s purely a suspension, or "hog-chain" affair, and the
blocks serve no purpose, but simply increase the load on the rod and its
stresses.

The author's second design is an invention of his own, which the
Profession at large is invited to adopt. This is really the same system
as the first, except that the blocks are continuous and, presumably,
fixed at the ends. When they are so fixed, the concrete will take
compressive stresses and a certain portion of the shear, the remaining
shear being transmitted to the rod from the concrete above it, but only
through friction. Now, the frictional resistance between a steel rod and
a concrete beam is not such as should be depended on in modern
engineering designs.

The third method is that which is used by nearly all competent
designers, and it seems to the speaker that, in condemning the general
practice of current reinforced designs in sixteen points, the author
could have saved himself some time and labor by condemning them all in
one point.

What appears to be the underlying principle of reinforced concrete
design is the adhesion, or bond, between the steel and the concrete, and
it is that which tends to make the two materials act in unison. This is
a point which has not been touched on sufficiently, and one which it was
expected that Mr. Beyer would have brought out, when he illustrated
certain internal static conditions. This principle, in the main, will
cover the author's fifth point, wherein stirrups are mentioned, and
again in the first point, wherein he asks: "Will some advocate of this
type of design please state where this area can be found?"

To understand clearly how concrete acts in conjunction with steel, it is
necessary to analyze the following question: When a steel rod is
embedded in a solid block of concrete, and that rod is put in tension,
what will be the stresses in the rod and the surrounding concrete?

The answer will be illustrated by reference to Fig. 10. It must be
understood that the unit stresses should be selected so that both the
concrete and the steel may be stressed in the same relative ratio.
Assuming the tensile stress in the steel to be 16,000 lb. per sq. in.,
and the bonding value 80 lb., a simple formula will show that the length
of embedment, or that part of the rod which will act, must be equal to
50 diameters of the rod.

[Illustration: FIG. 10.]

When the rod is put in tension, as indicated in Fig. 10, what will be
the stresses in t