Getting same pushover curves

[AmitKur]

I have modeled a 3 storey 3-D fame model using force based elements having 5 integration points and considering rigid diaphragm. I performed nonlinear static pushover pushover analysis for a drift of 4%. The concern is that I am getting the same pushover curves for frame without aggregating shear in fiber section and by aggregating shear to fiber section. As, I am trying to capture shear behavior too, so aggregated the shear in both y and z axis by defining elastic material having shear stiffness GA. I am able to get the shear force and shear deformation after aggregating shear, but the pushover curve is exactly same, don't know why?

Please provide me suggestions and If I am wrong, please correct me. Hoping to hear soon.

Thank You.

[mhscott]

Probably a modeling issue. You have to provide more details.

[AmitKur]

Sir I have defined 3D force based elements, Beams and columns, Linear transformation.
ops.section('Fiber', SecID,'-GJ',SomeLargeValue)
.
.
.
.
ops.uniaxialMaterial('Elastic',matTag,Gc*ShearArea)
.
.
.
.
And then agregated this material to previously defined fiber section
ops.section('Aggregator', NewSecID, matTag,'Vy',matTag,'Vz','-section',SecID])

[AmitKur]

And, Something more Sir.

I am getting 2-3% difference in eigen values as obtained from Opensees and SAP2000. Gravity Analysis is giving me base reaction equal to the applied vertical load. Moreover, pushover curves are matching with SAP2000. The only difference I am unable to figure out is that why the results are same even after aggregating the shear. Please help me in this regard Sir. Thank You.

[mhscott]

Try a simple cantilever with shear deformation and build up from there.

[AmitKur]

Hello Sir,

As per your suggestion I tried cantilever problem and 3-D frame problem, "OpenSees Example 2c. Nonlinear Cantilever Column: Inelastic Uniaxial Materials in Fiber Section" and "OpenSees Example 7. 3D Frame, 3-story 3-bayX 3-bayZ, Reinforced-Concrete Section". I am getting the same pushover curves before and after section aggregation, for both the cases.

I have attached screenshots and results for your reference. Please correct me if I am doing it wrong way. Thank you and hoping to get response from you.
[img]https://paste.opensuse.org/pastes/f4c7300547b4
[img]https://paste.opensuse.org/pastes/be91bc3273bc
[img]https://paste.opensuse.org/pastes/49bee58f50a0
[img]https://paste.opensuse.org/pastes/02969e6116f6

[mhscott]

I don't know what you're showing via the screenshots.

Build a simple cantilever with elastic sections, then aggregate shear. Don't start from someone else's script. Do it yourself, from zero.

[AmitKur]

Sure Sir

[AmitKur]

First screenshot shows the part I added for shear aggregation in Opensees wiki example, "OpenSees Example 7. 3D Frame, 3-story 3-bayX 3-bayZ, Reinforced-Concrete Section".
Second screenshot shows the part I added for shear aggregation in Opensees wiki example, "OpenSees Example 2c. Nonlinear Cantilever Column: Inelastic Uniaxial Materials in Fiber Section".
Third screenshot shows the pushover curves I obtained after running "OpenSees Example 2c. Nonlinear Cantilever Column: Inelastic Uniaxial Materials in Fiber Section" Opensees wiki example, both, with and without shear aggregation.

And the last screenshot shows the results obtained in tabular form.

And Sir, what's wrong in analyzing and taking help from the already well established Opensees Examples. I have written my script in python. I found some problem in that, so posted in this forum. You are telling me to start from Zero, right. Just tell me, If I am making mistake in my routines, will I be able to find the solution by ruining my routines again and again or by analyzing some standard examples from Opensees wiki page. Sir If you want to help, you are most welcome. If not, I will seek responses from other authors. Anyhow I have to learn and resolve the problem. Thank You for the all of your responses and time.

[mhscott]

You haven't really shown / provided enough information for someone to know what the issue is. I know for a fact that the section aggregator works for shear, so there's something wrong with your model or your results interpretation.

I recommended starting from zero with an elastic cantilever because you know what the solution should be and you can practice building models. Many examples online have subtle differences compared to what you want to do.

[AmitKur]

Sir, as you said in previous reply, "Probably a modeling issue. You have to provide more details", that's why I used standard Opensees wiki examples and shared the screenshots of the part I added. So that I can be helped because most of the peoples who are working in Opensees knows those standard examples and If the part that I am adding is wrong, they can correct me and help me.

If I try from zero, building a cantilever, I will be making the mistakes again and again, and peoples will always say, provide more information. Thats why I used standard examples.

Anyway, thankyou for you time Sir. We all always have hopes in getting help through this forum.

[milhan]

Hi,

Did you manage to solve your problem? I am having similar issues.

[caitlynfe]

Were you able to resolve your issue? I'm experiencing similar problems.