Built-Up Sawn Lumber Column
Built-Up Sawn Lumber Column
(OP)
I'm trying to create a new calculator for timber and sawn lumber columns. However, I decided to get fancy and add in an eccentricity check for both the x and y axis.
My question is: Does it make sense to use a flat use factor (Cfu) in calculating the allowable bending of the minor axis (Fby) when you more than one 2x4 or 2x6 mechanically fastened together (nailed). One stud or post makes sense to me but as soon as you start laminating the plies together the shear/slip of the nails would seem to negate the flat use factor in bending similar to the reduction that is taken in Cp with the Kf factor. Note that CL is taken as unity since the aspect ratio with bending in this direction prevents buckling.
My question is: Does it make sense to use a flat use factor (Cfu) in calculating the allowable bending of the minor axis (Fby) when you more than one 2x4 or 2x6 mechanically fastened together (nailed). One stud or post makes sense to me but as soon as you start laminating the plies together the shear/slip of the nails would seem to negate the flat use factor in bending similar to the reduction that is taken in Cp with the Kf factor. Note that CL is taken as unity since the aspect ratio with bending in this direction prevents buckling.






RE: Built-Up Sawn Lumber Column
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Built-Up Sawn Lumber Column
I've temporarily posted it here:
http://design.medeek.com/resources/column/
RE: Built-Up Sawn Lumber Column
I guess my question is with this sort of situation do you consider the built up beam as a whole or the laminations separately with respect to applying the flat use factor.
RE: Built-Up Sawn Lumber Column
Mike McCann, PE, SE (WA)
RE: Built-Up Sawn Lumber Column
RE: Built-Up Sawn Lumber Column
RE: Built-Up Sawn Lumber Column
With that being said the real question becomes what is the appropriate Cfu to use for this situation?