The Bridgeport evening farmer., 1917-01-31
new HELL CATE BRIDGE
READY TO CARRY TRAINS

lOadS every part was raised and NOV
ed into position to a nicely"
Watched by Engineering World.
Mr.. Lindenthaps brief. explanation
quite fails to tell anything but a
small part Of the story of this engin-
eering accomplishment. The under
taking has been followed with inter
ese SS' the whole engineering world
and there were some critics who per
sisted until the final union was made
In believing that something would fail
and millions Of dollars be sacrificed
In a. disastrous crash. They had In
mind the collapse Of the first Quebec
bridge, and their fears were some
what justified when the second Que
bee span gave way as the central pan
ell was being hoisted into position.
The secret Of Mr.. LindenthaPs sue
cess has laid in his capacity for in
finite plans in preparation. No de-
tail has been too small to warrant his
personal attention. No wonder, then
that his plans when exhibited at Leip-
zig two years ago, won for him the
the highest award and a gold medal.
10000 Tons of Steel Alone.
To-day the He'll Gate bridge rep
resents a sustained mass of $4,000
tons of steel alone. From pier to pier
the arch spans an interval Of LOTT
feet, This far exceeds the reach OF
any other bridge of the same gener-
al design. The enormous weight is
supported, by two great massive tow
ers of granite $50 feet high, and ends
Of the bridge rest upon four ponder
- ~,
100000 pounds, the largest castings
ever made
Tt is at these four points that the
arch is hinged. The purpose Of the
hinges was to permit the bridge to
be built temporarily on the cantilever
principle and to allow, ultimately for
the dwelling of the two sections of the
arch as they approached each other
and finally came near enough together
t. be joined.
To describe the process of construc-
ton popularity, it may be likened to
a person standing upon a narrow ledge
while leaning cut over space with one
arm extended backward and )gripping
the limb of a tree. The feet would
represent the hinged shoes of the arch
sections and the arm the temporary
backstay at each tower which kept
each growing half Of the arch from
falling into the ss,virling waters of
He'll Gate.
With the outstretched halves of the
arch once joined, the backstays, made
for the time being Of Orders later to
be used as track supports in the ap-
proaches, were no longer needed, and
or nt1 hn of
depended alone upon it's own tremen
dous dead weight and the firmness Of
the footings provided by the sustain
ing towers Of granite. The union
also meant period Of structural re-
adjustment, during which the arch,
previously kept aloft by the tension
Of the bac1kstays, became rigid by
virtue Of the compressive pulLof his
poDderous fabric of steel.
In short, it's capacity to endure is
the product of it's own crushing
weight It was necessary, therefore,
for the engineers to provide a men-
sure of flexibility which would admit
of this settling into place when the
arch became self disappearing and stood
upon it's own feet in straddling the
East River. Likewise, the engineers
had to make certain that there would
be a generous margin Of strength
that would guard against collapse du-
ring the long months of construction
when, panel by panel, each nalf of
the arch rose higher and reached
further out over He'll Gate.
bringing Arch Together.
The better to understand how well
this work has been carried to com
pletion it should be borne in mind
that each half of the arch weighed
$500 tons just before they were unit
ed by the insertion Of the central
panel, mass of 800 tons of steel
These outstretched arms were brought
into position and joined on October
1, 1915, and so precisely had every
part been built and set in place that
measurements taken across the gap
before the central panel was linked
up showed agreement within five
Sixteenths of an inch with the lengths
previously calculated
Here was the climax Of two years
Of abstruse computation and many
months of building together Of 49,
100000 pounds of steel. The lay
man will more fully grasp this engin-
eering marvel when he bears in mind
that the bridge and it's temporary
cantilever- structure utilized thousands
and thousands of pieces Of steel Of
varying lengths and thicknesses, and
only by fitting these together with the
greatest nicely was it possible to OBJ
tain this degree of accord. Further,
there was the question Of expansion
and contraction not only as the gen.
eral temperature changed but as the
heat of the summer sun affected UNI
equally different parts Of the growing
arch and the backstays.
Mr.. Lindenthal foresaw all these
difficulties and anticipated them by
providing the four enormous hydrau-
lie jacks already mentioned. These
jacks,~ especially built for the work,
made it possible to take care of any
temporary sagging in the half sec
tions of the arch held aIoft by the
tension Of the cantilever backstays.
They were able to raise the saddles of
the cantilevers where they passed over
the tops Of the towers.
In this way the cantilevers were
raised fifteen inches above their final
positions, lifting at the same time the
unjoined tips of the arch sections,
though of course not to the same ex-
tent. Finally by lowering the four
jacks the two cantilevers were brought
together, the loads on the backstays
were released and the arch SO joined
became self-supporting structure
Again, as further proof of the aston