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Re: Moment Footing w/ No Vert. Load

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Aaron,

In these cases you have to resist the moment using lateral reactions of the
soil, as Bill says, you have to use a flagpole footing. First you have to
determine how deep your pole will be introduced in the soil and then with
the reaction forces, design the reinforcement, if we are talking about a
concrete pole. You can use 50% of the modulus of subgrade reaction to model
horizontal springs representing the soil and run an iterative process in
order to find how deep you have to place the pole so the soil can resist the
loads in each spring, checking you don´t exceed the soil bearing capacity.
You run an analysis, then find which springs are in tension, eliminate them,
re run the analysis, re check and over, until no spring is in tension (soil
can only resist compression). Then you check the load in each spring, divide
it by the tributary area considered and check bearing pressures. If it goes
OK, then you have your resisting mechanism. Then you check the pole and
you´re done.

Hope this helps.

Walter


----- Original Message ----- 
From: "Bill Allen" <T.W.Allen(--nospam--at)cox.net>
To: <seaint(--nospam--at)seaint.org>
Sent: Tuesday, September 16, 2003 11:36 AM
Subject: RE: Moment Footing w/ No Vert. Load


> Aaron-
>
> Seems like the only vertical load you have is the weight of the footing.
> You need to satisfy equilibrium, i.e., summation of forces in the
> vertical direction = 0.
>
> Can't use a "flagpole" footing?
>
> Regards,
>
> T. William (Bill) Allen, S.E. (CA #2607)
> V/F (949) 248-8588
> San Juan Capistrano, CA
> http://members.cox.net/ballense/
>
> :-----Original Message-----
> :From: Aaron Moore [mailto:ae1188(--nospam--at)hotmail.com]
> :Sent: Tuesday, September 16, 2003 9:30 AM
> :To: seaint(--nospam--at)seaint.org
> :Subject: Moment Footing w/ No Vert. Load
> :
> :All the references I've seen for spread footings resisting moment use
> the
> :vertical load to calculate eccentricity.  I need to design a footing
> for a
> :post that will have a lateral load only (from a cable at the top).
> :
> :Can someone describe or give reference to a methodology for this case?
> I
> :plan on a rectangular footing with a pier.
> :
> :Thanks.
> :
> :_________________________________________________________________
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