eory, as in the
intricate beam theory commonly used, there is the assumption of an
initial unstressed condition of the materials. This is not true of a
beam and is still further from the truth in the case of an arch. Besides
shrinkage of the concrete, which always produces unknown initial
stresses, there is a still more potent cause of initial stress, namely,
the settlement of the arch when the forms are removed. If the initial
stresses are unknown, ideal determinations of stresses can have little
meaning.

The elastic theory stands or falls according as one is able or unable to
calculate accurately the deflection of a reinforced concrete beam; and
it is an impossibility to calculate this deflection even approximately.
The tests cited by Professor Lanza show the utter disagreement in the
matter of deflections. Of those tested, two beams which were identical,
showed results almost 100% apart. A theory grounded on such a shifting
foundation does not deserve serious consideration. Professor Lanza's
conclusions, quoted under the twelfth point, have special meaning and
force when applied to a reinforced concrete arch; the actual
distribution of the stresses cannot possibly be determined, and complex
cloaks of arithmetic cannot cover this fact. The elastic theory, far
from being a reliable formula, is false and misleading in the extreme.

The fourteenth point refers to temperature calculations in a reinforced
concrete arch. These calculations have no meaning whatever. To give the
grounds for this assertion would be to reiterate much of what has been
said under the subject of the elastic arch. If the unstressed shape of
an arch cannot be determined because of the unknown effect of shrinkage
and settlement, it is a waste of time to work out a slightly different
unstressed shape due to temperature variation, and it is a further waste
of time to work out the supposed stresses resulting from deflecting that
arch back to its actual shape.

If no other method of finding the approximate stresses in an arch
existed, the elastic theory might be classed as the best available; but
this is not the case. There is a method which is both simple and
reliable. Accuracy is not claimed for it, and hence it is in accord with
the more or less uncertain materials dealt with. Complete safety,
however, is assured, for it treats the arch as a series of blocks, and
the cementing of these blocks into one mass cannot weaken the arch.
Reinforcement can