Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Re: High Mast Light Pole Anchor Bolts

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Rich,
 
        The impression I get from reading the article you referenced is that anchor bolts and grout (although possibly contributing factor) are not likely to be the major cause of the failure.  reading this article I get the following impressions:
 
1.)  I have never heard of "Wind Hammer" but I have heard of wind induced vibrations, generally resulting from vortex shedding which could cause resonance with some of the natural frequencies of the poles.  I expect that this could be one of the major contributing factors.  As it happens, I once had to deal with 8" diameter engine exhausts that were in resonance with a 15 mile per hour wind but were rock steady with 50 mile per hour wind.  ASME have a standard dealing with welded steel stacks which includes the effects of vortex shedding and damping.  There is also a Canadian standard but you are probably not interested in that.
 
2.) The report photographs appear to indicate that the failure is in the area of the weld connection to the base plate.  I don't pretend to be a welding expert; but Chris Wright is; and he monitors and contributes to this list.  I am quite interested in reading what he has to say on this topic.  As an aside, they do make similar connections as this in the piping industry where they frequently connect light walled pipe to thick flanges; you might find some useful information in that industry.
 
3.) It would seem to me that you should have a national standard for these "poles".  Perhaps ASME, or AASHTO, or somewhere in the electrical industry.  Perhaps some of your cities or public utilities will have standards for streetlights, etc. that may give you some guidance.
 
        Be very careful about this one, Rich.  It looks to me like it has "LAWSUIT" written all over it!!
 
Regards,
 
H. Daryl Richardson
----- Original Message -----
From: Rich Lewis
Sent: Monday, May 04, 2009 4:21 PM
Subject: 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