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Telephone pole loading

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Subject: Telephone pole loading
From: (Stan Griffiths)
Date: Wed, 4 Dec 1996 22:43:14 -0800 (PST)
>Howdy all,
>Any CE/ME's (or others having them) have experience with phone poles
>70+ feet tall?

I had one that was 94 feet out of the ground in Canoga Park, CA in the mid
'60s.  Only had a TH6 and a 402BA on it so it was pretty lightly loaded.  It
was 110 feet long overall.  22 inches diameter at the butt and about 9
inches at the top if I remember right.  Weighed about 4500 pounds!!

>Wind loading capacity...

I never knew how to calculate that and I never worried about it with just
the two antennas I had on it.  I am more conservative now and I would do
more research and be more careful.  That is what age does to you.  I was in
my late 20s then and I'm in my late 50s now.

>Antenna mounting considerations, both atop and along the pole...

I used a set of crossarms at the top for a thrust bearing and a second set
of crossarms about 8 feet below the top for a second thrust bearing and a
prop pitch with selsyns.

>Cement embedment typically required at base?

I had a pole 48 feet out of the ground in the mid '50s when I was in high
school and living with my parents.  It was a fir pole cut from the local
woods near our house near Portland, OR.  It was not treated.  I set this one
in cement and it lasted about 5 years.  We replaced it with another
untreated fir pole scrounged from the woods that was 58 feet out of the
ground and it lasted for about 10 years and was set in soil, no concrete.
Someone gave some excellent advice and told me to look and see how the
telephone company and power company set their poles--virtually never in
concrete unless they have to set it into a sidewalk or something like that.
Their poles last a LOT longer than 10 years, but I think it has a lot to do
with the creosote (?) they treat them with to prevent rot plus the fact that
they avoid wood contacting concrete.  Have you ever seen fence posts set in
concrete rot off at the base?  They do, all the time.

>Other tidbits...

I have heard that a freestanding pole should be set in the ground to 10
percent of its total length plus 1 foot.  This would have meant 12 feet for
my 110 footer but I set it down 16 feet just to be safe.

The 48 footer was set down 7 feet (total length 55 feet) and I think the 58
footer was also set 7 feet (total length 65 feet).

I had one set of guys on all of these poles but I was told many times that
was overkill.  The guys were about 80 percent of the way up.

>Application is mountain top location, no frozen soil but it is crappy:
>  1000 PSF vertical, and 100 PSF lateral

Never did any soil analysis so you know more than I do about that.

Good luck with this project OM.


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