HVAC Unit anchorage on concrete roof - use Overstrength?

[dreber]

If I'm anchoring an HVAC unit to a concrete roof, do I need to apply overstrength?

AISC 7-10 13.3.1 reads "The overstrength factor, Ωo, does not apply".

However, in ASCE 7-10 Supplement No. 1, Table 13.5-1 includes Ωo and specifies "Overstrength as required for anchorage to concrete, See Section 12.4.3".

Section 12.4.3 reads "Where specifically required, conditions requiring overstrength factor application shall be determined in accordance with the following".

Then in ACI 318-11 Appendix D (Is a section in an appendix a requirement?) Section D.3.3.4.3(d) "The anchor... shall be designed... with E increased by Ωo"

ESR-1917 (For Hilti KB-TZ anchors) hardly mentions overstrength.

So which is it? To overstrength or not to overstrength?

 

[dougseason]

OP,

I believe ASCE7-10 supplement no.1 controls the design. We do a lot of anchorage projects in California for hospitals (OSHPD. OSHPD reviewers always comment if we don't use omega so I think the correct way is to apply the omega.

Regards

DS

 

[SAIL3]

for post-installed anchors, I automatically use the overstrength factor.....