Dear Pavlo,
1. I assume you have already read Troubleshooting, 2.1.19 Problems reaching convergence and understanding ATENA convergence parameters.

2. Have you already tried to allow more iterations or change the step length to reach full convergence (errors below the 1% tolerances)?

Regards.

Reagarding using Elastic predictor and update stiffness each step. As I understand this approach cannot be used to solve problem from zero to failure. It is only to pass problematic steps. The point is that almost all steps are not converged so this way is not applicable to my case, am I right?

Dear Dobromil,

I modified the model with shells and frames instead of all solids. However, I get the same problem in the same place even with ISOBEAM (see Fugure1 from link below). The point is that stresses in rebars in this joint are very low (15-20 MPa), and in concrete also very low: compression <3.5 MPa, tension 1.7 MPa while FT=2 MPa).
Regading this issue I have several questions:

1. I assume that the problem comes from the fact that crack occurs exactly at Master-Slave connection. Reaction between wto contacts should be equal to zero but it is always more than zero. Therefore, relative error is very high. Does it mean that I should always avoid Master slave where crack is assumed?

2. Elements in beams are not always bricks. Some of them are skewed. Is it OK? (see Figure 2)

3. Beams elements are connecred with MS contact (see Figure 2). Is this correct? Is there a need to make mesh consistent?

4. Beams are connected to walls and slabs with MS as well. Is this approach correct? (Figure 3)

5. Would you please review my model and advice what can be a problem with convergency in problematic node? (AtenaCalculation.rar - last nonconverged step results only, FT4_v10.gid.rar - GiD model without results)

https://drive.google.com/open?id=14VRRZ … TBEMcdGk2c

Dear Dobromil,

I changed the mesh. It seems normal now. However, I still have the same problem!

I kindly ask you to review my questions again and give your comments. Many thanks in advance.

1. I found that M-S connections was not a root of the problem. I changed mesh to compatible in problematic joint and got the same results. However, please comments whether it is possible to use MS condition while connecting incompatible mesh frame-to-frame and shell-to-frame.

2. Resolved

3. Beams elements are connecred with MS contact (see Figure 2 from message #7). Is this correct? Is there a need to make mesh consistent?

4. Beams are connected to walls and slabs with MS as well. Is this approach correct? (Figure 3 from message #7)

5. Would you please review my model and advice what can be a problem with convergency in problematic nodes? (FT4_v12.gid.rar - GiD model without results). Please note that in problematic beams stresses in rebars are very low (less than 250 MPa) and failure should not occur (see FT4_v12.avi from the link below).

6. Cracks in shells and frames are shown through the full height of the element (see CRACKS.PNG from the link below). It looks totally enormous from structural point of view. Is there a modeling mistake or is it a symbolic representation of ATENA?

https://drive.google.com/open?id=13xNmg … 4Drw1bUqw4

Dear Dobromil,

Here are my replies:

3,4 - OK, it is really good because compatible mesh preparation in GiD takes too much efforts.

6. Still crack pattern looks almost same on bottom and top surfaces while there should be no cracks at bottom surface. Please watch the video : https://drive.google.com/open?id=1cQ1y7 … w8stjl3CfN

Regarding solution method. I couldn't find Modified N-R in GiD 14 (script 16595). Does it mean that only Full N-R and Arc-Length are only available for GiD users?