Republican news item. [volume] (Laport, Pa.) 1896-19??, 1905-10-05

STEEL CONCRETE BRIDGE, PLAIEWELL,
MICH.
when a beautiful bridge is suggested
we take alarm at the cost and are apt
to decide offhand that the older type
without its good appearance is we'll
enough.
This is phase of the subject that is
very pertinent, whether it should be de-
plored or not. 1t is only by reason of
this careful consideration Of cost that
our country is able TO compete with
European countries in the construction
of bridges in foreign dependencies. 1t
has been said that any fool could build
Il bridge if he had money enough, but
it takes an engineer to do il econoM-
ically.
This matter of cost has compelled us
to limit the construction of stone arch
bridges to Il very small number and to
put i'll their place Il metal truss of
straight lines and sharp angles. 1t is
not that we have failed to appreciate
the beauty Of the curved arches, but
rather that we could not afford the lux
ury wien we needed so many of them.
Thirty years ago our bridge builders
were crying the need of reform as to
aesthetic design, but had TO offer us III
place of sham decorations only the
simplicity and harmonious construction
of IL well built truss suitably painted,
and there can be no doubt that great
improvement has been made. The
sheet iron denominations which covered
up the outlines of the truss and which
were what Ruskin would have called
CONSTRUCTED decorations have been
abandoned, and the bridge is left to
depend for it's beauty on the noble lines
of strength and the general symmetry
OF its construction.
AS progress has been made in the
building of our roads so have we moved
forward in the design of our bridges
For many centuries cement and broken
stone have been used to replace the eX-
pensive cut stone in arch construction
but only recently have we succeeded in
surmounting Il difficulty long recogniZ-
ed. Concrete is a building material
generally accepted when it is to be sub
jected only to Il compressive force. 1t
lacks sufficient strength if any pull or
tension is applied. This fact has so
limited us in the use of concrete that
only III rare instances has it been eco
nomical to use it in bridge construc-
ton.
y feature that requires careful con-
sideraton in the design of any engi-
neerng structure is the effect of the
u, tn,
terial used. The fact that steel and
concrete are affected in the same way
and to the same extent by heat first
suggested their use in combination
This idea has been developed now to
such an extent that we are able to use
the steel to resist the tension in our
structure and the concrete to take care
of the compression and to so design the
whole that there will he a sufficient
amount of each material and yet no
expensive waste. We have found the
stone arch too expensive and the steel
truss lacking in beauty Combine the
two, and the result is the steel-concrete
arch having the requisites as to beauty
and comparing very favorably as to
cost
When one is considering the construc-
ton of a bridge several points should
he considered
First. That it shall answer the util-
itarian purpose for which it is wanted.
Second.It should he monument to
the progressive ideas of the community
and serve as an education and an in
spiration TO others.
Third. 1t should be built for the fu-
ture as well as the present. and its per-
Inanence should he assured.
These can all be met by the use of
steel concrete.