A WEEKJ,Y JOURNAl, OF PRACTICAL INFORMATION, ART, SCIENCE, MECHANICS, CHEMISTRY,
Vol. LXXV.-1'io.
EST ABLl"URn lA45.
lS.l
NEW YORK, SEPTEMBER 26, 1896.
THE RIGID SUSPEN­
SION BRIDGE AT
LOSCHWITZ, SAX­
A YEAR.
with
a
width
near
Harburg of a b o u t
1,000
feet
of
deep
water and 2,000 feet
ONY.
BY ROBERT GRIMSHAW.
The
AND MANUFACTURES.
[$3.00WEEKLY.
in all.
At that time
the erection of piers
earliest sus­
pension b r i d g e s­
in
suggested
rivers with s a n d y
probably
deep
and
rapid
by the vine trailing
bottom was deemed
across from one tree
risky and unsafe, and
to another on oppo�
as the c a n t i l e v e r
'Site sides of a stream,
principle had not yet
was characterized by
been introduced, the
Bxtreme lateral and
bridging of the deep
verti c a I
portion of 1,000 feet
flexibility.
span was planned to
As in instance after
be effected by a sus­
i n s t a n c e this was
pension
found to be a source
bridge.
may be noted
of danger, engineers
(It
that
in successi ve suspen­
a f t e r w a r d girder
sion
en­
bridges have b e e n
deavored to give an
constructed both at
element of stiffness.
H a m b u r g and at
structures
em­
Harburg, with piers
ployed by Roebling,
only 100 meters = 328
at the Niagara wire
feet apart.)
One
method
rope bridge, was the
For stiffening this
addition of a wooden
proposed structure it
lattice girder;
was recommended so
but
to connect the chain
this did not give suf­
ficient
stiffness
with
to
hung from one end
on a pier and hinged
of speed.
way was planned be­
at the center to its
Seale, 1 : ]00.
Harburg, c r o s s i n g
mate.
As the bend­
ing influence of the
tween Hamburg and
the River Elbe twice,
roadway
formed a rigid beam,
of railway trains at
any but a slow rate
About 1856 a rail­
the
frame that each half
permit of the passage
live load was highest
COUNTERP OISE
ANCHORAGE.
RIGiD SUSP ENSION BRIDGE AT LOSCHWITZ. SAXONY.
© 1896 SCIENTIFIC AMERICAN, INC.
(Continued onp.248.)
J ,itutifi£ !tutricau.
THE
RIGID
SUSPENSION
BRIDGE
AT
rolled beams.
LOSCHWITZ,
[SEPTEMBER
The gaps in the U shaped flooring are
(Continued from first page.)
fir wood filled with asphaltum, which slopes from the
in effect near the vertex, the hinge was placed consid-
center line of the roadway to the footways at each
erably above the roadway frame.
side, and carries an oak pavement in which is laid a
attention was called by Claus
*
double track electric railway.
Koepcke, the engineer of the Hanoverian Railway, to
The footways are formed of two crossing diagonal
the fact that the proposed hinge system was applicable
layers of planks, borne by three length wise stringers
to arched bridges, aL'lO; and three-hinged arches were
recommended by him.
Since then, a number of three-
hinged arched iron bridges and roofs have been constructed;
a notable example
In the construction of the bridge there are intro-
being the roof of the
(1) Making the pillars part of the girders.
(2) Using springs in the hinges.
(3) Putting the center hinge at the level of the bot-
tom member.
(4) Using cross beams in net-like arrangement.
(5) Taking the pull of the bridge with loaded levers.
resting directly on the U irons.
(6) The use of the" bridge brake."
The material of the bridge is chiefly Siemens soft
(1) All previous suspension bridges had masonry or
basic stee� with a breaking strength of 51,000 to 64,000 iron columns to support the chains or girders; as at
lb. per square inch, having 20 to 30 per cent elongation
Manufactures and Liberal Arts building at the Chicago .in 20 cm.
Exposition.
18<)6.
covered by sheet iron, on which there is a sheeting of duced many innovations, the principal of w hich are:
SAXONY.
As far back as 1861
26,
=
7'87 inches.
The elastic
limit comes be­
Frankfort,
etc.
