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Re: Drilled pier cracks

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Rich:

It looks the bolts are failing.  We've done many towers and poles and have never used hooked anchor bolts.  The original calculations should provide you with the forces that the bolts are suppose to resist.  I always count on the surface of the embedded nut to resist pull out, using the cone section to transfer the anchor bolt loads over to the perimeter rebar circle.

First thing, which has already been suggested, is to provide some temporary guys and THEN do the fix, which will probably be redesigning the top of the pier and providing the repair procedures.  Depending on where you are, there are tower companies that can do this kind of work - such as temporarily supporting portions of the tower; concrete demo and replacement, etc.

If you are on the West Coast, Towers Structures, Inc. in Minden, Nevada, can do this.  


Neil Moore, S.E.
neil moore and associates

distressed structures investigations


---------- Original Message ----------------------------------
From: "Rich Lewis" <seaint02(--nospam--at)lewisengineering.com>
Reply-To: <seaint(--nospam--at)seaint.org>
Date:  Tue, 21 Jun 2005 14:18:14 -0500

>I was sent some pictures of a concrete drilled pier for a cell phone tower.
>The top of one of 3 piers is cracked.  The cracks radiate from the anchor
>bolt group.  There is a somewhat circular crack that surrounds the bolts and
>then about 8-12 cracks radiate out to the edge.  It appears the anchor bolts
>have been pulled up slightly.  I am told the top surface is out of level on
>this particular pier, with the crown in the middle.
>
> 
>
>I have a copy of some of the original calculations of the pier.  There are
>10-1" dia. Bolts per leg, 78" long.  The note says it is to have a 180
>degree bend.  I have never seen an anchor bolt with a 180 degree bend.  Is
>this common for this type of application?
>
> 
>
>In order to repair this I think I need to establish the extent of cracking
>and integrity of the pier.  Is there a reasonable way to establish this?  Is
>there an ultrasonic type test that can be run?  What kind of results would
>it tell me?  The pier is 6 ft. in diameter and 41 ft. deep.
>
> 
>
>Anyone ever run into a repair like this before?  Any suggestions on a fix?
>If I could establish that the pier was sound down a certain depth form the
>top I could request demolishing the bad section and repouring concrete if it
>wasn't too deep.  Another solution would be to drill 2 piers adjacent to
>this one and tie the existing leg into the new piers.  I would assume that
>taking the tower down is not an option right now.
>>
>Thanks for any suggestions.
>>
>Rich
> 

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