Error During Analysis

[nisaralikhan]

Dear STKO Team,
I built an RC frame in STKO which is running well, but when I added an infill wall it is not showing any result. Would you please be so kind as to check the model attached in a Zip. I am using Mosalam's model for infill walls that you explained in one of the webinars. for your convenience, I have also added the calculation file of infill properties in the Zip file.
I am looking forward to hearing your response as soon as possible.
Kind regards,
Nisar Ali Khan.

[STKO Team]

Errors:

1. The columns are detached from the infill face, therefore singular. I merged to obtain a single geometry.
2. The loads for a displacement control analysis MUST always use a Linear time series (0 to 1).

With those changes, the analysis runs but it fails early due to a sudden brittle failure. Check your material parameters if you think it's too brittle

[nisaralikhan]

Dear STKO Team, Thank you for your prompt response.
Attached please find the updated model, which is showing an error of "Forcebeamcol could not invert flexibility"
I tested the same portal frame and we applied an increment of displacement with 10mm in +ve and -ve directions till 100mm, as the load path defined in the model as "TS". I also put the materials' characteristics correctly, but all in vain.
The bare frame of the same model shows good agreement with the experimental results but infilled model show the above error.
Attached please find the model.
Looking forward to hearing your supportive response.
Regards,

[STKO Team]

The force beam column cannot invert flexibility because you are using a combination of Concrete01 without tensile strength and steel02 with b=0 (no strain hardening).
In the case concrete is in tension and steel is in plastic state the tangent is 0.

However the reason for failure of the second stage is that you are using Displacement-Control analysis with an imposed displacement.
This is wrong:
You either use an imposed load , and you control its magnitude with the Displacement control integrator,
or you apply an imposed displacement and control it with the LoadControl integrator

[nisaralikhan]

Dear STKO Team,
Thank you for your response.
I have run the model but it stops the analysis at a 20 mm displacement push. However, I have defined the load path as 100mm and the same was the case in the Laboratory test (Experiment).
I have also checked the material properties but it does not match the experimental result.
Attached please find the STKO Model and the experimental response of the infilled frame.
I am looking forward to hearing your supportive response.
Kind regards,
Nisar

[STKO Team]

The issue was the UmfPack. It cannot handle the automatic removal of the infill. I used SuperLU and it works with the auto removal.

Then I also made a few changes in the algorithm and the time step size of the second analysis. I also added the background plot for an easy comparison

20220725_Cyclic push.zip

(483.89 KiB) Downloaded 5 times

This is what I get

infill.png (138.22 KiB) Viewed 75 times

The progressive failure (softening branch) is not captured because this element does not provide it. When it reaches its peak strength, it will be removed. But it seems that the peak point (strength and displacement) are correctly captured, as well as the residual strength