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RE: Spread Footing for tower

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I do not see any reason this wouldn't work, as long as the allowable bearing pressure is not exceeded and the factor of safety of overturning and sliding are satisfied. 

I have seen many engineers limit the compression under the footing to various percentages (like 75% or 80%) of the footing area. 

When I have an isolated footing with moment, I generally try to use a rectangular footing to limit rotation.

Don't forget that we are calculating a theoretical soil pressure which is actually concave or convex depending upon whether it is clay or sand. All this has an affect on settlement.

Be conservative!

Jim K.

-----Original Message-----
From: Landon K. Anderson [mailto:landon(--nospam--at)oddogws.com]
Sent: Wednesday, May 11, 2005 12:36 PM
To: seaint(--nospam--at)seaint.org
Subject: Spread Footing for tower


For design of a footing with overturning moment, is it acceptable to
design for an eccentricity outside the kern as long as 50% of the
footing is in bearing? Overturning factors of safety of greater than 1.5
would also be satisfied. I typically use this for criteria for
foundation systems but was just thinking it through for the case of an
isolated non redundant footing.   

Landon Anderson
office: 970-945-1006
home: 970-984-3949
email: landon(--nospam--at)oddogws.com



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