Roof Screen MWFRS

[JSMHA]

For a rooftop screen, I have read that provisions for wind loading on rooftop equipment can be used if the screen is set in enough from the exterior wall. Otherwise, parapet loading should be used. This appears to be primarily for Components and Cladding load, as ASCE 7-16 Section 27.3.4 provides MWFRS values for parapets with GCpn of 1.5 for the windward parapet and 1 for the leeward parapet. ASCE 7-16 Section 29.4.1 is supposed to cover wind load on rooftop structures, but uses a GCr of 1.9 (assuming the area does not allow a reduction). This means the roof screen would actually produce more MWFRS wind than a parapet if it is treated as a rooftop structure, but less pressure for C&C. I am wondering what other engineers use for the MWFRS loading contributed by roof screens.

 

[JAE]

Don't confuse MWFRS wind and C&C wind. They are never additive, right?

Is that what I'm reading into your question?

 

[JSMHA]

Understood that MWFRS and C&C are separate and not additive. My main confusion is there is not a specific section under the MWFRS chapters that covers rooftop equipment (roof screens). Section 29.4.1 is the only section that I have seen be applied, but if applied for MWFRS actually gives a higher MWFRS load than the parapet section 27.3.4, which specifically addresses MWFRS for parapets. It does not make sense to get higher loading away further from the roof edge. Comparing parapet and rooftop equipment loading makes sense as Section 29.4.1 loading for C&C on rooftop equipment comes out less than the chapter 30 section for parapet C&C. Hopefully this clarifies.