In a counterfort, the inclined rods are sufficient to take the overturning stress.
These rods are the vertical and horizontal rods in the counterfort of the retaining wall shown at a, in Fig. 2.
The manifest and only function of the rib or counterfort is to tie together the curtain wall and the horizontal slab.
He seems to mean the force tending to pull the counterfort loose from the horizontal slab.
Mr. Mensch states that "it would take up too much time to prove that the counterfort acts really as a beam."