Just done a calc of foundation anchor bolts using hilti online software. The hilti bolt capacities (based on combined cone pull out) appear much higher than the Ec code capacity (based on bond stress between anchor an concrete). Is the hilti software reliable?. Been looking at previous discussions on this issue on the forum . Got mixed views. Any advise please?
RE: is hilti anchor bolts capacity software reliable?
I agree that Hilti is very helpful, you should be able to address any concerns with them.
A couple of findings from my limited experience:
I have checked their anchor bolt (epoxy and mechanical) capacities to my hand checks using ACI Appendiz D, and there were situations where they were using higher modification factors yielding a higher capacity than what I had calculated. I was able to reconcile this with the fact, that ACI states that other values may be used if certain tests have been completed. Hilti does a very good job of testing their products, and you can contact them if you would like these reports as I did.
As far as how the loads are distributed to the anchor bolts, Hilti assumes a perfectly rigid baseplate. This is fine for most cases, but I have had to deal with some unique/high load cases in which I needed to model my baseplate in FEA in order to determine the loads on the anchor bolts.
RE: is hilti anchor bolts capacity software reliable?
I've found the Hilti software to be very reliable. To be honest, whenever we've found an issue, it's wound up being about our not understanding the inputs and underlying theory well enough. I've used the attached document to aid in my understanding of the Profis methodology. No doubt Hilti has other documents that could address your particular issues.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
@jayrod12, I have set up a meet with Hilti to discuss my concerns. It appears that the general consensus is that the Hilti method is reliable provided the inputs are correct. Thats the re assurance I needed. I have also specified a pullout test load on of 3% of the total number just in case. Using proof stress of 1.1 x ULS load, saw that in the anchor bolt guidance. @andriver, It would be good to get a correlation between using the FEA to the assumption of perfectly rigid plate, is it 10%?. I have some workmanship issues with the contractor so would probably allow some generous safety margin anyway.
@msquared48, What is the Simpson?
@KootK thanks for the attached document, does clarify the Hilti elastic theory for anchor bolts, very well explained. I do have a spreadsheet for combined bending and axial force for columns so will tweak the spreadsheet with the hilti approach to see to if I can replicate the Hilti software output.
thank you all!
RE: is hilti anchor bolts capacity software reliable?
it's wound up being about our not understanding the inputs and underlying theory well enough.
I fully agree here. A lot of engineer were badly applying correction factors such as edge factor using table when calculating resistance manually.
The result is when using the software, resistance of often so much lower than (wrongly) expected.
Note that the LRFD transition to anchorage bring lower resistance to some failure mode.
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RE: is hilti anchor bolts capacity software reliable?
Hilti's tech department is fantastic at helping out. Talk to them, express your concern and see what they have to say about that.
RE: is hilti anchor bolts capacity software reliable?
A couple of findings from my limited experience:
I have checked their anchor bolt (epoxy and mechanical) capacities to my hand checks using ACI Appendiz D, and there were situations where they were using higher modification factors yielding a higher capacity than what I had calculated. I was able to reconcile this with the fact, that ACI states that other values may be used if certain tests have been completed. Hilti does a very good job of testing their products, and you can contact them if you would like these reports as I did.
As far as how the loads are distributed to the anchor bolts, Hilti assumes a perfectly rigid baseplate. This is fine for most cases, but I have had to deal with some unique/high load cases in which I needed to model my baseplate in FEA in order to determine the loads on the anchor bolts.
RE: is hilti anchor bolts capacity software reliable?
Mike McCann, PE, SE (WA)
RE: is hilti anchor bolts capacity software reliable?
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: is hilti anchor bolts capacity software reliable?
@msquared48, What is the Simpson?
@KootK thanks for the attached document, does clarify the Hilti elastic theory for anchor bolts, very well explained. I do have a spreadsheet for combined bending and axial force for columns so will tweak the spreadsheet with the hilti approach to see to if I can replicate the Hilti software output.
thank you all!
RE: is hilti anchor bolts capacity software reliable?
I fully agree here. A lot of engineer were badly applying correction factors such as edge factor using table when calculating resistance manually.
The result is when using the software, resistance of often so much lower than (wrongly) expected.
Note that the LRFD transition to anchorage bring lower resistance to some failure mode.