In this same paragraph Mr. Thacher states, concerning the third point and the case of the retaining wall that is given as an example, “In a counterfort, the inclined rods are sufficient to take the overturning stress.”  Mr. Thacher does not make clear what he means by “overturning stress.”  He seems to mean the force tending to pull the counterfort loose from the horizontal slab.  The weight of the earth fill over this slab is the force against which the vertical and inclined rods of Fig. 2, at a, must act.  Does Mr. Thacher mean to state seriously that it is sufficient to hang this slab, with its heavy load of earth fill, on the short projecting ends of a few rods?  Would he hang a floor slab on a few rods which project from the bottom of a girder?  He says, “The proposed method is no more effective.”  The proposed method is Fig. 2, at b, where an angle is provided as a shelf on which this slab rests.  The angle is supported, with thread and nut, on rods which reach up to the front slab, from which a horizontal force, acting about the toe of the wall as a fulcrum, results in the lifting force on the slab.  There is positively no way in which this wall could fail (as far as the counterfort is concerned) but by the pulling apart of the rods or the tearing out of this anchoring angle.  Compare this method of failure with the mere pulling out of a few ends of rods, in the design which Mr. Thacher says is just as effective.  This is another example of the kind of logic that is brought into requisition in order to justify absurd systems of design.

Mr. Thacher states that shear would govern in a bridge pin where there is a wide bar or bolster or a similar condition.  The writer takes issue with him in this.  While in such a case the center of bearing need not be taken to find the bending moment, shear would not be the correct governing element.  There is no reason why a wide bar or a wide bolster should take a smaller pin than a narrow one, simply because the rule that uses the center of bearing would give too large a pin.  Bending can be taken in this, as in other cases, with a reasonable assumption for a proper bearing depth in the wide bar or bolster.  The rest of Mr. Thacher’s comment on the fourth point avoids the issue.  What does he mean by “stress” in a shear rod?  Is it shear or tension?  Mr. Thacher’s statement, that the “stress” in the shear rods is less than that in the bottom bars, comes close to saying that it is shear, as the shearing unit in steel is less than the tensile unit.  This vague way of referring to the “stress” in a shear member, without specifically stating whether this “stress” is shear or tension, as was done in the Joint Committee Report, is, in itself, a confession of the impossibility of analyzing the “stress” in these members.  It gives the designer the option of using tension or shear, both of which are absurd in the ordinary method of design.  Writers of books are not bold enough, as a rule, to state that these rods are in shear, and yet their writings are so indefinite as to allow this very interpretation.