rizontal shear, thus relieving the U-bars. This is a factor in the
strength of actual work which theory does not take into account, and by
the author, no doubt, it would be regarded as insignificant;
nevertheless it is being done every day, with excellent results.

The action of these various agencies--the U-bars, diagonal steel, and
embedded stone--in a concrete beam, is analogous to that of bolts or
keys in the case of deepened timber beams. A concrete beam may be
assumed, for the purposes of illustration, to be composed of a series of
superimposed layers; in this case the function of the rigid material
crossing these several layers normally, and being well anchored above
and below, as a unifier of the member, is obvious--it acts as so many
bolts joining superimposed planks forming a beam. Of course, no such
lamination actually exists, although there are always incipient forces
tending to produce it; these may and do manifest themselves on occasion
as an actual separation in a horizontal plane at the junction of slab
and stem, ordinarily the plane of greatest weakness--owing to the method
of casting--as well as of maximum horizontal shear. Beams tested to
destruction almost invariably develop cracks in this region. The
question then naturally arises: If U-bars serve no purpose, what will
counteract these horizontal cleaving forces? On the contrary, T-beams,
adequately reinforced with U-bars, seem to be safeguarded in this
respect; consequently, the U-bars, while perhaps adding little to the
strength, as estimated by the ultimate carrying capacity, actually must
be of considerable assistance, within the limit of working loads, by
enhancing the stiffness and ensuring against incipient cracking along
the plane of weakness, such as impact or vibratory loads might induce.
Therefore, U-bars, far from being superfluous or fallacious, are,
practically, if not theoretically, indispensable.

At present there seems to be considerable diversity of opinion as to the
exact nature of the stress action in a reinforced concrete beam.
Unquestionably, the action in the monolithic members of a concrete
structure is different from that in the simple-acting, unrestrained
parts of timber or structural steel construction; because in monolithic
members, by the law of continuity, reverse stresses must come into play.
To offset these stresses reinforcement must be provided, or cracking
will ensue where they occur, to the detriment of the struct