Oxford Democrat. [volume] (Paris, Me.) 1833-1933, 1896-04-21
HIGHWAY BRIDGE BUILDING.

HIGHWAY BRIDGE BUILDING.
PROF. GEORGE l.. v0sE GIVES SOMf
VALUABLE SUGGESTIONS ON THIS
VERY IMPORTANT MATTER.
Editor Democrat:
Ia recent number Of your paper
noticed the statement that the covered
bridge" had been pronounced unsafe
and that II would probably be replaced
before long by q more substantial
structure. l wish TO make a few remarks
in order that the selectmen may proceed
In an understanding manner In getting
new bridge. We have In common use al
the present time In this country great
number OF bridges, some OF them made
of wood, some of wood and iron com
bined, some entirely Of iron. and some
Of steel, and these structures may ot
seen Of great variety Of patterns, OF all
sizes, and In every stage OF preservation.
OF late, so great has been the demand
for bridge work, that this branch OF en-
cheering has become trade by itself,
and we find immense works fitted up
with an endless variety OF the most ad-
mirably adapted machine tools, devoted
exclusively to the making Of bridges oil
iron or steel.
As In all division OF labor, the result
OF this specialization has been to i'm
prove the quality OF the product, TO les
sen the cost, and to increase the demand,
until many Of our larger firms reckon
the length OF bridging which they have
built, by miles. As usual, however, In
such cases, unprincipled adventurers are
not wanting, who, taking advantage OF a
great demand, do not hesitate to fit up
cheap shops, to buy poor material, and
10 flood the market with class OF
bridges made with single object in
view, viz, TO sell; relying upon the lack
Of knowledge among public officials Tor
custom. Not a year passes In which
some OF these wretched traps do not
tumble down, and involve the towns and
counties in more or less expense.
This evil affects particularly highway
bridges. The ordinary county commits
sioner or selectman considers himself
amply competent TO contract fora bridge
OF iron or steel, though he may never
have given a single day OF thought to
the matter before his appointment to
office. The result Is that we see all
over the country great number OF high
way bridges which have been sold by
dishonest builders TO ignorant officials,
and which only await an extra large
crowd Of people, q procession or some
thing Of the sort, to break down. The
state OF Maine can show to-day some OF
the most reckless and dishonest speci-
mems OF iron bridges in the country |;
bridges that were built under repeated
and vigorous protest from competent en-
gineers, for various towns and counties.
An impression exists 10 the minds OF
many persons that il is purely matter
of opinion whether bridge Ia safe or
not. La nine cases out Of ten, however,
IL Ia not at all matter Of opinion, but q
matter OF fact and OF arithmetic. The
whole question always comes 10 this :
Ia the material In this bridge OF good
quality? Is there enough of ity Ia II cor
rectly disposed, and properly put to-
gether? With given dimensions. and
knowing the load To be carried, 1t is u
matter of the simplest computation TO
fix the size Of each member. We know
what one square inch Of iron or
steel will hold, and we know the
total number OF pounds TO be sustained !;
and il Il no matter Of opinion, but one OF
simple division, how many times one
will 90 into the other.
We often hear IL argued that bridge
mus, be safe because IL has been submit
ted to heavy load and did not break
down. Such u test means absolutely
nothing IL does not even show that the
bridge will bear the same load again.
Much less does IL show that II has the
proper margin for safety. IL simply
means that il did not break down at that
time. Every rotten. worn out and de-
fective bridge that ever fell, has been
submitted TO exactly that test. More
than this, it has repeatedly happened
that heavy load has passed over n
bridge In apparent safety, while much
lighter one passing directly afterwards
has gone through. For the test OF a
bridge TO be In any way satisfactory we
must know just what effect such test has
had upon the structure. We do not lind
this out by simply standing near and
noting that the bridge did not break
down. We must satisfy ourselves be-
yond all question that no part has been
overstrained.
Some years ago the builders OF a
wretchedly cheap and unsafe iron high
way bridge In Massachusetts, in order To
satisfy the county commissioners that
the work was sound, tested II, by plac-
ing a heavy load upon Ii, and as the
bridge did not break down the COM
missioners accepted 1t, paid for 1t, and
pronounced il ''abundantly safe for all
practical uses" and in less than ten
years 1t broke down under a single team
and little snow, weighing in all not
over one-tenth part OF the load the
bridge was warranted TO carry, and not
over one-half the load with which it had
been previously tested. IL this bridge
had been tested by five minutes OF hon.
est arithmetic it would have been
promptly condemned the very day 1t was
finished.
The fact that bridge is made of steel
or Of iron Is no guarantee whatever OF
It's quality. There are many bridges,
especially on our highways, made of
iron and made Of steel, which are
wretchedly unsafe traps, not half ss
good as the old wooden bridges which
they have replaced; and one OF the
worst features of such bridges Is that no
ordinary inspection will detect the quail
ty Of the metal. In most cases a good
practical carpenter can detect rotten
timber in bridge; but town or county
officers have no means OF knowing any
thing of the iron or steel In finished
bridge, and as long as 1t looks well on
the outside they assume that 1t Is all
right. That Is exactly what the man
ayers of one Of our prominent railways
did In regard to one Of its bridges, which
after carrying the trains for n dozen
years, broke down under passenger
train, causing one of the most fearful
disasters we have ever had, and showing
wretchedly welded piece of iron, that
never should have gone into any bridge,
and which under proper inspection at
the beginning never would have been
permitted TO be used.
There are several concerns In the
United States that make a specially Of
highway bridges, and which, taking ad-
vantage of the ignorance of public
officials, are flooding the country with a
miserable set Of traps, that await only
the right combination of circumstances
TO break down. Dishonest builders cheat
ignorant officials, and the public suffers
the damage and pays the bills. Is human
life worth enough to pay for having these
structures properly made and Inspected
l.