Extract data from integration points

[miran]

Hi,

I wish to extract stresses and/or strains from a solid element from a dynamic analysis. I am using LK-conditions, MP constraints, SSPBrick and PressureDependMultiYield material.

I am able to visualize the stresses by choosing "stress" and "strain" in the custom window of MPCORecorder rather than "material.stress" and "material.strain", but I cannot extract the actual data for one or several chosen elements using "Chart Data".

stress_strain.JPG (19.84 KiB) Viewed 3118 times

If I however choose "material.stress" and "material.strain", I am able to select these stresses and elements from "Chart Data" and "Element gauss points" using a "Gauss Plot", but no actual Gauss points are selected. I was expecting one point per element in this case.

gauss.JPG (30.46 KiB) Viewed 3118 times

To sum up - is it possible to extract (chart or datafiles) stresses and strains from element-defined integration points in solid elements through STKO? If so how?

Is it perhaps easier to first create an dummy analysis, check the numbering of the element in question and then simply use "recorder Element" in OpenSees?

[STKO Team]

The fact that you see 0 in the 3rd column, is because the gauss index is 0-based. If you proceed with the extraction, it should extract what you're asking for.

Or did I misunderstand something?

[miran]

Thank you for the reply.

I believe I see what the problem was. When using material model PressureDependMultiYield01, STKO names the stresses C1-C7 which corresponds to the stresses defined by the model (σxx σyy σzz σxy σyz σzx and ηr). I was trying to show σ11, σ22 etc.

[STKO Team]

Oh Yes, that's right.
PDMY01 puts into the stress output also other internal variables. Thus STKO does not recognize it as a stress tensor, therefore it does not rename the components and it does not compute stress invariants.

The PDMY02 allows you to output optionally only the stress tensor with 6 components if you request for the "stress.6" result.

If you do this, STKO will recognize it as a stress tensor. STKO will be aware of this in the new version 2.0.0 which will be released soon.

In the meantime, you can unzip the JSON file in this zip file:

opensees.zip

(1.21 KiB) Downloaded 190 times

And place it in C:\Program Files\STKO\odb_rules

[miran]

Great, thank you.