New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1908-05-16
BRIDGE PROBE STARTED
Continued from first page.

tons. inferior materials faulty erection until
definite proof is established to the contrary
HAD CONFIDENCE IN DESIGN
| Tbus even after the disaster at Quebec, SO con-
fdent were engineering authorities OF the aoso-
lutte safety OF the design, manufacture ana
of the bridge that THE Engineering fseeoiu
pointed out that engineers generally WouIo Oe uii-
willing to attribute collapse to defective pro-
port,ons inferior materials faulty erection until
definite proof established Months AFTER thiS
comment appeared il was shown that the cohapSe
was due to an error in figuring the stresses OF
the superstructure. A commission reported that
the bridge failed with only three-quarters OF the
load 1t was designed to carry The most conVihe-
ing evidence produced that this was the cause
of the disaster was test made at the PhoerAViIe
shops of a model OF the main compression mem
Der which failed and allowed the bridge TO ran
Before making this test the investigating COM
mission escertained definitely that the MEMBER Oh
the bridge which failed under an actual stress
OF 1900 pounds to the square inch AT the uiie
The model that tested afterward failed at ex-
actIv the same stress establishing that there
had been a serious mistake made IN nsurlhs the
stresses of the bridge.
GREATER STRESS IN BLACKWELL'S BRIDGE
The Department Of Bridges admits the calculated
stress upon similar members of the Black~eils
Island bridge will be 10000 pounds TO the square
inch or a stress II per cent greater than that
under which a corresponding member in the Quebec
bridge failed. IL is declared by MT. Lnoehthai
the engineer who designed the Blackweus island
bridge originally. that the main compression men,
bers of the bridge erected inferior in design
TO the corresponding members of the Quebec
bridge. 1t is argued that MIR Lindenthai may De
all wrong In his opinion. but 1t Is equally true
that the engineers OF the city bridge department
may be overconfident of the safety OF the struct-
ure The strongest evidence in the report of the
Canadian commission OF engineers was the faet
that the model tested Phoenxville failed at ex-
actly the same stress as did the menoer Whlcii
caused the bridge to collapse.
Bridge Commissioner Stevenson gives two rea-
sons for refusing 10 have model tests made OF the
main compression members OF the Blackwelrs ISL
and Bridge suggested in The Tribune
The first reason is that his engineers ALSO
lutey certain the bridge is safe The answer TO
that is that the engineers of the Quebec bridge
were equally certain; that even after the collapse
engineers generally, according TO The Engineer
ing Record were unwilling 10 attribute the col
lapse to defective proportions inferior material or
faulty erection until definite proof to that effect
furnished
CLAUSE IN SPECIFICATIONS.
The second reason given by the Commissioning is
that nasmuch as his engineers perfectly
tain that the bridge Is safe. it would be waste
o public money make the suggested tests II
there is any virtue in this reason the answer can
be found in the specifications which accompanied
contract the erection OF the superstructure
OF the BlackweIrs Island Bridge. Clause No. 81 of
the specifications reads as follows:
Full size parts OF the structure may be tested
the option OF the engineer (the cttys engineer;
If tested destruction and proved satisfactory
such material shall be paid for at the price
parts. and the scrap value OF such tested parts
shall be deemed Il proper and sufficient offset to
the cost of making such tests If the parts do not
meet the requirements of the specifications they
will be deemed rejected material and be solely at
the OF the contractor.
The actual amount of public money that would
be wasted. according to the Commissioner. in max
ing these to determine the safety OF one OF
the citys largest bridges would he nothing more
than the remuneration of two three expert en-
gineers. not in any way connected with the bridge
department. who would superintend the making
the tests. and the bare OF the steel in the
members tested the contract price if they with
stood the test