how to get backbone curve from PDMY material

[BuuNguyen]

Hi STKO, :
Im trying to get backbone curve from PDMY material by using customCommand in STKO as follows:
recorder Element –ele $eleNum -file $fName -dT $deltaT material $GaussNum backbone $p1 <$p2 …>
But I can not get the output file. Please have a look at my model in attachment.
Thank you for your help,
Buu

[STKO Team]

You had 2 mistakes:

• The "-" sign before the "ele" keyword is no a simple minus sign. It was a special character you pasted from somewhere and OpenSees did not recognized it. Please change it to a simple MINUS sign
• the material ID should be 1-based (from 1 to 4 in your case)

Here's the correct command format:
recorder Element -ele 723 -file bbc.out -dT 0.0089 material 1 backbone 54000

[BuuNguyen]

Yes, I copied it from Opensees wiki.
It worked now
Thank you for your reply

[STKO Team]

You're welcome

[sebi_magi]

Dear STKO team,

Is it possible to extract backbone curves / tangent matrix with the .mpco recorder? I tried without success. It is indeed possible with the custom command and classic OpenSees recorder, but exploring the .hdf5 output files would be better for me.

Kind regards,

Sebastian

[STKO Team]

Have you tried adding this custom result string into the "custom element results" section of the MPCO Recorder?

[sebi_magi]

Dear STKO Team,

I could record the tangent with the custom element results section, thank you. I could not record the backbone curve, maybe because it is not a tensor but rather two vectors relating shear strain and Gs. In any case the backbone curve is always the same for a given element, so I guess I can just record it with the OpenSees default recorder.

Kind regards,

Sebastian

[STKO Team]

In any case the backbone curve is always the same for a given element, so I guess I can just record it with the OpenSees default recorder.

Yes, it's like a material parameters so it should be the same for all elements with that material.