bracing distance against lateral torsional buckling 3

[HanStrulo]

Hi guys,

I have a question regarding lateral torsional buckling.

usually, when i have a braced beam along uniform intervals i take that distance as my braced length when the moment diagram is positive or i take the distance between the points of inflections when i have positive and negative moment regions.

a client is arguing that the inflection points are not valid bracing and that i should take longer length.

any comments? any reasons for why or why not? Am I missing something?

Thanks alot

 

[haynewp]

AISC does not permit that as a brace point. See Appendix 6 in the 2016 edition of AISC 360.

 

[Agent666]

A point of inflection is not a bracing point. Unless you're attached to a slab say, where you essentially have full lateral restraint in the positive bending regions.

I wrote a blog post several years ago about this that shows/demonstrates why this is the case. This might be of interest to you to alter your perception that the point of inflection is a valid bracing point.

https://engineervsheep.com

 

[HanStrulo]

I read the blog and i love how you wrote it. Thanks. Do you know of any examples where this caused a failure somehow?

 

[dik]

One of the best explanations I've seen... kudos...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Tomfh]

Inflection points don't provide bracing per se, however codes typically allow you to take lateral restraints beyond the inflection point as bracing points, and thus it often works out much the same, given that most beams have an attached roof or floor etc.