Bismarck daily tribune. [volume] (Bismarck, Dakota [N.D.]) 1881-1916, 1902-06-16
FASCINATING DANGER,
The Perils That Beset the Builders
of Big Bridges.

of Big Bridges.
The design of a long bridge span is
of the most elaborate mathemat-
ical problems that arise in constructive
work. The stresses produced by its
own weight, by the weight Of traffic,
by locomotive drivers, blythe hammer.
ing of tiattened wheels, by the action
Of brakes on an express train, by the
high speed on a curved track, by the
wind and by the expansion and con
traction of the steel in summer and
winter are all accurately calculated.
The detection of the loaded and I'M
loaded bridge is determined, and com
plete drawings are made of every mem
Der of it. The bars of steel are tested
in machines which will pull in two a
horsehair OF a steel bar strong enough
to lift half a score of the heaviest To-
comotives at once, and which will
crush an eggshell Or a steel column,
and accurately measure the stress in
each case. The different kinds of men,
bers are forged, riveted, bored, or
planned in perhaps half a dozen remote
shops, and, although usually not fitted
togetherthere, are examined and meas
ured by specialists to see that they are
correct, and are then shipped by scores
Of carloads to the site Of the proposed
structure, where steam derricks unload
them and pile them many feet high in
stacks covering acres of ground.
The bridge piers may rise above the
yrafor h11p6ra1c 0f foot ,-o,4 I'll 80
mains to place them on a thousand ton
structure, high above a savage chasm,
over an impossible current or roaring
tide, where the water is deep, the bot
tom Of Jagged rocks or ~treacherous
quicksand, Or where an old bridge must
be removed and the new one built in
its place without ~interrupting traffic
On the bridge. 10 accomplish this the
engineer has timber, bolts and ropes,
hosting engines, derricks and a bans
Of intrepid builders who have PERHAPS
followed him FOR years through more
hardship and danger than fall to the
lot OF almost any other calling.
The complicated framework of a
great span is a skeleton with many
accurate joints and thousands of steel
sinews and bones, each of which must
go in exactly the right place in exact
~ the right order. The builder must
weave into the trusses pieces larger,
heavier and far more inflexible than
whole tree trunks, swiftly hoist and
swing them to place hundreds of feet
high, fit together the massive Orders
and huge forged bars with watchmak-
r. accuracy, support the unwieldy
masses until they are keyed together
and self sustaining, and under mil
lions of pounds of stress must adjust
them at dizzy heights to mathematical
lines. This he may need to do not de-
Hberately, but in dangerous emergen-
cies, at utmost speed, putting forth his
whole strength on narrow, springing
planks in a furious tempest, in bitter
cold or in blazing heat. He may be
in the heart Of a African desert, men,
aced by bloodthirsty fanatics, or in a
gorge Of the Andes, hundreds of miles
from tools or supplies, where there is
absolutely no supplement to his own
resources. Under such 4 conditions
bridge building is one of the most fas-
cinating and difficult of engineering
problems and requires a different So
luton for almost every case.-Frank
W. Skinner in Century.