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RE: Ridge beam/joist analysis

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Dmitri -

I would love to see how you got a collar tie to be an effective structural
component. A long, long time ago, I modeled a collar tie (a couple of feet
down from the ridge board) system consisting of the collar tie and two roof
rafters and analyzed the system on STAAD. The results were the same as what
I thought would happen, namely, an incredible tension load in the collar tie
resulting in a very large force at the connection of the collar tie to the
roof rafter and a very large horizontal displacement at the top plate.

After that, I concluded that a collar tie was Viagra for framers. You know,
an erection aid before the sheathing is applied.

Regards,

T. William (Bill) Allen, S.E. (CA #2607)

-----Original Message-----
From: Dmitri Wright [mailto:dmitri(--nospam--at)pciengineers.com] 
Sent: Wednesday, June 30, 2004 9:38 AM
To: Seaint
Subject: Re: Ridge beam/joist analysis

OK, you guys are scaring me.  Did anyone take statics in college?  Maybe the
comment last week about regular re-testing for structural engineers was a
good idea after all! <grin>

To be fair, when I had some ridge beam rafters, collar tied rafters, and
stair stringers to design (all on one job!) a few months ago, I had to sit
down and work through the free body diagrams to refresh my memory.  I wrote
a quick little excel spreadsheet for myself so I won't have to go through
the exercise again next time.  I will be happy to share it with any list
members who are interested.

Dmitri Wright, PE
Progressive Consultants Inc.



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