Effective Length
Effective Length
sketch?
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RE: Effective Length
RE: Effective Length
RE: Effective Length
out of plane, 9000
RE: Effective Length
RE: Effective Length
Yes, I'd say 1500 for all.
RE: Effective Length
Doesn't make sense to me but makes a huge difference in leg capacity.
RE: Effective Length
The 4.0M may refer to the overall column. A latticed column is designed as a unit and as individual ties and struts.
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Effective Length
The FEA will take into account the column shortening and relative stiffness of the members and how much load will go from the vertical columns into the diagonals.
If you have a massive W-shape column with light angle lattice work, not as much vertical load goes into the bracing as opposed to if the lattice bracing was a very heavy section.
For the most part, the heavy lattice columns I work with are latticed for lateral loading.
RE: Effective Length
For the lattice beam as a whole, Lbxx = Lbyy = 9m
FEA will deal with this as a 2nd order, P-Delta effect.
RE: Effective Length
It seems to me that the overall column could be less than full height, the overall base is, to all intents and purposes, fixed. The column bases are free to move up but they don't want to, they cannot move sideways or down, so I think moment and gravity loads for the overall column are resisted.
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Effective Length
RE: Effective Length
paddington - I recognize your point about the brace compressing and dragging the column in a little bit, but I don't believe that effects the buckling length of the column. The brace is still there and would prevent the buckling mode of anything greater than 1500. The buckling mode of the 1500 segment may be very slightly out-of-plumb as a result of the diagonal compression that you mention, but I don't believe it changes the buckling length.
RE: Effective Length
RE: Effective Length
However, I agree that for member design the unbraced length will be 1.5m with a k=1.0. But if we provide each member to 3 times its required strength and avoid member buckling as a failure mode, can't the system buckle globally? Just a thought....
RE: Effective Length
No, I agree the whole system can buckle. That's how you would check a latticed column. My comment was for the the individual vertical members.
I just have a really hard time believing that the global buckling would control the design for all but very tall pieces. I haven't put pencil to paper, but it makes intuitive sense to me. I, and, consequently, r increase as exponential functions of the distance between the individual vertical pieces. I could be way off base, but that's what makes qualitative sense to me.
RE: Effective Length
EIT
RE: Effective Length
This makes sense to me now - but I thought I was going mad!