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RE: Cracked Concrete?

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I attended an adhesive anchor seminar and they taught how critical it was to prepare the hole exactly as instructed.  “Blow, brush, blow”.  If you “Brush, blow, brush”, you won’t get the same adhesion.

 

And we use these things in life-threatening situations?

 

From: Harold Sprague [mailto:spraguehope(--nospam--at)hotmail.com]
Sent: Thursday, February 25, 2010 12:42 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Cracked Concrete?

 

Steve,
It was not on purpose.  I really can't talk about it, but to let it serve as a caution to me and others.  As you may guess, they do not use a 1" bolt with a 10" embed to hold a picture of a favorite uncle. 
 
"There are no secrets to success.  It is the result of preparation, hard work, and learning from failure" - Colin Powell
 
The corollary to this is that it is cheaper to learn from OTHER peoples mistakes. 

Regards, Harold Sprague


 


Date: Thu, 25 Feb 2010 11:47:21 -0800
From: sgordin(--nospam--at)sgeconsulting.com
To: seaint(--nospam--at)seaint.org
Subject: Re: Cracked Concrete?

Harold,

I wonder how this construction marvel was detected. 
Thanks,

--
Steve Gordin SE
Irvine CA



Harold Sprague wrote:

Sitting under my desk as I write this is an epoxy all thread bolt 1" diameter with 10" embedment.  It pulled out from concrete under a static load that was markedly lower than advertised.  There was no cone because there was little bond to the concrete.  The epoxy bonded well to the all thread.  The problem was the prep of the concrete.  I am very cautious when it comes to epoxy bolts. 
 
I would agree that it should be considered cracked unless otherwise proved. 
 
Always look at the ESR's and make them part of the special inspection. 

Regards, Harold Sprague


 


Date: Tue, 23 Feb 2010 21:10:02 -0800
From: sgordin(--nospam--at)sgeconsulting.com
To: seaint(--nospam--at)seaint.org
Subject: Re: Cracked Concrete?

Tim,

Cracked concrete needs to be considered "in the region of concrete where analysis indicates cracking at service load levels" (ACI 318-05 D.6.2.7).  In other words, for example, when it can be shown by rational analysis that stresses in the foundation will not exceed the tension resistance of non-reinforced concrete, concrete may be considered non-cracked. 

I design a lot of epoxy anchors, and did some research on the issue.  Based on my conversations with HILTI and Simpson, there are no recorded cases of the seismic failure of the epoxy anchor bolts - even those designed/installed 20 years ago.  Without "bodies", and with the code giving us clear guidance  - why over-design? 

IMO, the engineer needs to either demonstrate that the section is not cracked, or to use the cracked concrete properties.  
 

--
Steve Gordin SE
Irvine CA

 



Tim Rudolph wrote:

Hi,

I am looking at a submittal to replace 16 misplaced anchor bolts for a 38 ft diameter 16 ft tall bolted steel water tank in Seismic demand D area Old Zone 4 . The engineer submitted a epoxy anchorage of a 3/4" all thread rod with a 6" embedment for a 4500 lb tension only load in a grade beam 18"wide 24" deep with #5 stirrups @ 18"oc and 6 # 5 long bars inside the stirrups around the ring. (there are 26 of the 3/4" dia anchor bolts @ 4'7" oc spacing around the grade beam)  They called out for the Simpson SET-EP epoxy and they used the anchor system calc software.  now the question - The engineer did not select that the concrete was cracked.   Should I consider this foundation grade beam an element that requires a cracked section anchor solution?

 

Thanks

Tim Rudolph PE

 


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