A Treatise On The Principles And Practice Of Dock Engineering
Forfatter: Brysson Cunningham
År: 1904
Forlag: Charles Griffin & Company
Sted: London
Sider: 784
UDK: Vandbygningssamlingen 340.18
With 34 Folding-Plates and 468 Illustrations in the Text
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COTTANÇINS SYSTEM. 379
The most notable application of this system is to the construction of
concrète piles, which are considered in an earlier section of this work.
Cottançin’s System. —-The disconnected bars employed in the previous
methods are replaced by a jointless wire network J^ to | inch diameter, the
design varying according to circumstances. Two examples are shown in
figs. 367, 368, and 369. The inventor claims for his design a large increase
in strength for a given weight of metal.
There are many other proprietary systems which it would take too long
to enumerate and describe. The foregoing methods are largely typical of
the rest.
Eigs. 367, 368, and 369. —Cottançin’s Systems.
Three conditions are essential to the stability and durability of a floor
compounded of concrete and metal :—
1. The metal must be completely enclosed so as to be protected from
atmospheric and corrosive influences. As far as present knowledge goes,
the bedding of ironwork in Portland cement mortar is attended by none of
the evil results characteristic of bedding in lime mortar. Bars which have
been completely embedded for lengthy periods have exhibited not the least
sign of deterioration on close examination after disinterment. Exposed to
the atmosphere, however, gradual corrosion is inevitable, particularly in
maritime situations. Hence the necessity for a thorough covering of concrete
over all parts of the metal.
2. The coefficients of expansion must be the same for the two substances,
or very nearly so, within the limits of temperature to which they will be
subjected. This is necessary to prevent excessive mutual stress.
^. The coefficient of direct elasticity of the metal must be greater than
that of the concrete, otherwise the metal is useless. The ratio of intensity
. . . EA
of stress in an elongated prism of the combination is -------, where E is the
ea’
coefficient of elasticity of the concrete, e that of the iron, and A, a, their
respective sectional areas.
Shed floors should not be absolutely level. In order to get rid of any
wet blown into the shed during boisterous weather, it is advisable to give
the floors a rise of at least 2 inches in the first 10 feet.