New-York tribune., 1901-08-18
HOW TO BUILD A BRIDGE.
MODERN ART EXEMPLIFIED BY THE
NEW EAST RIVER STRUCTURE.
A SIMPLE STATEMENT OF THE USES OF THE VA
RIOUS PARTS AND THE WAY IN WHICH


Not far from two hundred thousand persons |
cross the old Brooklyn Bridge daily and sur
vey therefrom the one now in process OF
construction But only a few of them fully un-
derst;. - the relation of the different parts or IL
10 each other the methods employed In thls
highly interesting work.
The most important things I'm a suspension
bridge are the towers which hold up the cables, |
the anchorages in which the ends OF the cables |
are fastened, the cables themselves, the sus- |
penders by which the bridge proper is hung
from the cables and the truss work The engi- |
neer who designs the bridge plans all OF these |
with special reference to the work expected OF
the bridge and thinks out almost every detail |
Then the building is intrusted TO one or more !
contractors The John A. Roebngs Sons Com |
pany. for instance will construct the cables and
suspenders. The towers and land spans were |
built by a company that is now merged in the |
United States Steel Corporation. but was orig |
inally the New-Jersey Steel Company. and the
Pennsylvania Steel Company will build the APP |
proaches and the truss of the main span.
It is necessary that the towers shall be high |
enough 10 allow for the sag I'm the cables and |
keep the lower surface OF the bridge at the |
proper elevation above the water. In the old |
bridge the towers of stone. Those Of the |
new one are OF steel and apart from their |
foundations (Which extend nearly 120 feet be- |
low high water mark. weigh 10000 tons each |
The anChOTaEeS enormous masses OF ma |
sonry in which are imbedded colossal chains. In |
each Of the New East River Bridge anchorages |
there are four sets Of chains for each cable. |
Each set Of chains Is composed Of thirty-eight !
separate strands l2o feet long, and following
curved path backward and downward in the |
masonry. The links Of these chains fat bars |
nine inches wide, two inches thick and Of va
rious lengths Now when it Is remembered
that the anchorage In which these chains are
secured weighs about 10000 tons while the
middle span Of the bridge Will when completed.
weigh only one-tenth as much. one gets IA vivid
idea ~ the security Of the structure,
Work on the towers aud anchcrages was con |
Quoted simultaneously. because the two are in
dependent OF each other But it was necessary
10 bring both nearly quite TO completion be- |
fore beginning the cables. However the ma |
sonry has beea left open top Of the anchor
ages in order TO expose the upper ends 81 the
chains temporarily. one important prerequisite.
To the construction and placing ~ the cables is
the erection Of a light footbridge reaching from
one anchorage W To- the nearest tower thence /
10 the other tower and down To- The second |
anchorage. Another preliminary step is put
ting top Of IN. towers a kind of saddl, for
each cable to rest in. This must De- So designed !
as 10 allow the cable To slide little 10 ana fro
under the varying strains to which 1t is cventu-
ally subjected
The foothridge serves the purpose of a ma
sons scanold. 1t is a temporary structure on |
which ~orkmcn stand while erecting the pcrma- |
nent ediiice. The first step ia building the foot
brdges-for there are two parallel ard sixty |
feet aTart-Was 10 stretch small cables from
anchorage To anchorage over the towers There
are four of these. Their diameter is A.. Inches |
The space between the first and second cables is |
ll1- feet that between the second and third 80 /
ard that between the third and fourth H.. |
The first and second hold up one footbrdge |
and the third and fourth tn ether. The length |
OF the cross tinh~rs Of each bridge is upward |
over. In the interest of economy walks" only |
four feet in width are constructed along each |
edge. The total length Il the two bridges from |
anchorage 10 anchorage is :..nno feet While the |
horizontal distance from tower 10 tower is tGop |
Set the sag Of tie cables makes the middle |
span Of each foothrdge 1880 feet long. The |
fsneth cf each land span. from tower down 10 |
anchorage. is 90 feet
7" enable woTkIncn To pass from one foot |
bridge 10 the other crossbridges have been con |
strUctrd. Thcr- are nine Of these between the |
towers. and one between each tower and thc ad- |
jaccnt anchorage. An additional advantage uf |
connecting the two fo"tbridfes is that this |
double structure is thus stiffencd and better re-
sists the effect of wind blowing up down |