Lateral Torsional Support
Lateral Torsional Support
(OP)
We have an existing catwalk that we are adding load to. The bar grating on top can be removed, so I don't consider that for lateral bracing of the beam. The beams are 20' long, about 3' apart, shear connected at the ends. There are beams connecting these two beams at third points. Do these beams provide lateral torsional buckling resistance for the two main beams, even if only shear connected? Without the beams providing lat-tors support, the beams fail in the existing load condition.






RE: Lateral Torsional Support
If you "heard" it on the internet, it's guilty until proven innocent. - DCS
RE: Lateral Torsional Support
RE: Lateral Torsional Support
From the commentary;
"C5.4.2 Restraints at a cross-section
The case of a cross-section that is restrained against twist rotation but free to deflect laterally is not included because of the difficulty of providing simple guidance.
Some very stiff torsional restraints may induce buckling modes in which the cross-section acts as if fully restrained (Clause 5.4.2.1), while in other cases torsional restraints may be comparatively ineffective, and the restrained cross-section may deflect laterally."
RE: Lateral Torsional Support
www.SlideRuleEra.net![[idea] idea](https://www.tipmaster.com/images/idea.gif)
RE: Lateral Torsional Support
In your case, even though the braces don't technically provide support for lateral displacement, they provide enough torsional support to prevent LTB.
If you have any appreciable lateral load, however, I suggest SlideRuleEra's solution.
If you "heard" it on the internet, it's guilty until proven innocent. - DCS
RE: Lateral Torsional Support
RE: Lateral Torsional Support
For this problem, ask yourself the question: "Does anything prevent the beam from laterally displacing *OR* twisting at the proposed braced point?" You might have a "lean-on" bracing system.
swearingen, I'd say your first statement is usually true, but surely has exceptions. I've never heard of an actual test.
I like SlideRuleEra's advice in this case.
RE: Lateral Torsional Support
RE: Lateral Torsional Support
RE: Lateral Torsional Support
RE: Lateral Torsional Support
Paragraph 2 under Article 6.3 states:
I'd say you can brace one beam to the other, as long as you can prove the brace and connection can take the moment given in Paragraph 2a.
In fact, large power boilers are constructed in this way, with perimeter beams around the furnace (buckstays) bracing each other for the entire height of the furnace.
RE: Lateral Torsional Support
I'm looking at this like the beam tries to rotate, and the lever arm of the beam connected to it produces a relatively small force up/down on the beam next to it. Now if I just had a table of, or direct way of calculating, combined shear and moment capacity for shear connections....