil). My question is is the soil lateral load the only load that will come from the floor level? It seems to me that the soil on all sides will constrain the structure in a seismic event sufficiently to where I would not have to add any loads beyond the loads from the concrete wall design. Just wanted to post this to see if others are thinking along the same lines as me.

 

[bylar]

This issue has been discussed several times before

 

[Lion06]

Is the garage a slab on grade with a single, occupied level above and then a roof above that with soil up to the first occupied level? You will definitely have wind on the first floor (only half a story of wind, but wind nonetheless). As far as seismic forces are concerned, the load can still act in the direction of the open end. In that case you have the lateral load from soil, the lateral load from the seismic acceleration acting on the building mass, and I would argue additional seismic force from the retained soil.

 

[anchorengineer]

Can you post a sketch?

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