ACI 318-19 Section 17.10 - 17.10.5.3a

[oengineer]

I am looking at 17.10.5.3a & I had some questions about iii., iv., & v. Could someone provide some insight about these subsections of 17.10.5.3a?

It seems to me that 17.10.5.3a part vi. is referring to using the adjacent vertical rebar to help resist the tensile forces. Could anyone please provide clarity on iii., iv., & v.?

Comments/suggestions are appreciated

 

[ANE91]

Not sure why your other post got locked.

(iii): Ductility is defined in ACI 318, and the definition is conceptually no different than what we learned in Mechanics of Materials. Refer to Table 2 of ESR-3814, for example, and also to the attached.

(iv): For example, if your fixture is stood above the concrete by a nut, then the anchor could buckle in compression. A sleeve or channel may provide adequate confinement so as to preclude buckling, and the added advantage of this solution is the provided stretch length, when detailed properly.

(v): Makes sure that the anchor yields in the unthreaded portion of the stretch length instead of in the threads. I’ve always been told that this is due to concerns of premature fracture in the threaded portion, but I’m not certain that’s the complete reason.

 

[oengineer]

Not sure why your other post got locked.

(iii): Ductility is defined in ACI 318, and the definition is conceptually no different than what we learned in Mechanics of Materials. Refer to Table 2 of ESR-3814, for example, and also to the attached.

(iv): For example, if your fixture is stood above the concrete by a nut, then the anchor could buckle in compression. A sleeve or channel may provide adequate confinement so as to preclude buckling, and the added advantage of this solution is the provided stretch length, when detailed properly.

(v): Makes sure that the anchor yields in the unthreaded portion of the stretch length instead of in the threads. I’ve always been told that this is due to concerns of premature fracture in the threaded portion, but I’m not certain that’s the complete re

Thank you for the explanation.

I am still not clear on (iii). It seems like the code is asking for one to do a check for the anchor bolt while using an additional ductile
steel element to help resist tensile loads:

(iii) Anchors shall transmit tensile loads via a ductile
steel element with a stretch length of at least 8da unless
otherwise determined by analysis.

 

[ANE91]

It’s not an additional or separate element. An anchorage comprises a fixture, a substrate, and either a mechanical anchor (355.2) or adhesive anchor (355.4). The steel element is what’s relevant. It could be proprietary; it could have a mandrel on the bottom (e.g., wedge anchor). Or it could simply be a threaded rod inserted into epoxy. Adhesive anchor encompasses two components — the steel element as well as the epoxy. The intent of the code is that whatever steel steel element you’re using must be sufficiently ductile.

Colloquial usage between the terms “anchor bolt” and “anchor” and “rod and epoxy” muddy the water. The code could be better about this, imo.