BS 449 and Lateral Torsional Buckling

[gbom]

I am hoping that this might be an easy one for anybody with experience of BS 449. How does (if it does) the code deal with Lateral Torsional Buckling?

BS 5950 directly state that simply tying members together does not constitute restraint unless an adequate bracing system is in place to transfer load.

BS 449 has no such statement.

Can anybody explain how BS 449 considers LTB?

Thanks

 

[gbom]

Any advice anybody?

 

[tempeng]

This article from New Steel Construction gives a brief overview of how BS 449 dealt with things. Whether or not it can answer all your queries is another thing...

Click Me!

 

[WARose]

BS 5950 directly state that simply tying members together does not constitute restraint unless an adequate bracing system is in place to transfer load.

BS 449 has no such statement.

I haven't read the article tempeng references, nor am I familiar with the codes you cite. But common sense would dictate that you would indeed have to tie beams into the lateral force resisting system for adequate bracing (unless it was accounted for in the beam's design).

 

[BAretired]

Simply tying beams together does not constitute restraint because all beams can buckle simultaneously.

Tying the compression flange of any beam to a point which cannot translate parallel to the flange is an effective restraint for that beam against LTB.

Tying beams together such that torsional rotation of each beam is prevented constitutes an effective restraint against LTB.


BA

 

[gbom]

WARose as BAretired says, simply tying them together is not sufficient. BS5950 and EC3 have statements to that effect. BS449 is not clear how it accounts for LTB and if indeed the allowable stress design tables do consider it. The article tempeng has posted gives information.