Hilti Profis Problem?

[MacGruber22]

I am using Hilti Profis Anchor 2.4.9 with ACI 318-11 strength design. I think that Profis may be incorrectly limiting concrete breakout capacity of cast-in-place anchors. For ACI 318-11 design, Profis limits the embedment to 25” regardless of the thickness of the member. However, according to the ACI 318-11, this limitation does not exist anymore - I guess because test data *is* available. I have upgraded Profis to the latest version, but no change.

ACI 318-08 also imposed a 25 in. (635 mm) limitation on the anchor embedment depth for the calculation of concrete breakout strength using the provisions of appendix D. This limitation was effectively removed by section 1908.1.10 of the 2009 IBC. ACI 318-11 does not have this limitation anymore.

 

[UcfSE]

Did you submit your inquiry to your local Hilti engineer?

 

[MacGruber22]

Yes I did. Of course it is December 24th, so....yeah

 

[MacGruber22]

IBC 2009 permitted ACI equation D-7 with h_ef^1.5 can be used for embedment depths deeper than 25". It seems Profis has defaulted to equation D-8 and limited headed anchors to 25" embedment. Normally, this isn't a problem, but I have heavy moment frame bases with Mu = 520 k-ft and Pu (uplift) = 51 kips. Trying to keep anchors as close as possible to minimize base plate thickness.

 

[TehMightyEngineer]

Have you tried an alternative to hilti's software such as Simpson or Powers? I use powers' software myself.

Maine Professional and Structural Engineer.
(Just passed the 16-hour SE exam, woohoo!)

 

[MacGruber22]

Not yet, but I will when I get a chance.

 

[ztengguy]

Did you check the answer by hand?

 

[dcarr82775]

Just do it by hand, would have had the answer weeks ago.

 

[MacGruber22]

I did check them by hand, and as I suggested, the only difference I see is between equations D-7 and D-8.

It may not really be an error by Profis, but a limitation they chose to keep so people don't go crazy with embeddment depths.

 

[dcarr82775]

By the time you get to 25", wouldn't it be easier to just lap with rebar and throw App D provisions away?

 

[MacGruber22]

dcarr - yes! That is what I wanted to do, but the contractor didn't want to lower (thicken) the footings in order for me to develop those bars. Since then, I was able to come up with a configuration with embedded plates at the anchor rod head which sufficiently increased the breakout projected area.

 

[slickdeals]

There is an update to the AC308 document that the epxoy adhesive manufacturers are testing to. Basically, it will let you use ACI Chapter 12 development length equations to epoxied anchors and not have to go through Appendix D. It makes a lot of sense, since the behavior of these bars is quite different from a headed anchor in concrete. I had a very lengthy discussion with a Simpson rep and their SET-XP adhesive will meet the requirements this year.

http://shop.iccsafe.org/ac308-post-...-elements-approved-may-2014-pdf-download.html

 

[MacGruber22]

Thanks, slickdeals!