New-York tribune., 1908-05-13
DANGER In BRIDGE
Continued from first page

not safe The chief engineer will discuss 'nd'
phase of the subject with you
CHANGE IN BRIDGE PLANS
NJ .1ngersoll. with two of his assistants. re-
ceived the reporters. and answered all aues'iOii'
put to him.
+ained :, said Mr. IngersoiI, from the Board OF
Aldermen on December L. 1901. The contract
had been awarded in 1903 The original plans
uere nrenared under the direction of Mr.. Lin
denthaI who was then Commissioner he Iell
! the department after the contract was a"ardeo-
Commissioner Best who succeeded him, decided
to increase the traffic capacity OF the bridge
This necessitated a change in the plans.
..When was the first material for the super
structure delivered?" Mr.. Ingersoll vas asked
..rrhe fret of the steel was delivered in Sep
tember 1904 but this material consisted of the
lighter parts The first shipment of the large
carving members was delivered in March,
1905
Were the revised plans prepared before that
time?'
Yes; the revised plans. with the new stresses
carefully figured out, were prepared before
pound of steel for the structure was faor1cateo-
1t is true the change in plans was authorized
| onlv in December 1904. but the new plans were
| prepared before that In the new plans the live
/
foot to 1900 linear foot The dead load was
| increased from 100000 pounds to 1u:'.Wose
! pounds The capacity of the main compression
| members was increased by % per cent
A request for information as to the increase
| In the size and capacity of the lower chord
| brought out the blue prints of the revised strain
| sheets which showed that both the wind and
/ live load stresses had been reduced when COM
pared with the ma ximum strain sheets under
which the contract for the superstructure was
awarded. These revised strain sheets also bore
! a stamp indicating that they had been received
| in the department March rs. 1906
| What Is the highest stress pound estimated
| in the main compression members Mr. Inger-
! soil was asked
The highest estimated stress in the main
! compression members in the revised plans is
/ twenty thousand pounds a square inch
But did not the Quebec bridge fall at
stress upon the main compression members of
: eighteen thousand pounds a square inch?
! 1T makes all the difference in the world how
| the main compression members are designed.
! They could be designed to carry safely Z stress
| of forty thousand pounds square inch The
| main compression members Of the BlachvelTs
Island Bridge designed as to sustain a
stress of twenty thousa nd pounds more.
Great emphasis was laid by Chief Engineer
! IngersolI upon the fact that nickel steel had
/ been used to some extent in the erection Of
: the superstruCture. and it was carefully ex-
pIsined that nf:kc' s,ecI was fully 20 per cent
! stronger than the ordinary carbon steel used
! in the quebec bridge. 1t is we'll known. how
! ever that the strength of nickel steel is tensile
| and that it could not be used to advantage in
! the lower or compression members Of the
! bridge Its use was confined exclusively To the
! tension or upper numbers. and has no bearing
| on tie question whether MT the all com
! preston e1nbers beloF under too great
/ {, stress.
! Csustave I.indentllal former Bridge Commits
! sioner under whose direction the original plans
! and strain sheets for the BlackwelTs Island
! Bridge we're prepared. was seen by a Tribune
reporter and asked about the statement made
by Bridge Commissioner Stevenson that the
! plans and specifications of the bridge were evi
| IDENTIFY prepared in a hurry
/ DIsAPPROVEs THE CHANGES.
| ..I1 is not true" said Mr. Lindenthal that the
| plans and specifications for the BiackWelIs
| Island Bridge we're prepared in hurry The
/ contract provided for the preparation OF the de-
tail plans or working drawings for the super
structure ny the contractors under the direction
! Of the Bridge Department and the cost for this
work was covered in the contract price for the
work The preparation of these detail working
plans can always he much better done by the
| exnerienced drafting force employed by bridg.
! contractors always subject. "f course. To ths
! direction and approval of the cttys engineers in
/ the Fridge Department
..Therefore. the entire success of the design
| dspends upon the skill of the City'S engineers
without the city being put to the expense of
! employing large force of craftsmen. which
| would have to be dismissed when the work ,f
preparing the working drawings was completed
! This is the practice approved by long expert
| ence and followed in all important bridge work
| in this country In other words. the skill and
science for the work must be furnished by the
! purchaser and the routine work is left 10 the
contractor under the supervision at all times of
| the citys engineering staf.
! Il assume full responsibility for the plans o..
| the Blackwelrs Island Bridge up to the time
! left the department. With regard to the revised
| plans | know nothing except what / saw pub
| lished recently in the engineering papers but I
am free to say that would never have approved
either of increase in the traffic capacity of the
bridge OF the increase in the number OF trolley
I tracks the structure. because consider
! the increase which has been made "a shameful
| and unnecessary waste of public money. The in
creased traffic facilities can under no possible
| combination of trafic conditions ever be utilized
Furthermore. I would never have approved OF
/ the form Of the main compression members act
', ually used because / consider the design much
: inferior to the design of the main compression
of the Quebec bridge which has failed.