Wall Behavior under bi-directional cyclic loading

[Nayera Sakr]

Greetings,

I am trying to model the C-shaped wall (TUB) by Beyer that was introduced as an example during the webinar "Modelling RC Shear Walls in OpenSees and STKO - MVLEM and SFI-MVLEM".

I have tried to model a wall under a Quasi-static cyclic bi-directional loading and trying to capture the hysteretic behavior of the C-shaped concrete wall. The wall is modeled as MVLEM3D. I defined a timeseries in E-W direction and another one in the N-S direction with the load values from the experimental data. I used a load control analysis to study the behavior of the wall. While Monitoring the results, I can see the load pattern drawn successfully, but the values of the output displacement is reached only in the first ductility level and the values are not increasing anymore. It is limited by the displacement values of the initial cycle values.
So I tried to make alot of trials to adapt the behavior required but it is not affected neither by the material model of concrete nor the steel material. I made also trials on the stiffness of the Springs that are used to prevent the twisting of the wall; it cause an change in the initial values but still the other cycles are not affected.

I am thinking if my model is behaving linearly, because I can see that the resulted displacement graph is almost the same of the input force values pattern.

So I would appreciate it if I could ask for your support to guide me in my problem. I would be so glad if I could share the model with you.

Note: The units used in the model are (N,mm)

Best Regards,
Nayera Sakr