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Interesting result with anchor design 1

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ReverenceEng

Structural
Feb 18, 2016
81
Often times we will use Hilti profis or Simpson designer to get values on their respective products. However, I am seeing some funny results that I don't know how to interpret when evaluating a base plate dumping a moment into anchors as with a sign or light post.

Basically, as we increase embedment, the D/C goes down as there is more resistance to tensile breakout and pullout.However, once we cross a "depth threshold" (my name for t - this is what I cant figure out), the tensile breakout capacity starts to climb, often to over capacity. How is it that 8" of embedment works great, but 24" works way worse? I don't get it. What do I not understand?

I can contact Simpson for advice, but if there is some mechanism I am not familiar with, I figure you all might know!
 
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The spacing factor is likely screwing you. You're running into a situation where now the breakout cones are overlapping.
 
When you look at the development of the equations, much has to do with edge distances etc. And edge distances are generally about the ratio of the edge distance to the effective embedment depth on the anchors. As you go super deep, that ratio gets super small and things go off the rails numerically with regard to our real world, rational expectaions. That's partly why, in your other related thread, I recommended abandoning the appendix D stuff in favor of a reinforced concrete methodology. The appendix D provisions were developed around shallow anchoring technologies and get a bit wonky for deeper embedments like this.

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.
 
>>>That's partly why, in your other related thread, I recommended abandoning the appendix D stuff in favor of a reinforced concrete methodology.<<<

Any chance I could get a link to that thread? I tried the search feature but was unable to find it.
 
Welcome x2. Rationally, I don't see that one would have to accept a deep embedment capacity that was actually less than the max shallow capacity that could be obtained.

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.
 
As you go super deep, that ratio gets super small and things go off the rails numerically with regard to our real world, rational expectaions.

I totally agree with this assertion and thus my feelings towards Appendix D:

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Ok, now I have another question for a link: this time the one required to buy that shirt![2thumbsup]
 
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