Double ceiling beam 1

[lsmfse]

Can anyone give me a reference for lateral stability of unbraced ceiling beams? I have two horizontal beams with king posts @ the one third points. I plan on spacing the beams 3 1/2" apart and providing a spacer block sandwiched between the clg beams below the king posts. Spacer block will be bolted thru the clg beams with an all-thread.

 

[boo1]

Beam Stability, CL is controled by lateral support, not bearing. Without lateral support or proper design considerations, the compression side of a beam may buckle prematurely at a load much smaller than what was intended in a normal bending mode. But, the height to thickness ratio of typical wood headers (2-2"x12" or 2"x10"), 3:1 or 4:1 ratios requires ends of members by blocking, bridging, hangers to have CL=1.0. Typically the number of trimmer and cripple studs are selected by the span and provide this support. Additionally the interior and exterior sheathing provides additional support.

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