Shear capacity increase for wood header or plates
Shear capacity increase for wood header or plates
(OP)
Is there an allowance or duration increase allowed in shear capacity when designing a wood moment frame in place of a shear wall (with wind only) for either the top plates or header such as the 1.4 allowed in panels per IBC section 2306.3.2?
Example, SYP #2 has a value of 90 psi. Can this be increased for a wind only collector and if so how much (1.4, 1.33, 1.6)?
Any opinions or thoughts are appreciated.
Thanks !
Example, SYP #2 has a value of 90 psi. Can this be increased for a wind only collector and if so how much (1.4, 1.33, 1.6)?
Any opinions or thoughts are appreciated.
Thanks !






RE: Shear capacity increase for wood header or plates
The local building code may be more restrictive than the NDS.
You should contact APA-EWS for more information. I believe that they publish information on the design of wood portal frames.
RE: Shear capacity increase for wood header or plates
You might want to use a "Portal Frame" as outline by APAWOOD.
RE: Shear capacity increase for wood header or plates
I also agree with Mike that a wood moment frame is pretty tough to detail - the bolts tend to gouge the holes a lot and leave you with a much more flexible frame than you might think.
RE: Shear capacity increase for wood header or plates
If I stay with SYP #2, I'll have 725 psi Ft, 1660 Fc, and 175 Fv all adjusted to Cd 1.6 to work with.
My problem with the APA portal frame is if I read them right, I am maxed out at 10 feet tall. This wall is 18'-6. Also, for wind, I am limited to minimum 3.5:1 ratio with a wood wall panel, and nowhere in this 24 foot long wall segment do I have a clear 5.3 foot wide section to bring the shear down. That's why I was looking at using one or a combination of several wood moment frames (PSL columns on the cords anchored to the footing, with headers or top plate collecting between). The moment connection at the top of the frame was gong to determine if I needed multiple frames or not. I really don't want to start in the direction of the Simpson SSW walls and felt I could engineer this low V (total 1500 lbs along 24 feet..63 plf) into a wood moment frame.
Any other thoughts/suggestions?
RE: Shear capacity increase for wood header or plates
If I was trying to do what you are describing, I would put in some small steel tube frames. Another option might be to put in some diagonal wood bracing.
RE: Shear capacity increase for wood header or plates
Mike McCann
MMC Engineering