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Unbalanced Snow Loads
- To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
- Subject: Unbalanced Snow Loads
- From: Eric Tompos <etompos(--nospam--at)ntainc.com>
- Date: Thu, 07 Jun 2007 23:31:00 -0400
ASCE 7-05 has
provisions for "simply supported prismatic members" and "all other gable
roofs." Obviously, trusses are not prismatic and the later provisions
apply to designs of trusses. But, what load is intended to be used for the
design of the structure itself?
If the structure
uses a truss I've been using the "all other gable roofs" provisions to match the
truss reactions. However, I was recently told that the "simply
supported" provisions are meant for the design of the building, regardless of
whether the framing is a rafter or a simply supported truss (for
W<=20). If this is done, the resulting design loads can be considerably
different from the truss reactions.
I realize that snow
doesn't know the difference between a rafter and a truss, but what is the intent
of ASCE 7 with this regard? Should the building be designed for different
snow loads than the roof framing?
Eric Tompos, PE,