Seismosoft | Earthquake Engineering Solutions

hi everybody,
I'm looking at the lumped plasticity approach to model a cantilever structural wall, I'm using elastic beam-column frame element (elfrm) coupled with nonlinear links (Simplified bilinear Takeda curve). I calibrated the link and I assigned a convenient response curve for all 6 degrees-of-freedom.
I'm wondering if there is the possibility to assign a negative post-yield stiffness to the moment-rotation relationship.
I think it could be realized putting a negative values for the parameter "alfa" but I'm not allowed to do it. Is there another way to obtain the same result?
thank you,
Sabrina

Dear Sabrina,

Limits such as the one you describe have been introduced in the different models to make sure the latter behave as designed (for instance, a negative post-yield stiffness is typically incompatible with the unloading/reloading rules).

In the upcoming version of the software (likely to come out this month), hysteretic response curves featuring post-yield negative stiffness will be available.

Seismosoft Support