Snow drift against parapet on flat roof 1

[Alexander Usdan]

Anyone have any good (retrofit) solutions to prevent/limit snow drifts against a parapet?

(Even though it summer thought I would shake things up with a winter related question

 

[BridgeSmith]

KootK and Once, do I understand correctly that the 0.59 coefficient would be multiplied by the assumed density of the snow? If so, it's not much pressure, certainly not enough to compete with the wind load, unless the parapet was really tall with a very deep drift (or what I remember for the density of snow is way off).

 

[BridgeSmith]

Based on what I know of how snow fences work, I think the grating on the kickers would make the drifting problem worse instead of better.

 

[KootK]

@HR: I'll leave that question to Once2006. He's my source and I've not yet looked into it myself.

HELP! I'd like your help with a thread that I was forced to move to the business issues section where it will surely be seen by next to nobody that matters to me:

http://www.eng-tips.com/viewthread.cfm?qid=456235

 

[albanyYEM]

we have used the method of, essentially, displacing the potential snow drift by building up a void space before with success.

that said, i've brought up the sheathing of the kickers option to architects previously and they have been concerned about creating a concealed space that might need to be sprinkled depending on other factors that may be in play.

 

[Once20036]

HotRod,
The whole procedure is a coarse approximation, give that the density of the snow varies with depth and its not truly a cohesionless material.
The 0.59 creates a triangular pressure distribution that varies with depth, like soil on a retaining wall.
I don't recall if they get into how density varies with depth...

On my project, I was in a high wind region with FM global safety factors, and looking at a 3'-6" parapet to serve as fall protection.
Mu-wind = 3360 ftlb/ft
Mu-snow = 1540 ftlb/ft
Mu-fall = 800 ftlb/ft

 

[BridgeSmith]

Yeah, those loading numbers are about what I would have expected, Once. I was thinking that for vertical snow load that the common 30-40psf corresponded to several feet of depth, so that would put the density around 10pcf, maybe as high as 20pcf. I also remember from watching weather forecasts that it takes 3 to 12 inches of snow to equal an inch of water, which would also put the high end for density around 20 pcf. Even 20pcf at a k value of .59 would still produce far lower forces and moments than the typical wind load, unless the parapet was extraordinarily tall.