reinforcingsteel as moment-rotation

[bkosbab]

I've been struggling to find a material that includes the Bauschinger effect that can also model strength degradation. Ideally, I would like to put inelastic rotational springs at the joints between elastic members in a steel frame.

To start with, I have modeled a cantilevered column with a rotational spring at the base, and performed pushover tests. I have tried to use the ReinforcingSteel material to define a moment-rotation relationship and use its fatigue parameters to model degradation. With an essentially rigid column, this approach works well. Unfortunately, introducing flexibility into the column element causes numerical issues that I haven't been able to resolve, with or without fatigue defined.

I have also tried to use the beamwithhinges element and define a moment-curvature relationship within the base hinge length. Using the reinforcingsteel material gives a "bad trial strain" warning, accompanied by numerical issues.

I understand that the ReinforcingSteel material is not meant for moment-curvature or moment-rotation models, but what else is there that has the traditional steel behavior and can incorporate strength degradation (be it cyclic or energy-based)? Are there any plans to incorporate degradation into Steel02 or similar?

[silvia]

you could use any material in moment-curvature, but reinforcing steel is not a fully developed material.
you might want to combine hysteretic material and steel02 in parallel....

[bkosbab]

I understand how that could provide a degrading backbone curve, but do you have any suggestion for including cyclic strength degradation?

[silvia]

i think hysteretic has it.

[bkosbab]

Thanks, I see it now. I'll play around with hysteretic and steel02 in parallel.

[silvia]

i'd just make sure that hysteretic alone doesn't do all you really need.
s-