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
From: NRoselund(--nospam--at)aol.com <NRoselund(--nospam--at)aol.com>
To: oakford(--nospam--at)rsec.com <oakford(--nospam--at)rsec.com>
Cc: seaint(--nospam--at)seaint.org <seaint(--nospam--at)seaint.org>
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?