Wood studs composite with sheathing?

[rrmiv]

I have been asked to review an existing wood-framed building. My client wants to look at the wall studs as composite with the exterior OSB sheathing. I have never analyzed a wood-framed wall in this way and have a few concerns. One is the shear stress transfer to ensure composite action. Another is a thin-flanged beam taking axial load in combination with bending compression.

Does anyone know of an established design procedure for this?

 

[DaveAtkins]

I have looked at studs this way. The problem is the sheathing is not continuous, vertically (OSB is often laid up horizontally), and so under suction wind load the sheathing cannot help in resisting bending.

About all that can be said is the sheathing reduces deflection.

DaveAtkins

 

[rrmiv]

DaveAtkins, good point about the discontinuity of the sheathing. If we were able to determine that no joints occur in the sheathing though, do you know of an established procedure? Have one of the wood organizations addressed this?

 

[DaveAtkins]

I do not believe the wood organizations have addressed this. It gets back to checking shear flow (VQ/I) to verify how composite the section is.

DaveAtkins

 

[jike]

I know one of the metal stud manufacturers (I think Clark-Western) had some tables for deflection that were based upon non-composite and composite. Realistically, however, I would not count on composite action for strength because of the lack of control of the joints, fasteners, spacing, etc.

 

[ChipB]

Just based on my experience, if this was a viable application, the engineered lumber companies would be all over it. The last TJI I looked at, had an OSB web, and Solid member top and bottom chords. That leads me to believe OSB is great for shear, but not so much in Tension/Compression. Otherwise, we'd see TJIs made completely out of OSB since it's so much less expensive.

 

[rrmiv]

Thanks to all for the input. I am very skeptical of the composite approach also. Just wanted to check whether there is an accepted procedure for this that I didn't know about.

 

[msquared48]

I have looked at and used the concept with the Berkley Roof panel system to justify smaller members in the past. In that the panels use 8 foot spans between joists, the plywood discontinuity issue never came up in that application.

I had to apply a reduction factor for the plywood based on the ply construction. I wonder how this would apply to OSB with the random grain orientation?

Mike McCann
MMC Engineering