Alexandria gazette. [volume] (Alexandria, D.C.) 1834-1974, 1900-04-10
THE MEMORIAL BRIDGE.


the Secretary of War yesterday sent to
both houses OF Congress the report of
the Board of Army EoRineers and
Architects appointed last February to
receive and recommend lans for a
M mortal bridge across the Potomac
river, extending from the old Naval
Obser vatory to a point directly across
the river on the old Arlington estate.
The board recommends the construc.
ton of a bridge which will cost about
81, $50, 900.
The report views at length the plans
submilted by four prominent bridge
asca t cts and engineers, and selects
those of William Il. Burr, OF New
York, as conforming most closely to
the general specfcatio ns called for.
The general outline specifications
governing the competition, issued un-
der date of July 81, 1899. called for the
presentation OF two designs for bridge
with a draw openings one design to
provide for street cars as well as tor or
dinary vehicles and for pede strians; the
street cars t. be below (underneath)
the highway. The width of the struc-
ture to be sixty feet, including side.
walks. Material mainly granite and
steel. The second (alternate) design to
be for O bridge with draw opening, but
without provision for street cars.
Mr.. Burr's design. the one approved
ov The board, with few alterations, is
sum married in the report as follows:
"This is a design for single deck
bridge, 60 feet in width between rail
ings. providing for two sidewalks, each
10 feet wide and q roadway 40 feet
wide. This design makes no provision
for street railway tracks. The total
length of the open work OF the bridge
proper and approaches is about 3,4Oo
feet.
This bridge proper is to consist OF 3
1872. loot span masonry arches, one steel
draw span having clear width OF l59
feet and 8 more 192-foot span masonry
arches.
"The l92. foot masonry arches are cir
cular (segmental), the springing line
oeing "a feet above mean low water,tne
rise above the spring 20 feet, end the ra
dius of the intrados 1888 feet.
THE clear head room under the
crow of the arch ia 53 feet. A clear
mead room OF about 81 feet at low water
il provided under three arches for o
width of 80 feet at the centre and OF
| about As feet four inches for width OF
100 feet. The face OF the arch ring
IS of granite but the construc'
ton OF the main part OF the ring is on
the Melan system, there being i've
main concrete steel ribs. The granite
arch ring is 5 feet inches deep at the
crown and 8 feet inches deep at the
spring, while the concrete steel ribs are
30 inches deep at the crown and Z feet
3 ie ches at the spring. A solid mason,
ry spandrel wall, partly OF granite ana
partly of concrete, rests upon the gran
lie arch ring. The asphalt roadway
and granolithic sidewalks are support
ed by concrete floor arches between
beams. The weight of this floor sys-
tenn ia carried down TO the arch ring by
framed steel posts. between the above
masonry spandrel walls.
"Tbe draw span has two bascule
arms supported on trunnions, balanced
nv rear extensions and counterweights
| Tne clear opening is about 1876 feet, the
clear span at low water level 169 feet
and the span from centre to centre o.
I.truouions ITO feet. The bascule arms
are composed OF FIVE steel trusses OF tn'
lattice girder type with parallel cordi
twelve feet six inches deep between
centres. The clear head room is aoo1
fifty -one feet when the draw Is ciosed
The floor is to be of asphalt cork blocks
mel led to fit the buckle plates
which q 9 supported by the floor BEAM
and stringers carried BY the trusses: 1
is proposed to operate the draw by lou
Fl ~ horsepower electric motors.
+ THE Washing on approach 10 TO COZ
stat of twelve six y-f)ot span masonr!
arches, back of which is an cart nerl
embankment about five hundred an
fifty feet long.
1.-The sixty- foot span masonry arcne
are full semi-circular, the springipI
line being twenty -four feet above io'
water. the rise above the spring toirt
f,.et. and the radius of the intrados taii
tv feet. The arch il constructed OF tn
s,me materials and in the came man
ner as the l92-foot masonry arch abov
described. The granite arch ring
four fe.t deep through bout, while To
concrete and steel ribs are sixtee
i, inches deep at the crown ana lor'y
eioh, inches deep ct the spring. =,
The principal divisions Of the bridg
80 ,narked nv massive masonry arche
= and towers, decorated with emoIemAu