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Re: High Mast Light Pole Anchor Bolts

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Daryl,

Thank you for your response, and the others who have responded.

I don't think the anchor bolt problem I encountered is related to the light
pole failures as listed in the article.  I believe I stumbled onto a
problem unrelated to my initial request to inspect poles for the Whitco
failure.  

My concern for this situation is whether I can count on the existing anchor
bolts to function adequately.  I would assume the bolts have been subject
to a "pounding" type force as it rocks on the base.  I'm researching right
now what that does to the bolt anchorage and strength. I wondering if a
test can be performed on the bolts to see if they  are now loose in there
setting in the pier.  Also, someone mentioned elongation of the bolt.  I
don't know what type of bolt was used.  I don't have copies of the original
design.  Reflecting back to my study of bolted connections, I recall that
minor yielding of the steel doesn't affect the overall strength of the
bolt.  My concern is whether or not the buried end still has adequate
anchorage.  Also, if the bolts have more than minor yielding then the
strength could be affected.  I'm discussing possible testing procedures
over with a testing agency.

The more I think this over the more I'm convinced I need to recommend the
pole be lifted out of place and regrouted.  My thinking is to lift the pole
up and place 4 steel shim packs below the base plate.  Reset the pole in
place and pack the base with non-shrink grout.  After the grout has set the
bolts can be tightened.  The next question to answer is how tight the nuts
should be.  Should I request an impact hammer tightness or snug tight? 
Since the nuts and bolts are galvanized a hand snug tight probably is not
adequate.  An air impact wrench will give me a tighter fit, but what should
be the cutoff?

I would appreciate any further insight or comments that may be given.

Rich



On Mon, 4 May 2009 18:21:04 -0600, "Daryl Richardson"
<h.d.richardson(--nospam--at)shaw.ca> wrote:
> 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 
>   To: seaint(--nospam--at)seaint.org 
>   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

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