The "Flora" horticul­
Pittsburg, Wheeling,
Brooklyn, N iagara,
In some cases (as at Rowe, Italy) iron levers were
used. But here the pillars form
tural establishment at Charlotten­
t!Je back frames of the center gir­
burg, near Berlin, was the first roof
ders.
example;
against wind and' centrifugal force
and
three-hinged
good
instances
suspension
of
bridges
(as
This
gives
proved
great
during
stability
severe
equi­
are seen in the 80 meter = 262 foot
noctial
foot·bridge
pansion and contraction from load
at
Frankfort-on-the­
storms), and
permits
ex­
Main, one over the Tiber at Rome,
and
and the 244 meter=800 foot Point
The pillars are supported by square
Pittsburg.
cast iron bed plates, weighing 7,632
bridge over the
Monongahela at
over
temperature changes.
swing blocks on rollers resting on
More recently we have the Tower
bridge
from
kg.
the Thames at Lon­
=
16,850
lb.
each.
The total
movement of a pillar between the
don, the two side spans of which,
extremes of minimum load in sum­
each 305 feet
mer and no load in winter is 7 cm.
=
92 meters long, are
each composed of two unequal sec­
tions, one 188 feet
the
other
117
=
=2'8 in.
57 meters and
feet
=
35
The stone piers, which get but
meters,
slight horizontal pressure from roll­
hinged at pillars and at center of
ing
length; and the same system is ap­
plied in Koepcke's bridge between
members of the side spans are kept
Elbe, just above Dresden.
in position by toes sliding length­
Although this bridge was design­
wise in the pillars, and hence are
ed only for ordinary street traffic,
held against lateral
it would safely bear a double track
road 7
sides being
There is a carriage
meters
=
36'5
to
feet.
Provision
is
SPRING HINGE
to
attach
brackets
prolongations of the cross beams, outside of the
girders, for the support of two additional footways,
should these be demanded by increase of traffic.
center span is 146'68
The
24
with a height of
meters
meters
=
0:.:
481 feet long,
main
The
78'7 feet.
chain is an inverted arch, the curve of which is an
hyperbola having the vertex equation
y
1'871 v'40 x +
=
nates respectively.
Each side span is 61'76 meters
-=
202'6 feet.
main chains are in circular arcs with 375 meters
Their bottom flanges
rise with a gradient of 0'0225.
VERTEX
OF
MAIN
access to summits and bases, and,
HINGE.
in fact, to all parts, of the pillars,
for the p u r p 0 s e of
Their
=
1,230
are straight, and
The vertex, with aver­
reductioll at the breaking point is 40 to 65 per cent.
(2)
The use of springs in the hinges was suggested by
The bed plates on the masonry are cast iron, and the the bad performance, in common suspension bridges, of
square blocks between them and the anchors, as well pin joints, which have been in some cases found entirely
as those between the rollers and the pillars, are of cast immovable.
steel.
The
side
abutments
each
girders are
to
built
The foundation, which re�ts on solid gravel, has been all the deformations of the chains, whether b y load or
made within sheet piling, the masonry is cement con­ by temperature, to take place only by bending of the
The total weight of iron and steel in the girders and
anchors is 3,800'5 metric tons, which, together with the
lead slag, wooden roadway and footways, with two sets
of tramway tracks, gives a total weight of 6,708'7 tons.
The total pel'manent load of the girders is 2,787'2 tons.
links, in consequence of which discovery the permissi­
ble traffic had to be reduced.
Now, while the halves of a rigid suspension bridge
may not be so flexible as a single chain link of a com­
mon suspension bridge, the friction, if pins were used,
might cause bending of adjoining parts of the girders;
This load of 2,787 tons, distributed over 270'2 meters especially
as
room
the
pins
must
The spring
link
producing at the
10'5
or
be of large diameter.
principle
consists
*
in
joints pulling resistances
the
in two crossing directions; hence care must
anchors,
be taken that the combination of stresses
connected at
loaded levers
in a
An instance of this was discovered at the
Tetschen bridge over the Elbe, when Fraenkel found
age temperature, rises 0'608 meter or with
an inclination of 0'0083.
inspection,
tween 30,000 to 40,000 lb. per square inch, and the ar�a painting, or repairs.
crete and quarry stone covered with sandstone.
