shear stiffness as a function of the axial force

[Katrin]

Dear all,

I am trying to set up a model of a wall where I want to allow for shear transfer along the base gap only if there is an axial force present. So I was looking for a spring-like element where the stiffness in lateral direction (x) is dependent on the force in vertical direction (z):

e.g. kx=alpha*Fz (and kx=0 if Fz positive, i.e. if there is tension across the gap).

I could not figure out what would be the best way to do it and it would be great if someone could give me an idea of how I could approach the problem.

Many thanks!
Katrin