Lateral torsional buckling bracing tension flange or at neutral axis

[firstps00]

Lateral torsional buckling causes a beam to deflect laterally and rotationally together, so if lateral deflection is restraint, will rotation still occur (ie will lateral torsional buckling)? Typically the compression flange is braced to restraint lateral and rotation deflection, but what happens if it is laterally restrained at the neutral axis instead(ignoring any local buckling of the web) and not restraint for rotation, will it still rotate with no lateral displacemnet?

And also what would happen if it was only based laterally at the tension flange? My thought is torsional stresses will be introduced. Thoughts? How would you quantify the torsion loading if this is the case.

Thanks

 

[Celt83]

give this thread a read: Link

My Personal Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

Open Source Structural GitHub Group:

https://github.com/open-struct-engineer

 

[JAE]

Dr. Yura at the Univ. of Texas always asserted that a beam needs either bracing against lateral translation of the compression flange....or.....bracing against rotational twist of the overall section. One or the other but both aren't needed together.

 

[JoshPlumSE]

what happens if it is laterally restrained at the neutral axis instead(ignoring any local buckling of the web) and not restraint for rotation, will it still rotate with no lateral displacemnet?

My understanding is that lateral torsional buckling of a beam is a lateral displacement of the top flange mostly, with almost not displacement of the bottom flange.

In this respect, a lateral brace at the tension flange would do NOTHING to prevent LTB. Lateral restraint the centroid of the section? I wouldn't count on it at all. Not unless it also provided ROTATIONAL restraint of the beam at that location.