huangyhg

post-installed anchors
i have a general question for everyone regarding post-installed anchors. we just had a brief discussion at my office regarding this, but i wanted to get others opinions.
when designing post installed anchors, do you generally use the capcaities provided in the hilti/powers manual or do you follow apendix d of aci 318?
it was mentioned in the discussion this morning that the hilti/powers manuals are vastly under-conservative when compared with values obtained using appendix d of aci 318. hilti apparently has software called profus (i think i spelled that correctly), which takes appendix d into account when arriving at capacities.
i have used the capacities in the manuals and applied my own factor of safety, usually around 10 (depending on the application) for critical components.
how do all of you approach this?
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from what i have learned over the past 5 years using the appendix d - formerly in another document, the values from hilti, simpson, etc. cannot be compared directly. i have always used the manufacturer test values if available. i know simpson and i think hilti have a couple of anchors that can be used in cracked concrete.
when using appendix d, you have to use the coefficients that the manufacturers give you, but there aren't too many anchors out there that fall into this category.
i use appendix d, for anchor bolts and headed studs. i use the manufacturer catalogs/programs for the others.
from a presentation i attended last month, simpson, and i assume hilti, are preparing new editions of their product reports for use with aci 318-05.
with the appendix d design model, you must consider cracked concrete in most cases. as such, only a few post installed anchors are acceptable for use.
simpson has seminars to help explain (the guy in ga really does provide a non biased technical presentation), aci has seminars and so on. it really does seem to be a big step from what has been the status quo.
expect some changes.
good luck!
daniel
for manufactured post-installed anchors, i use the test report values that is adopted by the jurisdiction. traditionally, the code shear and tensile capacities for embedded anchors were much smaller than the test report allowable values for post-installed anchors with comparable diameter and embedment. though i haven't used appendix d enough to get the "feel", i anticipate similar.
i agree with rgerk to use appendix d for embedded bolts and test report values for proprietary post installed anchors (expansion anchor, adhesive anchor, shot-pin, screw anchor, etc).
be aware that if you use icc reports (icbo reports) for manufactures values, as of january 1st of 2007, all icc reports for mechanical anchors that are not approved for the new criteria of aci 318 app. d have been canceled and deleted. check
am i the only one who notices a huge difference in anchor embeddment requirements when comparing an epoxy anchor to a cast-in anchor. we've had a recent project where the contractor wanted to change from a 1 1/4" epoxy anchor (power-fast by powers) with 15" embed to a cast in anchor. i calculated that they'd need to replace it with a 1 1/4" j-bolt with a 32" embeddment. not sure if appendix d is just more conservative or if epoxy anchors are just that much stronger.
j-bolts now have much less tension load compared to headed studs or a rod with a nut on the end. recalculate with a headed stud using app. d and your answer will be much more reasonable. i would estimate that j bolts are about 1/4 of the tensile load of a headed stud using the new calculation method.
are j-bolts really as poor as the formulas suggest?
i used euro standards. there's one annex dedicated to post-installed anchors. i.e. etag annex b. hilti has published capacities according to the test procedures given by the eota - european organization for technical approvals.
in profis also, there's one option is to design using etag.
for a 1-1/4 anchorbolt, a 20" headed bolt should develop the capacity of the bolt...
dik
the story goes like this straight from the mouths of the fastener manufactures and the guys as aci.
to use the proprietary post-installed fasteners such as hilti or simpson, the post-installed fasteners have to be qualified under a testing procedure which is stated in aci 318 appendix d. there were problems with the original testing procedure in aci 318-02. none of the manufacturers tested any on their products because they did not want to waste their time and money, therefore none of their porducts were qualified to use in aci 318-02. aci has since revised the testing procedures for post-installed anchors and anchor manufacuturers have started testing their anchors to qualify them for use in aci 318-05. the manufacturer has to test the anchors and submit design information for the anchors. as of today, hilti has several anchor qualified for appendix d and simpson has a couple. i am unaware of any others. the new hilti 2006 catalog has the design values for use in aci 318-05 appendix d for their anchor which are qualified. contact hilti or simpson representatives. i have a good relation with the hilti rep in pittsburgh and he is very helpful. i have an entire design binder from them.

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