he width of the flange, and
_V_ = the total vertical shear at the section.

This equation gives very erratic results, because it is based on a
continuous web. For a non-continuous web, it should be modified to

_V_
_v_ = ------------- (2)
_K_ _b_ _d_

In this equation _K b d_ represents the concrete area in compression.
The value of _K_ is approximately equal to 0.4.

Three large concrete beams with web reinforcement, tested at the
University of Illinois[K], developed an average maximum shearing
resistance of 215 lb. per sq. in., computed by Equation 1. Equation 2
would give 470 lb. per sq. in.

Three T-beams, having 32 by 3-1/4-in. flanges and 8-in. webs, tested at
the University of Illinois, had maximum shearing resistances of 585,
605, and 370 lb. per. sq. in., respectively.[L] They did not fail in
shear, although they appeared to develop maximum shearing stresses which
were almost three times as high as those in the rectangular beams
mentioned. The concrete and web reinforcement being identical, the
discrepancy must be somewhere else. Based on a non-continuous concrete
web, the shearing resistances become 385, 400, and 244 lb. per sq. in.,
respectively. As none of these failed in shear, the ultimate shearing
resistance of concrete must be considerably higher than any of the
values given.

About thirteen years ago, Professor A. Vierendeel[M] developed the
theory of open-web girder construction. By an open-web girder, the
speaker means a girder which has a lower and upper chord connected by
verticals. Several girders of this type, far exceeding solid girders in
length, have been built. The theory of the open-web girder, assuming the
verticals to be hinged at their lower ends, applies to the concrete beam
reinforced with stirrups. Assuming that the spaces between the verticals
of the girder become continually narrower, they become the tension
cracks of the concrete beam.[N]

JOHN C. OSTRUP, M. AM. SOC. C. E.--The author has rendered a great
service to the Profession in presenting this paper. In his first point
he mentions two designs of reinforced concrete beams and, inferentially,
he condemns a third design to which the speaker will refer later. The
designs mentioned are, first, that of a reinforced concrete beam
arranged in the shape of a rod, with separate concrete blocks placed on
top of it without being connected--such a beam has its strength only in
the rod. It i