Hello, my suggestions are 1- Solve your project as semi-rigid diaphragm, 2- You can reduce the thickness of the basic raft, (remove the reinforcement on the raft) 3- Geometry check Correct error messages, 4- Check the wall loads, 5- Check the stair bracing when you solve it as a semi-rigid diaphragm , if you are not going to fix it semi-rigid, take the ladder loads, 6- let the rib beams center the columns, 7- put beams under the walls at the console ends, 8- space edges,
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