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Re: FOS forOvtg clarification

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     Yes, the 10 Kips vertical load and 3 Kips horizontal load will be both 
     overturning load.
     If you are generating a program to distinguish the two, I would 
     suggest you provide a menu for overturning loads and another for 
     stabilizing forces.
     I am a small time programmer myself and that's what I did until better 
     softwares came by and completely made my program severely simplistic.
     However, the basic concepts remain nonetheless.

______________________________ Reply Separator _________________________________
Subject: FOS forOvtg clarification
Author:  MIME7:MSSROLLO(--nospam--at) at INTERNET
Date:    6/26/98 3:27 AM

I have got several responses concerning the background of this problem (wind 
loading, type of fdtn etc) and would like to clarify this.  I really 
appreciate all the responses.
I am trying to find a consensus on whether the vertical load should be 
considered an overturning force or not.  For sake of this, I will say that the 
vertical load and horizontal load are actually a Dead Loads created by a 
cantilevered beam on a rigid frame.  So all loads are Dead loads.
The foundation is poured on top of the ground.  Therefor there is no passive 
soil pressure present.  Once there is somewhat of a consensus on this, I would 
like to change the problem a little, such as the force is a DEad and wind 
force and that the column is a little off-center.
For now though, I am concerned with a centered column with a 10k upward load 
induced by dead load.
#1.  Is the vertical force an overturning force?..and why/why not
#2.  What would be the correct calculation for FOS about the right toe as 
shown by the loading in my AutoBadd sketch.
I have included the original posting below.....Thanks again for the help...I am 
trying to fine tune a footing program that at least models what a consensus of 
experienced engineers beleive.  I was hoping this group would at least clear up 
whether the force is an overturning one or not and the correct calculation for 
the FOS.
 have a question regarding the correct factor of safety for overturning for a
foundation subjected to an uplift force.  For purposes of this discussion, 
assume I have a single footing with a horizontal force or 3 kips (to the 
right) and a upward vertical force of 10 kips, both applied at the center of 
the top of the footing.
Assume the footing is 15 kips in weight and is 8'x 6' x 2' thick. Pardon the 
phony graphics, I am using AutoBadd.
            ^ 10k
     ------> 3k
     |             |
     |             | 2'
     |             |
1.	In calculating the FS for overturning, is it correct to call the 10k load 
an overturning load?  The load is at the center of the foundation and does not 
actually induce any overturning except if you do statics about a toe.  The 
load itself actually does not cause overturning.  Even statics claims that is 
overturns about both sides simultaneously.  I realize that the footing weight 
is always a stabilzing force in both directions of rotation.
2.	Assuming you do think it should be included as an overturning force, would 
the correct calcualtion be Movtg = 3x2 + 10x4 = 46 and Mstab= 15x4 = 60, 
therefore FS = 1.304   OR is the correct one: Movt = 3x2=6 and Mstab= 
(15-10)x4=20  FS = 20/6 = 3.333.  By definition, it would appear that the 1.3 
answer is correct and that algebraically adding common forces is not 
3.	Assuming you do not think the load is an overturning load, what if I move 
it off center to the right 1".  What is the magnitude of moment to attribute 
to overturning of the right side?
Thanks for any help on this..