Steel Stair Tower Moment Frame Question

[Bdon88]

Hello,
I am designing a steel stair tower to act as a fire escape for a existing building. I am in seismic category D and I planned to use steel moment frames in one directions and braced frames in the other direction for my seismic system. My questions is am I required to use special moment frames or can I make intermate work? When the code talks about if it is one story with the dead load less then 20 psf for the roof its hard to apply that to a stair tower that doesn't have any complete floors or roof. It just has the platforms and stairs. Which is going to made of bar grating. I checked the non building structures seismic code and it appears to be the same rules as for the building? Does anybody have any ideas on where I should be looking at in the code?

 

[driftLimiter]

I believe this falls under 'Egress Stairways not part of the building seismic force resisting system' per ASCE 7-16 Ch 13 Table 13.5-1. Rp = 2.5 for this. No real detailing requirements here other than those indicated in Section 13.5.10. Seems like an OMF using R = 2.5 is a reasonable approach.

Can also check out AISC Design Guide 34 for more information about the stairwell lateral components.