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RE: Design of Valley Beams

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I don't count on collar ties providing any structural capacity. I am
resolved in knowing that this is more of a construction aid than anything
else. A long, long time ago, I once modelled a framing system with two roof
rafters and a single collar tie yielding a 2'-0" wide coffered ceiling.
First of all, the deflections were enormous and unacceptable. Secondly, you
would not believe the nailing required between the roof rafters and collar
tie.

I recommend that you design this framing with a ridge beam and add a collar
tie just to provided the coffered ceiling look.

Regards,

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

||-----Original Message-----
||From: Paul_Reilly(--nospam--at)dot.ca.gov [mailto:Paul_Reilly(--nospam--at)dot.ca.gov]
||Sent: Tuesday, August 08, 2000 11:16 AM
||To: seaint(--nospam--at)seaint.org
||Subject: Re: Design of Valley Beams
||
||
||
||
||>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,
||
||Do you have a reference for this seed?  I have been tearing
||through the
||light-frame conventional framing section of the UBC to no avail.  SBC,
||Manual of Practice, publishes some analytical methods for
||deriving member
||thrust and tension forces at the heel & ceiling joist of
||common rafters and
||also for hip/valley reactions.
||
||I have toyed with several models to consider clinched nailing
||designations
||to meet these demands and note the marked increase in tension loads
||reported by these modeling techniques for cj's raised above
||the top plate
||for "coffered" ceiling arrangements.  Off-topic, but what about those
||collar ties?  Not much benefit to servicing outward thrust at
||the heels
||unless cj's are set below, then it seems the collar tie might
||just as well
||be specified as a LSTA ridge tie since the all service
||tension would be
||serviced by the cj's.  Please advise.
||
||thx
||
||
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