Hello, this error occurs because you defined a column on the curtain on the last floor. As an analysis logic, do not enter a column on the screen. You can prevent this calculation error by creating the geometry you want with the tear detail on the curtain. Also, for basement curtains 50 cm high above the foundation, enter the curtain settings and mark them as basement curtains. My suggestion is that you do not include such elements in the model and make them in the drawing. Of course, the important thing here is whether a short column is formed or not. Accordingly, you decide and model if necessary. The raft base is the thinnest possible. I recommend making it less than 50 cm. Optimization in reinforced concrete is made with more iron, as you know, its price is much higher. You can compare the iron you will use on a 50 cm basis with the iron you will use on a 60 cm basis and compare the quantities.
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