Trusting Appendix D of ACI

How many others out there have serious doubts about the validity of ACI’s anchorage system (Appendix D)? I think that much of it is based on research and good theories, but there are parts that appear so far out of any intuitive common sense that I find myself continually questioning results, either by hand calcs or by something like Hilti Profis. Most common are the “concrete edge break-out” results which seem to always control the designs - despite adding huge edge distances to a problem.

With this lack of intuitive rationality in App. D results, I find myself wanting to blow it off as inaccurate and sometimes “go my own way” with an anchorage scheme that Profis tells me is failing.

Anyone else suffer from “App D sucks syndrome”?

Yeah it seems they did some really specific test cases and ran out of funding and decided what they had was good enough, if not overly conservative, to put out in the open to start dictating anchor design.

My biggest complaint is that every test they performed to come up with the equations was done in an unreinforced block of concrete, per ACI plain concrete really isn’t even allowed anymore so in my mind they should have at least followed their own recommendations and put in temperature and shrinkage reinforcement and perhaps (2)#4 or #5 edge bars that most of us are detailing anyway.

Your example of huge edge distances for the edge break out is spot on, once you enter any number for the edge distance that allowable value tanks really quickly.

Personally, I have used hairpins with metal buildings for years to avoid breakout - an industry standard.

Regarding the edge #4 or #5 bars at the edge of a slab, I do not feel that they help to resist breakout unless the transverse bars are tied in with end hooks.

I am not familiar with the Hilti Profus program, as I use Simpson Anchor Designer. If I remember correctly, the Simpson program does have an allowance for the presence of edge bars, and a provision to ignore the breakout failure mode with proper detailing present as described above.

I am not privy to the test results leading to Appendix D, but have found some of the imbedment depths to be ridiculous in my opinion. Depending on the choice of anchor type, too, the depth will be affected, as well the pass/ fail scenario.