Existing Truss Strength Increase

[SteelPE]

Has anyone heard of increasing the strength of an existing wood truss by covering it with plywood that is to be glued and nailed to the members?

This is for new construction where a change was made and more strength out of the existing trusses is needed.

 

[COEngineeer]

Yes you can do that. You just have to proof it that it will meet your design. If I were you, I would just model the truss like if you were to thicken each truss member another .75" or .5" or double for each side (plywood thickness). But theoratically your truss should be stronger since you have plywood in the bay also.

Never, but never question engineer's judgement

 

[SteelPE]

COEngineer

Basically they applied the sheeting to the entire truss depth (however deep it was). What you are saying is that this is acceptable but you would only count on the increase in the member strength due to the increased chord thickness.

How would make sure the forces were transferred properly between pieces of plywood? This would become critical on the tension chord.

 

[MiketheEngineer]

While I am sure it would help - how much is up for discussion. What about the breaks in the plywood - the type of glue - the size of nails????

I might buy into a 10 or even 20% increase but thats about it. What about the extra weight of the plywood??

How much increase do you need?? Many trusses are already over designed and there may be enough "fat" already to cover your concerns.

 

[civilperson]

This method is good for addition of a concentrated load at the plywood panel location, (increase in shear strength). The minor increase in the area of the chords is as Mike the Engineer states, 10% - 20% increase in bending strength at most and plywood weighs more than 40 pounds per cubic foot.