Wood Design Cf Factor Question

[logokster]

Question concerning use of the Cf factor for wood design. I am using NDS 2012.

Evaluation of a 4"x6" rough sawn lumber in bending subject to both strong axis and weak axis bending. For strong axis bending with Width (depth) = 6" and Thickness (breadth) = 4", it is straightforward and Cf = 1.3 for Fb. For weak axis bending, is it still appropriate to use Table 4A with the Cf table and if so what is the factor? The reason I ask is Table 4A does not offer a Cf option for Thickness (breadth) for greater than 4" for Fb.

Thanks.

Brandon

 

[Triangled]

Fbxx I'd use Fb x Cf
Fbyy I'd use Fb x Cf x Cfu

as I understand the Cf and bending design values are based upon loading edgewise (ie about xx axis). Cf of course adjusts the basic Fb, and then Cfu is a further adjustment to the Fb x Cf for flat use conditions (ie about yy axis).

I'm guessing, and it seems reasonable, that it applies equally to rough sawn lumber as to S4S lumber, but cannot recall chapter and verse for that.

Then if bending forces occurred simultaneously, that is you have a biaxial bending circumstance, you would use the biaxial bending formulae in NDS with associated bending magnification terms.