If negative stress has arisen in the Foundation, this means that; In this negative region, the foundation tries to displace upwards, and the springs resist this displacement and negative stress is generated, and as a result, less positive stress is generated in areas with positive stress than it should actually be. In reality, such a situation does not occur and the ground springs cannot resist this displacement.
In areas with negative stress, I repeat the calculation by making the bed coefficient multiplier a small value and look again, to see if there is negative stress, if there is still, I will interfere with the bed coefficient multiplier in these negative areas and look again. The method I recommend can be used safely without making a non-linner calculation to stay within these limits.
The method I propose below allows you to evaluate the condition of your foundation without applying my nonlinear foundation solution method.
"In the combination of negative ground stress, if the maximum positive stress value is half or less of the soil bearing capacity, you do not need to deal with negative stress.
Also (the area where the negative stresses arise/total raft area) <0.20 you do not need to worry about it again.
These values are very rough values. Negative stresses should be reviewed and evaluated by the engineer. If the
ground stresses due to vertical loading are not abnormally asymmetrical, you may not consider the negative stress at all.
If vertical loads create abnormal asymmetric stresses, it is more important to first make the structural system of your structure symmetrically balanced and correctly arranged in terms of vertical loads. "