New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1894-12-26
BRIDGING THE HUDSON.
A SINGLE SPAN PERFECTLY FEASIBLE.
e,.srAv H. scHwAB EXAMINES THE ARGUMENTS
OF THE BRIDGE CoMPANy-A SUSPENSION
CHEAPER THAN A CANTILEvER

he built without pier in the river. the NeN-i"i n
and New-Jersey Bridge Company has tried 10 prove
..o. a s,pp,c-snan bridge would be financially i'm
,ossib,e At the same time the treasurer OF said
conneny tells the public eve shall try with All our
mower to raise the money and build the Drldge' IL
,s manifest that this will be useless attempt ana
that not dollar be raised IL the promoters oi
The bridge have no better inducement for capitalists
than TO tell them that the enterprise VIII DC to'ai
failure and that money invested VIII bring no returns
Fortunately for capitalists interested in this briiSe'
the arguments and figures or the New-lorA anu
New-Jersey Bridge Company can be easily reiu'eu'
and il can be shown that money may De as sdieN
snvested in a one-span suspension bridge as IN a
two-span can;ever bridge.
The first arguments Of the New-Nork ana New
Jersey Bridge Company refer to the grade of the
foor 10 the number OF tracks needed for the trat-
fic and TO the probable income. all OF which 'he
bridge company GAINS should have been cons'aered
bv the Board OF Experts before giving verdict IN
favor of a snglespan suspension bridge !; Is difA
cult for anybody to understand what these matters
have 10 do with the determination OF the length or
span or the typs of construction, or, rather 1t IS
easy 10 see that either kind of bridge can be con-
structed with any desired grade and any NUMBER OF
tracks may, therefore. pass over those remarks
and turn at once TO the second part OF the bTldSe
companys arguments referring 10 the cost ana
time of construction OF the respective designs and
on referring these arguments to the engineering
counsel employed by the special committee or the
Chamber of Commerce of which committee am
chairman Mr.. w Hilienbrand. who was the first
assistant Of Colonel W. A. Roebng in the building
of the Brooklyn Bridge, | am supplied win ample
material to refute these arguments.
II the arguments Of the New-York and New
Jersey Bridge Company were correct, 1t WOULD ap-
pear that a suspension bridge costs more than
twice much as a cantiever. and woula require
twice the time for erection. These results were
obtained through certain calculations and by re
nv object to answer these questions and TO show
that the New-York and New-Jersey Bridge com
pany is totally wrong in its premises.
To make the matter clear. let us first recall TO
mind that the Board of Experts made two esti-
mates of cost Of suspension bridge: one for what
NAV be called a "theoreticaP' bridge. based on
improbable assumptions as TO loads and strains
which were more unfavorable than the assumptions
for the cantilever; and another Tor practlcdl
bridge based on more rational and more equitable
assumptions. The difference of cost between the
theoretical and practical suspension bridge Is ac-
cording to the figures of the Board of Experts re-
port about s5,OOoOOo but in reality amounts TO &c.,
900 900 when all the corrections are carried ont
which the Board Of Experts suggested. CThe EnGi-
neering News of September 10 has published the
calculation OF these corrections in detail)
The New-York and New-Jersey Bridge Com
pany in its arguments. invariably uses the figures
given for the theoretical suspension bridge. and
no; as found by the Board of Experts. but as esti
mated by the engineer of said company. 1t is
manifest that this mode Of comparing cannot give
any fair results. and that correct comparison
only be obtained by using figures based on the
same premises such were given by the Board OF
Experts for both kinds OF structures Whether
these figures are absolutely correct does not mat
ter so long as they relatively correct
Basing therefore. my arguments on the calcula-
tons of the Board OF Experts alone, we ma Gh-
ferent results from those stated BY the New-York
and New-Jersey Bridge Company.
In the report of the Board of Experts we find the
following figures:
Corrected in accordance with the suggestions OF 100 ~
Cost Of substruc;ure Of cantilever bridge.
elusive Of anchorages /.
Including anchorages iVV0
It is reasonable to suppose that the construction
Of the substructure for the cantilever will take at
least six months time than for the suspension
bridge. account OF the river pier recurring a
foundation 26O feet Deep 10 feet more than for
any Of the suspension bridge piers The New-York
and New-Jersey Bridge Company. however. assumes
the time required for the suspension substructure
al four years and that for the cantlever sub
structure al three years 1t would be puZzing TO fnd
any plausible reason for this assertion.
Referring to the above-given figures. we find the
loss Of interest money preparatory 10 beginning the
superstructure follows:
SIS COO 900 at per cent for IL years sl39jNo
Or according TO the corrected estimate Of oo
For the cantlever:
si5.5Oo.ooO at per cent for u. $4,000
This shows that as far the subs;ructure is con-
cerned there is no financial disadvantage in the sus
pension plan. but actual gain Of about 100000
the cantilever plan Comparing now the super
structure of the two types OF bridges we notice
that the New-York and New-Jersey Bridge Com
pany assumes three years az the time needed for
erecting the cantever and eight years for erecting
the suspension bridge. The latter figure was arrived
by assuming five years for making the cables
and three years for suspending the floor system
and the stifening trusscs. In estimating the time
from the precedent of the Brooklyn Bridge cables
The actual working time for making these cables
S %as " of tbe bridge as the NewYork and New
Jersey Bridge Company has stated that me time
various causes. principally TO delays in getting
money. which also was the reason that the building
tended over a period Of six years Following the
same reasoning which the New-York and New
denbe the lime that was necessary for making the
Brooklyn Bridge cables. we find that t9e probable ,a
Bridge will be eighteen months, and not five years
as assumed by said company.
liberal allowance for contingencies. We VIII add
another six months and assume two years as
Turning now to the erection OF the floor and
trusses. learn from the report Of the Board OF
Weighs 5000 tons and that OF the practical suspen,
sion bridge 80 500 TONS only 10000 tons corrected
as mentioned before. The New-York and New
Jersey Bridge Company assumes time OF three
wears for erecting either supersructure. suppose
tina, the time Of erection be proportional 10 the
weight OF the material TO be erected ana assuming
that the bridge company is able 10 erect the can't
lever in three years II would take; at most. only
wear and three quarters to erect the suspended SUI
pers;ructure. In reality. the erection OF the latter
lever because the cables form bridge which makes
1t possible to erect simultaneously at many points.
while the cantever work can go on only AT four
points at the same time The fears OF the New ork
and New Jersey Bridge Company that the unequal
loading OF the cables would create difhculties in
matohIng rivet holes and making connections are
unfounded. This difficulty could only arise In plac-
ing TOP chords and d!agonais In position. but none
ct ali were encountered In erecting the trusses OF
the Brooklyn Bridge. There will be less difficulty
IN the North River Bridge, because the floor system
and cables being proportonatey much heavier the
Weight OF top chords and diagonals Is such an nsig