warning in eigen value

[fmk]

do a "print node" after it fails and find a node with an ID of 25 .. either node is free, not enough conatrstints or ele framing into it are producing a negative value for kii .. in which case either incorrect definition, or material is yielding and you have chosen the wrong type of solver as matrix no longer symmetric POSITIVE definite

[fmk]

it is typically not something that can be ignored as it typically means that the analysis has stopped .. if only occuring in the eigen command, do you get eigenvalues?

[AngusHunter]

Node: 2101
Coordinates : 0.381 4.572
Disps: 0 0 0
Velocities : 0 0 0
commitAccels: 0 0 0
Mass :
2.5 0 0
0 1e-016 0
0 0 1e-016

Rayleigh Factor: alphaM: 0
Rayleigh Forces: 0 0 0
Eigenvectors:
-2.16529e-017 6.77502e-008 -1.23543e-009
-0.447214 -4.26859e-008 7.6036e-010
0.053354 -5.90529e-008 1.05151e-009

Hi I get some Negative eigenvectors when I use command “print node”. Is it right? I am not sure, PLEASE help me !

[selimgunay]

Negative values of eigenvectors at some nodes are fine. It all depends on the mode shape

[robertomartinez]

can eigenvectors be negative even for the first mode shape ?