Pinching4 Material Model

[MichaelDupuis]

Hello All, I am trying to model a material with the Pinching4 uniaxial material model. I need to model a material which is elastic-perfectly plastic and loads and unloads directly along the backbone curve during cyclic loading . I also need to make it so that the material is stronger in one direction than the other. I have been messing around with the 34 input parameters for the material model and can't produce a hysteretic model which I am happy with. I am having problems producing the deisred unloading along the same path that loading occurred (the backbone of the EPP hysteretic curve). Any help or suggestions are greatly appreciated, thanks
Mike

[vesna]

Are you looking for self-centering material that does not have a loop (does not absorb any energy)? Such element does not exist in opensees. The closest material to that one is SelfCentering Material (http://opensees.berkeley.edu/wiki/index ... g_Material). This material can produce flag shaped hysteresis. By setting the material parameters you can come up with the material whose area of the flag is close to zero.

[MichaelDupuis]

The SelfCentering material can do exactly what I want with one exception. I need to be able to model different strengths in the positive and negative directions and as far as I know this is not possible with the SelfCentering material. Thanks for the help though, do you have any more suggestions?

[MichaelDupuis]

Anyone with any suggestions?

[vesna]

I'm sorry but such material does not exist in OpenSees. You will have to create it yourself.

[em17]

if you put your self centering material in series or parallel with some elastically perfectly plastic gap materials then you can change the compression or tension description while maintaining the other...I have a material that basically takes no compression but follows a trilinear tension behavior so I put it in series with a very stiff material to cancel out the compression side of the self centering material's description. I hope this addresses your question.

[vesna]

I figured out there is a material in OpenSees that can solve your problem. It is ElasticBilin material: http://opensees.berkeley.edu/wiki/index ... n_Material