ACT Ceiling for Hospital, Ip=1.5?

[elance301]

Should the ceilings in a hospital have an importance factor = 1.5 with regards to ASCE chapter 13 calculations? From section 13.1.3, the Ip is 1.5 for:
"The component is in or attached to a Risk Category IV
structure, and it is needed for continued operation of the
facility or its failure could impair the continued operation
of the facility."
I would figure that the ceiling collapsing would qualify an Ip of 1.5 (same for partition walls).

But I am reviewing OSHPD OPD document for suspended ceilings and trying to back calculate what they used for their wire strength.
(

https://hcai.ca.gov/construction-finance/preapproval-programs/oshpd-preapproved-details-opd/)

For a 144 sq ft area shown on page CL2.22, the max Sds is 1.15. I calculate an ASD brace wire force of 472 lbs at Ip = 1.5 and 315 lbs for Ip = 1.0. This does not compute with what I think a 12 ga. wire strength is. A 70 ksi 12 ga. wire (0.106") should be 618 lbs. Using a reduction factor of 2 means an allowable strength of 309 lbs. The 2 reduction factor isn't listed in the OPD but is listed in the DSA IR 25-1. IR 25-2 also uses the same charts for Sds and bracing area. Which leads me to believe the OSHPD document does not set the ceiling importance factor = 1.5! Am I off base here?

DSA publications (

https://www.dgs.ca.gov/DSA/Publications#gypsum)

 

[Clerical Forensics]

If Ie=1.5 then Ip=1.5. We generally, reduce the bracing spacing so that a 12 ga wire can still be used along with the same anchors. Another option, though less favorable by both me & the contractor, is to switch to 10 ga wire but this generally requires more embed for the anchors. I've not back calculated the wire capacity from OSHPD. We tend to use 60 ksi for wire, since some manufacturers still list the lower value.