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Allowable Bearing Pressure - Should loads be factored?

Allowable Bearing Pressure - Should loads be factored?

Allowable Bearing Pressure - Should loads be factored?

(OP)
The geotech has provided an allowable bearing pressure of 2000psf. Because the provided pressure is allowable, I'd like to confirm that my loads (live, dead, hydrostatic, etc.) should not be factored?

RE: Allowable Bearing Pressure - Should loads be factored?

that's correct as far as I've always interpreted the word allowable.

RE: Allowable Bearing Pressure - Should loads be factored?

Yes, bearing pressure for footings is almost always done at allowable levels, so use ASD load combinations. The footing design itself is almost always done at ultimate levels, using LRFD load combinations.

RE: Allowable Bearing Pressure - Should loads be factored?

For service limit states (bearing, sliding, overturning) use ASD, unfactored loads. For strength limit states use LRFD, factored loads. Pay attention to whether your allowable bearing pressure is net or gross.

RE: Allowable Bearing Pressure - Should loads be factored?

(OP)
Thank you everyone.

Motorcity: What is the difference between net and gross allowable bearing pressure?

RE: Allowable Bearing Pressure - Should loads be factored?

Quote (StructureMan44)

What is the difference between net and gross allowable bearing pressure?

Oh, now you've done it. :P

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
www.americanconcrete.com

RE: Allowable Bearing Pressure - Should loads be factored?

Kidding; allowable and net soil pressure is one of those things that everyone asks about at least once in their engineering career. Kinda like LRFD vs ASD.

Here's a reasonably quick and easy to understand explanation of net vs allowable: https://risa.com/news/gross-and-net-soil-pressures...

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
www.americanconcrete.com

RE: Allowable Bearing Pressure - Should loads be factored?

(OP)
In order to provide the gross soil pressure wouldn't the geotechnical engineer need to know (or make an assumption) about the applied load?

RE: Allowable Bearing Pressure - Should loads be factored?

To provide the gross soil pressure (a load) they would, to provide the allowable gross soil pressure (capacity) they do not.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
www.americanconcrete.com

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