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Re: Adding nail values to bolt values

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This might not apply to your current situation, but as an academic argument, couldn't you combine the shear values of nails and lag bolts? If the lags were installed properly (i.e. not in oversized pre-drilled holes), they should begin resisting load at a similar displacement as the nails. I agree that nail and bolt values should not be combined because of the different load displacement properties. The same logic is used to prohibit combining skin friction and end bearing in piles, or welds and bolts in steel connections.

Dmitri Wright, PE
Cascade Engineers
Portland, OR

I now agree (from different posts to my original question) that the two =
should not be added.  But, it seems from your reply that you think my =
problem stems from a conventionally framed rafter system with rafters =
and collar ties.  It is not (if that is what you are thinking, which may =
be from my poor explanation), but the framing is made up of site built =
trusses.  they are made up of 2X6 top and bottom chords and 2X4 webs =
with plywood gussets at the panel points.  We've had these discussions =
before on the list about site built trusses, but that is what I have.  =
These trusses (as I have stated the ones that are still in one piece) =
have worked very well for over 30 years.  I think that they may have =
been engineered, but back then there wasn't a building department here, =
so no plan reviews.  I suspect there was never a snow load in the =
original design (If there was one), because otherwise things are close =
to "calcing" out with dead load only.

The boss will just have to go with metal plates and bolts or replace the =
trusses all together (as I have already suggested as there is not that =
many of them.  That suggestion was rejected).

Thanks for your reply,

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