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Re: High Mast Light Pole Anchor Bolts

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Rich,

I have seen freeway light standards without grout, just nuts above and below the base plate, and it always makes me nervous.  I personally would remove or jack up the poles, remove the existing grout, add couplers to extend the anchor bolts, put in 3/4 to 1 inch of very good non-shrink grout, reset the pole, snug tight the nut (as in AISC snug tight), then put on a second lock nut (which could be a half height jamb nut).

If you are looking for similar reference material you might look at the NAAMM, Guide Specification (or Manual) for Design of Metal Flagpoles, or ASCE, Design of Steel Transmission Pole Structures.

Thomas Hunt, S.E.
Fluor




"Rich Lewis" <seaint04(--nospam--at)lewisengineering.com>
05/04/2009 03:21 PM
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High Mast Light Pole Anchor Bolts





I’ve been asked to inspect several school high mast light poles due to a rash of failures.  Here is a link to an article about the failures:
http://www.statesman.com/search/content/news/stories/local/04/12/0412lightpoles.html
 
It seems the failures have been linked to one manufacturer, Whitco Co LLP poles.
 
While doing an inspection last week I ran across a problem not associated with the pole failure in question.  At one of the high mat lights all but one of the anchor bolts was loose on one high mast light pole.  I could wiggle the washers around.  I couldn’t wiggle the bolt, but I could wiggle the washer.  The bolts are 1.25” diameter.  In addition, the grout pad below the base plate was broken into pieces.  The grout pad was very thin, perhaps 0.25” thick.  The base plate is probably about 26” in diameter.
 
I need to recommend a repair for this condition.  What I’m wondering is what would be wrong with the following procedure:
1.       Tighten the nuts up on the base plate.
2.       Pressure inject grout below the base plate.
 
I have thought of the following concerns:
1.       Should the bolts be snug tight or pre-tensioned.  I do not know anything about the original design.  The bolts are galvanized.
2.       What if the bolts have loosened at the base?  Is it possible to do some testing to determine if the bolts are still bonded to the concrete or if they have deformed somehow at the embedded base of the bolts and don’t have adequate anchorage?
3.       Can I pressure inject such a small gap on such a large base plate and be assured the grout has adequately filled below the base plate.  The base plate is 2” thick.
4.       Should the pole be lifted up first before grouting below the base plate, or just fill in the thin gap as exists below the plate.  If I required lifting the pole first and installing a new grout pad then I could get a thicker grout pad below the base plate.  Obviously lifting the pole requires bringing cranes out to lift the pole.
 
I’m guessing some of you that have experience with large highway mast poles can give me some insight on this issue.  I would appreciate any help you could give.
 
Thanks in advance.
 
Rich
 
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