ACI 318 Chapter 17 Clarification

[CaliEng]

Hello,
Seeking a bit of clarification in Chapter 17 of ACI 318-14.

Section 17.4.1.2 defines the nominal strength of the anchor in tension, N_sa as Area*1.9*AnchorYield
However, 17.2.3.4.3(a) says "The steel strength shall be taken as 1.2 times the nominal steel strength of the anchor."
So is this just an additional 1.2 factor to the steel strength in addition to the 1.9 factor that would be taken into account to increase N_sa?

Thanks

 

[OldDawgNewTricks]

17.2.3.4.3(a) is just one option that is available for preventing brittle failure of anchors that resist high seismic (SDC C or greater) loads. If this option is chosen, the concrete strength must be greater than 1.2 times the steel strength so that the brittle failure mode (concrete breakout) does not occur before the ductile failure mode (steel yielding).

 

[le99]

It makes sense. As section 17.4.1.2 specifies the nominal strength of anchor in tension; Section 17.2.3.4.3 specifies material strength requirement for seismic design, and section 17.2.3.4.4 specifies the anchor design strength for resisting earthquake forces.