ACI 318-11, Appendix D Anchorage Ductility

[palves]

Hi All,

I'm currently designing the anchorage for some mechanical units and ran into something in the new code that I hadn't realized. Section D.3.3.4.2 of ACI 318-11 specifies that we need to ensure anchor ductility, but there used to be a provision in the IBC (Section 1908.1.9 in the '09 IBC) that gave an exception for non-structural components. It looks like this exception is no longer there, and I'm disappointed in that because ensuring ductility seems like a pain. Is this truly what I have to do from now on with non-structural components or is that exception hiding somewhere else just waiting for me to find it? Let me know. Thanks everybody (or at least the people who reply).

Jason

 

[wannabeSE]

I think the 2012 IBC section 1905.1.9 is a mess. The code section modifies ACI 318 section D3.3. Except it modifies ACI 318-08 instead of ACI 318-11. The ACI made substantial changes to this section between 08 an 11. Look at the IBC amended section 3.3.6 exception 1. This might provide some relief to the ductility requirements for non-structural component anchorage. There has been a couple errata to this section of the IBC. I haven't sorted out the meaning or intent. See

http://www.iccsafe.org/cs/codes/Errata/2012I-Codes/2012IBC/2012-IBC-19.pdf.

And, there is errata changing the referenced ACI code in chapter 35 for this section at

http://www.iccsafe.org/cs/codes/Errata/2012I-Codes/2012IBC/2012-IBC-35.pdf.

The plot thickens. If you look at current ICC evaluation reports for expansion anchors it may say something like: "For the 2012 IBC, Section 1905.1.9 shall be omitted. Modifications to ACI 318 D.3.3 shall be applied under Section 1908.1.9 of the 2009 IBC, or Section 1908.1.16 of the 2006 IBC"

I think it may get worse before it gets better. ASCE 7-10 supplement 1 has added overstrength factors for component anchorage in chapter 13. The 2015 IBC will probably reference this supplement.

 

[jdgengineer]

In conversations with various anchor reps (Simpson, & Powers) it is my understanding that yes the exemption for nonstructural anchorage has been removed. It was not an exemption in the 2006 IBC, was one in the 2009, and now they have removed it in the 2012.

The one small piece of consolation is the 1.3 amplification factor for anchorage to concrete has been removed.

 

[jdgengineer]

The 2012 IBC references the 2008 ACI 318 because apparently ACI didn't have the new standard ready at the 2012 IBC printing. I agree its a huge mess.

 

[BUGGAR]

ASTM F1554 Gr 36 will meet the specified ductility. I think Gr 50 may meet the ductility spec too. And of course, A36 specs comply.