Shear Wall Strength

[pioneer09]

I have a typical stud framed construction building utilizing 2x6 at 24" o.c.. Based on the usage of the building, there will be 2x8 boards running horizontally and attached to the 2x6 stud framing to 8' above finished floor and then T&G boards to eave height which is at 12'. What is the best way/approach to determine the shear wall strength that will be achieved from the horizontal framed members.

 

[jayrod12]

So there will be nothing from floor level to 8'-0"? Why not?

 

[pioneer09]

See attachment. 2x8 to 8' then T&G to 12'.

 

[jayrod12]

Is there a reason for 2x8 over some form of plywood? Why not just run the T&G down to the bottom?

Is this on both faces or just 1? If the latter, what's on the other side?

 

[pioneer09]

There is no plywood. Just horizontal 2x8 and T&G on one side. The other side has a really light gauge liner panel that I was not counting on to get much shear resistance from. Secondly, the T&G boards will not be full height due to the usage of the building and in general the nails used to secure the T&G board will be smaller and not provide much shear capacity.

So to conclude, in my opinion it seems the 2x8 will be providing most of the shear resistance. Just how to calculate this resistance is a little fuzzy. I would think it would be by how much resistance I can get at the nail connections of the horizontal 2x8's to the vertical 2x6 studs at any one location along the wall.

 

[KootK]

You don't really have collector elements at the top and bottom of your shear panel so I'm not sure that conventional shear wall analysis methods would even apply.

I might look at it as a four level moment frame with some cantilevered columns projecting from the top. Each crossing joint would become a little moment connection. I think that this is pretty consistent with what you've described above.



I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[jayrod12]

So is this an existing structure?

If not, that's why I asked about plywood, a 3/4" sheet of plywood costs roughly the same as your solid 2x8s and has similar durability, but gives you the added benefit of actually being classified as a diaphragm.

 

[msquared48]

On page 267 of my 1958 "Douglas-Fir Use Book", it shows A shear wall with 8" DIAGONAL sheathing with a rigidity ratio of 8.0. The same page shows HORIZONTAL 8" sheathing with a rigidity rating of 1.0 to 1.5.

Based on page 273, although it is not specified as to the orientation of the sheathing or stud spacing, 200# per foot might be reasonable. I would have to check further though before I used that value...

I would certainly use diagonal over horizontal sheathing though. Much stronger.

Mike McCann, PE, SE (WA)

 

[jayrod12]

Depending on how thin the metal is it may be good for more strength than you'd think.

NFBA has some tested and published values for light gauge metal roofing and siding. Seems to me somewhere around 75PLF was not unrealistic, even with the smallest gauge.