The Richmond palladium and sun-telegram. [volume] (Richmond, Ind.) 1907-1939, 1915-09-06


Of light and unimportant traffic can
not be held to apply to the case in
hand. There should be something
more than close avoidance Of col
lapse. The factor Of safety against
Unexpected contingencies Of loading
and unavoidable deterioration should
not be trespassed upon.
H Our technical analysis of the stress
es in the present Main street bridge
shows that this factor Of safety has
been largely encroached upon: and
that the stresses figured in the main
members approach tn limit Of their
capacity. In some cases where
substantial portion OF the metal has
rusted away, the members must be
| held to be dangerously stressed when
/ the bridge is loaded with present traf-
fic.
How Bridge May Collapse.
The account of the condition of the
| bridge below (appendix) recites the
physical facts, not only in main sec
| ton, but at gusset plates, joints, and
| in bracing struts. It must be pointed
out that the collapse of some of the
tower bracing, which shows signs of
undue reformation and rusting, would
be followed by the collapse of the
bridge.
| ca We find that with an Interur-
ban car and a uniform live load of 100
lbs. per So. it., allowing no loss due
to rust. that the main members of the
floor system and trusses under the
car track are over-stressed from so to
100 percent, and that, when deteriora-
ton has been allowed for, the stress
approaches the elastic limit of the
/ - r<~rNr
would disappear
Appendix No 1 shows the results of
a detailed examination of the bridge
in which all the defects are specified
and located by reference to drawing
of the bridge
! This survey shows a very serious
deterioration about the stringers,
| floor-beams and top cord over South
truss, and the bracing system of the
towers. The riser blocks are nearly
all broken At the East end of the
bridge the pedestals are both crushed
and the portion of the ablitment badly
cracked. There is general deteriora-
ton throughout the entire structure.
| Repairs. j
In estimating the cost of repairs,
we have fixed as an end the original
strength Of those parts of the struc-
ture, such as struts and bracings and
| the re-arranging of the floor system.
| The main members of the towers, the
trusses and the floor beams and the
stringers are not restored to their orig
inal sectional area. The work of re-
pairs is summarized as follows:
1.-THE removing of all pavement from
both main roadway and sidewalks.
The supporting of the $50 foot span
and the four so foot spans Of false
work
The removal of all struts and sway
!bracings and the introducing Of the
new members in their stead.
The substituting Of steel plate ris-
ers at points of beam and joist bear
ings, for cast blocks now in use.
The thorough cleaning and painting
Of all metal work in the structure.
The providing of an asphalt con-
crete base over buckle plates in the
together with proper drainage for said
roadway.
The laying Of creosote block pave
ment on the main roadway, and creo-
, sote plank floor on the sidewalks.
The removal of the present block
floor and concrete base, together with
the concrete pavement, will be more
or less expensive, depending on the
character of the old concrete work and
their will be no salvage
Other New Material. =
The horizontal struts in both tow
ers and spans have SO deteriorated par
ticuIarly at the connection points that
new material will be required. These
repairs will require new sway brac-
ing and possibly a new lateral sys-
TEN.
To safely introduce new struts and
sway braces in the towers, will re-
quire false-work supporting the spans.
OF course, close examination Of
the supported joints may reveal rust
and damage that is not now apparent.
The broken cast-iron risers on
which the strngers rest must be re-
; placed with steel risers.
The cleaning and painting of the
entire structure is of paramount inn
portance. This work must be thor
oughly done. If solid floor is to be
placed on the repaired bridge, an as
phalt seal is necessary to prevent
further dripping of the drainage and
consequent further rust.
Repairs Total $25, 900
The estimated cost of the repairs emu
thousand dollars.
After such repairs are made, the
bridge will serve for ordinary high
way traffic, not including street cars,
interurbans, roadrollers, traction en-
gines or other heavy concentrated
loads for a limited term of years.
The cost of the repairs will not put
the structure back to its original con-
dition. Metal permanently lost with
rusting of the main members of the
trusses, and of the floor system is not
restored. The members are cleaned
and painted. For instance, the
strength of the upper cord of the
struss has been seriously lessened by
the rustins of the covered plate. But
it is not practical to attempt to repair
this top cord and yet if this repair is
not made, the other repairs, provided
for in the estimate will be largely in
effective. The detailed account of
~ . ii