Slenderness - Wood - Bending

[brane23]

I have a question about the slenderness requirement for bending in ANSI NDS 97'... Page 17

My Span is 10 ft. = 120 in. = Lu
Member Subject to Bending = 2x6 = 1.5x5.5
Effective Length for Lu/d > 14.3 is Le= 1.84*Lu = 220.8 in
Slenderness Ratio = Rb = ((Le*d)/(b^2))^(1/2) = 23.23
Rb recommended less than 50.

@ Rb = 50 a 2x6 can span 46.5 ft?????

Does this sound right?

Something seems off.... maybe I'm missing something.

 

[boo1]

Use (L/D1) or (L/D2) whichever is larger. The slenderness ratio may not exceed 50 except that during construction it may not exceed 75.

L/D1<50 L/5.5<50 L<275 inches or 22.9 Ft allowable length

 

[UcfSE]

A 2x6 will probably never span 46+ feet. There's more to it than that of course. That requirement was developed mroe for large glulam beams though it applies also to sawn lumber, according to my Donald Breyer book p 6.18.

 

[brane23]

Thanks Boo and UCF...