hysteretic material,pinchx & pinchy

[mohammadkh]

Hello dear friends,
If I want to define a material which has hysteresis behavior, how I can do it.
another question about Hysteresis material. In hysteresis material ,there are pinchx, pinchy and beta. In opensees wiki, there are some magnitudes for them. I want to know, how these magnitudes obtained, experimentally or theoretically? if there are buckling in the members of space structures,hysteresis material can consider this buckling or not?
thanks
Kheirollahi