snow load on RTU's 1

[bjb]

With RTU's is it too conservative to apply the basic roof snow load to the top of them, or can you assume that wind removes some or all of the snow? I haven't found anything that addresses this. It seems to me that if you have a large unit up on a platform, you should be applying the full snow load to it. That is the case I currently checking. I think a large unit on a platform creates a "shadow" that prevents snow from getting under it, so a snow load should be applied to the top. The question is, is it reasonable to assume that the wind will prevent a full snow load from developing on top of the unit.

 

[SperlingPE]

See the roof projections provisions for snow load. I design roofs for the snow load over the entire roof. The weight of the RTU is in addition so any snow that is on the RTU is accounted for. If the RTU meets the provisions for roof projection, I include a drift load around the RTU.

 

[bjb]

I agree with you for an RTU that is not on an elevated platform. If it's on a platform, I think the unit takes the snow because the snow can't get to the roof. Depending on the column arangement for the platform, the snow load on the unit can be distributed as a point load to other roof members that are already seeing a balanced snow load.