huangyhg

height of snow for 100 psf snow load
a customer is asking us to design for 100 psf snow load. just curios as to how high the snow would have to be to cause this loading. aisc manual show 8 pcf for fresh fallen snow. this would be 12.5 ft high! ice is 56 pcf, so this would be 1.79 ft.
per asce7 density = 0.13*pg+14 but not more than 30pcf. so it depends on your ground snow load
in my area of vermont, code min is 70psf snow. i could see up to about 100 psf total here. i got about 1.5 ft of ice on the eaves of my apartment before it came crashing down on my neighbor's car. the stuff packs down quick when it sits on the roof. it goes through surficial freeze/thaws and consolidates until the stuff is like shovelling concrete.
"ground snow heights" are figured in our area by assuming 1 foot of depth per 25 psf of snow, so 100/25 would be 4 ft. this is stated in the local ordinances.
i think it depends a little on the region. if you haven't, i would speak with an inspector/engineer at the building department. they might have data for that area.
i have designed for over 200 psf in parts of colorado.
actaul density of snow varies quite a bit - i have heard of 8 to 15 pcf depending...mix in a little sleet, hail or frozen rain and it can get pretty heavy
some parts of california (not usually associated with snow), design snow load may exceed 200 psf.
those are all for light weights. try designing for the ski areas and park areas of western washington. cascade sludge can be like having a 10 ft deep swimming pool on your roof. here is the structural engineer's of washington's snow report with a listing of some of our ground snow loads up to 760 psf at sunrise on mt rainier in pierce county. i personally have only had to design houses for 300 psf. i believe that some of the snow loads here are based on over 40 pcf due to the possible high moisture content of our very wet cascade mountain range snow.
3.70 ft according to asce 7-05... i'm assuming that you're talking about 100 psf ground snow and not a minimum roof snow. if that's the case, then roof snow is discussed in flat roof snow and sloped roof snow, pf and ps, respectively.
if you're talking pf=100 psf, then i'll assume it's 100/0.7, which is 143 psf ground snow, which will yield 30 pcf. then you'll get 4.77 ft.

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