Springs stiffness

[Entey91]

Can you explain to me how OpenPile calculates the spring stiffness after calculating the ground pressure?

[TchilDill]

Is this comment related to issue #42?

[Entey91]

Yes, i calcolculated spring stiffness with tangent method, but my results are differents.
In particular what is the stiffness when py curve si horizzontal?