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ACI 318-11 Appendix D allowable modes of failure

ACI 318-11 Appendix D allowable modes of failure

ACI 318-11 Appendix D allowable modes of failure

(OP)
I have designed the foundations and piers for a PEMB. ACI 318-11 15.8.3.3 states "Anchor bolts and mechanical connections shall be designed to reach their design strength before anchorage failure or failure of surrounding concrete. Anchor bolts shall be designed in accordance with Appendix D." I take this to mean that the anchor bolt strength needs to be the controlling strength in my pier designs. Correct?

But when I look at Table D.4.1.1, I see that the required strength of concrete breakout in tension shall be larger than the total factored tensile force applied to the anchor group. I would think it should require the concrete breakout in tension to be larger than the steel strength in tension.

Summary of results:
Factored uplift = 17k
Steel Strength of Anchors = 62k
Concrete Breakout = 18k (governs)
Pull-out = 104k
Side face blowout = 190k

Does appendix D allow the concrete breakout strength to be the limiting mode of failure?

Thanks!

RE: ACI 318-11 Appendix D allowable modes of failure

For low seismic applications, you do not need to have a ductile failure, so your concrete can fail first. In moderate to high seismic applications, the goal is to create a ductile failure of the rod before it breaks out of the concrete. This can be challenging for some cases, so often you will see plate washers and heavy hex nuts tack welded to the end of a threaded F1554 rod. There's a good thread going around about the validity of this method.

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