Cyclic response in the Bilin Material

[burnningcat]

Dear Sir,

I try to run a cyclic analysis using the model from the example of the “2-Story Moment Frame” with concentrated plasticity.
http://opensees.berkeley.edu/wiki/index ... ment_Frame
The plastic hinge uses the Bilin Material of Modified Ibarra-Krawinkler deterioration model with bilinear hysteretic response:

http://opensees.berkeley.edu/wiki/index ... n_Material

But I find in the cyclic analysis, when I reverse the load, I can not observe any “Unloading” in the response-The response just go along the same line of the monotonic curve, even there is the softening branch.

Then I just build a single section and apply the cyclic displacement, again I can not see any “Unloading”, and the response just go along the same line of the monotonic curve.

But I check the code of this Bilin Material, and it is very complex, so it should have the unloading and reloading branch. So I kindly ask if somebody can tell me how can I get the cyclic response using this Bilin Material? Many thanks to you!

[vesna]

I never tested Bilin material and I'm unable to respond to your question.

Try contacting Laura Eads who created the example. She should be able to resolve your problem.

Are you using the latest version of OpenSees? This material did not work on earlier versions of OpenSees.

[lewu009]

Me too. I never tested it. I will find some answer about that.

[burnningcat]

vesna wrote:
> I never tested Bilin material and I'm unable to respond to your question.
>
> Try contacting Laura Eads who created the example. She should be able to
> resolve your problem.
>
> Are you using the latest version of OpenSees? This material did not work on
> earlier versions of OpenSees.


I am using the version of 2.2.2, and should it be the latest version?
And would you please tell me the email of "Laura Eads"? Thank you very much!

[vesna]

The latest version is 2.2.2.f.

Also, on a Bilin Material page on wiki I posted a paper (reference #8) that explains the material parameters. This may be helpful.

[vesna]

At the bottom of this post: http://opensees.berkeley.edu/community/ ... =2&t=30954 I posted an example of a rotational spring that uses Bilin material. It is exposed to a static cyclic load.

[leads]

burnningcat -- Are you still having problems when you use version 2.2.2.g of OpenSees? If so, what are you plotting when you say that there is no unloading? The moment vs. rotation of a certain zeroLengthElement?

[burnningcat]

Thank you very much for your help. In the new version of 2.2.2g there is no problem. Many thnaks!