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RE: Ridge beam/joist analysis

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Actually, I only edited out a reference to a figure in that sentence. The
figure shows the collar tie some distance below the ridge. However, it does
go on to say that "This solution is reasonably feasible only for very short
spans (such as single car garages) and should use rafters of reasonable
stiffness." 

William C. Sherman, PE 
(Bill Sherman) 
CDM, Denver, CO
Phone: 303-298-1311
Fax: 303-293-8236
email: shermanwc(--nospam--at)cdm.com
 

> -----Original Message-----
> From: Daryl Richardson [mailto:h.d.richardson(--nospam--at)shaw.ca] 
> Sent: Wednesday, June 30, 2004 2:32 PM
> To: seaint(--nospam--at)seaint.org
> 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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