Diaphragm evaluation

[Fr109]

HI! I need some tips on how to handle lateral soil loads (15 kips x 1.7 per lineal ft? at base only) on a 2 story concrete cold storage building approx 75 x 100' with 3 interior shear walls -- to be built into an embankment, buried on 3 sides. Back wall is 30 ft deep,(possibly on bedrock) bottom floor 13 ft tall & top floor is 16. Is it feasable for the walls & poured-in-place floors to resist. How much axial load can a 30'x 30' plain concrete slab-on-grade handle, or the upper floor designed for 400 psf... or do I have to think about buttresses.

Any help will be greatly appreciated.!

 

[civilperson]

The slab must be reinforced to keep the thickness to an economical size. 30 feet of bury for 120 pcf soil with at rest soil lateral loads are near 54 kip/ft horizontal shear loading at base. Use simple beam design for vertical walls, (postpone backfill till floors and roof are complete), and brace the horizontal dimension with interior walls or pilasters/buttresses. First run through gives me minimum wall thickness with 15 foot horizontal span of 18". Horizontal shear on the soil/slab interface can be resisted with a shear key into the rock/soil.

 

[msquared48]

I don't know what your geotech report says, if you have one, but sometimes the lateral soil load will increase to a certain depth and not increase after that. What does your getoech say?

Mike McCann
MMC Engineering

 

[Fr109]

Thanks for the replys!
I don't have a geotech report but was using a soil program which gives me 32 kip/ft for the total wall... not conservative enough? The embankment is cut back at 45° starting a few feet from the base, so the pressure will be mainly from the sandy backfill.

Does someone have any hints to where I can find on the web some guidelines or a program to help check the floors acting as diaphragms?

 

[msquared48]

Fr109:

NO. My implication was that the pressure you have shown at the base may be too much...

Mike McCann
MMC Engineering