New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1908-11-06
EXPERTS REPORT
Continued from first page


mum live load called for in the contract to $50
pounds Iineal foot of bridge for each track
Accompanying the report is a strain sheet
showing the stresses which will result from the
live load recommended as stated after the speci-
fled reductions in dead weight have been duly
made. This strain sheet shows that under the
recommended live load the stresses will be as
follows:
Nickel steel eyebars. 10000 pounds per square
inch; structural steel bars and shapes. 1850
pounds per square inch; compression members
l. over r less than twenty. 1900 pounds per
square inch; and compression members l. over
X above twenty 10000 pounds per square men
There Is a quietly stated. inoffensive paragraph
in the report which says that strain sheet has
been prepared showing the stresses under the
loads specified In the contract. and stating that
it found that the bridge erected would
not carry the loads specified. This strain sheet
does not appear among the schedules attached
to the report and the Commissioner OF Bridges
stated in response to inquiries. that he had
never received the document in question This
is remarkable because this particular strain
sheet must have been the basis upon which the
experts based the recommendations contained
in their report. Some idea of what this missing
strain sheet shows is given by another para
graph in the report. which says that the experts
find that the bridge will carry live load of
three thousand pounds lineaI foot of truss.
l1 six thousand pounds lineaI foot of bridge.
PROVIDED the dead load is first decreased by
one thousand pounds a Iineal foot Of truss or
two thousand pounds lineaI foot Of bridge.
ONLY ONE-HALF REGULAR LOAD.
1t is obvious from this clause in the report
that if the full dead weight specified in the con-
tract should be used it would be impossible to
allow more live load than two thousand pounds
de
lineai foot Of bridge. The contract called for
maximum live load of sixteen thousand pounds
a lineal foot OF bridge, or a regular" live load
of eight thousand pounds a lineal foot of bridge.
so that the bridge If completed according 70
contract would be able to carry only one-quarter
of the maximum load, or One-half the regular
load for which it was designed and contracted
The other findings in the report that the
metal used is good. the contract specifications
explicit the workmanship good. the erection
work all right and the shipping weights Of metal
put into the structure correct.
The last clause in the report states that no
other moving loads beyond those specified can
safely be added the structure unless there
is first further reduction in the dead load,
weight of the bridge itself. than the reductions
described in the report, to keep the unit stresses
down to the safety values shown upon the
strain sheet indicating what the bridge will
carry which accompanies the report =
The experts are also careful to state that the
full length of the steel structure including the
approaches upon the Manhattan and Queens
side Of the river. is 5000 feet. and that the
cantilever spans are only 3.12412 feet in length
The report deals only with the cantever spans.
and does not take into account at all the mile
so of steel structure which constitute the ap-
proaches on either side of the river
BURR CoNCURs IN REPOT,-'
The report OF Professor Burr concurs in the
findings of Messrs. Boiler & Hodge SO far
the actual overloaded condition of the bridge is
concerned if it was completed and equipped for
traffic facilities called for in the contract specii-
cations The opening paragraph Of the report
contains an assertion by Professor Burr that he
regards his. instructions sufficiently wide
include the question of the safety and stability
of the bridge without reference TO the pro-
visions of the contract specifications
Both reports agree that for the present the
four elevated railway tracks. with which the
upper floor of the structure was to be equipped
cannot be used. leaving the roadway for. vehic-
ular traffic, the two passenger walks and the
four trolley tracks. with the allowance for maxi
mum live load reduced the only traffic IA
cilities of the bridge at present.
Professor Burr does however outline a plan
providing for. the use of two of the four elevated
railway tracks planned for the upper floor of
the bridge at some indefinite time in the future.
This plan involves a further reduction in the dead
load of the bridge beyond that recommended
in the report of Messrs. Boiler & Hodge and
an increase in the unit stresses involving
duction of the margin of safety deemed prudent
by the independent Investigators But the
port adds that there are at present ele-
waited railway connections at the Queens end of
the bridge and immediate prospect OF such
the bridge will not be required to
carry any elevated traffic for some indefinite
period after its completion.
The changes recommended by Messrs. Boiler
& Hodge providing for the abandonment of all
four elevated railway tracks included;
The removal Of the stringers for the two in
side elevated railway tracks. the doing away
with the proposed overhanging balconies for foot
passenger walks, the reduction in the maximum
live load specified in the contract for the road
way and passenger walks and the spacing of the
trolley traffic.
The plan proposed by Professor Burr. in the
hope of providing for the future use OF two OF
the four elevated tracks calls for further
in dead load of the structure
by the laying of a lighter concrete road
way than the which has already been con-
tracted for and partly laid. by increasing the
unit stresses by one-third, thereby reducing the
factor of safety insisted upon by Messrs. Boiler
& Hodge and by still further spacing and reg
ulating both trolley and elevated traffic beyond
the spacing already recommended in the report
of the other investigators. The plan also in
wolves the removal OF the two concrete foot
PASSENGER walks now laid upon the strlngers
which 1t is proposed at some time In the future
TO utilize for elevated railway tracks and sub
shutting therefor a lighter foot passenger walk
presumably in the centre Of the upper deck