X2
x and y being the vertical and the horizvntal co-ordi­
feet radius.
AT
=
made
as described
under (6). Internal spiral stairs give
6'75 feet; the clear di stance be-
tween railings being 11'12 meters
pressure, be­
braked against longi­
tudinal v i b r a t i o n
23 feet wide, and
on each side a footway 2'06 meters
=
maximum
each of the four pillars. The bottom
Loschwitz and Blasewitz, over the
steam railway.
friction, have the
vertical pressure of 1,090 tons from
by direct pull and by bending do not ex­
meters =- 34'4
ceed certain limits.
feet long, and transferring the pull of the
in three-hinged
bridge through four working points to the
The angular motions
arches or in three-hinged
abutments, WhICh it reaches at a depth of
suspension bridges are caused more by tem­
7'5 meters
perature changes than by load variations.
=
24'6 feet below the roadway.
In
The constructive weight of each anchor
is 225 tons; t its load is in all about 1,535
weight
niches of the abut­
39'4 feet) is
of which latter would
effectually aid in holding down the struc­
The
lated at 400 kilogrammes per square meter=
railway
trains,
occupying
=
the
vertex
is
0·00583
=
0'42 m. ; or 21 cm.
8'3 in. above, and the same
10 C.
=-
below, the
l'go F. change
=
f�
of
inch mo­
The stress in a spring of the thickness d or
outside footways 2 meters wide, on brack­
the coefficient fj of change of its length, 1,
a
in consequence of bending it to an arc, w,
load of only 50 per cent more than at pres­
may be found from the equation
ent possible, it may be safely assumed that
this bridge is safe beyond all possibility of
beams are
of
span being 73'34 m. or
tion at the vertex.
case of Widening the bridge to the extra
The cross
=
0'00583, or about 20
temperature causes 4'5 mm.
meter, or 100 lb. per square foot; and as in
douht.
x
=
motion
neutral position.
the bridge only to 480 kilograIllmes pel' sq uare
have
vertical
240'5 ft.) n-M
the
whole distance between girders, would load
ets, the constructive parts would
--
therefore (the half
82 Ib. per square foot) should be trebled.
two
0·07 m.
12 m.
minutes of arc.
ture, even if the norma! bridge load (calcu­
As
the angular motions of
center of height of the pillar, or 12 meters
As additional anchorage, the lower anchor
ments, the
bridge
(the motionless point being nearly in the
tons.
frames are placed in
this
each pillar, both sides of the vertical axis
SPRING
laid diago-
HINGE
AT
TOP
OF
�::=
PILLARS.
dw
-
21
Now the middle horizontal spring IS made
nally, and intersect each other; one of each
up of three parts: two side parts each of two plates of 2
= 886'5 feet, gives 10,316 kilogrammes per meter (=20,800
cm. = 0'8 in. thick and 100 cm. = ;39'4 in. wide by 165
the other of 94 cm. = 3'08 feet, so that their flanges are lb. per yard) run.
The movable load is estimated as 736 lb. per square cm. = 68'9 in. long, and a middle part made of four
uninterrupted.
To counteract the interruption of
plates of the same thickness, 54 cm. = 21 '3 in. wide and
the webs of the wider beams, there are at each cross­ yard, or 8,968 lb. per yard run.
The maximum horizontal strain is 826 tons for each 330 cm. = 130 in. long; the cross sectional area being
ing four angle irons.
Between every pair of wide
1,232 sq. cm. -= 191 sq. in.; the greatest tensile stress is
cross beams there is placed, to divide the interstice girder.
The minimum stress caused by the bridge weight is therefore
to be bridged by iron sheets of inverted U section,
crossing parr having a height of 115 cm. =3'77 feet and
a
rolled
I
beam.
rests on bars
the
middles
To
2 cm.
of
the
=
prevent rusting, this I beam
0'787
inch
wide cross
square, laid along
b eams and
of the
• See Civil Engineer and Architect's Journal of that year.
t All
the tons here mentiolled lire metric, of 2,200 lb. avoirdupois; the
dI1ference between these and our legal tons beinl: unimportant.
826000 kg.
1,158'6 tons, or 579'3 tons per girder.
This bridge was built for the Saxon government,
from the
---
=670kg.
