What is “Secondary members” in IBC code?

[tmgczb]

In IBC-2018, Section 202, "Secondary members" include "roof construction not having direct connections with columms". In this way, such secondary members should be a part of "roof construction".
However,Table-601 gives fire resistance for "roof construction and associated secondary members". It seems that roof construction does not include some secondary members.
My concern is if "secondary members" include roof purlins in steel shelters.
Do we need to consider fireproofing for cold form C or Z shape purlins? What is the fire resistance for cold formed C purlins without being painted with fireproofing materials?

 

[BridgeSmith]

I don't know the IBC all that well, but just from what you've posted, I don't think you'd be successful in making the case that the purlins would be exempt from the fireproofing requirements. If they get soft from the heat, and buckle, the roof could collapse, right? That's not the place where I'd be trying to cut corners.