Self-Weight of AbsorbingBoundary3D

[Satoru]

Dear STKO Team,

I am performing a 3DFE analysis of nonlinear (UCSD) soil with AbsorbingBoundary, and I find that when I perform the analysis with AbsorbingBoundary, the confining pressure of the soil domain is not calculated as I would expect in gravity analysis, and I assume that the value of stress does not include the self-weight of the AbsorbingBoudary.
In this analysis, I performed the gravity analysis by setting the self-weight in $b3 in the Brick Element option.

Could you please teach me how to properly account for the self-weight of the AbsorbingBoundary in gravity analysis?
If there is a way to properly account for the self-weight of AbsorbingBoundary, I would be happy to share a sample data.

Best Regards,

[STKO Team]

Can you share a sample model?

[Satoru]

I created a sample data with AbsoringBoundary and without AbsoribingBoundary of gravity analysis. Please check the sample below.

FF1Brick_fix.zip

(95.89 KiB) Downloaded 127 times

FF1Brick_abs.zip

(86.59 KiB) Downloaded 127 times

[STKO Team]

... I assume that the value of stress does not include the self-weight of the AbsorbingBoudary ...

You are right, this is the difference between your 2 models.


As I explained in your previous post (viewtopic.php?p=9959#p9959):

Drawbacks in the current implementation:
Works only for the 3D version, not for the 2D one.
The FF columns now need the same self-weight (if any) given to the inner soil domain. Therefore you cannot use the ASDAbsorbingBoundary3DAuto, but you have to use the manual version (ASDAbsorbingBoundary3D), in this way, you have the extrusions of the absorbing layers on which you can apply the selfweight. On the contrary, the ASDAbsorbingBoundary3DAuto extrudes the absorbing layer "on the fly" when STKO runs the analysis. We need automation to make it work with the Auto version

We just finished implementing the above-mentioned automation. It will be available for everyone in the next STKO release 4.0.1.
In the meantime, you can:

• Unzip this python file

  ASDAbsorbingBoundary3DSelfWeight.zip

  (2.54 KiB) Downloaded 91 times

  in C:\Develop\STKO\external_solvers\opensees\conditions\Loads\Force
• Unzip this python file

  ASDAbsorbingBoundary3DAuto.zip

  (7.1 KiB) Downloaded 91 times

  in C:\Develop\STKO\external_solvers\opensees\element_properties\absorbingBoundaries, and replace the existing one

This is how you can implement it in your file:

FF1Brick_abs.zip

(91.49 KiB) Downloaded 104 times

You need to create the condition without assigning it to anything. It will automatically apply the self-weight to all absorbing boundaries generated via the ASDAbsorbingBoundary3DAuto condition.
Of course you need to put it in a pattern to include it in the opensees analysis.


Let us know if it works or if you have any doubts

[Satoru]

Thank you for your response and sending data.
I saved the python file and tried the method you showed me, but the error window in the URL below was launched when Write Input File. Do you know what the problem is?
https://www.dropbox.com/scl/fi/9abkczy1 ... jk4sg&dl=0


I also have a couple of questions.
1. Is it possible to give different self-weights to several AbsorbingBoundarys? I think this method gives a same self-weight to all Absorbing Boundarys.
2. Is it possible to set different self-weight for different Absorbing Boundarys in STKO Ver. 4.0.1? We plan to perform analysis with several layers of ground in the future, so it would be great if this functionality is provided.
3. When is STKO Ver. 4.0.1 to be available?

[STKO Team]

Thank you for your response and sending data.
I saved the python file and tried the method you showed me, but the error window in the URL below was launched when Write Input File. Do you know what the problem is?

This error means you only installed the ASDAbsorbingBoundary3DSelfWeight.py file, but you did not override the other ASDAbsorbingBoundary3DAuto.py replacing the existing one.

1. Is it possible to give different self-weights to several AbsorbingBoundarys? I think this method gives a same self-weight to all Absorbing Boundarys.

You are right, in this way it will assign the same to all absorbing boundaries.

Try to test it now with a uniform layer. In the meantime I will change the code so that in the ASDAbsorbingBoundary3DSelfWeight.py you assign the gravity acceleration vector. Then the code will assign, to each absorbing element, a self weight based on the g vector and the mass density from the absorbing material. Does it sound good for you?
I think I'll be able to provide you with the updated file between today and tomorrow

[Satoru]

This error means you only installed the ASDAbsorbingBoundary3DSelfWeight.py file, but you did not override the other ASDAbsorbingBoundary3DAuto.py replacing the existing one.

The analysis of one brick element I received worked fine! The problem seemed to be that the old python file was renamed and still existed in the same folder.

Try to test it now with a uniform layer. In the meantime I will change the code so that in the ASDAbsorbingBoundary3DSelfWeight.py you assign the gravity acceleration vector. Then the code will assign, to each absorbing element, a self weight based on the g vector and the mass density from the absorbing material. Does it sound good for you?

I will check the results in a series of gravity to dynamic analyses to see if it works correctly.
As you say, it would be great if you could set the load due to gravity based on the mass density of AbsorbingBounday element.

[STKO Team]

Update with these new files:

ASDAbsorbingBoundary3DSelfWeight.zip

(1.6 KiB) Downloaded 104 times

ASDAbsorbingBoundary3DAuto.zip

(7.35 KiB) Downloaded 101 times

In the self-weight now b is the gravity acceleration vector, and will be multiplier by the rho of the absorbing material while computing the self weight load.

Let me know if you encounter any issue

[Satoru]

Thank you for your response!
I performed the analysis using the python file you created and got the response I expected.
I will contact you again if I need any further assistance!

[STKO Team]

You're welcome