Mr. Godfrey does not seem to be familiar with the tests made by good
authorities on square slabs of reinforced concrete and of cast iron,
which latter material is also deficient in tensile strength. These tests
prove quite conclusively that the maximum bending moment per linear foot
may be calculated by the formulas, (_w_ _l^{2}_)/32 or (_w_ _l^{2}_)/20,
according to the degree of fixture of the slabs at the four sides.
Inasmuch as fixed ends are rarely obtained in practice, the formula,
(_w_ _l^{2}_)/24, is generally adopted, and the writer cannot see any
reason to confuse the subject by the introduction of a new method of
calculation.


WALTER W. CLIFFORD, JUN. AM. SOC. C. E. (by letter).--Some of Mr.
Godfrey's criticisms of reinforced concrete practice do not seem to be
well taken, and the writer begs to call attention to a few points which
seem to be weak. In Fig. 1, the author objects to the use of diagonal
bars for the reason that, if the diagonal reinforcement is stressed to
the allowable limit, these bars bring the bearing on the concrete, at
the point where the diagonal joins the longitudinal reinforcement, above
a safe value. The concrete at the point of juncture must give, to some
extent, and this would distribute the bearing over a considerable length
of rod. In some forms of patented reinforcement an additional safeguard
is furnished by making the diagonals of flat straps. The stress in the
rods at this point, moreover, is not generally the maximum allowable
stress, for considerable is taken out of the rod by adhesion between the
point of maximum stress and that of juncture.

Mr. Godfrey wishes to remedy this by replacing the diagonals by rods
curved to a radius of from twenty to thirty times their diameter. In
common cases this radius will be about equal to the depth of the beam.