wood stud wall with opening

[Cmfg]

I have to design the (seismic) strengthening of a wood stud wall. The wall is 11’x 8’ with an opening at the center of 3’ x 4’. I don’t know how to compute the tension forces on the reinforcing straps located at top and bottom of the opening. The total shear force is 3000lbs

 

[csd72]

Look at the publications on this page under 'perforated shear walls'.

http://www.awc.org/Publications/download.html

csd

 

[Cmfg]

That publication presnts how to calculate the force in the holddowns only. I need the forces on the horizontal straps located at the boundary of the window.

 

[skier1578]

If you can find it, the SEAOC Design Manual, Vol. II has a full example of a perforated shear panel, problem 1, part 9.

 

[KeySol]

Cmfg-

Skier1578 is right there is a really good example and description of how to do this in the SEAOC manual, but also there is an example in Wood Engineeing Construction Handbook by Faherty & Williamson. There are lots of typos in this book though so my reccomendation is the SEAOC manual.

The one issue taht teh SEAOC manual does not address is that you dont have to design the nailing and sheathing to take the shear at teh midle of the header. You can use the header to resist shear.

 

[GRV530]

KeySol,
Could you elaborate on your last statement, "You can use the header to resist shear."? I have used this example before for design and I have always specified the shearwall nailing above the opening to be as the calculations warrant. As you know, the shear can be about 1.5 times the shear at the piers to the left and right of the opening, and I'd like to know if there's a better way.
Another question for you is, what about below the opening?
The shears are always higher above AND below the opening (in my experience with these).
Thanks

 

[KeySol]

GRV530

Your right that usually the bottom segments of the wall have greater shears then the middle segments. I use whichever of thos is greater for the nail spacing. And yes, if you have a header over the opening you can use it to resist shear. So this means that the nail spacing used for the entire wall is based off of the bottom or middle segments. On projects i do this kinda of design on i use 4x header product so it is definitly strong enough to handle the shear loading. Also i use 4x blocks between wall studs because i dont think the people in the field are stich nailing the (2) 2x together correctly if at all.