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Re: 25% snow load is Conservative

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Dan Vines wrote:

. > Please forgive my ignorance (before you mountain dwellers jump on me), 
. > but, being both a young engineer and someone who has lived his whole life 
. > in the southeastern US (where 1 inch of snow shuts down a city), I would 
. > like to know where snow loads like these can occur. 400 psf is like 6-1/2 
. > feet of WATER. What are the depths and densities of snow that can produce 
. > loads of this magnitude?  Where do they occur?
. > 
. > Thanks
. > Dan Vines, EIT

In the early 1970's, the Structural Engineers Association of Oregon did a 
snow load study for Oregon.  It was/is a very comprehensive county-by-county 
study of Oregon snow loads and even accounted for the difference in snow 
loads on the north and south slopes of mountains.  Their study, if I recall 
correctly, showed ground snow loads of 700 psf in some areas.

In 1973, the Structural Engineers Association of Arizona published a similar 
study.  H. M. (Mac) Elliott, P.E. was the principal researcher in this study 
and used results from Soil Conservation Service snow course measurements, U. 
S. Forest Service reports and estimates made by Mac Elliott.  Even in 
Arizona, ground snow loads measured by the SCS can range up to 250 psf.  In 
the winter of 1967, Arizona experienced some of the heaviest snow falls on 
record with over 100 inches falling on the Navajo Reservation in northeast 
Arizona.  Numerous roofs collapsed, even in Flagstaff, Arizona, which with an 
elevation of 7000 feet is accustomed to heavy snows.

I did not participate in either study.  My knowledge of the Oregon study was 
because I was the representative of SEAOA to the Western States Conference of 
Structural Engineers Associations when Oregon published its study.  I'm sorry 
that I can't name the principal investigator(s) for Oregon to give them the 
credit that they so richly deserve, but I loaned my copy of the Oregon study 
to someone and never got it back.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona