New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1882-03-26
THE EAST RIVkR BRIDGE.
PEpnRr RY GENERAL NEWTON.

THE STRUCTURE LOWER THAN REQUIRED BY The
WAR PARLIAMENTARY THE ORIGINAL EsTI-
MATES AS TO WEIGHT WERE EXCEEDED.
General John Newton head of the corps of United
States Engineers in the Department of the East,
was instructed by General II. G. Wright, Chief OF
the Engineer Corps, to examine the East River
Bridge and report whether or not the conditions
recommended by the Commission appointed by
the Secretary of War in 1869 had been complied
WITH including an additional condition imposed Dy
the War Department that the height OF the centre
of the main span shall not he less than l3o feet IN
the clear at mean high water mark of the spring
tides. The conditions recommended by the COM
mission were as follows:
FiysThnt the dimensions and coecens OF stability
various parts Of the structure shall moi he reduced
below those represented in thc papers submitted 10 inc
SocoldThat the centre of the main span shall under
no conditions of load or temperature be less than the
height in the clear above high water of
spring tide, established by the United States COAST
third That portion of the 81 aee or enrockments
OF the pier tower foundations noove the natural bed
hshed by the laws OF the state OF New-lork ,
Fomthrnst no guys or stays shall ever be attached i
TO the main span OF the bridge winch shau hahS OoIo"
the bottom chords thereof
General Newton has made his report on the SUBJ
ject and the report aud correspondence were shown
by him yesterday to reporter of The tribune.
The towers were found TO exceed slightly the re-
quirements. 1t found that there was DIS
crepancy in the data furnished as TO the amount OF
the load which the cables would have to carry. w.
A. Roeblng the chief engineer OF the bridge, In re-
Spouse to the questions Of General Newton, replied
that the distributed dead weight Of supersructure
per hneal foot was . 3lJ-lO0Otons the distributed
dead weight of the four cables 0Sj-l000; the
moving load at 80 pounds per square foot across %
feet of platform, 765-lC00; and twenty passenger
Il, at ll-l(
total of 665-lO00 tons per lineal foot. The
stretch of the cables according to the tension pro-
duccd by the MAXIMUM load. was l 71s-1000 feet,
the cross section of each cable being 135
sanare inche6. The actual strength of the cable
wIre AS found by tests, 10000 pounds per
square inch of steel section; Engineer Il. II. al
colt submitted report Of his laD0rs in measuring
the height of the bridge. An elaborate calculation
gives the vertical distance of the bottom of the "a
bicS above mean high water of spT1ngtldes aC
1873 2g4- l0U0 feet, and deductlng the distance OF
the bottom Of the lower chord OF the BRUCE below
the bottom of the cable, which is 99f- 600 feet,
gives an elevation of 1873 35-luO feet, l 65-1OO
feet less than the height required In answer TO
questions as To the weight of the bridge, Engineer
Roebng first gave II is G.202 2J1OO tons, and sub
scooeutI w. Oh calculation that certain portions of
The main cables at either end self-supp0Tng,
gave che weight a. $500 tons. Engineer Hllden-
brand gave The result OF his calculations 0,lo6
tons.
From the data gwen him General Newton made
series of calculations, ana wrote TO PRESIDENT
Henry &. Murphy. 0i Tue 1rdGe trustees aPpiisl"S
him of the result. A1ieI IecOuuJuS WnaJ Iau Occh
done. he said
As the results obtained have been determined not by
strict mathematical means bur ;atuer from system Of
,n,rox matils II is quite likely that certain minor i
terenccs would exist Uf necessity However, tle dnor-
cnee uf the OF safety toetween Al ana can
moi thus be planned The height, 1917, with all the
correction possible from shortening the s!spendcrs
supposed 10 Dc l25 feet would SUI not be sufficient
mi. letter was replied to by Engineer RoeDling,
who said that he agreed with General Newton mat
the margins Of safety were very low IN
the towers and cables of the bridge.
The anchorages it had been possible 10
reinforce so that recalculatiOn gave margin of
safety OF over times, which was enough where
mere dead weight was concerned. lie gave as the
principal canHes winch had produced the results
complained OF the nsuinclency OF the rignal
nlaus AID estimates, coupled with the attempt TO
tuiid TO! IS 100000 work which would cost
SI4 900 900, aud the disposition TO accommodate TO
the verge. of prudence the locomotive interest. To
satisfy tins tine structure had been srcngl hcned,
The trussrs raised i've feet and the weight Increased
80 that whole polht III the margin 0l safety had
been wiped out, and the pressure on the tower
masonry raisea to 80 tons per square foot. Mr.
Ruebng concluded as follows;
While anticipate not even sign of weakness, relief
can had any time ny Tightening The supes.Tucture
Inc margin Is great no Niagara ana greater than
at Cincinnati The commission on tne BlackWeIs Island
Bridge recommended margin OF safety OF only three
During tue recent reconstruction vi tne Niagara bidge
he permanent load was reduced 200 tons Ihe cables
rose four incnes showing Jhat In twentyscyen years
In. elasticity of the cables had not been impaired.
General Newton was asked by the reporter If he
deemed the bridge safe Tor traYei IN view OF the
inYestI cation which he mad made. lie lepntd tnaC
that vas largely matter OF opinion. as The bridge
was 10 a certain extent an experiment. the span
being the widest of any suspension bridge yet con-
structcd. he margin OF safety was az great
as tnat at Niagara which has been III Use Tor
more than twenty-five years, and greater than that
at Cincinnati lie thought It would bear the strain
Of ordinary traffic. People were Tor a time tllnid
about using the elevated railways Duu no one now
hesItated to use them.
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