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Re: Footing design for uplift

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Jorge, you must have a lot more geotechs than we do and owners far more willing to spend money on soil work. 45 degrees is easy to calculate and doesn't rely on soil properties which are approximate at best. For slabs, I use the 45 degree number and if that doesn't work I might try yield line. Usually I just add more concrete - it's cheap. I can add at least 8000-10,000lbs of uplift resistance to a building for what an hour of my time costs.


Jimenez, Jorge A. wrote:
In the 'Structural Engineering Handbook', Gaylord & Gaylord, 3rd Edition
there are a discussion about this issue. The text gives a formula that
have the soil angle for internal friction and coefficient for lateral
pressure, among other variables.

Jorge Jimenez, PE

-----Original Message-----
From: Javier Encinas [mailto:jencinas(--nospam--at)] Sent: Thursday, January 11, 2007 9:17 PM
To: seaint(--nospam--at)
Subject: Footing design for uplift

Sometimes in hurricane-prone zones the controling load in footing design
uplift. However, the text books are silent about methods to estimate the
selfweight to counteract the uplift force. In addition of the concrete
footing we have also the soil cover and the slab on grade. What angle of
cone is appropriate (45 degrees?), and what is the tributary area of the
slab that helps to keep the footing in place? Any good reference on the
subject, or full scale tests? Thanks in advance,

Javier Encinas, PE

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