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CivilEQuinn (Civil/Environmental)
9 Nov 06 7:31
Hi all, What is the rule of thumb in choosing to use either an epoxy anchoring system or a wedge anchor?  In my limited experence it appears wedge anchor would be used in overhead or vertical situations and epoxy anchors on horizontal applications.  This is for air diffuser supports (low pullout forces) within a waste water channel (12 ft deep).
Thanks
Helpful Member!  DaveAtkins (Structural)
9 Nov 06 7:50
I use adhesive anchors in situations where a mechanical anchor cannot be used, because it is too close to the edge of the concrete.  Otherwise, they have similar values.

DaveAtkins

Helpful Member!  miecz (Structural)
9 Nov 06 8:47
Besides close edge distance situations, I use chemical anchors for vibratory situations like machinery hold downs.  Otherwise, it's mechanical.
RARWOOD (Structural)
9 Nov 06 9:16
Another option is Simpson's Titen HD anchors.
UcfSE (Structural)
9 Nov 06 11:19
It's a toss-up.  I prefer epoxy anchors because it's too easy to drill a bad hole and totally mess up the capacity of the wedge anchor where a slightly oversized hole for epoxy wouldn't hurt as much.  The con is getting the epoxy hole cleaned properly.  I think if you ask for special inspection you'll have done the best you can.
jt12 (Structural)
9 Nov 06 13:26
I don't know if it's still the case, but 6 years ago or so, the epoxy (or other non-epoxy adhesive anchors) typically had undergone better testing and had their paperwork more in line that they would be accepted by a building official.  I personally try to avoid using wedge anchors unless loads are small and vibration isn't a concern.  
jhoulette (Structural)
9 Nov 06 18:17
For wedge anchors you have to be careful if you are working in cracked concrete.  I'm not positive but I think Hilti is one of the few (if only) manufacture to address this case for the new codes.  I prefer epoxy, ran into too many oversized holes when workingwith wedge anchors.
samdamon (Structural)
9 Nov 06 18:50
If you expect to be installing the anchors in the cold  (Its getting to be winter now), if using chemical adhesive make sure it can still cure at lower temps.  Usual lower bound limit is about 40 deg F.  I don't think any mech anchors have a temperature limit during install.

If you expect to have high temps during service life of the  anchor, if using adhesive, suggest using a higher SF because depending on the mfgr the adhesive can lose strength and stiffness over time when heated.  Mfgrs catalog should tell you more.

If you have moisture or water in the holding substrate, also be especially careful if specifying an adhesive anchor.  Some of the adhesives out there are sensitive to moisture, others actually need it present to cure.

As other posters have noted, I usually do not use a mechanical anchor if its holding something that vibrates, because the anchor can be rocked loose over time and lose holding power.



Tomfh (Structural)
9 Nov 06 20:36
I hate wedge anchors. Half the time they are crooked, or the hole is too big, or the sleeve protrudes, or something or other.
DaveAtkins (Structural)
10 Nov 06 8:42
I also use adhesive anchors when attaching structural elements to a fire wall.  I have been told the epoxy melts in a fire, allowing the structure to collapse without pulling the fire wall down.

DaveAtkins

FSS (Structural)
10 Nov 06 16:55
Go to either Simpson Strong-Tie or Hilti websites.  They will explain all kinds of info for you on these subjects.
KCRatnayake (Structural)
11 Nov 06 10:39
You generally cannot use Epoxy anchors in tensile zone of concrete. Some wedge anchors also not goon in tensile zone. Hilti has developed a chemical anchor (Hybrid type)that can be used in tensile zone.
dik (Structural)
11 Nov 06 11:13
You might want to check some info on the Big Dig Collapse... see thread 507-159632.  This has a lot of discussion about using epoxy anchors for pull-out and some of the issues to watch for.

Dik

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