Some Mooted Questions in Reinforced Concrete Design

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Some Mooted Questions in
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Title: Some Mooted Questions in Reinforced Concrete Design
American Society of Civil Engineers, Transactions, Paper No. 1169,
Volume LXX, Dec. 1910
Author: Edward Godfrey
Release Date: November 23, 2005 [EBook #17137]
Language: English
Character set encoding: ISO-8859-1
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AMERICAN SOCIETY OF CIVIL ENGINEERS INSTITUTED 1852
TRANSACTIONS
Paper No. 1169
SOME MOOTED QUESTIONS IN REINFORCED CONCRETE
DESIGN.[A]
BY EDWARD GODFREY, M. AM. SOC. C. E.
WITH DISCUSSION BY MESSRS. JOSEPH WRIGHT, S. BENT
RUSSELL, J.R. WORCESTER, L.J. MENSCH, WALTER W.
CLIFFORD, J.C. MEEM, GEORGE H. MYERS, EDWIN THACHER,
C.A.P. TURNER, PAUL CHAPMAN, E.P. GOODRICH, ALBIN H.
BEYER, JOHN C. OSTRUP, HARRY F. PORTER, JOHN STEPHEN
SEWELL, SANFORD E. THOMPSON, AND EDWARD GODFREY.
Not many years ago physicians had certain rules and practices by which
they were guided as to when and where to bleed a patient in order to
relieve or cure him. What of those rules and practices to-day? If they
were logical, why have they been abandoned?
It is the purpose of this paper to show that reinforced concrete
engineers have certain rules and practices which are no more logical
than those governing the blood-letting of former days. If the writer fails
in this, by reason of the more weighty arguments on the other side of
the questions he propounds, he will at least have brought out good
reasons which will stand the test of logic for the rules and practices
which he proposes to condemn, and which, at the present time, are
quite lacking in the voluminous literature on this comparatively new
subject.
Destructive criticism has recently been decried in an editorial in an

engineering journal. Some kinds of destructive criticism are of the
highest benefit; when it succeeds in destroying error, it is
reconstructive. No reform was ever accomplished without it, and no
reformer ever existed who was not a destructive critic. If showing up
errors and faults is destructive criticism, we cannot have too much of it;
in fact, we cannot advance without it. If engineering practice is to be
purged of its inconsistencies and absurdities, it will never be done by
dwelling on its excellencies.
Reinforced concrete engineering has fairly leaped into prominence and
apparently into full growth, but it still wears some of its
swaddling-bands. Some of the garments which it borrowed from sister
forms of construction in its short infancy still cling to it, and, while
these were, perhaps, the best makeshifts under the circumstances, they
fit badly and should be discarded. It is some of these misfits and
absurdities which the writer would like to bring prominently before the
Engineering Profession.
[Illustration: FIG. 1.]
The first point to which attention is called, is illustrated in Fig. 1. It
concerns sharp bends in reinforcing rods in concrete. Fig. 1 shows a
reinforced concrete design, one held out, in nearly all books on the
subject, as a model. The reinforcing rod is bent up at a sharp angle, and
then may or may not be bent again and run parallel with the top of the
beam. At the bend is a condition which resembles that of a hog-chain or
truss-rod around a queen-post. The reinforcing rod is the hog-chain or
the truss-rod. Where is the queen-post? Suppose this rod has a section
of 1 sq. in. and an inclination of 60° with the horizontal, and that its
unit stress is 16,000 lb. per sq. in. The forces, a and b, are then 16,000
lb. The force, c, must be also 16000 lb. What is to take this force, c, of
16,000 lb.? There is nothing but concrete. At 500 lb. per sq. in., this
force would require an area of 32 sq. in. Will some advocate of this
type of design please state where this area can be found? It must, of
necessity, be in contact with the rod, and, for structural reasons,
because of the lack of stiffness in the rod, it would have to be close to
the point of bend. If analogy to the queen-post fails so completely,

because of the almost complete absence of the post, why should not
this borrowed garment be discarded?
If this same rod be given a gentle curve of a radius twenty or