Dear all,
I am studying how to conduct lateral-torsional buckling analysis of a simply supported beam. The beam is purely elastic, and the boundary conditions are shown below.
I started with a linear perturbation buckling analysis to obtain the critical buckling load and normalized mode shapes. Then a geometric imperfection was introduced by scaling the obtained first mode shape for post-buckling analysis. After that, the load is applied by prescribing the obtained critical load from the linear perturbation buckling analysis. Finally, the model was solved by three methods and the results were compared (please find the attachment). Surprisingly, the force versus out-of-plane displacement curves obtained by these three methods is different.
Furthermore, it was found that different loading scheme (i.e. force vs displacement control) yields different out-of-plane displacement at the same level of in-plane vertical displacement. Even more strange, when displacement control is used (solving by either Dynamic Explicit or Implicit), the out-of-plane displacement vs in-plane displacement relation changes if the prescribed displacement is changed.
Could you please suggest what may be the reasons?
Many Thanks!
Regards,
YL
Dynamic analysis generally gives less displacement for the same load until you use quasi static analysis.
For static analysis using riks step, make sure you draw the relation between the force and displacement not the force not force with arc length
Khaled Megahed
Hi Khaled,
Thanks for your response! I found that the loading time may be attributed to the mentioned problem. For the Risks method, inertia and damping effect so it should give the most reliable result for this kind of problem. On the other hand, Dynamic solver takes account for inertia effect and the Static stabilized method considers the effect of damping. In this case, therefore, the step time has a great influence on the results.
Regards,
YL
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