CSA A23.3-14 D.6 Clarification

[EngDM]

Recently when running an epoxy rebar anchor for tension in Hilti I came across a procedure in their design calcs that appear to be pretty ambiguos with the code. When calculating steel resistance of an anchor in tension, Hilti refers to equation D.2 which Nsar = Ase * phi_s*f_uta*R. The sentence below this in the annex D puts f_uta as being equal to 1.9*f_ya, however Hilti appears to take the f_uta from the G30.18 rebar standard. Logically this makes sense to do, but I am curious as to why that decision was made when the code does not explicitly indicate to do that. If I were to run this check by hand, I would not be given any instruction to go find this information and would likely just apply 1.9*f_ya. Further, Hilti treats R as 0.7, treating rebar as a brittle steel element. In contrast, Simpson Anchor takes R as 0.8; rebar as a ductile steel element.

The inconsistency behind the design calculations is making me wonder if they are just overly conservative. Perhaps someone here has pondered this in the past.

 

[WinelandV]

I'm looking at Chapter 17 of the ACI 318-14 => 17.4.1.2 states:

f_uta shall not be taken greater than the smaller of 1.9*f_ya and 125,000psi

Then looking at the commentary:

The limitation of 1.9*f_ya on f_uta is to ensure that, under service load conditions, the anchor does not exceed f_ya. ... Although not a concern for standard structural steel anchors (maximum value of futa/fya is 1.6 for ASTM A307), the limitation is applicable to some stainless steels.

I think you should always be using the actual f_uta for your anchor design, and then verifying that it doesn't exceed either of those limits.

American, not Canadian (I am assuming you're Canadian), your code may vary, standard disclaimer, yadda yadda...

Please note that is a "v" (as in Violin) not a "y".