Recorders for Moment-Curvature of columns of 3D RC frame

[geoStru]

Hello everyone, I built a 3D RC frame and I would like to study the ductility of the columns (moment-curvature).
The example of the wiki uses the zeroLength element, but it is a only column with axial force N=constant.
For my structure which recorder can I use? And should I use the zeroLength element?

[mhscott]

recorder Element $eleTag section $secNum forceAndDeformation

should record force and deformation at section number $secNum (1...Np)

[selimgunay]

It is better to use a beam column with a fiber section that can capture the effect of axial force on the moment capacity.

You can use these to record the moment-curvature of the sections of beamcolumn elements

force – section forces

example: recorder Element -file ele1sec1Force.out –time -ele 1 section 1 force

deformation – section deformations

example: recorder Element -file ele1sec1Defo.out –time -ele 1 section 1 deformation

[mhscott]

The 'forceAndDeformation' option will put section forces and deformations in one file.

[geoStru]

Yes, it works.
For the output of the force I think that I geo:
-time N M1 M2 ? ?
And for the deformation? I attacching the string of the ultimate time of pushover (disp=0.05*7.2m=0.36m)


| time | deformation | force
1.71018 0.0471195 -0.241791 7.63915e-05 -2.61472e-19 -2.61472e-19 16847 -323270 109.477 -2.61472e-09 -2.61472e-09

this is a base section of a node (with fix 1 1 1 1 1 1). Is it normal -0.24 for the second deformation?
I use N and m for the units

[selimgunay]

You can add the xml option here to your recorder to figure out what each column represents

recorder Element <-file $fileName> <-xml $fileName> <-binary $fileName> <-precision $nSD> <-time> <-closeOnWrite> <-dT $deltaT> <-ele ($ele1 $ele2 ...)> <-eleRange $startEle $endEle> <-region $regTag> $arg1 $arg2 ...

[geoStru]

Thank you for reply. The file -xml is very useful.
Now I trying to get a curve M-ϑ but I couldn't be wrong
The curve F-s of 3D RC frame seems right
But the curve M-ϑ doesn't decrease and I don't get the collapse (I used concrete02 and steel02).WHy?
I am attaching the link for the images https://drive.google.com/drive/folders/ ... sp=sharing

[mhscott]

The steel strain hardens indefinitely, so you'll have to try wrapping the material with MinMax

https://opensees.berkeley.edu/wiki/inde ... x_Material

[geoStru]

The steel strain hardens indefinitely, so you'll have to try wrapping the material with MinMax

https://opensees.berkeley.edu/wiki/inde ... x_Material

#Steel02
set Fy [expr 450*$Nmm2]; #N/mm2
set Es [expr 200000*$Nmm2]; #N/mm2
set Bs 0.01;
set R0 18;
set cR1 0.925;
set cR2 0.15;


set IDSteel02 3
set IDSteel 4
set minStrain -1.0e16.0
set maxStrain 0.0675
uniaxialMaterial Steel02 $IDSteel02 $Fy $Es $Bs $R0 $cR1 $cR2; STEEL02
uniaxialMaterial MinMax $IDSteel $IDSteel02 $minStrain $maxStrain;
but WARNING invalid option:-1.0e16.0 uniaxialMaterial MinMax tag: 4
I tried many values (-0.0675;0.0,...) but there is the same error

[mhscott]

You have to use -min and -max

uniaxialMaterial MinMax $IDSteel $IDSteel02 -min $minStrain -max $maxStrain;

[selimgunay]

With p-delta and increased axial force, moment-curvature would have a descending portion. You can compute the ultimate curvature as the curvature corresponding to a) ultimate strain of concrete, and b) fracture strain of the longitudinal reinforcement, whichever happens first.

[geoStru]

With p-delta and increased axial force, moment-curvature would have a descending portion. You can compute the ultimate curvature as the curvature corresponding to a) ultimate strain of concrete, and b) fracture strain of the longitudinal reinforcement, whichever happens first.

Infact I thought the curve is wrong. I am trying to use uniaxialMaterial MinMax with the Steel02 with range of values -0.0675 to 0.0675 (67,5‰)
For the concrete02 I set the confined and unconfined materials. Should I do the same for the concrete (with uniaxialMaterial MinMax)?
To compute the ultimate curvature how to described, how can I do?
If it help, I can attacching the script of my materials

[selimgunay]

You should record the strains of the outermost confined concrete fiber on the compression side and the outermost steel rebar on the tension side

[geoStru]

Dear selimgunay and mhscott, during my thesis I should run many parametric analysis to study the ductility of global structure and the elements (columns). The behavior of concrete is correct.
If I put, for the Steel02, minmax to 0.0675 (for the def) a lot of analysis didn't converge.
In the other way if I dindn't use the minmax the curves M-ϑ reamin costant after the peak (but the analysis converge).

Which material could I use to obtain the correct behavior? I am thinking to use the "Ibarra-Medina-Krawinkler" material fot the reinforcement longitudinal. Could it be correct?

[selimgunay]

So you are trying to model the steel rebars right? If it is Grade 60 steel the ultimate strain is more than 0.0675 and in the order of 0.12.

What you can do is two things:
1. Run all analyses without minmax and monitor the strains. If they are below the ultimate strain, it means all your analyses are valid.
2. Try another materials, two options are:
https://opensees.berkeley.edu/wiki/inde ... l_Material
https://opensees.berkeley.edu/wiki/inde ... c_Material