Stability Factor Cl in Wood Beam

[bylar]

Does anyone have example of calculating the Cl in Wood Beam Design? I have looked at several well respected design programs and none agree on the Cl with the same set of data!

 

[OldPaperMaker]

The equations for calculation C sub L are found in Section 3.3.3 of the 2012 NDS.
Examples of the calculations can be found in the Beam Design chapter in the book Design of Wood Structures by Donald Breyer, et al

 

[bylar]

I am aware of chapter 3 and chapter 4 of the NDS but there must be a reason why these programs come up with such different answers. It seems that the make different assumptions as to the loading even though that reference is clear when it comes to uniformly load either simple span or cantilever and has a longer list of various loading and also has a formula when none of the above apply. I have used all of the conditions and cannot duplicate their results. if have the correct E'min and the Fbe/Fb so it has to be in how they come up with le. I hate to see a program like Sizer having an incorrect result.

 

[bylar]

In table 3.3.3
Cantilever 1 do these formula only apply to the cantilever section or the whole beam that has a cantilevered section?
Same with simple beam are those only for a simple beam of the or also for the uncantilivered section of a cantilevered beam?
Or should the entire beam fall under the last formula that is other loading conditions?
I have study the use of this and get people that seem to use all different combinations

 

[RFreund]

Check out American Wood Council's Technical Report 14 "Designing for Lateral-Torsional Stability in Wood Members".

I believe the method in here removes the need to calc the effective length.

EIT

http://www.HowToEngineer.com

 

[bylar]

RFreund Yes I am aware of that publication. I have read it and it appears to be just another way of getting the Cl both of which are optional. The first section does not apply to cantilevered beams which I am mostly concerned with. The last approach seems to be very similar to the older approach even though I have not studied the difference in results. One of my concerns was what they mean when the specify cantilevered beam do they mean with a cantilever or does it mean a beam with a cantilever. It appears that most are using the formula for cantilever beams only for the cantilevered section of a beam. Just confusing to me!

 

[jayrod12]

Once the beam passes the first support then it no longer needs the same stabilization as the cantilever portion. Therefore I think it's reasonable to apply the method to the cantilever portion only.