Buckling Load Factor

[ptc-380107]

ProM Users:

I just used the ProM Buckling analysis module and have some questions.

To my understanding, a typical buckling study first involves a typical
static analysis. From this, a buckling analysis can be performed using and
based on the original static analysis. This all seemed to go well.

Does anyone have answers to the following questions on this topic:?

1. The B.L.F. (buckling load factor) is the only relevant data derived from
this study and is indicative of the magnification factor of the P(critical)
required to push the model to the critical deformation producing buckling?

2. The von mises stresses and deformation data produced from the buckling
study is not accurate.

3. The higher the B.L.F factor the buckling study produces, the less prone
to buckling your model will be. In other words, a higher B.L.F. is better
if your intent is to avoid buckling?

Any light anyone can shed on this topic would be greatly appreciated.

Greg Saiter
ABB Inc.
Columbus, Oh

[david.reid]

Greg

Sound to me like you've got it right.

Remember that this buckling capability only predicts the onset of buckling.
Beyond that things get all very complicated and non-linear.

Yes - a BLF of 1 or less indicates that your assigned load will cause
buckling.

No - it gives you more information than just that - it tells you what the
buckling mode shape will look like. But yes be careful about taking stress
and displacement data from these results - they involve linear
extrapolation.

If you get a negative BLF then this indicates that a buckling mode would be
initiated if the load were reversed.

If you have a thin structure under compression then the load required to
cause regular failure will often be much higher than that required to
inititate buckling. My recommendation is that you add features to your
model to prevent buckling, until the BLF gives you a decent safety margin.
I use the buckling mode shape to guide me to the best place to position
stiffening ribs.

I've seen many designs that have many regularly spaced ribs (supposedly to
prevent buckling) but these have clearly been added purely based on human
intuition. I'd rather use a more scientific approach to add them where they
were most efficient.


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David Reid
davidr@optima-design.co.uk
Optima Design Services Ltd
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