PySimple1 applicability

[blnbouwmeester]

Hi there!
I am looking for somebody with in-depth knowledge about the PySimple1 material as I am checking its applicability to monopile foundations. I made some observations in which I have difficulty explaining.
Through conducting displacement controlled analysis (sinusoidal unit displacement applied) on a single degree of freedom I found the that for soil type 1, soft clay, there is a 20% reduction in ultimate capacity pult after initial loading (for Cd < 1). For sand (soil type 2), this is not the case. Why is that, and what hard-coded parameter controls this? I tried looking in the source-code but without success.

Then, we see some reduction in stiffness after virgin loading which is the case for sands as well. This reduction disappears only after setting the drag resistance parameter Cd sufficiently high e.g. 10. My intuition was that by setting the material drag resistance equal to the ultimate capacity of the material (Cd = 1) stiffness would be the same after initial loading.
If the ultimate capacity pult is not reached in virgin loading, then we see some increase in reaction force for both materials. I dont think that this is happening, physically speaking, but I still want to understand how this is happening numerically speaking.

The material in piling application (laterally loaded pile example from OpenSees documentation as reference) shows some differences in stiffness after virgin loading even for Cd=10. The load applied here is a sinusoidal unit displacement at pile head.
Thanks in advance!

(I also posted this on the FaceBook page. Please see the post there for figures regarding the questions.)
https://www.facebook.com/groups/opensee ... 578891492/