Linear buckling with perturbation?

General Questions
1

Hi all, does anyone have an example or other guidance for running buckling including the perturbation from a previous static step? Also how best to understand the results? I am getting numbers like 0.933 when I expect something like 100 000?

I can run a normal beam, apply end constraints etc and get results similar to manual calculations but I can’t get anything meaningful including the previous step.

I am sure I am doing something incorrect, just not sure what. The documentation is rather light on the topic.

If it wasn’t obvious already FEA buckling analysis in general isn’t something I have done much with. On the rare occasion I needed it I would just do a basic manual calculation but it would be nice in this case to include more detailed BCs as they make a huge difference to the results. (we are a talking about a 4,5m long 80mmx4 square steel post with a couple connections along the length)

thanks

Luke

2

The general procedure is simple. You just have to include the PERTURBATION parameter in the second (linear buckling) step. All the loads from the first step will be removed and only the one defined in the buckling step will be used. As a result, you will get a buckling factor that has to be multiplied by the magnitude of the applied load (that’s why a unit load is often used). I would suggest trying with a basic beam for which you have an analytical solution first and then adding the preload step if the results are correct without it.