The San Juan islander. [volume] (Friday Harbor, Wash.) 1898-1914, 1908-10-31


than ever before, says a writer In the
Scientific American.
This rather surprising result Is due
largely to the fact that after the orig
inal bridge plans had been completed
and the bridge had progressed to q
point where it was ready for the string
ing of the cables, it was decided to sub
stitute steel wire for the iron wire
which it was originally intended to use,
and, with wise provision for future In
creases Of load, it was decided to main
tain the same diameter as was chosen
for the iron cable, and thus secure the
great increase in strength resulting
from the substitution OF steel. The ad-
vantage of this change has made itself
felt throughout all the history OF the
bridge: for in the subsequent investl-
cations Of its strength, which became
necessary whenever increased loading
was proposed, the main cables have al
ways been found to be amply strong to
take care Of the added weights. SINH
larly, the vertical suspender cables and
their connections to the main cable
have proved able to meet the new con-
ditions.
The weakest part Of the bridge has
always been the floor system, with it's
shallow trusses and light latticed floor
beams. The stiffening trusses, whose
duty it Is to prevent undulation Of the
roadway and preserve it in true line
under uneven loading, are altogether
too light for their work and at various
times during the past ten years, when
there has been an unfavorable cOnjunc-
ton of circumstances, such as heavy
concentration Of load due to break
down on the roadway or the cable
tracks during a period Of extremely hot
weather, the trusses have given way,
either by the buckling Of the bottom
chords or by the breaking of the dag
onals. There was also serious fail
ure a few years ago of several Of the
vertical suspenders near the expansion
joint at the center of the main span
an accident, by the way, which came
within an ace Of causing the whole OF
the suspended roadway to strip from
its hangers and drop bodily into the
East River Both Of these accidents,
however, were quite preventable and
their occurrence was due to lack Of
proper maintenance and repairs Of the
bridge itself. Following Immediately
upon the alarm caused by the breaking
away Of the roadway, the maintenance
Of the bridge was placed in the hands
Of qualified engineers and strict regula-
lions were laid down for the proper
spacing Of the traffic and the proven
ton of congestion Of the trains and
vehicles.
It must be remembered that the
Brooklyn bridge, designed as it was
over a quarter Of century ago, neces-
sarily embodies some Of the crudities
of design and construction, especially
in the details, which characterized the
earlier stages Of the development Of
American bridge building. But during
the past few years the whole structure
has been carefully gone over and as
far as possible the poorly designed
parts and fittings have been removed
and better work inserted, the details
being in certain instances also strength
ened. Consequently, when the engineers
especially appointed to the task made
their recent investigation of the bridge
they were able to report that SO far
from it's being in poor shape it was
actually, in spite Of the increased loads,
in as good if not better condition than
ever before in its history. Moreover,
it is intended shortly to undertake
reconstruction Of the floor sys-
tenn, during which the present roadway
will be an entirely new structure, with
deep and stiff trusses and solid plate
floor beams and stringers. The in
creased load Of the new floor will be
taken care Of by supplementary cables
carried upon Independent steel towers
built into the present masonry towers