Shear wall models

[Pytor14]

Hello, first time posting.
I am trying to model a shear wall with its boundary elements. I am planning to model the wall with shell elements and boundary elements as rectangular fiber sections. Shear wall (shell) will be using unconfined concrete with appropriate rebar.Boundary elements use confined concrete models, which have been calculated in the RectangularFiberSection menu.

Since I am only starting with STKO, my question is which one of these models do you think is the best. I have created 3:

First model (picture bellow) is modeled with Beam fiber sections that are distanced from the shell element (wall) and then ofsetted so that they reach the wall. I assume that this isnt the best way

Second model (picture bellow) is modeled with the same length of the shear wall, and then the beam fiber sections have been assigned to the edges of the shell.

Third model (picture bellow) is modeled similarly to the second model, but I used different wall length for the different sections of the wall, to simulate the different length of unconfined concrete.

I have added comments on attached pictures to label models.
Honestly, just a simple answer will do. I am trying to save time, as to not to do three different models which may or may not work, considering I just started learning STKO

[STKO Team]

Short answer:
The last model is the most accurate.

If it's necessary or not (with respect to the first model, which is the easier to implement) depends on many factors. The most important is how your boundary elements are real "beams". If they are slender enough there is no huge difference

[Pytor14]

Thank you for the reply. In the end I chose the model you recommended.

I just have one more short question. I proceeded with the analysis, but I encountered problems with modal analysis. Currently I am checking the results with ETABS. The thing is when i get the results of the modal analysis in the console, the mass is only calculated in MZ, in other words there is no translational mass in X and Y directions. I tried everything. I even made a model of a simple cantilever beam and still there is no mass in X and Y. I only added node masses and i didn't add any rotating masses, because I read that the software will do it on its own.
When only vertical mass is taken into consideration in ETABS, the results match. But when I include lateral mass in ETABS, allowing oscilation in X and Y direction, the period is different.

Again, a short answer or a guess as to what might be the problem would be very helpful.

[Pytor14]

Just figured it out. I only added the Z value in node masses. Thank you for the reply.

[STKO Team]

You're welcome