Soil Perscriptive Bearing Capacity
Soil Perscriptive Bearing Capacity
(OP)
I routinely design foundations based upon the provision in the 2006 IBC for perscriptive bearing capacity based upon soil profile. Typically this ends up being on the low end at 15oo psf.
I have always used this as gross bearing capacity simply because I cannot find anything in the code that would allow this to be considered "net". By net, I mean being able to neglect the weight of the foundation itself.
The frost depth in the area varies between 3' and 4'. The columns are wood, so we do not want them to be in contact with the soil. A 4' deep footing weighs 600 psf, and essentially uses 40% of the bearing capacity self weight.
Does anyone know if the code allows for the use of net bearing capacity as I described above?
I have always used this as gross bearing capacity simply because I cannot find anything in the code that would allow this to be considered "net". By net, I mean being able to neglect the weight of the foundation itself.
The frost depth in the area varies between 3' and 4'. The columns are wood, so we do not want them to be in contact with the soil. A 4' deep footing weighs 600 psf, and essentially uses 40% of the bearing capacity self weight.
Does anyone know if the code allows for the use of net bearing capacity as I described above?






RE: Soil Perscriptive Bearing Capacity
* Geotechnical reports almost always give the net allowable bearing pressure
* 1500 psf (or 2000 psf, for that matter), are conservative allowable bearing pressure values, compared to what you get when you have a geotechnical investigation done
* If 1500 psf is GROSS allowable bearing pressure, any soil deeper than about 12' below grade could not even carry the weight of the soil above.
DaveAtkins
RE: Soil Perscriptive Bearing Capacity
RE: Soil Perscriptive Bearing Capacity
Garth Dreger PE
AZ Phoenix area
RE: Soil Perscriptive Bearing Capacity
Garth Dreger PE
AZ Phoenix area
RE: Soil Perscriptive Bearing Capacity
RE: Soil Perscriptive Bearing Capacity
RE: Soil Perscriptive Bearing Capacity
RE: Soil Perscriptive Bearing Capacity
You could consider using a spread footing with a pier, no?
Of course, the soil overburden still adds weight.