Rock Island Argus. (Rock Island, Ill.) 1893-1920, 1899-12-04

ing Elevated Six Feet. and Travel
over 1t by Electric Cars Not Inter-
fered with-Some Unique Contriv-
ances Employed In the Work.
Out on the Chevy Chase car line in
Washington, between the west en-
trance to the geological garden and
tie pretty suburb of Cleveland Park,
is i very large bridge, which is the
object of the greatest interest to engi-
neers at the present time. One of the
nioSt unique featS known to engineer
ing science is being performed there,
and, while something similar may have
been done elsewhere, there is an orig
lnality about the work that renders 1t
little short of marvellous.
The bridge, which is an iron Struc-
ture about 400 feet long and weighing
over 400 tons. is being raised six feet,
while the traffic of the electric cars and
the wagons is not delayed an instant.
and, according to the statement of Mr..
i. L. Slater, the foreman, will not be,
says the Washington Post. Little by
little the bridge is rising, and at the
same time the approaches are being
levcled up. while the car tracks are
raised i'll proportion.
The work is the result of an appro-
priatiOn passed by congress at its last
session. The bridge was located in Il
hollow between two hills, and it was
thought it would be best TO have it
raised, as the bridge would then last
longer and the steepness of the grades
from both directions would be reliey-
ed The contract for raising the struc-
ture was given to a Washington firm
which has been associated with big
jobs of this character for some time.
Mr.. j. Il. Slater, the foreman in
charge of the work. has had quite a ca
reer in the construction line. He does
not pretend to be Il scientific man and
says that his knowledge is all prac-
teal He was chosen by Chief En-
gineer Menocal to build the break
water at Nicaragua several years ago.
Later on he superintendent the con-
struction of the jetties at Charleston.
He is as hard at work as any of his
men all the time and says lie lies
awake half the night planning the de-
tails for the next day.
When the firm got the contract. it
was 4 puzzle as to how the task was to
be performed without interfering with
the traffic. There was practically no
precedent under the existing condi-
tons. In some places it is over 40 feet
from the bridge to the ground below,
and the raising of the great mass of
iron beams was no child's play, eSpe-
cially when cars and other vehicles
were crossing during all hours of the
day.
After much dcliberation a plan was
decided upon. Heavy channel irons
were bolted along the sides of the
stiff legs or uprights. Timbers were
placed above and below the channel
irons. and the jackscrews We're placed
beneath them. In this way Il 'pur-
chase" was obtained for the jack
screws. One side of the bridge was
raised six inches ut a time. When one
side had been elevated, the other was
brought up to n level. Wooden crib
bling was placed under the capStone at
the base of the stiff legs" and Il tenn
porary pier was made.
The bridge is in four spans, with
great iron girderS connecting them.
The Orders are relieved somewhat by
Struts" or braces. and by interme-
diary stanchions. united by rods. The
shoes of the Orders at the bridge rest
upon stone pier at the approach TO
the structure. The pier is being built
up as the work progresses. although
the shoes at present rest upon wooden
crfbbing. The bridge is being raised
so rapidly that the workmen actually
have trouble in keeping the track of
the street railway level with it.
At present the bridge has been rails
ed two feet. and it will be raised four
the required height, the wooden crib
bling will be removed from beneath the
capstone on which the stiff legs or
dinarily rest, and stone piers will be
built. So far from weakening the
structure the raising will result in it's
being stronger than ever. Great care
will be taken with the stonework. both
beneath the uprights which sustain
the weight near the center and on the
stone pier at the approaches
Mr.. Slater says that the firm was
laughed at when it first outlined the
plan. The great trouble encountered
was to secure some method of over
coming the lack of purchase" The
channel irons are cross pieces firmly
boIted to the sides of the legs. Tim
bers are placed under these, and then
the jackscrews have something to
lift against. This is a novel feature,
and its application has interested n
great many contractors. The work will
probably be completed by the end of
October. and the average person who
rides across the bridge in the electric
car will doubtless see nothing wonder
full in the fact that bridge was mere
ly raised six feet without making the
passengers wait for even Il moment