Cyclic Test (Input Validation)

[Zouatine]

Dear STKO team,

First of all I wish you a happy new year.

I am reaching out to kindly ask your insight about the following point:

So I just modelled a 2D model of soil (1mX1mX1m) and did run a cyclic loading test, the analysis is running fine as following:

cyclic_test.png (180.63 KiB) Viewed 184 times

I had given as input of Normalized modulus reduction with respect to strain :

Strain (%) G/G0
1e-05 0.98
3e-05 0.95
0.0001 0.85
0.0003 0.6
0.001 0.3
0.003 0.15
0.01 0.06

with refshearModul equal to 1.35e+08, then from the results of the first cyclic loading test (displacement Vs shear force) , I did selected the first cycle (tiny displacments) , from where I derived the Shear Modulus G0 got the value of 7.00e+07 so the input stiffness is quite 2 times higher then the output + I also extend the preprocessing and derive the G/G0 and strain and it is quite different as you can see in the figure below:

Input_Output_Comparison.png (46.17 KiB) Viewed 184 times

would you please help me to identify where is my issue ? the model as well as the results are in the following file.

Lotung_Site_Full_layer_Real_GM_NonLinear_Soil_V1_Only_Lateral_Load_One_Element (2).zip

Thank you,

Zouatine

[STKO Team]

You should revise your model.
You used absorbing boundaries that are not correct in this example.
You should use equalDOF on the vertical sides, to impose a shear motion.
Optionally (if you discretize your quad with more that 1 element) you need an equalDOF on top to avoid rotaiton (Equal UY)