Lateral Torsional Buckling
Lateral Torsional Buckling
(OP)
Say you have floor joists spanning over cross beams (beam sitting on top of the flange of another beam,) does this constitute a brace point if the bottom flange is welded to the top flange of the beam it is sitting on? If not, then how can we make it a brace point? (Stiffener?)






RE: Lateral Torsional Buckling
RE: Lateral Torsional Buckling
RE: Lateral Torsional Buckling
Using this as a brace point is all about stiffness and detailing. I would encourage you to consider a bolt plate welded to the top of your beam and fastened through the joists, or directly welding (NOT bolting) the joist to the top of the beam. Again, stiffeners are required.
Hope that helps,
Cheers,
YS
B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...
RE: Lateral Torsional Buckling
Clansman's situation appears to fit the criteria provided the joists are suitably restrained longitudinally. Welding of the joists to the beam will improve the restraint by also providing some torsional restraint.
RE: Lateral Torsional Buckling
Again, apsix was quite right in saying that it is the compression flange that is key, however my comments were made with the understanding that you are considering a continuous beam accross a supporting member. In that case the top beam sees this as a brace point only if a stiffener is provided and the connection is torsionally rigid.
I think dgkhan has the most appropriate post: Clarify what you meant!
Cheers,
YS
B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...
RE: Lateral Torsional Buckling
RE: Lateral Torsional Buckling
RE: Lateral Torsional Buckling
If it is a continuous beam or is subject to uplift then it needs restraint to the bottom flange and the configuration is not sufficient.
RE: Lateral Torsional Buckling
RE: Lateral Torsional Buckling
Cheers,
YS
B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...
RE: Lateral Torsional Buckling
RE: Lateral Torsional Buckling
I was referring more specifically to the beam that sits on a supporting orthogonal beam.
RE: Lateral Torsional Buckling
That would be classed as 'partially restrained' by AS4100.
RE: Lateral Torsional Buckling
Need either fly braces or welded stiffeners to restrain the top flange.
There is a good gouide put out by the Australian institute of steel construction (or whatever they are called now) that gives good examples of what is what.
I think its called 'design of unrestrained beams' I suggest your office gets a copy if it doesnt have one already.