1232
designs of Geheimerrath Koepcke and Mr.
Manfred Krueger, the latter of whom was resident ·en­
gineer.
The builders were the Marienhuette firm, of
Cainsdorf, near Zwickau.
© 1896 SCIENTIFIC AMERICAN, INC.
• Published in the Zeitschrift of the Hanoverian Engineers' Association,
18811.
1. Citutifir �tUtri,au.
26, 1896.]
SEPTEMBER
2xO'00583
the pillars, we have Il
x
8
= ------- =
2
x
Elbe at Riesa.
0'000141
=
of
2
i2
car
wheels.
The brush runs in a
precaution taken to permit easy access to all parts of tom, and it is arranged to work both ways, a reversible
say 28,446,000 lb. per square the anchorage system, which last has often been rapidly steel deflector being arranged above the brush.
inch, this Il corresponds
0'000141
or cables of suspension wheels and to the brush, the brush making five revolu­
The chains
bridges are usually anchored to the natural rock or tions to one of the
confined in walled abutments; but there is seldom any cylindrical case which is open at the top and the bot­
330
The coefficient of elasticity being about 2,000,000 kg.
per square centimeter
249
The
to a change of tension of destroyed by rust. The anchors of the Loschwitz bridge car consists of an upper platform, in the center of which
2000000 = 282 kg. = 619'6 lb., or to a change are accessible in every part, so that their coat of coal is a sht'lter or cab containing the motor, and a lower
141 kg. = 309'8 lb. greater and less than the 'tar can be readily inspected, and, when necessary, re­ closed section into which the street rubbish is thrown.
x
=
Therefore the tensions newed. The anchors bear, in addition to their regular Its lower floor is formed in parallel sections, which are
in the horizontal spring at the vertex will vary between load, the roadway, which covers them, and which is· of hinged transversely to the car, and by the operation of
670 + 141 and 670 -141; or 81 1 and 529 kg. per square slag blocks on Monier plate, their ends being inserted a lever can be opened for dumping out the refuse. The
stress at the mIddle position.
into the walls.
centimeter or 11663 and 8676 lb. per square inch.
They cannot give way by any increase
nearly the full width of the street if so desired.
hence t'ach one may bend separately, the difference in
1n operation these cars are used in connection with
tensions in the uppermost and the lowermost fibers is
only � of that above calculated; the other
:J4
manual labor, the sweepings of the gutters and sides
of the
of the street being thrown toward the center, where they
141 kg. being manifested as a difference of tensions,
common to all constructions.
broom, wl;1ich ordinarily, as shown in the illustration,
is the full width of the car, can be extended to cover
As the spring plates are not riveted together, and
There is, then, ·nothing
are picked up by the car, which thus sweeps its own sec­
1
risky in using springs or plates for hinges, as the mate­
tion of the road, and also takes the place of the refuse
carts.
rials will sustain the bending without damage, the
The car is the invention of A. Jackson Reynolds, of
more so as the maximum temperature changes occur
Montreal, who states that when sweeping it travels at
only at long intervals, and the changes caused by load
the rate oi six to eight miles an hour, and that it car­
variations are but a small proportion of those caused
ries refuse, snow, etc., out of the city at a cost of $2.1')0
by temperature changes.
per mile.
The double vertical plates in the center withstand
For removing snow a car specially wide and
long is constructed; and it is claimed that by running
the shearing stresses caused by loads passing that point.
the car continuoUl:;ly during a snow storm there is no
The springs at the abutments have but slight angular
difficulty in keeping a street open.
motion-that due to flexure of the side span girder by
A self-loading car is
now being built which will be one of the largest street
load variations, temperature changes being here with­
cars in the world, being 8% feet wide and 45 feet in
out influence.
It will have a capacity for cleaning 25 miles
length.
Similar sprmg hinges have been applied to small can­
of street without stopping.
tilever bridges in Dresden, to prevent lifting of the
.. ....
girder ends on the four points of support.
AN IMPROVED
(3) The vertex hinge has been put below the roadway
FEED
WATER
HEATER.
The illustration represents a heater in which troughs
surfact' to get the necessary horizontal stiffness by mak­
ing the roadway framework a nearly straight girder
MUNDAY'S
FEED
WATER
connected with the supply pipes distribute the water
HEATER.
over tubes in thin streams or a thin sheet, within the
with uninterrupted flanges, connected by
the cross
beams, which here form the wind bracing.
