New-York tribune., 1908-11-11
EXCEED DANGER POINT
% PER CENT
OYER ELASTIC LIMIT.
Nero QueeHsboro Bridge STRAIN
Sheet Shoes Great Ercess of
Stresses OUer Contract


BlackwelFs Island. or greensboro. Bridge dsar
extensively with the question of what the bridge
erected would safely carry. the language OF
both reports made IL clear that the detailed In
structiOns given 10 the investigators did not
permit them to demonstrate In their reports the
extent to which the structure falls short OF the
contract requirements.
The Commissioner OF Bridges at the request
OF The Tribune has given out strain sheet
prepared by Boiler & Hodge which was not IN
cluded in their report tnat shows exactly how
far the bridge as erected falls short in carving
capacity Of the structure which should have
been erected according 10 the specifications
The details Of this strain sheet now made
public for the first time show concIusively thar
if the BIackwelFs Island Bridge had been COM
pleted according to contract il would have
failed with three-auarters OF the stresses speci-
fed in the contract.
This strain sheet also demonstrates the extent
to which some Of the figures given in the on
ciaI report OF Professor Burr. who examined the
bridge on behalf Of the Bridge Commissioner.
were so stated as to minimize greatly the seri-
Gus Importance OF the grave engineering blum
der made by the officials of the Bridge Depart
ment Professor Burr makes statements which
are absolutely cOntradicted by the results OF the
investigation made BY Boiler Hodge. the in
dependent investigators employed by the Board
of Estimate
DISCLOSED SO MANY WEAK POINTS
The strain sheet given out Is the one which
the Boiler &. Hodge official report refers to IN
the following paragraph;
We made stress sheet for the loads called
for in the specifications. out IL evident that
the structure could not safely carry these loads
had TO find the maximum safe carrying
capacity Of the structure.
When the official reports Of the experts were
given out last week The Tribune called atten-
tion to the fact that this particular strain sheet
did not accompany the Boiler & Hodge report.
although II was obvious that II must have
formed the basis Of the entire investization-
/ Commissioner Stevenson when asked about II
i said that such document had ever been re-
I ceived BY the department Alfred P Boiler. OF
/ the firm of Boiler & Hodge. admitted that such
/ a strain sheet had been prepared. In answer
/ 10 the question why it had not been submitted
/ with The official report he said that the sheet
/ had disclosed SO many weak points in the briage
/ that it became necessary 70 prepare another
showing what the structure would carry with
as much dead load as possible eliminated
The details of the mile Of complicated
arithmetic which constitutes the strain shseL
nov made public bear eloquent testimony 20
| the accuracy OF the statement made By Mr. Boil
/ Ter. Not only were the stresses specified IN the
contract exceeded. but they were exceeded by as
much as ~ per cent In some Of the tension
! members the excess much - per
cent beyond the elastic limit. or breaking point.
of the steel of which the members are made
KNEW CONDITION OF BRIDGE
The first noticeable thing about this strain
sheet is that it is dated September / 1900.
which would Indicate that the condition OF ths
! bridge was known at least 10 the investigators.
| more than a month before they were permitted
to give their report 10 the public The highest
stresses which the strain sheet disclOses for
| congested live load are as follows
] Nickel steel bars 49OOO pounds square inch
| The contract specifies maximum stress OF not
more than $1,000 pounds square inch. This
| is an Increase OF % per cent over the maximum
/ specified in the contract
| Riveted structural steel tension members 2ss-
/ 200 pounds square inch The contract speci-
/ fes a maximum stress OF not more than II OsO
pounds a square inch This is an Increase 0f
| As per cent over the maximum specified in the
| contract
/ Compression members 21.2O0 pounds a square
I inch The contract specifies a maximum stress
OF not more than an average OF 13.0O0 pounds
a square inch the specified stresses being slight
/ " above and slightly below the figure given.
/ according to the length OF the member This =
an increase OF fl per cent over the maximum,
/ specified in the contract
/ Structural steel bars 3I.3OO pounds square
/ inch. The contract specifies 24.0l0 pounds
square inch This is an increase Of 30 per cent
/ over the maximum specified in the contract
While the stresses given above with the per-
I centages over the stresses specified in the con-
I tract are the highest that appear on rne strain
! sheet they are by no means isolated cases ot
/ Overstrain. for there are many other stresses
I which closely approximate the figures given
! STARTLING INCREASE IN STRESSES
/ The most startling increase in the stresses
/ given over those specified IN the contract Is
4 that quoted FOR riveted structural steel tension
/ members OF 35,2O0 pounds a square inch.
/ 11.2OO pounds square inch greater than the
maximum stresses specified in the contract. The
elastic limit. or breaking point. OF the steel from
which these members are made is stated in the
/ contract 10 be 2S.t.0 pounds a square inch
1 This means that if the bridge had been com
pIeted according to contract the members under
| the stress quoted would have failed under
| live load 200 pounds a square inch less than
/ the maximum live load which they would have
been subjected TO- In other words. the structure
/ would not have been able to take more than I5
per cent OF its specified live load without failing
From these figures il is clear what might have
happened il The Tribune had not called atren-
ton five months ago 70 the fact that the bridge
was being dangerously overloaded
In his report upon the Blsckweiis Island
Bridge Professor Burr states that he also pre-
pared a strain sheet SIMILAR TO that made by
Ness-s Boiler & Hodge. a synopsis of which
I is given above While Professor Burr admits
In his official report that his stress sheet dis
+ closed specific Instances OF Overstrain- com
parison OF the figures given above and those
Z 49,