first plastic hinge

[imancivil]

Hi all

i use nonlinear analysis (material is steel02). how can i find when the first plastic hinge in a structure occur?

tnx.

[silvia]

you have to do it in post-processing.
you can either look at the overall pushover curve, and/or look at all the critical hinges and watch their response.

[amir70007]

Hi All...
Which recorders are used to obtain elastic or/and plastic rotation in an element?

How can I find out that the plastic rotation is in which integration point in a FBE or DBE?(Does plastic rotation take place in IPs in DBEs too like FBEs?)
Does it report rotations for all of the integration points in an element?

Is there any source about nonlinear hinges that I can verify my results with that?

Thank you

[vesna]

There is a recorder (plasticDeforamtion) on a FBE that records plastic rotations at the element ends.

Several users complained about this recorder. You can test it out yourself. In case it does not work for you, you can record curvature at the integration points and calculate elastic and plastic rotations from it. There are the posts on the message board that describe the procedure.

[amir70007]

Thank Dear Vesna...
I could not find the posts about calculate elastic and plastic rotations from curvature at the integration points.

[amir70007]

Hi...
I am not sure if curvature at the IPs is related to chord rotation.
FEMA uses chord rotation for evaluating plastic hinges.
I want to compare FBE rotations with FEMA criteria.
I want to know how does opensees calculate curvature and if it raltes to chord rotation?
Thank you

[vesna]

In case you need chord rotation, the recorder is basicDeformation

Check out this OpenSees webinar on FBE: http://opensees.berkeley.edu/wiki/index ... ed_Element
If you go over it carefully you will see how FBE calculates basic deformation given the curvature.

[amir70007]

Thank you for your reply.

I've seen another answer for chord rotation from Frank here...
http://opensees.berkeley.edu/community/ ... hp?t=20859
As you see Frank said that chordDeformation is the recorder for chord roation.
What is the difference between chordDeformation and basicDeformation to get chord roation in a FBE?

And the other question is that can I use curvature results in an element to obtain chord rotation in that element?
Thank you

[vesna]

There is no difference between chordDeformation and basicDeformation. Both will give you the same result.

Yes, you can use curvatures at integration points of the element to obtain chord rotation.

[le2night]

vesna wrote:
> In case you need chord rotation, the recorder is basicDeformation
>
> Check out this OpenSees webinar on FBE:
> http://opensees.berkeley.edu/wiki/index ... ed_Element
> If you go over it carefully you will see how FBE calculates basic
> deformation given the curvature.

Dear vesna
i want to know how OpenSees caculating the basicDeformation, integrating the curvature to the rotation Or just using (nodeRotation-ChordRotation).
And could u tell me in which folder/file of source codes from SVN i can find the formula of caculating the basicDeformation.

[vesna]

Here you can find presentation on force-based element: http://opensees.berkeley.edu/wiki/index ... ed_Element

Basic deformation is denoted by vector "v" on the slides.