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Re: big dig structural failure - epoxy anchors overhead supporting gravity

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Great photo, Steve.

The bolts w/ epoxy look pretty small in diameter!

Hole prep & concrete condition have an enormous effect on pullot loads.

A number of years ago I  tested 100's of "chemical" anchors (cyclic loading protocol & cyclic loading to failure).  Hole prep was meticulous!

FYI  the Hilti hole cleaning method is brush, blow, brush.  Which I found to be counter intuitive (but ultimately correct).

Being a rather curious fellow, did some holes where I used a "better"  (I thought) cleaning sequence

brush, blow, brush, blow

this method resulted in very large reductions of pullout load

My hypothosis was that a "final blow" coated the hole with fine dust that acted as a release agent, where as, a final brush mechanically removed the dust thus exposing "clean" concrete to the epoxy.

If the bolts in the Big Dig installation were undersized to ease installation or hole prep was skimped on..............

cheers
Bob

On 7/14/06, Gerard Madden, SE <gmse4603(--nospam--at)gmail.com> wrote:
Look at those 4 dinky bolts MAYBE 6" long total holding a thick WT with huge clevis.... no wonder.

-g


On 7/14/06, Paul Feather < PFeather(--nospam--at)se-solutions.net> wrote:

Looks like the entire epoxy plug pulled clean with inadequate bond to the concrete, not the bolts pulling clean without epoxy on them.


From: S. Gordin [mailto:mailbox(--nospam--at)sgeconsulting.com ]
Sent: Friday, July 14, 2006 11:56 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: big dig structural failure - epoxy anchors overhead supporting gravity

 

Paul,

 

This is exactly how it looks.

 

 

Steve Gordin SE
Irvine CA

----- Original Message -----

Sent: Friday, July 14, 2006 9:10 AM

Subject: RE: big dig structural failure - epoxy anchors overhead supporting gravity

 

<...> If the report is that the epoxy bolts pulled "clean out", it is most likely the holes were not properly cleaned of drill dust and latent material and the entire piece separated cleanly, bolt with epoxy and all. 

 




--
-gm