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Collar tie roof system

Collar tie roof system

Collar tie roof system

(OP)
Do you have an easy way to manually calculate rafter forces in a collar tie system?

What I've come up with is to check the rafter as a cantilever with span from the tie connection to the bearing for deflection; and check combined bending and axial for the full rafter length, using same moment from cantilever.  This seems to match computer results fairly well.

Thoughts?

Thanks in advance
David B.
Fredericksburg, VA

RE: Collar tie roof system

Do you have ceiling joist in addition to the collar tie?

Or do you have rafters  where the only tie between them is a collar tie several feet above the supportts?

RE: Collar tie roof system

(OP)
High ceiling only.  I'm wondering about a general, simplified approach.  I think my deflection may be too conservative, but have only looked at one case so far( 22' span, 12:12 pitch, tie at 6' above bearing point).

RE: Collar tie roof system

The wood frame construction manual.  You can order one from AF&PA.

Jordan

RE: Collar tie roof system

You might find  a thread posted under the structural engineering topic on this web site, helpful.

I believe the thread is IBC Collar Tie Conflict.

RE: Collar tie roof system

Conventional framing:
How to calculate 'Rafter Thrust' thread507-105386

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