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RE: Design of Valley Beams

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Just don't forget to divide the applied load (based on tributary area) by
the square root of two if the beam is at a 45 degree angle to the roof
framing. Same with hip beams.

Just my $0.02

Bill Allen, S.E. (CA #2607)
ALLEN DESIGNS
Laguna Niguel, CA
http://www.AllenDesigns.com

||-----Original Message-----
||From: Nels Roselund [mailto:n.roselund(--nospam--at)worldnet.att.net]
||Sent: Tuesday, August 08, 2000 8:13 AM
||To: seaint(--nospam--at)seaint.org
||Subject: Re: Design of Valley Beams
||
||
||John G.,
||
||I don't believe there is anything special about designing a
||valley beam, if
||it is truly a beam with a span between reactions.  The tributary load
||pattern is interesting the first time you figure it out, but
||otherwise, it's
||nothing special.
||
||If the valley is part of a conventional framed roof with a
||slope not less
||than 3:12, valleys (like hips and ridge boards) need not be designed,
||providing the rafters are tied by ceiling joists, and rafter
||ties.  The
||valley, then becomes a part of a three-dimensional space
||truss.  I know of
||no analytical rules for design of that kind of system, but I
||think you can
||figure out the load paths by using statics.  I've stopped
||trying to make a
||conventionally framed roof system "figure" by following the
||load paths -- my
||experience is that the connections in a roof designed by the
||conventional
||light-framed provisions will be overstressed if the rules for
||loads and
||allowable stresses of other parts of the Building Code are
||applied.  But
||that's O.K. if the building's structural system fits within the narrow
||limits imposed by the Conventional Light-frame Construction Design
||Provisions -- the system has stood the test of time "pretty well".
||
||Nels Roselund
||Structural Engineer
||
||
||
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