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RE: Pole Foundations

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Neil,

Well, in my opinion this program in spread sheet should be useful. You'll appreciate, the calculation of wind moments at the base is quite a tedious exercise; you tend to make mistakes also, if you are attemting to do it by first principle.

Also, you have to start with an assumed size of footing which you will establish thru preliminary calculations. Once you have established the wind moments, the actual task of satisfying the stability requirements begin. The initial assumed size of footing may not work, so you have to revise the size of footing & begin those steps all over again. And, it might take a couple of trials before you really settle down with a size that actually satisfies the stability requirements. Manual calculation would become tedious while the program would help you with as many trials as are required to fix a final size of the footing.

And, once the size of the footing is established, the design of spread footing is a child's work, really.

SYED FAIZ AHMAD; MENGG, MASCE
SENIOR STRUCTURAL ENGINEER
SAUDI OGER LTD
RIYADH, SAUDI ARABIA.



From: Neil Moore <nmoore(--nospam--at)innercite.com>
Reply-To: <seaint(--nospam--at)seaint.org>
To: <seaint(--nospam--at)seaint.org>
Subject: RE: Pole Foundations
Date: Sun, 09 Dec 2001 08:00:22 -0800

Dennis:

A plan checker will kick back your design if you leave the pole forces out.
 Some poles can be up to 86" in diameter, depending on the architect and
the structural requirements.  Example Problem 10 on page 161 of the Wind
Commentary to the Uniform Building Code published by the Structural
Engineers Association of Washington (1991) provides an example.

For the guy who didn't know how to design a pier footing, page 166 of this
example provides guidance.

Sign poles can also be designed by the Standard Specifications for
Structural Supports for Highway Signs, Liminaires and Traffic Signals
(1994) published by AASHTO.

As you said, the spreadsheet doesn't design the pole size or the footing.
Apparently the spreadsheet just provides some lateral forces and an
overturning force for the signs only.  I don't know what Enercalc has to
offer, but most of us who do pole structures always integrate an automatic
design of the pole portion into our spreadsheet or program.


Neil Moore, S.E.
neil moore and associates
consulting structural engineers
shingle springs, california



At 04:12 PM 12/8/2001 -0800, you wrote:
>If you are an Excel user, there is a spreadsheet that will calculate the
>moment in the pole due to the wind applied to the sign area. It follows
>each of the steps in the basic logic that Syed indicates below with a
>couple of exceptions:
>1. The spreadsheet allows for up to three signs to be placed on one
>pole.
>2. The spreadsheet calculates the height of the signs above the base to
>determine the wind load applied. In other words, if the sign lies
>between two regions where the wind load changes then the area of that
>sign section is broken into two and the wind pressure is applied to each
>area above and below the line.
>3. The wind on the pole is neglected in this spreadsheet. I suppose it
>can be argued that the pressure against the area of the pole is
>significant and it would be if the area of the sign is quite small.
>4. The moment is calculated due to each sign segment so that the
>designer may change the pole section as the moment increases or
>decreases.
>5. The pole and foundation is not designed in the spreadhsheet - this is
>left to another spreadsheet or one of the commercial programs such as
>Enercalc. However, if someone is ambitious and would like to improve the
>spreadsheet, you are welcome to do so.
>
>The spreadsheet is available on The Structuralist.Net Professional
>Discussion forum 'Cybrary' in the Spreadsheet Template forum. The
>Pole-sign spreadsheet is available along with nearly 20 other
>spreadsheets available for download at:
>
>http://www.structuralist.net/cgi-local/yabb/YaBB.cgi?board=Spread_Tplts
>
>Enjoy!
>
>Dennis S. Wish, PE
>California Professional Engineer
>Administrator - The Structuralist.Net
>Website:
>http://www.structuralist.net
>
>Professional Forum:
>http://www.structuralist.net/cgi-local/yabb/YaBB.cgi
>
>Public Forum on Housing:
>http://www.structuralist.net/cgi-local/yabb2/YaBB.cgi
>
>
>-----Original Message-----
>From: syed faiz ahmad [mailto:syedfaiz23(--nospam--at)hotmail.com]
>Sent: Saturday, December 08, 2001 12:26 PM
>To: seaint(--nospam--at)seaint.org
>Subject: Re: Pole Foundations
>
>Randy,
>
>You have to do it by first principle; its simple.
>
>For such a height wind will govern. You have to proceed as follows:
>
>
>  -  establish wind pressure; use ASCE manual
>     for the purpose.
>
>  -  from the given geometry of the luminaire,
>     establish C.G of the luminaire; for all
>     practical purposes the center of the
>     luminaire should be its C.G.(CENTER OF
>     GRAVITY).
>
>  -  establish the C.G of the light pole
>     itself; use simple mathematics to do
>     that.
>
>  -  the next step is to determine the
>     surface area of the luminaire & the
>     light poles;that is the surface exposed to the
>     wind.
>
>  -  apply the wind pressure to the surface
>     areas to establish the wind loads.
>
>  - apply these wind loads to the C.G of both
>    the luminaire & the light poles; multiply
>    the wind load with the lever arm to
>    determine the wind moments at the base of
>    the pole.
>
>  - after determining the wind moments, make
>    stability checks; that is checks to
>    satisfy:
>
>         -  stability against overturning
>         -  stability against sliding
>
>  - the contributions for the stabilising
>    moments would come from:
>
>         -  dead weight of the footing
>         -  soil overburden weight
>         -  passive resistance from the soil.
>
>  - the size of the footing should however be
>    first established through vertical
>    reactions divided by the bearing capacity;
>    however, the size would ultimately have
>    to be such as to satisfy the stability
>    requirements.
>
>Hope that helps. Regards,
>
>SYED FAIZ AHMAD; MENGG, MASCE
>SENIOR STRUCTURAL ENGINEER
>SAUDI OGER LTD
>RIYADH, SAUDI ARABIA.
>
>
>
>>From: Randy Diviney <rsdiviney(--nospam--at)hayeslarge.com>
>>Reply-To: <seaint(--nospam--at)seaint.org>
>>To: seaint(--nospam--at)seaint.org
>>Subject: Pole Foundations
>>Date: Tue, 04 Dec 2001 15:27:54 -0500
>>
>><< attach1 >>
>
>
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