Question:
Why does the vertical position of a result member in my model have no influence on the bending moment My of the member?
Answer:
The change of the vertical position or an eccentricity only causes a difference in the bending moment My if other forces act on the model that influence this moment, such as a normal force in the following example.
A slab, supported as a single-span beam, is only loaded vertically on the left in the image. The bending moments of the result members positioned above and below the slab do not differ.
On the right, the slab is additionally loaded by an axial force. Therefore, the result members obtain additional negative or positive moments. The eccentricity acts as a lever arm.