Error Analysis : Laterally loaded pile with BNWF

[darmawan]

Dear STKO Team

I am trying to run a lateral cyclic loading analysis on a steel pipe pile in sand. I am using beam on nonlinear Winkler foundation to consider the soil pile interaction following this OpenSees example.
https://opensees.berkeley.edu/wiki/inde ... Foundation

I am stuck with the error of my analysis. Any suggestions to solve this error are very appreciated. Thank you in advance.

[STKO Team]

Dear user, the analysis error was due to a singularity in your model:
The slave nodes should be fixed also in Ry and Rx (you only fixed Rz). Rx should be fixed for imposing a 2D constraint in the XZ plane, as you did in the pile.
But the Ry should be fixed because the QY-TZ springs do not offer any stiffness in that DOF, and it is not linked to the beam Ry DOF via the Equal DOF.

(another minor error was in the monitor: you used a curly bracket in the Label, which is a reserved character in TCL)

So here is a working version of your original model:

Steel pile BNWF.zip

(188.92 KiB) Downloaded 213 times

Note that in STKO it is not necessary to manually draw the slave nodes and the EqualDOF between the beam and the slave nodes.
If you declare the ZL material as 3D-U (not 3D-UR) it will use 3 DOFs per node. Then STKO realizes that you linked it with a 6-DOF node, and it automatically creates an extra node with 3 DOFs, linking it with the beam nodes with an EqualDOF.
If you want to check it, look at the elements.tcl file generated.
Here is how I would do it, same model, same results, but the CAD model is cleaner.

Steel pile BNWF v2.zip

(174.86 KiB) Downloaded 204 times

[darmawan]

Thank you, STKO Team!!

I tried to use fiber section with Steel01 material and i get this problem, what does it mean? And where is the problem?

[STKO Team]

In your fiber section, GJ is 0.
So your beam is singular in torsion.

[darmawan]

ooh i see, thank you

[STKO Team]

You are welcome!