These stirrups can take but little hold on the reinforcing rods--and
this must be through the medium of the concrete--and they can take but
little shear. Some writers, however, hold the opinion that the stirrups
are in tension and not in shear, and some are bold enough to compare
them with the vertical tension members of a Howe truss. Imagine a Howe
truss with the vertical tension members looped around the bottom chord
and run up to the top chord without any connection, or hooked over the
top chord; then compare such a truss with one in which the end of the
rod is upset and receives a nut and large washer bearing solidly against
the chord. This gives a comparison of methods of design in wood and
reinforced concrete, as they are commonly practiced.

Anchorage or grip in the concrete is all that can be counted on, in any
event, to take up the tension of these stirrups, but it requires an
embedment of from 30 to 50 diameters of a rod to develop its full
strength. Take 30 to 50 diameters from the floating end of these shear
members, and, in some cases, nothing or less than nothing will be left.
In any case the point at which the shear member, or stirrup, is good for
its full value, is far short of the centroid of compression of the beam,
where it should be; in most cases it will be nearer the bottom of the
beam. In a Howe truss, the vertical tension members having their end
connections near the bottom chord, would be equivalent to these shear
members.

The sixth point concerns the division of stress into shear members.
Briefly stated, the common method is to assume each shear member as
taking the horizontal shear occurring in the space from member to
member. As already stated, this is absurd. If stirrups could take shear,
this method would give the shear per stirrup, but even advocates of this