About the plastic rotation of the dispBeamColumn

[caosasa]

Dear all,
i am computing the plastic rotation of piers of bridge with OpenSees.
The pier is about 20 meters in elevation.
Fiber section and dispBeamColumn are used for all the elements.
Each element is 2 meters in length.
The number of the element is from bottom to top of the pier.
The element at the foot of the pier is number 1.
The plastic rotation of element 1 is -0.0033242, 0.00331776 for node 1, 2.
The plastic rotation of element 2 is -0.00160693, 0.00159828for node 2, 3.
i have two questions:
1. why the plastic rotations up and down node 2 are different? shouldn't they be identical?
2. can the plastic rotation of element 1 be computed as lp*(0.0033242+0.00331776)/2?
Thanks!

[caosasa]

Dear vesna, would you please consider my question? Thank you very much.

[vesna]

I would avoid using plastic rotation recorder for nonlinear elements. I would rather use curvature and plastic hinge length to calculate plastic rotation.

[caosasa]

vesna wrote:
> To get plastic rotation of plastic hinges for element 1 here is the
> command:
>
> recorder Element -file Element1.out -time -ele 1 plasticDeformation
>
> The file will contain 4 columns. The 1st is time, the 2nd is axial plastic
> deformation, the 3rd is plastic rotation at node i, and the 4rt is plastic
> rotation at node j.

Dear vesna, i appreciated your reply.
I saw your answer in the "how record the rotate in Hinges in steel frames" post to get
plastic rotation of plastic hinges. i am confused now:
1. why can't i use plastic rotation recorder in this situaion? is plastic rotation recorder
fit for beamwithhinges element, but not nonlinear elements?
2. how can i use curvature and plastic hinge length to calculate plastic rotation? would
you show me an example please? i have record the curvatures at integration points.
subtract the yielding curvature from it. calculate the plastic rotation with the integration
rule. isn't it?

[vesna]

From the time I posted the answer on how to record the plastic rotation I had many users complaining about results that would not make sense. That is why I suggested not to use the recorder but to calculate it indirectly.

[caosasa]

Dear vesna, thank you for your reply.
I saw other users are also confused about how to compute the plastic rotation.
Would you please consider the question 2:
how can i use curvature and plastic hinge length to calculate plastic rotation? would
you show me an example please? i have record the curvatures at integration points.
subtract the yielding curvature from it. calculate the plastic rotation with the integration
rule. isn't it?

[vesna]

if you search the message board you will find answer to your question.

[paperairplane]

Dear caosasa ,i still cannot understand why the ratation of node 2 are different?

[caosasa]

paperairplane wrote:
> Dear caosasa ,i still cannot understand why the ratation of node 2 are
> different?
will you give me your email please,
i will send you a PDF about it.

[paperairplane]

caosasa wrote:
> paperairplane wrote:
> > Dear caosasa ,i still cannot understand why the ratation of node 2 are
> > different?
> will you give me your email please,
> i will send you a PDF about it.
shaohaiyipiao@gmail.com
thank you!

[amir70007]

Dear caosasa
Would you please send the PDF for me?
amir70007-@-yahoo.com
thank you

[saijbz]

Dear caosasa
Would you please send me the PDF too?
saijbz@126.com
thank you

[linzhidan]

dear caosasa
would you plase send the pdf to me ?
zhidanlin@sina.com
thanks
and do you find the ways to calculate plastic rotation form curvature and plastic hinge length?

waiting for your reply

[sabir]

dear caosasa
would you plase send the pdf to me ?
sabir_lotfi@yahoo.com
thanks
"""and do you find the ways to calculate plastic rotation form curvature and plastic hinge length?""""""

please told me do you find the answer of question 2 (how can i use curvature and plastic hinge length to calculate plastic rotation)
Regards