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Re: Ridge beam/joist analysis

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Bill,

I have posted my thoughts on this a few times with little or no response. In
short I don't think you can effectively transfer shear across the ridge the
way most houses are constructed. I will try to find what I have previously
posted. but it may not be today.

As for the referenced quote: That can be a very large moment to resist at
the rigid ridge as I think you mentioned. You have to have a diaphragm for
lateral loads anyway why complicate the ridge connection detail?

Rand


----- Original Message ----- 
From: "Sherman, William" <ShermanWC(--nospam--at)cdm.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Wednesday, June 30, 2004 1:28 PM
Subject: RE: Ridge beam/joist analysis


> According to the book "Design for Lateral Forces" by Ambrose & Vergun:
"When
> a ridge beam is used to support the upper ends of the rafters ... the
> outward thrust at the lower ends is essentially removed." (Ridge beam must
> be supported at ends.) Also, "Another means for restraining inclined
rafters
> is through the use of a collar tie ... this turns the top joint into a
rigid
> connection, and stability becomes dependent on the bending of the
rafters."
> If the ridge beam is not vertically supported and a rigid connection is
not
> developed, you have a three hinged arch, which requires thrust restraint
at
> the sides.
>
> Unfortunately, I was looking in this book for a good description of how
> lateral wind forces are transferred thru a gabled roof via diaphragm
action
> - but despite the name of the book, the section on gabled roofs only seems
> to address vertical load effects. I once convinced myself that the two
> plates act effectively as one diaphragm with shear transferred at the
ridge
> beam, but now I am having trouble reconfirming that conclusion using
> free-body diagrams. Is there a reference that explains in detail how
forces
> are transferred in a gabled roof diaphragm?
>
>
> William C. Sherman, PE
> (Bill Sherman)
> CDM, Denver, CO
> Phone: 303-298-1311
> Fax: 303-293-8236
> email: shermanwc(--nospam--at)cdm.com
>
>
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