RC Frame Pushover Curve

[ugurozmen]

Hello everyone,
I have e question about the section and pushover curve
I am using Concrete02, ReinforcingSteel materials, fiber section and forceBeamColumn for 2d rc mr frame. When I do a pushover analysis the pushover curve is almost linear till the end after the peak point and not degrading.
https://pasteboard.co/JFm9hUU.jpg

If I use the concentrated plasticity model and define rotation springs to the elements I think I will be ignoring the axial load o columns arising from the lateral pushover load. So the column section capacities will be unrealistic.

So what is the best way to get similar curve like SAP2000 in the screenshot while considering the axial load on columns.

[selimgunay]

Which result is more realistic depends on the type of your frame. If it is a special moment RC frame with well-confined sections designed according to seismic codes, OpenSees result seems more realistic. If it is a nonductile RC frame, SAP2000 looks more representative

[ugurozmen]

Which result is more realistic depends on the type of your frame. If it is a special moment RC frame with well-confined sections designed according to seismic codes, OpenSees result seems more realistic. If it is a nonductile RC frame, SAP2000 looks more representative

Thanks for your fast response.

I will try to explain the question with another example.
https://pasteboard.co/JFmWsFd.jpg
According to the stress-strain diagrams, concrete fibers (top, bottom and center) crushing at the very beginning of the pushover. Despite this concrete behavior, is it possible for the section to keep capacity like that? So isn't opensees model suppose to degrade like sap2000 curve?

[selimgunay]

It should, but you can make the same stress-strain checks for the fibers of the section at the top end of the column and the beam end. If you are using a constraint that sets the elongation/shortening of the beam to be zero, that has an unintended consequence of introducing axial force on the beam section, increasing its flexural capacity.