Embedded rebars with shell

[crisjaqueplaza]

Hi!

I have a question: is it possible in STKO to model a shell element with embedded rebars inside? I know that it is possible with solid elements but I want to know if it possible in shell element? Thanks in advance!

[crisjaqueplaza]

Hi again!

I am generating a model of a confined masonry wall with embedded rebars in the columns. The columns and the wall are shells, so the rebars are embedded in shells. But I am getting the error that I attach as a screenshot. How can I fix that? Please I need an answer. I attach the model in STKO by the way.

Thanks in advance!!!

[crisjaqueplaza]

Please, any suggest? This is urgent for me, it's an important part of my research.

[crisjaqueplaza]

Hi!

I solved the problem about the embedded rebars in the shell, but right now I can not generate a contact in the roof of the wall with the goal to avoid the push/pull effect in a cyclic analysis. I followed the guidelins of the webinar "Modelling RC Shear Walls in OpenSees and STKO - Shell and Solid Models with Embedded Rebars". In this video, Massimo Petracca developed an embedded solid model, but I tried to do the same with a shell on the columns as you can see on my model. I really appreciate if someone could help me with this.

[STKO Team]

This works:

Yacila_Cyclic03.zip

(630.8 KiB) Downloaded 135 times

Errors:

• The push point should be the outer ones (I moved them apart so that you can see the changes)

  

  push point.png (128.28 KiB) Viewed 2906 times

• You forgot to assign the local axes (local Z is the normal contact vector and is oriented along the global X axis)

  

  assign local.png (38.79 KiB) Viewed 2906 times

• Master -> Slave direction should be consistent with the normal contact direction

  

  MS direction.png (105.47 KiB) Viewed 2906 times

• Finally, I removed the rigid link in the contact points (it's useless, you can simply apply the imposed displacement on both points, so that they move of the same amount in X). Ans you also need to fix all DOFs but the UX in the contact points (they are just used to apply the Ux motion)

It runs now, but it seems softer than the reality. make sure your top beam is stiff enough

[crisjaqueplaza]

Dear STKO,

I want to really thank you for your help with this, I made some modifications on the model and I could fix this softening problem that you notified me.

Right now, I have another question with this model, which really it is more related to the set up of the cyclic analysis. As you can see in the model that I attach, the numerical solution is stiffer than the experimental one (which it is the back curve on the monitor) in the first cycles. I want to know the reason about that: ¿is it something related to the solution's algorithm? ¿is it a feature of ASDConcrete3D that I am ussing in the masonry panel and RC columns? ¿is there a solution for that? I asked that because of I tried to improve my results in the first cycles reducing the tension's properties of the concrete -like ft and Gt- but it didn't work, so I think that maybe the reason for this problem it could be in the solver parameters or in the ASDConcrete3D. ¿Is there some literature that you could recommend maybe for understand this issue?

Thanks in advance!

[STKO Team]

If the solution is stiffer from the very beginning, you either used wrong Young's moduli, or you did not reproduce properly the boundary conditions of the experimental setup (this is the most critical part)

[crisjaqueplaza]

Thank you for your answer, I am going to see if I can improve my results changing the boundary conditiones, which it can be better and more similar to the experimental test.

[crisjaqueplaza]

Hi!

I am trying to introduce new boundary conditions and spite of I obtain differents results, my main problem it's the stiffness's degradation. As you can see in the image that I attached, the red zone is the envelope of three experimental results; the STKO results works fine in large displacements but it doesn't fit fine in the first cycles. I had tried by reducing some tension's parameters in the columns and the masonry's panel, but I can't avoid this effect. I don't know if this is a feature of the ASDConcrete3D, the setup of the cyclic analysis or something like that.

[STKO Team]

From the experimental envelope it seems the overall stiffness degradation starts at earlier displacements. Check some pictures of the experimental damage pattern at that stage to understand if that overall degradation is due to cracking (in this case it means you have to adjust tensile parameters).
If there is not cracking at those displacement, it means that the apparent initial stiffness degradation is due to something else