Evening star. [volume] (Washington, D.C.) 1854-1972, 1903-05-19
FOR HIGHWAY BRIDGE
GEN. GILLESPIE APPROVES THE
REVISED SPECIFICATIONS.
Steel Truss Structure Consisting Of
Eleven Fixed Spans Supported
by Twelve Piers.


pared by Colonel Allen, the engineer offi-
Ger in charge of local rive and harbor i'm
provements. Prompt action was had in the
matter in order to avoid further delay in
the prosecution Of the work. The speoifca-
tons have been returned 20 Colonel Allen
with instructions to issue advertisements in
accordance Herewith, giving the bidders the
usual forty-five days MOTIFS
According to the approved specifications
bids will be invited for bridge of steel
truss structure. 2.666 feet in length be-
tween end pins. consisting Of eleven fixed
spans of PIG feet each from center to center
OF piers, supported by twelve piers and two
abutments Of concrete and granite masonry,
all with concrete and pile foundations.
The first span from the Washington end
VIII extend over Potomac Park 100 feet,
IN order to leave space for drive and
walk on the shore OF the river under the
bridge. The bridge will have a roadway
forty feet wide between curbs. with sheet
asphalt pavement and two SIDE walks. each
eight feet wide, with granolithic pave
ment. On the roadway will be laid a dou-
Bile track for an electric railway arranged
for an overhead trolley On the outer
side OF each side walk will be an orna-
mental steel or iron railing. The draw
span will be operated by electric motors
and provided with a pile and timber pro-
lection system.
SO4s 6AACA SOAA"SAIS
''It is especially required" says Colonel
Allen. that the top chords Of all trusses,
for both fixed and draw spans, be straight.
except In the tower and adjaceR. panels Of
the draw span, where they may be slightly
elevated If desired. Clearance under the
trusses of 215 feet for the draw span and
IT feet for the spans adjoining the abut-
ments will be required the clearance of the
intermediate spans to be in proportion. In
case a curved bottom chord Is adopted this
minimum headroom must be maintained for
q width of at least so feet in the draw
and two adjacent spans, and must be car
ried over two-thirds of the width of the
river drive on Potomac Park. No portion
of the steel superstructure shall extend be-
which is slightly below the highest observed
freshet level. A grade not to exceed 1 per
cent may be introduced on the bridge road
way. sloping from the draw span, which
The elevation of the roadway at the abut-
ment line is not specifid. but 1t is desired to
keep 1t as low as possible. This elevation
as affecting the cost of approaches, will be
considered in canvassing the bids.
Any style of truss presenting straight
upper chord may be used. Bidders are In
vited to submit their own designs Tor the
bridge, being limited only by the sssecifica-
prescribed and the general dimensions,
clearances. etc, stated. The length Of
spans. width of roadways and sidewalks.
location Of piers and abutments and gen.
eral dimensions of same under coping and
at water line, as well as their dep, s. are
described in detail.
Privileges Accorded.
Except as stated the accompanying
drawings are merely suggested, and are in
no way intended to be rigidly adhered to
by bidders, who are privileged to adopt any
1,1a ha1 90 hn ,.in
which they individually may consider most
economical, subject only to the approval of
the engineer. These specifications are writ
ten with a view to covering the design de-
tail and workmanship of a through-truss
bridge with horizantal draw span. Should
q different type be adopted. as is possible,
the necessary notifications of specification
requirements will be made to secure the
same character of work in every particular.
In case a horizontal swing span Is used,
these specifications, two draw openings
each 100 feet in clear width, are intended
to be provided
If bidders, desire, however, plans may be
submitted for bascule draw span, instead
Of the swinging span shown, and in this
case, one clear opening of LOO feet Will be
considered equivalent to two separate ones
of 100 feet each. The bascule must be
the trunnion, rolling lift. roller lit. OF ;sny
other practicable type which has been sue
cessfully installed and operated in other
localities. Its width, carrying capacity,
time of operation, ETC., must conform strict
ly to the requirements of the swing span.
the specifications for which will be In
force"
Number Of Spans Unchanged.
In an accompanying letter to the chief
of engineers Col Allen says that the re-
vised specifications retain the same number
and lengths Of spans as were provided for
in the advertisement for proposals opened
March 81 last: also the same width of
roadway viz, forty feet from curb to curb
and the same number and width of side
walks.
The clearance or head room above low
water Of the bottom chord Of the bridge
is modified somewhat. He says the new
specifications give as much latitude to bid
ders In presenting their own designs as
would be desired.
ut will be SEEM says Col. Allen. that
in a case of trapezoidal truss the elevation
of the roadway decreases 2812 feet at the
draw to 23h feet at the abutment at Poto-
mac Park. which would give slight slope
practically not Observable) to the line OF
upper chords of the trusses.
''This 1t Is believed is not at variance with
what was decided at the late conference as
to the bridge. and the same, 1t is believed.
also applies to any of the forms. arch or
otherwise, of trusses that bidders may pre-
sent
by making the approaches to the bridge
palmer we might reduce their cost so as
struction of the work contemplated in the
accompanying specification"
The total appropriation for the bridge is
$685.