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Re: Connection between rafter and ridge

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The tread on the incompatibilities at ridge lines for steep roofs came up
last year I think.  At that time I was looking into this behaviour.  Using a
piece of paper, fold as a roof and then apply the possible load conditions
to it.  In in-plane shear your observation is very clear.

Thor Tandy  P.Eng  MCSCE
Victoria BC

-----Original Message-----
From: NRoselund(--nospam--at) <NRoselund(--nospam--at)>
To: oakford(--nospam--at) <oakford(--nospam--at)>
Cc: seaint(--nospam--at) <seaint(--nospam--at)>
Date: Friday, April 30, 1999 5:56 PM
Subject: Connection between rafter and ridge

>If there is a ridge beam so that there is no truss action, ties may be
>required to keep the roof from separating along the ridge, as in the
>Jim Kestner and Thor Tandy cited.  But, I can't visualize a tension force
>this case and would like to see how it is determined.
>I've based my trussed roof designs on there being no need for a strap over

>The action of this force would be to un-zip from the downward-displacing
>diaphragm a nailed over-the-ridge strap.  In trussed roofs for which the
>ridge connection has no designed capacity for gravity-induced shear at the
>ridge, this may be an important force to consider.  I can cite nether
>examples nor an analysis approach for this effect -- but I do include
>across-the-ridge shear capacity in my designs for retrofits of buildings
>trussed roofs that brace heavy walls.  Has anyone else thought about this?
>Nels Roselund
>Structural engineer