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Re: Ridge beam/joist analysis

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Rand,

        Actually, I was thinking of a tie much lower down nearer to the bottom
end of the rafter, something that could be connected with a hand full of nails.

        A tie near the ridge could transfer moment if the detailing was designed
to accommodate the magnitude of the tension and the moment encountered.

        Thank you for writing.

H. Daryl Richardson

"Rand Holtham, P.E." wrote:

> 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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