indicate formation of plastic hinges in FBE, fiber section

[cxc08]

Dear all,
Now I am confused with some basic questions..
I want to track the locations of plastic hinges formed in a 3D steel frame model during time-history analysis.
I use fiber section with forceBeamColumn elements. The sections are H-shaped and box shaped thin-walled sections.
But I wonder how deep and how long the plasticity development of fibers indicate the formation of plastic hinges.
I also want to know whether it is feasible to focus on plastic hinges because usually in steel structures there are local buckling but not plastic hinges happening at the end of beams and columns elements.

Looking forward to your help~

[xiell]

I think this quite relys on the distribution of the integration points and the discretization of the specimen.
I'm also interested in this topic.

[mhscott]

You can use the 'plasticDeformation' option in the element recorder (computed as shown in Fig.1 of http://dx.doi.org/10.1061/(ASCE)0733-9445(2007)133:9(1341) ) and/or record section forces in order to determine length of the plastic hinge. xiell is correct, it depends on the distribution of the integration points.

[xiell]

If we want to get the length of the plastic hinge as accurate as possible, maybe we should subdivide the specimen into several elements or increase the number of integration points. But this will bring some other issues such as convergence problem and soften phenomenon.
Dear Scott, would you like to give us some advices on how to balance the accuracy and robustness when we choose the integration points and the discretization scheme according to your experience.
Maybe there will be some other issues we should pay attention to, would you like to point it out simultaneously.
Gratitude

[mhscott]

Some of the issues are discussed here: http://dx.doi.org/10.1002/nme.2386 and here: http://dx.doi.org/10.1016/j.compstruc.2012.03.018

[xiell]

Thank you for your generous help!
Appreciate.