Plywood Gusset plates

[StructuralPoke]

I am working on a repair of existing press-plate trusses. Some of the existing press plates have either torn in two or withdrawn. We want to use a plywood gusset to repair the joint, but I have no idea how to come about this. It was suggested that I simply look at the thickness of the plywood and find the shear/screw value out of NDS, and use that, but I don't think that's quite right. I am not having any luck with google either. I've got a couple example trusses (here), but no info on the design of the gussets.

Any help?

 

[StructuralPoke]

Oh -- and the American Wood Council page points me only to the Midwest Plan Service Structures and Environment Handbook, w/o any design info...

 

[ODB_PE]

The way we do it you is pretty close to what you have described - figure out your stresses and size your plywood accordingly. Another way to do it is to calculate the shear/tensile capacity of the plate you are replacing and work from there.

We glue and nail plywood gussets to both sides and I guarantee you it is much stronger than the plates that were there. The glue alone is good for 90psi in shear. typical size would be 16 x16 or so, Leave it square if nobody will see it. It is very cheap to over-engineer this connection, and the glue is usually the limiting element so using surface area of the glue is usually what I do and then the rest is just gravy.

 

[StructuralPoke]

Well, I didn't think the process was too far off, but I wasn't too sure. Sounds like that's the way I'll go about it. Where do I find info about glue?

What I was planning on doing was take the max axial in a web member in these trusses and from there determine the req'd # of wood screws and avoid the glue if possible, but I'm not sure it is. I'm looking at ~ 22 screws and that seems excessive...

(If you haven't guessed, my wood knowledge is at the very bottom of all the other materials I know...)