g.alshamsi
Civil/Environmental
- Sep 29, 2020
- 53
Hey all,
I'm modeling an assembly of a steel shear wall using S4R elements. I'm using a elastic-perfect plastic material model and a relatively fine mesh (10 mm global seed).
I want to include geometric imperfections in my displacement controlled general static step; from my research and what I understand through reading the manual, these are the steps that I took:
1) Make a copy of the original model (called it BUCKLE)
2) Perform a linear perturbation step to find the critical eigenmodes (requested 1st 5).
3) Edited the keyword file by adding
*NODE FILE
U
4) After the analysis is complete, I went back to the original model (lets call it Pushover) and added the following keywords:
*IMPERFECTION, FILE=BUCKLE, STEP=1
1,0.4
2,0.2
3,0.08
Where 1,2,3 refer to the eigen modes and 0.4,0.2,0.08 refer to the scaling factor (percentage of the wall thickness); I then ran the analysis and plotted the force-deformation shape of the new analysis against a previous one that doesn't include imperfections.
My issue is that, the models are exactly the same; in terms of deformed shape and F-D plot. I rechecked the .DAT file of the 2nd analysis and it reports that geometric imperfections were indeed considered:
*imperfection, file=BUCKLE, step=1
OPENED RESULTS FILE BUCKLE
RESULTS FILE WRITTEN BY Abaqus RELEASE 6.19-1 27-Sep-2020 01:58:15
READING RESULTS FILE BUCKLE
***WARNING: THE PART INSTANCE FOR SOME NODES IN THE OLD MODEL COULD BE FOUND
IN THE CURRENT MODEL. THE NAMES OF REQUIRED PART INSTANCES MUST BE
CONSISTENT.
***WARNING: THE PREVIOUS ANALYSIS CONTAINED 61067 NODES, BUT ONLY 60571 NODES
WERE FOUND ON THE RESULTS FILE
IMPERFECTION DEFINED BY LINEAR MODAL SUPERPOSITION
MODE NUMBER SCALE FACTOR
1 0.400000
2 0.200000
3 8.000000E-02
Can anyone shed some light on this issue? My gut feeling is that the software is not considering imperfections in the 2nd analysis however I can't confirm that. Is there another way to confirm that ABAQUS did indeed introduce the imperfections to the geometry? I looked at the deformed shape of the assembly at t=0 in the post processing mode with a high scale factor, however there seems to be no change. I tried increasing the scaling factor of the eigenmodes as well (multiplied by by 10) and there was no difference.
Any input is greatly appreciated, thanks in advance.
G-.
I'm modeling an assembly of a steel shear wall using S4R elements. I'm using a elastic-perfect plastic material model and a relatively fine mesh (10 mm global seed).
I want to include geometric imperfections in my displacement controlled general static step; from my research and what I understand through reading the manual, these are the steps that I took:
1) Make a copy of the original model (called it BUCKLE)
2) Perform a linear perturbation step to find the critical eigenmodes (requested 1st 5).
3) Edited the keyword file by adding
*NODE FILE
U
4) After the analysis is complete, I went back to the original model (lets call it Pushover) and added the following keywords:
*IMPERFECTION, FILE=BUCKLE, STEP=1
1,0.4
2,0.2
3,0.08
Where 1,2,3 refer to the eigen modes and 0.4,0.2,0.08 refer to the scaling factor (percentage of the wall thickness); I then ran the analysis and plotted the force-deformation shape of the new analysis against a previous one that doesn't include imperfections.
My issue is that, the models are exactly the same; in terms of deformed shape and F-D plot. I rechecked the .DAT file of the 2nd analysis and it reports that geometric imperfections were indeed considered:
*imperfection, file=BUCKLE, step=1
OPENED RESULTS FILE BUCKLE
RESULTS FILE WRITTEN BY Abaqus RELEASE 6.19-1 27-Sep-2020 01:58:15
READING RESULTS FILE BUCKLE
***WARNING: THE PART INSTANCE FOR SOME NODES IN THE OLD MODEL COULD BE FOUND
IN THE CURRENT MODEL. THE NAMES OF REQUIRED PART INSTANCES MUST BE
CONSISTENT.
***WARNING: THE PREVIOUS ANALYSIS CONTAINED 61067 NODES, BUT ONLY 60571 NODES
WERE FOUND ON THE RESULTS FILE
IMPERFECTION DEFINED BY LINEAR MODAL SUPERPOSITION
MODE NUMBER SCALE FACTOR
1 0.400000
2 0.200000
3 8.000000E-02
Can anyone shed some light on this issue? My gut feeling is that the software is not considering imperfections in the 2nd analysis however I can't confirm that. Is there another way to confirm that ABAQUS did indeed introduce the imperfections to the geometry? I looked at the deformed shape of the assembly at t=0 in the post processing mode with a high scale factor, however there seems to be no change. I tried increasing the scaling factor of the eigenmodes as well (multiplied by by 10) and there was no difference.
Any input is greatly appreciated, thanks in advance.
G-.