Problem: Abaqus - non linear buckling analysis - mode - scale factor?

[PiusCottier]

Dear colleagues
Problem: Abaqus - non linear buckling analysis - mode - scale factor
I try to do a non linear buckling analysis of an i profil. After completing the eigenvalue analysis, i got several modes. I tried to implement the first mode (global buckle) with an imperfection according to the Swiss code. This is l/300. For me this equals to 0.02m (l=6m).
As I implement it with :
* IMPERFECTION, FILE = Knickfiguren_IPE600_6m, STEP = 1
1,0.02
my critical load becomes about 0.5* what it should be. I try to adjust the scale factor, and for the correct critical load it should be around 0.00002.
This looks like an unit problem, but I check it several times and there is everything correct. I used SI units, everywhere. If I run it without imperfections, the results are correct. So the only thing I change is the new line in the keywords with the imperfections.
Does anyone know what the problem could be? Did I something wrong with this scale factor?
And is there good literature available for combination of the modes for later purposes?
Thanks a lot in advance
Pius

 

[FEA way]

Structures with imperfection sensitivity may give incorrect results when imperfections are based on a single buckling mode. Try adding more modes to the imperfection. And check the paragraph "Imperfection sensitivity" of the Abaqus documentation chapter "Introducing a geometric imperfection into a model".