1. ## Lateral Torsional Buckling

For both beams you are required to: -
Q6. Size an UKB that satisfies a deflection limit of δ<Span/300. -
Q7. Verify the cross-sectional resistance allowing for interaction if required. -
Q8. Verify the lateral torsional buckling resistance considering that lateral restrained is provided only by the primary beams (i.e. beams spanning from column to column). -
Q9. Discuss the results and propose changes that could be made if your calculations show that the sized profile in Q6 is inadequate.

I do not understand question 8. Would I just find the lateral torsional buckling of Beam 32. As it is a point load its effective length would be half of its original length, 12m so, the effective length would be 6m.

Do I also, find the LTB for Beam 34 as well even though it is not a primary beam. Or is it something to do with SLS, ULS or Steel Grade?

I know how to do LTB I just don't get what the question is asking me to do

2. ## Re: Lateral Torsional Buckling

If there is sway of columns B3 and B4, what torsion will this induce in beams B32 and B34?

If there is sway of columns B3 and C3, what torsion will this induce in beams B32 and B34?

Note because of the orientation of the columns, one grid direction is stiffer against sway than the other.

The question tells you that the primary beams are those from grid intersection point to grid intersection point, where the columns are.
Thus both B34 and B34 are primary.

The secondary beams go left to right but not up and down between these eg beam B14

3. ## Re: Lateral Torsional Buckling

Originally Posted by studiot
If there is sway of columns B3 and B4, what torsion will this induce in beams B32 and B34?

If there is sway of columns B3 and C3, what torsion will this induce in beams B32 and B34?

Note because of the orientation of the columns, one grid direction is stiffer against sway than the other.

The question tells you that the primary beams are those from grid intersection point to grid intersection point, where the columns are.
Thus both B34 and B34 are primary.

The secondary beams go left to right but not up and down between these eg beam B14
Ok thanks. I understand now why both are primary beams. So, do I just work out the LTB for both beams normally then.