Hi @moguzhan, you may have over constrained your model.
I’ve run your simulation again, but changed the feet constraints so that your structure can move more in line with how I would expect. I may be on the wrong track here because I’m not familiar with your application.
Here is a top view of your original model (20x deformation).
Here is a top view of the modified simulation (20x deformation).
You can see that the stress in the structure is higher with the new constraints. However, the stress is still not high enough to explain the failure you’ve observed. Are you sure your load magnitude and direction is correct?
Here is a link to my copy of your project.
[!!!THIS LINK IS NO LONGER AVAILABLE!!!]