Mr. Worcester says:  “It is not necessary that a stirrup at one point should carry all the vertical tension, as this vertical tension is distributed by the concrete.”  The writer will concede that the stirrups need not carry all the vertical shear, for, in a properly reinforced beam, the concrete can take part of it.  The shear reinforcement, however, should carry all the shear apportioned to it after deducting that part which the concrete is capable of carrying, and it should carry it without putting the concrete in shear again.  The stirrups at one point should carry all the vertical tension from the portion of shear assumed to be taken by the stirrups; otherwise the concrete will be compelled to carry more than its share of the shear.

Mr. Worcester states that cracks are just as likely to occur from stress in curved-up and anchored rods as in vertical reinforcement.  The fact that the vertical stretching out of a beam from the top to the bottom, under its load, is exceedingly minute, has been mentioned.  A curved-up bar, anchored over the support and lying near the bottom of the beam at mid-span, partakes of the elongation of the tension side of the beam and crosses the section of greatest diagonal tension in the most advantageous manner.  There is, therefore, a great deal of difference in the way in which these two elements of construction act.

Mr. Worcester prefers the “customary method” of determining the width of beams—­so that the maximum horizontal shearing stress will not be excessive—­to that suggested by the writer.  He gives as a reason for this the fact that rods are bent up out of the bottom of a beam, and that not all of them run to the end.  The “customary method” must be described in literature for private circulation.  Mention has been made of a method which makes the width of beam sufficient to insert the steel.  Considerations of the horizontal shear in a T-beam, and of the capacity of the concrete to grip the steel, are conspicuous by their absence in the analyses of beams.  If a reinforcing rod is curved up and anchored over the support, the concrete is relieved of the shear, both horizontal and vertical, incident to the stress in that rod.  If a reinforcing rod is bent up anywhere, and not carried to the support, and not anchored over it, as is customary, the shear is all taken by the concrete; and there is just the same shear in the concrete as though the rods were straight.

For proper grip a straight rod should have a diameter of not more than one two-hundredth of the span.  For economy of material, it should not be much smaller in diameter than this.  With this balance in a beam, assuming shear equal to bond, the rods should be spaced a distance apart, equal to their perimeters.  This is a rational and simple rule, and its use would go a long way toward the adoption of standards.