Anchor Rod Embedment when using Anchor Rod Reinforcing

[StressedandStrained]

Per ACI 318-14 Fig R17.4.2.9 you are allowed to use rebar to resist concrete break out. Say you have a 20" footing and are using U shape anchor bars to resist concrete break out and your Ldh and Ld both equal 10". Would you make your anchor rod embedment 10" so you had 10" for Ldh above and 10" for Ld below? To answer my own question, yes, that makes sense. My next question: Would it be unconservative to extend the anchor rod embedment to the bottom of footing = 20"? My gut tells me a deeper embedment is better but my brain tells me I need to force the breakout plane to have enough Ldh/Ld above and below. Does anyone have any back up to support one direction or the other? (I understand that my example uses unrealistic numbers and does not account for cover or slope of breakout plane as it passes the anchor reinforcing but just wanted to keep it simple)

Thanks

 

[ATSE]

Confirming your answer to your 2nd question: Deeper embedment is always better, and there is no code penalty.

 

[dik]

Generally, but not when it comes to wasting resources. I suspect there is a limit.

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

-Dik

 

[skewl]

If you extend l_dh to 20", wouldn't that mean your l_d = 0" and your anchor reinforcement no longer qualify as having enough development? So you have to use concrete breakout strength instead of anchor reinforcement strength. Your concrete breakout strength may be higher than the anchor reinforcement strength due to a larger breakout cone.