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Re: Foundation bearing pressure per 1997 UBC

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You get the increase gradually by 20 percent for every foot of embedment. By the
time you reach the 6000 psf, you footing depth will be awefully deep. And if  I
have to have such a high soil bearing capacity, I would pursue to get a soils
investigation report done.

Chris Tse, SE
San Jose, CA

"Sherman, William" wrote:

> I was looking at the 1997 UBC for prescriptive bearing pressures when
> specific soil's test data is not available. Table 18-I-A shows a 1500 psf
> allowable bearing pressure for sand, which seems reasonably conservative.
> But then I looked at footnote 2 and saw that this is based on a 12-inch wide
> and 12-inch deep footing and the allowable bearing pressure can be increased
> up to 3 times the tabulated value for deeper and wider footings. Also a
> one-third increase can be taken for wind load design. Using these
> provisions, the allowable bearing pressure becomes 1500 X 3 X 1.33 = 6000
> psf. This seems excessively high to use without specific soil's test data
> but the code seems to allow it. Am I missing something here??
>
> William C. Sherman
> Camp Dresser & McKee, Inc.
> Denver, CO
> Phone: 303-298-1311
> Fax: 303-293-8236
> email: shermanwc(--nospam--at)cdm.com
>
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