National Republican., 1874-04-01
THE NEW CHAIN BRIDGE.
DEsCRLPrIox OF THE IMPosIyo
AND BEzUTLEUL srRUcrURE.


THE DESIGN. MATERIAL. AND cosT-Accu
RATE DIMENSIONS = EsTIHATR OF THF
sTRENGTH-CuMPL OF THE NEW
FREE HIGHWAY BETWEEN THE DISTRICT
AND VIRGINIA.
The completion Of the new and substantial
bridge over the Little Falls Of the Potomac
afording as Il does easy communication be.
tween this District and the numerous thriving
villages Of Londoun, Fairfax, and other coun,
ties Of Virginia, must be source of grasiica,
tion TO every one interested in the progress and
prosperity Of the people. The great industries
of this rich section Of the Old Dominion State
have long suffered for the want Of such a con,
venience. Lengthy marches over wretched
roads had 10 be accomplished, and heavy tolls
paid before the products could be placed in de.
sired markets, entailed trouble and expense tc
both purchaser and seller.
= An this is now happily changed, and If the
people on the other side Of the Potomac are
only true to their own interests and encourage
Immediately the formation of good roads and
the prosecution of the improvements, they may
rely upon rapidly increased community, the
advancement Of industrial energies and the
development of all the attributes and resources
with which nature has endowed their soil
Hundreds Of people visited the new bridge last
Sunday, and to judge from the interest and
satisfaction manifested on all sides the compile
ton Of the work must be regarded as of the
most vital importance to q large proportion Of
the inhabitants of the upper portions of the
District and their neighbors across the water.
The plan for the new bridge selected by Gen.
Ba5coek as best adapted for this site is what
Is known as the "Murphy-Whipple Truss" 1t
is divided into eight spans; two of 160 feet and
six of III feet each. The entire length is
1889 feet. The spans are separate and in
dependent of each other, resting on cast-iron
bridge seats, securely anchored to stone cop
ings; one end of each span is fixed, and the
other rests upon friction rollers provided for
the expansion and contraction of the iron. The
trusses are twenty-eight feet in depth and
placed twenty-five feet apart from centre to
centre. Each truss of 172 feet span is divided
into twelve panels, and each truss of 100 feet
into eleven panels of fourteen-and- d-a-half feet
each. The upper cords, main and intermediate
posts, are formed of Phoenix column iron, and
the lower cords, main and intermediate
ties of tie forged links, without weldil
The posts are fitted to cast
iron caps and seats, the bottoms of the former
and the tops of the latter being truly turned
for that purpose. Turned wrought iron pins,
three inches in diameter, lock in one connec-
ton the caps Of the columns and the diagonal
ties, also the bottom cords, the seats of the
columns, the diagonal ties, and the floor beam
suspenders. The floor beams are 15-inch
Phoenix rolled beams, and the floor joists and
flooring are of the best North Carolina pine,
three inches thick and not over six inches wide,
with edges sawed Straight, laid close, and
securely spiked. There are no sidewalks, but
an iron railing four feet high is placed on
either side of the carriageway. The width OF
the roadway is twenty feet, and the bridge is
proportioned SO as to safely carry, in addition
to the weight of the structure, 100 pounds for
each square foot of roadway, and the maximum
strain produced by this load is 10000 pounds
per square inch of section, or about one-inch
of It's ultimate strength. The contract price
for the entire work was Se4 900, which was
paid by instsllments, as each span was CON-
pleted.
Mr.. Theodore B. Samo was the engineer in
charge of the work, and the contractors for
building the bridge were Messrs. Clark, Reeves
& Co., Phenixvilie Works, near Philadelphia
At the point where this bridge is built the chan
mel Is quite deep, the bottom rocky and uneven,
the current swift and running close to the Vir-
ginia shore, There have been several bridges
Ou IulS elJc, duu Oh cdCu buCCcSSiVc Ouc DclI1
built the defects in. the plans and construction
of the former ones have been avoided. The
first bridge erected on this site was constructed
about forty years ago, which was an iron sus-
pension bridge, supported by immense cable
chains stretching from pier to pier, from which
thesterm, "chain bridge, was derived.
This bridge was destroyed by ice and drift
wood, which lodged against the chains and
piers. The bridge has been continually re-
paired up to the time of the construction of the
present one. The long stretch of rocky flats,
nearly five hundred yards in width, between
this channel and the canal, on the District side,
is seldom covered with water, except in times
of freshets. Immediately below the Little
falls the depth of water is over so feet, and
continues very ceep until the Aqueduct bridge
is reached. So disastrous hitherto have the
foods been to the bridges here that General
Babcock has taken the precaution in this in
stance of having all the old piers raised two
feet additional, thus giving more elevation and
afTording more room for the fee and driftwood.
In 1872 Congress appropriated $1,000 for
rebuilding the Chain bridge, from which appro-
pristion the work has been done.