wood headers
wood headers
(OP)
When designing a wood header in a wood framed building, and the header is below the double top plate with cripple studs sitting on it, should you assume that the compression edge is adequately braced so that the beam stability factor doesn't need to be applied? It seems that since headers are usually multiple pieces nailed together with sheathing on each face, that applying the stability factor is over-conservative.
Also, in the case where the header is under the top plate in exterior walls, should the design should account for weak axis bending of the header from wind loads?
Also, in the case where the header is under the top plate in exterior walls, should the design should account for weak axis bending of the header from wind loads?





RE: wood headers
Cheers
RE: wood headers
RE: wood headers
With the 6" wall the ratios are even lower. Rule of thumb for wood beams.
For Height:Thickness to assume CL=1.0
2:1 and less case, no supports are required
3:1 or 4:1 case, At ends of members by blocking, bridging, hangers.
5:1 case, then the lateral stability requirements are:
a. The compression edge is held in-line the entire beam length
b. The member ends are held in position with full depth blocking, hangers, or bridging.
Beam Stability Factor Equation:
CL=((1+Q/1.9)-((1+Q/1.9)**2-Q/0.95)**1/2)</= 1.0
G=Fbe/Fb*
Fbe=(Kbe/Ey'/Rb)**2 Kbe= 0.438 Lumber, graded
0.610 Glulamms
Ey'=Ey(Cm)Cl
I hope this is helpfull