The neutral axis of reinforced concrete beams under safe loads is near the middle of the depth of the beams.
This vertical line is the neutral axis joining the poles of white and black, which represent the opposites of light and darkness.
This higher position of the neutral axis is the one more generally shown by tests of beams.
On one side of the dark band we have strain, on the other side pressure, the band marking the neutral axis between both.
It can be safely said that the neutral axis is at, or a little above, the center of the beam.
Analogy with a riveted truss fails; even the anchorage above the neutral axis is far from realization.