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RE: Overturning check

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Martin

I believe your assumption that the allowable soil pressures would insure a
given factor of safety is based on a continious foundation under a wall or
braced frame where there is a triangular stress distribution in the soil.  

Alternately you could have a braced frame with a rectangular spread footing
under the column at each end.  In this configuration you would assume a
uniform soil stress distribution which could be consistent with a 1.0 FS
against overturning.

It is interesting to note that the 1967 UBC has a J factor which is used to
reduce the overturning moment.



Mark Gilligan


++++++++++++++++++++++++++++++++++++++++++
Message text written by INTERNET:seaint(--nospam--at)seaint.org
>Several people mentioned that an overturning ratio of 1.0 would be ok. 
The code
has no specifiec number, however, from a practical standpoint, 1.0 can
never be
used because the soil pressure would equal infinity at a ratio of 1.0. 
Normal
checks for the maximum soil pressure (including the 1/3 increase commenly
taken
for seismic) tend to limit the overturning ratio to the range of around
1.5.

regards,
Martin
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