Hello everyone,
I have performed a modal analysis with Lanczos of a steel structure. Before optimizating it i used the following step
*STEP, NAME = MODALANALYSE
*FREQUENCY, EIGENSOLVER = LANCZOS, NORMALIZATION = DISPLACEMENT
50,0.0 ,200.0 ,,,
*BOUNDARY
fixed_points,1,6,0.0
*OUTPUT, FIELD, FREQUENCY = 1
*NODE OUTPUT
U,
*ELEMENT OUTPUT
S,
*OUTPUT, HISTORY, FREQUENCY = 1
*MODAL OUTPUT
*END STEP
pretty standard...
The problem comes with the meaning of the amplitude of the movement. For me, that wasnt ever really relevant. What important for me was the response of the structure and the frequencie at which this response happened.
But now I am a bit disconcerned.
I stiffened the structure with some beams and the first frequency comes later, as expected. But the first two eigenfrequencies have a displacement in the order of 1E-3mm... I need a scaling of 1000 in order to notice what its happening. Later on, I have another frequency in the range of 1mm.
In my opinion, the first two frequencies are low kinetic energy eigenfrequencies, and this is what Lanczos is telling me with the small amplitude. But IMO its strange that this comes at lower frequencies than bigger kinetic energy eigenfrequencies.
Could be something be wrong?
Thanks for your help in advance.
Best regards
I have performed a modal analysis with Lanczos of a steel structure. Before optimizating it i used the following step
*STEP, NAME = MODALANALYSE
*FREQUENCY, EIGENSOLVER = LANCZOS, NORMALIZATION = DISPLACEMENT
50,0.0 ,200.0 ,,,
*BOUNDARY
fixed_points,1,6,0.0
*OUTPUT, FIELD, FREQUENCY = 1
*NODE OUTPUT
U,
*ELEMENT OUTPUT
S,
*OUTPUT, HISTORY, FREQUENCY = 1
*MODAL OUTPUT
*END STEP
pretty standard...
The problem comes with the meaning of the amplitude of the movement. For me, that wasnt ever really relevant. What important for me was the response of the structure and the frequencie at which this response happened.
But now I am a bit disconcerned.
I stiffened the structure with some beams and the first frequency comes later, as expected. But the first two eigenfrequencies have a displacement in the order of 1E-3mm... I need a scaling of 1000 in order to notice what its happening. Later on, I have another frequency in the range of 1mm.
In my opinion, the first two frequencies are low kinetic energy eigenfrequencies, and this is what Lanczos is telling me with the small amplitude. But IMO its strange that this comes at lower frequencies than bigger kinetic energy eigenfrequencies.
Could be something be wrong?
Thanks for your help in advance.
Best regards
