the distribution and the
intensity of the resistance in the concrete to a force acting parallel
to the rod. A similar triangle may be drawn, Fig. 11, showing the
resistance of the rod and the resultant distribution in the concrete to
a force perpendicular to the rod. Here the original force would cause
plain shear in the rod, were the latter fixed in position. Since this
cannot be the case, the force will be resolved into two components, one
of which will cause a tensile stress in the rod and the other will pass
through the centroid of the compressive stress area. This is indicated
in Fig. 11, which, otherwise, is self-explanatory.

[Illustration: FIG. 12.]

Rods are not very often placed in such a position, but where it is
unavoidable, as in construction joints in the middle of slabs or beams,
they serve a very good purpose; but, to obtain the best effect from
them, they should be placed near the center of the slab, as in Fig. 12,
and not near the top, as advocated by some writers.

If the concrete be overstressed at the points where the rod tends to
bend, that is, if the rods are spaced too far apart, disintegration will
follow; and, for this reason, they should be long enough to have more
than 50 diameters gripped by the concrete.

This leads up to the author's seventh point, as to the overstressing of
the concrete at the junction of the diagonal tension rods, or stirrups,
and the bottom reinforcement.

[Illustration: FIG. 13.]

Analogous with the foregoing, it is easy to lay off the stress triangles
and to find the intensity of stress at the maximum points, in fact at
any point, along the tension rods and the bottom chord. This is
indicated in Fig. 13. These stress triangles will start on the rod 50
diameters back from the point in question and, although the author has
indicated in Fig. 1 that only two of the three rods are stressed, there
must of necessity also be some stress in the bottom rod to the left of
the junction, on account of the deformation which takes place in any
beam due to bending. Therefore, all three rods at the point where they
are joined, are under stress, and the triangles can be laid off
accordingly.

It will be noticed that the concrete will resist the compressive
components, not at any specific point, but all along the various rods,
and with the intensities shown by the stress triangles; also, that some
of these triangles will overlap, and, hence, a certain readjustment, or
superimp