Buckling of beam on elastic foundation 1

[dedwardn]

Hi.

I'm pretty new to ABAQUS, and I'm trying to make a simple model of a cantilever on a elastic foundation. I wanted to model the foundation with springs, but can't seem to get the model to take into account the spring stiffness. I've been using this video (

http://www.youtube.com/watch?v=YQLoQqinbdo)

to set up my model and then added springs under engineering features.

I would expect the eigenvalues to increase when the stiffness is increased, but nothing happens.

Can someone help me with this? I've attached the file.

 

[lec235]

I'm running into the same issue with my model. I'll let you know if I come up with something!

 

[rb1957]

assuming you're modelling right (a big assumption), maybe the modes being detected by the eigenvalues are not restrained by the supports ?

 

[lec235]

Interesting thought. But would that be the case if the model is 2D and the mode shapes look right?

 

[ESPcomposites]

Have you tried changing the spring stiffness values by a large amount? Perhaps they are too soft and not making a substantial difference.

Brian

http://www.espcomposites.com

 

[lec235]

Brian,

That's what I'm finding is working. If the values in the initial eigenvalue analysis are large, you have to change the stiffness values a lot more than you expect. For example, in my model I started with k=1 and the mode 1 eigenvalue was 2.72747e05. Changing to k=100 gave a mode 1 eigenvalue of 2.728e05.

 

[rb1957]

a stiffness of 1 lb/in sin't much at all ... 100 lbs/in is only a little more ... 1E5 is more "realistic" ... EA/L ... E = 1E7, A = 0.1in2, L = 10in ...