error in pushover response in the case of plasticity.

[mohsenrock]

Hi experts,
I have a really clear question.
In the pushover analysis of my RC 2D frame, I am using different types of elements. I expect that when using nonlinear elements (force based or dispbased), the initial pushover response gives nearly the same values as when using elastic elements. I have tested many elements such as forcebased with 5 Intps, forcebased with 10 Intps, 5 forcebased elements for each beam or column with 5 or 10 Intps, 5 dispbased elements for each beam and column with 5 and 10 Intps. However, none of them provides the initial branch of the pushover diagram as the one with elastic elements. In order to check my model, I ran on the analysis once with elasticbeamcolumn elements and once with nonlinearbeamcolumn with fiber sections but with elastic material and they are exactly the same. My elastic response is correct since I have compared it with my own code in MATLAB.

please help.
thanks in advance.

[fmk]

it is probably the initial stiffness of the concrete materials. check this out by changing them to steel with same E.

[mohsenrock]

Thanks a lot for your answer. I used a concrete material with a minimum value for tensile strength and it works.

[venkateshyadav]

mohsenrock wrote:
> Thanks a lot for your answer. I used a concrete material with a minimum
> value for tensile strength and it works.

Hi
are you getting same results for the different cases you have mentioned.
I have used 5 dispBC elements for representing one beam and run the pushover analysis. and also using forceBC element I had run the model.
In these two cases am getting different results? Can you help me with this that which element to be used for better results?
And also which steel material to be used for RC frame for better output? Is it steel01 or steel02 or reinforcing steel? Currently am using Reinforcingsteel
Thanks in advance