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Re: 25% snow load is Conservative

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  What are the depths and densities of snow that can produce 
>loads of
>this magnitude?  Where do they occur?
>
>Thanks
>Dan Vines, EIT
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I've always thought the reason these snow loads were so high is that some
structures built under previous snow loads failed and the local authority
would just bump up the psf load a few notches.   Many of these hyper
loads I've dealt with were for rural counties or areas where the building
department consisted of one or two guys who came up through the building
trades.  I suspect they were getting drawings "certified" by someone for
a certain load with serious design flaws that later failed and there was 
no serious forensic investigation.  Their solution was probably  to
increase the required load from maybe 85psf to maybe 180psf.

In the case of the horizontal load, I would expect shear failure in the
accumulated snow in most situations would greatly reduce load transferred
to the structure.  It is hard to imagine a 14:12 slope roof maintaining
several feet of snow for very long.


Patrick Quinn
Henderson, Nevada

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