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Re: Wood truss

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Ed.Haninger(--nospam--at) wrote:
>      I have a wood truss design that I would appreciate feedback on.  This
>      truss is to be used for roof support on a barn.  It uses 2x4's (flat
>      side out) for chords and diagonals with OSB "gussets" nailed on both
>      sides.  The trusses have a 20 foot span, 4:12 side slope and spaced at
>      24" on center.  The nails are to be driven and "clinched" (bent over
>      on the far side).  With the double shear on 10d nails I need 6 nails
>      per member on the largest loaded connection.  Some connections are not
>      concentric, so this number would go up.
>      Things I was wondering about:
>         1) Will OSB work OK vs. plywood in this application?
>         2) What is the recommended nail spacing and edge distance?
>         3) Any other special considerations for gusset size?
>         4) What is the best way to brace the bottom chord for wind uplift?
>      Ed Haninger
>      ed.haninger(--nospam--at)
1)  I have successfully used OSB gussets in design of field applied
gusset plates.  
2)  If the wood is not new, I recommend using 16 gage staples (see NER
272 for load criteria) or screws instead of using nails.  They do not
tend to split the wood as much.  I recommend a 4" spacing between nails
or a 1" spacing between staples.
3)  I recommend that all gusset plates be glued to the wood framing with
APA rated glue for the full contact area.  I design the staples to
resist the tension forces as a minimum.  The gussets should also be
checked for shear through the plate.  Generally the nail spacing
controls the size of the gusset plate.
4)  Try using 1x or 2x member horizontally nailed to each truss chord at
a spacing determined by the compression force in the bottom chord.