negative post-yield stiffness

03-Analytical/modelling capabilities
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sabrina.simonini
Posts: 6
Joined: 22 Feb 2011, 09:09

negative post-yield stiffness

Post by sabrina.simonini »

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
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seismosoft
Posts: 1263
Joined: 06 Jul 2007, 04:55

Re: negative post-yield stiffness

Post by seismosoft »

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

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