River Falls journal. [volume] (River Falls, Pierce County, Wis.) 1872-2019, 1883-12-27

The bridge is located about 300 feet above the
old railroad suspension bridge. spanning chasin
| $40 feet wide between the bluffs aud over zoo
| fest deep As the foaming rapids at this point
rendered 1t impossible to build piers in the river or
erect temporary supports, 1t was necessary 10 de-
sign a structure which could be erected without
such ia se work: to tain this end bridge OF the
cantilever type adopted which would be SELF
supporting during erection. The principle Of the
cantilever is that OF beam supported at or near
Its center, with arms extending both ways, one arm
being held down by anchorage or counter
weight so that tho load on the overhsnging arm
produces an uplifting force in the opposite end
which is resisted By the counterweight Ihe
structure consists Of tEO InSn steel
resting on stone piers thirty-niue feet
high. Each Of these towers supports a cantileveE
1895 feet 5-16 inches long One end OF each
tower rests upon abutment at the 0dge OF the
bluff, while the other end extends out over tbs
river. The shore ends Of the cantilevers are
anchored TO the abument masonry or anchorage
piers, and both river arms are cted py an m
termediate span of 100 feet, which Is Suspended
from the extreme ends Of the river arms The total
length OF the bridge proper Is 81 feet 4s lEches
between the ceners Of the anchorage piers; the
clear span between towers being 47O feet. Inc
height from surface Of water to base OF rail is Z39
feet The towers are braced steel structures, con-
tanning four columns each. which are made up OF
plates and angles riYeted together, braced
with horizontal struts and tie roas. Tue
batter of the columns at right angles
10 the center line of the bridge is Ia g. and 3aral
lei to tire center line in "a The trusses are two
10 number. % feet apart between centers: the va
inches, ga inches, and SO inches in diameter,
turned accurately so as to fit the bored pin holes
within "a Of an inch. The depth Of the eanti-
LIVER trusses the towers is Sc feet and at the
shore ends q feet. az at the river ends % feet
The lower chords and centerposts are made of
plates and angles rivted together ard latticed, the
| intermediate posts being Of IL by l5-inch chan
nss, lattieed. The upper chords OF the cantlevers
are S-inch bars, the shore arms having a
compression member IS inches deep COM
posed Of plates and angles packed between the
chord bars The shore ends Of The cantiIevers are
attached TO short links, oseillang pins anchored
| to the abuiment masonry, which serve as anchor
ages and also as rockers TO allow for expansion aud
contraction OF the shore produced by changes
| Of temperature. EXPANSION joints are also pro-
yided for at the connection Of the Intermediate
span with the river ends Of the two cauiilevers
The structure Is proportional TO carry, IN addition
to its own weight, freight train on each TRACK al
the same time, weighing one ton per lineal foot,
with each train headed By two 76-ton consolidation
engines with factor Of fafeiy Of .. Tne wind
bracing has been proportoned for pressure Of 80
pounds per square foot on surface twice the area
Of one face Of The truss plus area OF floor system,
plus the Of side Of train taken as 10 feet YER
Z - ta=a