This video discusses the distribution of the statical moment.
First, we draw the z-t distribution, then integrate the individual surfaces, which leads to determination of the statical moment Sy.
The s-coordinates help here. The sensible orientation of these coordinates has a great effect on this distribution.
This video shows the difference between calculation by the central axes and a more precise calculation.
Since, in the simplified system, the height goes from the web to the central axes of the flanges, a higher value of the governing statical moment will result.