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Re: [SEAOC] Tiltup Retrofit Anchors

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>>Dennis Wish PE wrote:
>>I concur with Tom Honles assessment of expansion anchors, although the 
>>Tilt-up committee had taken a position on "under-cut" anchors and felt 
>>that these would be perferable to expansion anchors. The Under-cut 
>>anchor, though, requires a special bit since the end of the hole is 
>>widened (bell shaped) to gain a greater hold with less tension against 
>>the sides. 
>>I perfer, and always have - especially with retrofit into poorer grades 
>>of concrete - to use the Hilti Hit anchor system with their C-100 epoxy 
>>adhesive for solid based materials. Covert Anchor uses a similar 
>>adhesive as does a typical SAE 1018 threaded rod and the Simpson 
>>"Epoxy-Tie" adhesive system.
>>Hope this helps.
>        I have found recently that DSA/SSS and OSHPD do not allow this type
>of epoxy attachment system due to a lack of "long-term durability testing".
>We were forced to go to sleeve and/or expansion anchors on recent hospital
>jobs because of that "lack" of testing.
>        I'd be curious if anyone else ran into similar design challenges.
>                - Terry Weatherby

My experience with them on this topic is:

Don't use sleeve or drilled anchors for situations with cyclic loading such
as earthquake loads.  Don't use epoxy because there are no long term
testing.  (If they would have started it 30 years ago when I first strarted
engineering they would have the long term tests).

What they do accept, and what I use, is high strength, non-shrink, quick set
grout.  I have used this for many years with success.  On school projects,
testing is requied, 10% of them as I recall unless one fails then you test
them all.  I can recall very few situations where they failed.  We just
finished a large school renovation where thousands were used.  Only a couple
failed.  The failures were more from the concrete at edges of members
failing rather than the rebar or bolt into the grout.


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