Vilas County news. [volume] (Eagle River, Vilas County, Wis.) 1896-1927, 1897-02-08
\ oyanIe Bridges.

There is no special field of structural
development which exhibits the ready re-
Spouse of modern engineering resource
to any demand that may be made upon
it in higher degree than the recent de-
signs of movable bridges. While the
movable bridges in the draw and bascule
type is, of course, one of the oldest of
bridge patterns, and while lift bridges
have for many years been successfully
used in connection with such works as
the Erie canal, all such instances have
been on small scales and have required
the solution of no very serious engineer
ing problems. Within the last three or
four years, however, and essentially
since the proposed bridging of the Du-
luth ship channel through Minnesota
point, situations have arisen in which the
magnitude and difficulty of the problems
have given them what really constitute
new characters.
In the particular instance of the Duluth
channel the span was about 175 feet and
1t was required that the structure should
be no impeachment to the entrance of any
vessels that might seek the harbor. The
revolving type of bridge was excluded
from consideration on account of the
room required for it's operation and re-
treating draw was specified. In addition
to plans on the latter system j. A. L..
Waddell, member of American So
ciety of Civil Engineers, offered plant
for a lift bridge which was subsequently
developed for and realized in the South
Halsted street bridge at Chicago. The
completion of this latter structure marked
a distinct advance in movable bridge con-
struction. The span is about 135 feet
and the lift is 1926 feet: it is a heavy
city street bridge, greatly different in
magnitude and character from the small
lift structures hitherto in use and reQuir'
ing devices and machinery of the most
advanced design. The retreating draw
type required by the Duluth authorities
has been abandoned practically, i'll the
movable bridge development. Although it
has some advantages it is less compact,
occupies more room and the track con-
StructiOn and maintenance are expensive.
The bascule and lift types, therefore,
have displaced it in the minds of design
erS.
About the time of the construction of
the South Halsted street lift bridge the
bascule type began to be recognized as
possessing some marked advantages, and
it has been admirably developed in the
ingenious Scherzer system and in others
either executed or proposed. Although
Chicago, with it's numerous city bridges
over navigable waters, and Milwaukee
seem to have been the chief fields for the
development of the advanced types of
movable bridges, the recent competition
in the designs for the Newtown Creek
DFlQSo mas given TO the ClIy OF brOOklVu
a prominent place in the same line. This
competition brought out both lift and
bascule types and the latter in great
variety both as to form and mode of
operation. The plan accepted for con-
struction is the design by Mr.. Thomas e.
Brown, Jr., NJ. Am. Soc c. E.. involving
tower on each side of the stream for
the CONFERENCE.-The of the two leaves of
the bridge, the operating power for the
two leaves themselves being furnished
by hydraulic machinery located in the
basis of the towers This was described
in the Engineering record Of October 81,
1896 The total width of the bridge is
so feet, and the span between the rotat
ing axes is about 1T feet. Only one
plan of the lift bridge was offered which
was quite similar to that of the South
Halsted street bridge at Chicago-En-
gineering Record