certain types of
design, it is unquestioned that some schemes of arrangement undoubtedly
produce designs with dangerous properties. The speaker has several
times called attention to this point, in papers and discussions, and
invariably in his own practice requires that the spacing of spirals,
hoops, or ties be many times less than that usually required by building
regulations and found in almost every concrete structure. Moersch, in his
"Eisenbetonbau," calls attention to the fact that very definite limits
should be placed on the maximum size of longitudinal rods as well as on
their minimum diameters, and on the maximum spacing of ties, where
columns are reinforced largely by longitudinal members. He goes so far
as to state that:

"It is seen from * * * [the results obtained] that an increase in
the area of longitudinal reinforcement does not produce an increase
in the breaking strength to the extent which would be indicated by
the formula. * * * In inexperienced hands this formula may give
rise to constructions which are not sufficiently safe."

Again, with regard to the spacing of spirals and the combination with
them of longitudinal rods, in connection with some tests carried out by
Moersch, the conclusion is as follows:

"On the whole, the tests seem to prove that when the spirals are
increased in strength, their pitch must be decreased, and the
cross-section or number of the longitudinal rods must be
increased."

In the majority of cases, the spiral or band spacing is altogether too
large, and, from conversations with Considere, the speaker understands
that to be the inventor's view as well.

The speaker makes use of the scheme mentioned by the author in regard to
the design of flat slabs supported on more than two sides (noted in the
sixteenth point), namely, that of dividing the area into strips, the
moments of which are determined so as to produce computed deflections
which are equal in the two strips running at right angles at each point
of intersection. This method, however, requires a large amount of
analytical work for any special case, and the speaker is mildly
surprised that the author cannot recommend some simpler method so as to
carry out his general scheme of extreme simplification of methods and
design.

If use is to be made at all of deflection observations, theories, and
formulas, account should certainly be taken of the actual settlements
and othe