Topic: TOPIC: Performance Index – PostProcessing

Dear Atena users
One of my students is writing his Diploma Thesis on punching shear and we try to generate a Finite-Element model for some existing data.
This worked pretty well and the results are good. However, at the postprocessing my student found the item “Performance Index”. We do not really know how to interpret this parameter as we, to be honest, never looked at this. In the Atena-Handbooks this parameter is also mentioned just very briefly (and we couldn’t find any additional information about it) but it says it is an error measurement regarding the material model.
We always look for the chosen convergence criteria (0,5-1%) to be fulfilled and check the overall behaviour of our model. As mentioned, our model behaves like expected and we are able to catch the experimental results. However, when we look at the Performance Index, we get pretty high values where large areas are above 0,1 as seen in the uploaded picture:

We work with Material "CC3DNonLinCementitious2".

Could you please elaborate what this parameter exactly means and, if it is meaningful how we could improve this?

Any help is appreciated, best regards!