Daily Kennebec journal., 1901-09-07
BUILDING; BRIDGES.
A Glance at the Intricat" WORK "t
Building a Big Structure.

The most important things in sus-
pension bridge are the towers which
hold 10 the cables. the an,horages IN
which the ends Of the cables are fast
ened. the cables themselves. the sus-
penders BY which the bridge proper y
hung from the cables. ana the truss
work The engineer who designs me
bridge plans all Of these with spt cill
reference to the wHrk expected Of n"
bridge. and thinks odt almost every de
tail.
Ii is necessary that the towers shall
he high enough to allow FOR the sag in
the ca bles and keep the lower surfaccoi
the bridge at the proper elevation atov"
the water In the old brIdg- the tow -
are Of stone. Those of the new one are
Of steel, and. apart from their founda-
tions (which extend nearly Il" feet be-
low highwater nRrk). weigh 4o.,0V tors
each
The anchora ges are enormous masst $
Of masonry in which are imhedded col
Cs.al chains. In each of the new East I
riyer bridge anchcrages there are four
gets Of chains one for each able. Each
set of cha iiS is composed of ~ separate
strands l21 feet long. and following q
curved path backward ana downward
in the masonry. The links of thee
chains are flat bars nine inches wide.
two inches thick, and of various
lengths New. when it is remembered
that the anchorage in which these
chains are secured weighs aboGt 10000
tons. while the middle span Of the
bridge will. when completed. weigh on 4
~ ~ / u
idea of the security Of the structure.
Work on the towers and anchoraSes
was conducted simultaneously. because
the two are independent of each other.
6ut ii was necessary to bring both
nearly or quite to completion before
beginning the cables. However. the
masonry has been left open on top Of
the anchorages in order to expose the
upper ends Of the chains temporarily.
One important prerequisite to the con
struction and placing Of cables Is the
erection of light footbridge reaching
from one anchorage up to the neare-t
over thence to the other tower. and
- down to the second anchorage. An
other preliminary step is putting on
top. of the towers a kind of saddle 70.
each cable to rest IN. This must be 50
designed as to allow the cable to slide
a little to and fro under the varying
strains to which it Is eventually sub
jected.
The footbridge serves the purpose Of
mason's scaffold. 1t is a temporary
structure. on which workmen stand
while erecting the permanent edifice.
The footbridges hang just three fe 4
below the level Of the future main "a
cles all the way across. Thus the lat
er will be about opposite the waists Of
he Workmen engaged in making them.
tightly TO adjust the small temporary
;abIes which sustain the footbridges
vas probably one of the most delicate
md difficult tasks in the whole under
aking. 1t was necessary to foresee
changes which would result from
stretching and other causes. AS ori-
ginally hung. these small cables were
lO'2 rect higher than the positions they
now occupy over the middle of the
river. But the latter are correct. and
the engineer calculations have been
beautifully verified.
Further preparations for construct
ns the cables WIN be made within the
ext lew weeks. These will consist of
tEe erection of wire rope tramwav
rom one anchorage to the other. The
-pparatus will closely resemble that