Fb of Built up Beams
Fb of Built up Beams
(OP)
I know that there are span tables available that take this into consideration, however I have some confusion as to how the allowable bending strees is derived for built-up beams. Is it just simply multiplying appropriate factor(s) to the tabulated Fb? For example, a Double 2x10 w/ 1/2" plywood flitch. Is the the Fb of one 2x10 adjusted or is there more to this?
Any info would be greatly appreciated.
Any info would be greatly appreciated.





RE: Fb of Built up Beams
Where
Fb is allowable bending stress in NDS supplement.
CD is load duration factor, (see NDS Table 2.3.2 reproduced below)
CM is wet service factor, (use when moisture of timber is higher than 19%)
Ct is temperature factor, (when timber is used in temperature higher than 150°F)
CL is beam stability factor, (See below)
CF is size factor, (apply only to visually graded sawn lumber members, and to round timber bending members, not apply simultaneously with Cv for glued laminated timber)
CV is volume factor, (apply only to glued laminated timber bending member)
Cfu is flat use factor, (when 2”-4” timber is loaded at wide face)
Cr is repetitive member factor, (apply to dimension bending member 2”-4” thick)
Cc is curvature factor (apply to curved glued laminated bending member)
Cf is form factor. (for round or diamond section)
Consider the effects of :
repetitive member
lateral stability
size factor
volume factor
RE: Fb of Built up Beams
RE: Fb of Built up Beams
RE: Fb of Built up Beams
I also enjoy reading your replies to previous threads. Both take the time to give a thorough response, full of info.
Thanks again