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Re: Ridge beam/joist analysis

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Daryl,
The collar tie is the tension member at some distances d from the
compression stress (max at the top of the ridge) that forms a couple and
thus moment transfer. Making the two rafters act as a continuous beam over
the ridge support.

Rand
----- Original Message ----- 
From: "Daryl Richardson" <h.d.richardson(--nospam--at)shaw.ca>
To: <seaint(--nospam--at)seaint.org>
Sent: Wednesday, June 30, 2004 3:32 PM
Subject: Re: Ridge beam/joist analysis


>
>
> > "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."
>
> William,
>
>         This seems to me to be a mistake.  Perhaps you edited out more
than you
> intended.
>
>         It would seem (to me at least) that the collar tie would
effectively
> turn the rafters into a three hinged arch with the lateral restraint force
taken
> internally by the collar tie.  The only moment that I can see being
transferred
> through the ridge joint would be limited to the axial load in the rafters
> multiplied by the small eccentricity between the effective centre of the
contact
> area and the centrelines of the rafters.
>
>         I agree with everything else in your posting.
>
> Respectfully submitted,
>
> H. Daryl Richardson
>
>
>
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