you have to choose proper case/combo in "Auto Hinge Assignment" dialog box in SAP2000. There is also a couple of radio buttons which have to be chosen correctly.

best regards

Please see the following helpful link:

https://wiki.csiamerica.com/pages/viewpage.action?pageId=1742143

Take a look at these:

https://research.iaun.ac.ir/pd/izadiniaold/pdfs/HomeWork_2092.pdf

https://www.youtube.com/watch?v=y2G0wXuvWIE

@Rasha The problem is that the element with plastic hinges resists even after reaching its capacity (Moment increases).

@Jose @Hamdi Thanks, I will take a look

Users must assign concentrated hinges to frame elements which may experience nonlinear behavior. Definition of nonlinear material behavior does not enable plastic behavior, though it is necessary for the generation of the interaction surface and moment-rotation curves which characterize the yield criteria of a nonlinear frame element.