New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1883-12-02
CANTILEVER BRIDGES.
THEIR CONSTRUCTION EXPLAINED.

AND BUILDING.
@Tell me what n cantilever bridge is SAID Il
TRIBUNE reporter TO engineer of one OF inc iaHoS'
bridge companies I'm the country. see that the new
bridge across the Niagara River to connect inc NeM
York Central and the Canada Southern Railroads. VIII
be the first bridge OF that style built In America
Tbat is true" was the reply But first you ask me what
cautileycr is We borrow the from architecture
means bracket used TO support balcony etc NoW'
IN cantilever bridge there two brackets opposite
each other each resting pier The shore ends OF the
brackets rest upon and fastened down TO another
per the outer ends projecting the water, sustain
central span merely resting upon them and free TO re
spOnd the changes in the temperature To get rude
idea of the principle OF the cantever bridge place two
chairs feet apart put oOtrule each chair held
down by a book; the ends Of the rules viii not meet
the space separating the two chairs but by resting
third rule upon their the bridge is complete This
skeleton idea Now in place Of the chairs substitute
four piers Of masonry instead of the two rules balance
upon the piers two beams resting upon the intermediate
piers and with the shore ends Of the beams placed upon
and fastened to the two extreme piers another span
resting upon their outer ends substituted Tor the lrd
rule and this is the cantilever bridge.
The shore Of the cantever or bracket rests as
have said upon a second pier built back Of the first one
at the rivers brink If there no such support any
wcigh-like that of railroad tranif placed upon the
shore arm would depress toward the ground ana cor
respondingly elevate the outer stream end II would
IL, "
should place a weight at end of the plank But this
is not enough Suppose the railroad train has passed
under the tower the main pier out upon the outer
end cantlevcr or balanced hcam the extra weight
would depress outer end and at the same time elevate
the inner or end SO the shore end not only rests
npon support masonry Lut Is fastened TO it. 10 pre-
vent the train tipping the beam NJ into the air and
falling into the stream"
ADVANTAGES or THE CANTlLEVER PRINCIPLE
"What are the advantages claimed for the canticycr
bridget" asked the reporter
For bridges having long spans the system Is asserted
10 he the most economical less material need he used
TO secure the strength gdy and stiffness than in
a suspension bridge for instance Less false work or
scaioding is needed for the erection Of cantiicver
bridge than for any other braccd STRUCTURE thereby
making 81 capable of construction With more aud
less danger OF disaster and with obstruction 10 nayga
ton The central span resting upon the outer or stream
ends OF the brackets freely expand with the
heat Of summer and contract with the cold weather
one end of this central span Il fastened 70 Of the
brackets other end being placed upon rollers. The
DETECTION from the horizontal under the fnoad capac
ity Of the bridge not half great it would be
suspension bridge Of the same length Of span
By explaining in general way, the process Of con
strcting bracket cantever bridge, You will be able
10 see the economy and Of the work We will start
with one iron hnilt upon pier Of masonry, the
cast shore Of The fret panel Of the bridge Is
swung into place for the shore Of the bracket and
fastened this iron timber support for each
panel IL IS put into place is all the false work required
in building the shore end. Of these panels
built, by of derrick the first panel Of tho
stream arm tied TO the tower The extra weight
of the panels for the shore end Of the bracket viii
po,itc director over The water With this done that
panel itself supplies the false work from which the next
one can he placed III position and boted to the nrst
panel In this way panel 10y panel can be- adv anccd nm
I'll me Outer or s'Gn arm 81 hue oq a IS G"
advance Of that on the outer arm the weight Of
the latter will not Oycrbalancc the former, which, when
completed can he placed nIon tue second pier ana
anchored. on the west Ghe opposite shore Of tho
constructed in the way. Roughly 10 illustrate the
idea, take sheet OF paper and draw two - on the
The perpendicular strokes represent the piers the
respective shores OF the stream The two horizontal
tbc two c % or bradSets Make Two downward
Gc "T from the left hand end Of the tons Of The right
hand and tic left hand respectively: these represent
your bridge complete except the placing Of the central
CONNECT The Two free ends Of the r. This done by
running wooden truss into the Intervening space a Ger
tau distances by means OF derrick fastening cables 10
opposite canteyer then by pushing and pulling. the
truss is gotten entirely across the space II furnishes
iron work which viii make the span complete from
10 tower The only false work needed, you Sec
the wooden truss for building the central span aud The
supporting tmbeTs for the construction Of the shore
OF the brackets cantcycrs. These the general
principles and the methods OF work IN the construction OF
the Cantlcyer bridge"
SOME HISTORICAL FACTS.
The principle Of the cautcycT bridge must have been
known centuries ago. there many old bridges in
Switzerland built In accordance with IT. The
River bridge however IS the first bridge Of any mag
nitudc actually built upon this system The first In
Europe will be the great bridge the Firth Of Forth
Scotland building The engineers in charge Of the
latter work i. Baker, G. E., and John Fowler Mr.
Baker is considered the foremost bridge engineer prob
ably in the world and his publication in sG7 in London
entitled Long Span Railway Bridges" contains what
regarded the standard treatise the cantlcver prn
cipc. The Forth bridge was originally designed 10 be
the Inflated Eay bridge which blown down in gale
in 1850. Mt. COUGHS plans contemplated stiiencd
suspension bridge "A cost OF abOut R2 900 600 The
disaster the Tuy raised question as 10 the engineers
abltes ana Messrs BAKER ana Fowler were engaged TO
Mr. GOnch's plans condemned ana IL decided TO
build the bridge on the cantcycr principle Work was
begun in issi and IT is expected that the structure viii
be finished within two years at cost OF FL 1868 900 II
Is 10 he donblerac railway bridge having two clear
spans each 200 feet long and shore spans each 600
/ feet long tho total length being 494o feet
honor Of raising the first cantleyer bridge in America
the rsl design for large sPan eyer accepted was made
| Company OF ScwYork, for tho ew-YOrk and Long
Island Bridge COMPANY THIS company was organized
channels Of the East River at Blackwes Island The
ty 10 support the traffic OF double line Of rail way two
| wagonways and two sidewalks The two spans
height Of 1876 feet above mean high tide MoreoTer II
was stipulated that In building the bridge false
that would obsruct navigation 10 he used series
OF prizes offered by the bridge company. and com
mission consisting OF o. Chanuto, G. T., Major General
J. O. Barnard T. Z. A. and MajOF-tienera O. A. GIL
more u. s. A. awarded the first premium IN May 1875
TO the design for cantiever bridge submitted by Mr.
Mcdonald The cost Of the bridge be So 900 600
including the approaches For various reasons, not
affecting the dcs gn, the bridge has ct been con
strnccd The Delaware Bridge Company II now engaged
in constructing bridge across the Ohio River connect
ing the cities Of Louisville aud New Albany to ne half
mile long and have two cantievcr spans OF 400 feet
each. The bridge will cost about 1900, 900 and Will
| be finished next year.