element type

[po0oya]

dear all
hi
in my model, both beams and columns carry significant amount of moment and axial loads and they are subject to formation of plastic hinges both at their ends and even in spans. corresponding to code, beams and columns should be remain elastic however only the two ends of beams allowed to form plastic hinge. I am hoping that someone could suggest me what kind of element should I use for modeling of beams and columns(in pushover analysis) in a way that makes it possible to control of their internal forces or deformation. in other word if I use nonlinear beam-column element for column, I can directly use the demand to capacity value taken as the beam-column interaction equation from AISC (axial moment interaction) to check it, however I don't have any idea about modeling beams. how should I model and check beams for remaining elastic at in-spans and only formation plastic hinge at their ends.
Thanks in advance.
thank you very much.

[fmk]

you can explicitly model the hinges as zero length elements with elastic elements in between as is done here:
http://opensees.berkeley.edu/wiki/index ... ment_Frame

or use the beam with hinges element: http://opensees.berkeley.edu/wiki/index ... es_Element

[Sanaz Ahlehagh]

Dear Sir,
Please note that in the "beam with Hinges" script given in the link you sent, the plastic hinge stiffness "ks_col" or "ks_beam", is not correct.
The stiffness is now: Ks_col=6*E*I_col/Lp_col
but shall change to Ks_col=6*E*I_col/L*Lp_col.

using forceBeamColumn/HingeRadau and the corrected Ks as I mentioned above, I get results which are close to the model with zero length element.

Please correct me if I am wrong.
thanks, Sanaz

fmk wrote:
> you can explicitly model the hinges as zero length elements with elastic
> elements in between as is done here:
>
> http://opensees.berkeley.edu/wiki/index ... ment_Frame
>
> or use the beam with hinges element:
> http://opensees.berkeley.edu/wiki/index ... es_Element