New-York tribune., 1908-05-13
BRIDGE DESIGNER SUG-
GEST.S TEST OF MODEL.
City Officials admit Estimated
Stress of 10000 Pounds -
Quebec Bridge Fell Under
1900 Pounds.

Bridge on account of the large increase in the
weight of material put into the structure over
the quantities provided for in the original plans
raised no end of storm in the Bridge Depart
rnent and among city officials generally.
Mr.. IngersoIl, the chief engineer of the Bridge
Department asserted that The Trihune's story
vas absolutely without foundation, did the
assistant engineers OF the department in per-
sonal charge Of the work. James w stevenson,
the Bridge Commissioner, characterized the
story as utterly absurd Mayor Mcclellan face
tiously remarked that he expected the Bridge
Commissioner let him know when the col
lapse was expected that he might be present
The engineers OF the Bridge Department admit
led however. that the maximum stress to which
the main compression, or carrying, members OF
the bridge viii be subjected when the structure
Is completed was estimated at twenty thousand
pounds to the square inch. When this admission
was made il was pointed out that the Quebec
bridge fell under a similar stress OF eighteen
thousand pounds square inch. The reply was
that the capacity of the main compression MEM
fers TO withstand stress depended upon their de-
sign and that these members in the Blackwells s
Island Bridge were so designed as TO withstand
safely the maximum estimated stress of twenty
thousand pounds a square inch if that stress
VAS ever put upon them
Custave Lindenthal, former Bridge Commits
siouer Who personally superintended the prepa-
ration Of the original plans for the Blackwells
Island Bridge upon which the contract for the
superstructure was awarded. stated in the most
positive manner that the design of the main
compression members of the BlackwelTs Island
Bridge as erected was inferior TO the design OF
the corresponding members of the i'll fated que
bec bridge. He stated also, that he was strongly
Of the opinion that if these members of the
BlackweII's Island Bridge were ever subjected TO
the maximum stress of twenty thousand pounds
a square inch there would be grave danger Of
the structure coapsing.
AGREE WITH MR.. LIHDENTHAL.
The statement made by Mr Lindenthal re-
CardIng the design Of the main compression
members Of the Blackwelrs Island Bridge bears
out opinions expressed by other competent
fridge engineers if it is true that the main
compression members Of the Quebec bridge were
better and more strongly designed and still
1aiied under z stress of 1900 pounds a square
tnch. il is difficult see how the corresponding
members of the Blackwelrs Island Bridge if
they are. as stated. less strongly designed. can
Withstand stress OF 2oeo0 pounds q square
:nch. or Il per cent more than the stress under
Dhich the Quebec bridge failed
Il seems plain to the ordinary lay mind that
under such conditions the main compression
members Of the Blackwells Island Bridge can
not be expected TO sustain a stress Of 10000
There is, however. q simple and comparatively
Inexpensive way IN which all controversy re-
gar1ing the safety Of the new bridge can be set
a. rest. The same course, suggests Mr. Linden
thai could be followed as was followed in re
spect to the Quebec bridge. only before and not
after any possible disaster. A model Of the main
compression members that may be subjected to
this maximum stress Of twenty thousand pounds
square inch of such proportionate size that it
ting
machine in the country could be maGe and sub
r1ftted TO test up to the limit of the load it is
expected 10 sustain.
This would demonstrate satisfactorily whether
the Bridge Department has made the mistake of
providing for q stress upon these members past
the point Of safety. Such test, The Tribune is
informed. could be made within a single month
sn5 st q cost small enough to be insignificant
when compared with the cost of the bridge and |
the great importance Of the issue.
The Tribune has been handed z lemon this |
tr1e." vas the remark made by Mr.. Stevenson |
when 2 Tribune reporter Joined the numerous !
gathering Of newspaper men that besieged the |
Bridge Commissioners office yesterday morning. |
The entire story is absurd. and I aston |
ish=d that il was printed without first being re
ferre6 this department for its side Of the
With reference to the financial end Of the sub |
1eCt there had been expended upon the Black |
wells Island Bridge up TO March Of this year |
&l4 0s4J ono Of which amount S73aoo0 was for /
rsal estate. The rest represents the amount of /
soney that went into the bridge proper
Is il true that after the fall of the Quebec |
bridge your engineers were instructed TO 80 |
over the stresses the Commissioner was asked. |
* INCREASE OF % PER CENT.
Yes they did make an investigation. but no
-rrreQ report was r,rer,ared The result OF the |
Investigation was given to the chief engineer
and myself ,erbaly. and that result was that
The actual stresses did not exceed the calculated
stresses 10y more than IA per cent. The weight
&" The sgpers1ructure originally planned was
o4t|f1rOn pounds, and the actual weight VIII
oe lE30o00yO pounds There viii be in
crease Of about - per cent in the amount Of
ste'l used. but that increase in weight has been
provided for by an increase in the carrying
ceIacitY Of the main compression members.
II IS not true that the whole increase Of
N13l""0O in the cost of the superstructure over
the contract price. as stated in The Tribune.
itDIeseuts the increase ia The amount OF
'eral put into the suspended part Of the super
structure Part Of the amount viii be used to
Provide material TO be used in other than these
parts
when the original plans and specifications /
l'f the bridge were prepared the work evil
gently done in a hurry for no detailed working
cravings we're prepared by the department.
i1e contract consequently was awarded upon
te basis Of weight 4 pound OF material sup
p-ee. and the contr tors had To prepare their
oA" working drawings from the strain sheets
SAd general plans of the bridge. The original
Pans were changed because il WAS decided to
eoa 10 the traffic capacity Of the bridge Natu-
'siiF ln working out the plans the weights
re Increased over those estimated in the con-