Hilit Profis - Rigid plate analysis sc not checked against ACI Max Bearing 4

[Celt83]

This may not be news to some folks but doing some back checking of Hilti Profis I found that the rigid analysis performed by the free version allows σc to go beyond the code maximum bearing stress with out tripping any user warnings. Since they don't design the base plate you'd probably catch this during that design but I know some folks may be using these free tools as a quick way to get anchor forces.

My Personal Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

Open Source Structural GitHub Group:

https://github.com/open-struct-engineer

 

[KootK]

Unfortunately, that is news to me.

Since they don't design the base plate you'd probably catch this during that design

I wouldn't count on it. If the concrete bearing stress is out of whack, that pretty much invalidates the plat / anchor configuration, does it not.

Thanks for the PSA.

 

[Celt83]

If the concrete bearing stress is out of whack, that pretty much invalidates the plat / anchor configuration, does it not.

yep, but my hunch is they are expecting that you designed the base plate prior to jumping into their software and are just using it to do the anchorage checks. So if you designed the plate ahead of time then the geometry should have alreay limited the bearing stress and Hilti's bearing and anchor tensions should match your external design within a few percent. It's looking like their FEM option does check this so you have the option to turn that on if your a paying customer or still within the demo period.

My Personal Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

Open Source Structural GitHub Group:

https://github.com/open-struct-engineer

 

[Celt83]

Hilti Check OK:

Hilti Compressive Stress > 0.65*.85*f'c*2 = 4972.5 psi:

Hand Check of Rigid Plate Analysis close agreement with Hilti, I use the density based Ec formula and maybe a higher decimal place on the bolt tension area:

Upsizing the plate so the hand check works:

Same in Hilti, again close agreement on the stress and anchor tension values:

My Personal Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

Open Source Structural GitHub Group:

https://github.com/open-struct-engineer

 

[Settingsun]

Does it trigger a fail if you increase the load further? The number you showed was less than 5% over at the peak. Could they be using a less simplified model to account for the varying stress? Quite possibly not in free software, but a thought.

 

[dik]

That's what I've always done just because I've always done it that way... but, didn't realise there could be a problem if I didn't... Thanks for the heads up.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Celt83]

steveh49:
nope, interestingly enough if I pump the axial load another 60 kips in that example problem it reports a better utilization ratio but the compressive stress is now nearly 3,000 psi above the allowable. I'm almost certain they are doing a simple triangular stress distribution and maintaining strain compatibility between the plate bearing and anchor tensions.

My Personal Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

Open Source Structural GitHub Group:

https://github.com/open-struct-engineer

 

[Celt83]

My biggest gripe with this is that the pressure is only reported in the detailed pdf report, which isn't the default report setting, if they were to display the bearing stress in the user interface along with the anchor utilization ratios it would be much less of an issue even still without warning the user. Ideally they add the pressure to the web interface and also make it green, yellow, red for below, at, or above the allowable bearing stress.

My Personal Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

Open Source Structural GitHub Group:

https://github.com/open-struct-engineer