Abnormal results of nonlinear dynamic analysis

[shiRo]

Dear STKO team，
I am learning incremental dynamic analysis and I have tested my model at a PGA of 0.1g, 0.2g, and 0.3g, but I am getting what appears to be an anomalous result. As shown in the figure, the displacement at the top of the column shows the exact same displacement trend for the three different PGA cases, and it also has anomalous displacement data I think. I then checked the model settings but I still haven't been able to find the cause of this result, can you help me find where the problem is? Thank you very much!
Best regards

[STKO Team]

The follow the same trend and they seem to be a scaled version of each other. probably your structure is still elastic under those inputs. Did you check it?

[shiRo]

The follow the same trend and they seem to be a scaled version of each other. probably your structure is still elastic under those inputs. Did you check it?

Thank you for your suggestion, after reading your suggestion I verified your conjecture on an elastic frame structure and did get displacement results with the same trend but different values.
I then ran the complete analysis from 0.1g-1.2g and I found that the analysis process was interrupted unexpectedly at 0.4g and 0.7g, but I could run the analysis normally at the subsequent 0.5g and 0.8g cases, and the interruptions also occurred at 1.1g and 1.2g, what caused this to happen?
One more thing, as I mentioned before there is the same displacement trend at 0.1g, 0.2g and 0.3g, similarly at 0.9g there is the same displacement trend as before, but there is no such trend at any other condition between 0.3g and 0.9g, so I speculate that there may be some wrong parameter settings in my model that are causing these anomalies, and I have modified one of the settings and now it can run the analysis under every seismic wave, can you help me to check it and give me some new suggestions? Thank you very much!

[STKO Team]

Try using Adaptive Time Step (instead of Fixed Time Step) in your dynamic analysis.
In this way STKO will try to adapt the time step size if a convergence issue is encoutered