ACI Anchor bolts design 3

[BAGW]

Hi,

ACI has two phi factors for the design of anchor bolts tension capacity. 0.65 for brittle failure and 0.75 for ductile. What circumstances will the brittle factor apply?

AISC DG does not address this. The phi is always 0.75 per AISC DG.

Trying to understand the phi=0.65 brittle failure mode.

 

[dauwerda]

Brittle is for any of the concrete failure modes (pullout, breakout, etc.).
Ductile is steel anchor material failure mode (yielding).

 

[BAGW]

That's what I thought. Thanks for clarifying.

 

[KootK]

A lot of the stuff that you see in the AISC design guide uses reinforced concrete principles to achieve tension anchorage whereby the tension is basically passed from the anchor bolts to rebar nearby. Hence the 0.75 everywhere. The 0.65 tends to apply to situations where you're relying on the tensile strength (pullout / breakout) of concrete to move the anchor bolt tensions into the body of the concrete element.

 

[JStephen]

In ACI-318-14, "ductile" and "brittle" steel elements are defined in Section 2.3, helpfully alphabetized under "steel element, brittle" and "steel element, ductile" rather than just "brittle" and "ductile". Actual phi is then given in 17.3.3.

 

[dauwerda]

JStephen has it right, that's what I get for not opening the code up before answering.

 

[ProgrammingPE]

I imagine the next question everyone is wondering is what is the minimum elongation percentage and reduction in area for F1554 anchor bolts since it is the preferred specification. Grades 36, 55, and 105 meet all of the requirements to be considered ductile steel elements.

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