All other of the bridge load within the limits of
suspension bridges have the vertex considerably above strength.
the
bridge shell of the heater, with whose upper portion steam
inlet pipes are connected The improvement has been
�6) The bridge brake consists of clamps which oppose patented by George'.r. Munday, Brenham, Texas. On
the roadway, to get necessary vertical stiffness. Thus
in these qthers the transmission of stresses through the to the sliding or vibratory motion of various parts of a opposite sides of the interior of the shell are secured
vertex distorts the connecting members and causes bridge a certain amount of sliding friction, regulatable angle irons forming tracks, on which the tubes are re­
by springs, by bolts and nuts or otherwise, and thus movably supported by means of a supporting frame at
Besides t,his, there is difficulty in making the hinges absorbing much of the vibration or other injurious each end. as shown in Fig. 1, and in the sectional view,
as single links (as in the Thames and Monongahela motion. It is most successfully applied in the bl'idge Fig. 2, a transverse shaft of the frame carrying rollers
which travel on the tracks. The tubes are open at
bridges) with pins, for heavy stresses, as the narrowing here described
injurious horizontal motions of the whole girder.
At a trial of the stiffness of this bridge a load of steam their ends, to permit the free circulation through them
and horse road rollers, vehicles, etc., amounting to of steam admitted to the heater, and extended above
ing the two main springs at the vertex of the Losch­ 150 tons, caused a center deflection of but 9 millimeters, the tubes are troughs supported by the end frames,
witz bridge is 2'8 m. = 8'5 ft., and besides these, there = % inch, and a company of soldiers marching over it the edges of the troughs being serrated to cause the
breaking up and fine distribution of water flowing
are also two horizontal plates under the roadway, con­ in step caused scarcely perceptible vibration.
of the free space bet ween the girders must be avoided.
On the contrary, the tota:1 breadth of the plates form­
•
necting the hips of the cross beams; and a pair of ver­
tical plates for carrying the vertical stresses caused by
moving loads passing the center opening.
AN
ELECTRIC
from them, each feed pipe discharging into transverse
.' .
SELF-LOADING
CAR FOR
STREET
troughs.
Below the tubes is a wire cloth screen, alSo
supported by the movable frame, designed to receive
CLEANING.
Thus con­
Among the many novel applications of electricity falling scale, and in the bottom of the shE'll is aD
The diagonal cross beams take part of the one of the latest is that shown in the accompanying outlet blow-off pipe. When the tubes and troughs
lengthwise stresses; while they also resist shearing ef­ illustration, where it is utilized, through the medium are to be removed from the heater, for cleaning. and
the removal of scale, the
fects, such as those caused
siderable additional stiffness in the roadway has been
obtained.
head of the shell is taken
by the wind blowing un
equally
on
otf and extensions of the
the different
angle iron tracks, as shown
halves of the girder. These
connecting
springs
within
them below the roadway.
and
passing
,-,hen
1861
in
the
Civil
the
as
the
rapid
heat
nearly
as
with
the
formation
of
may be
re­
scale, which
this brac­
moved
with
but
little
trouble.
sition of the middle hinge
•••
at the level of the lOWe!
PROI''. WM. H BREWER
flanges, in tht' Loschwitll
contributes to the Yale Sci­
bridge, may be seen in the
entific Monthly an account
fact that its lateral motion
passage
water
boiler pressure, and effect
ing, together with the po'
the
interior
It is designed
corresponding
Engi·
nal of J anuary 1.
during
manner,
whole
possible to the temperature
and in
neer and Architect's Jour·
The value of
the
with this heater to
as 1860, in the Hannover'
Zeitschrift;
the
supported
desired
drawn out.
were
recommended as far back
'sche
heater,
mechanism may be readily
wmd
loads
any
III
zontal lattice which stIffens
against
the
tensions being
crossing each other diago­
bridge
conneCted
outer ends of the track ex
bea ms
nally so as to make a hori­
the
are
with the ends of the tracks
only be applied by placing
(4) Transverse
FIg. 3,
in
could
of observations during the
of
past 45 years on earth tre­
thirty-six men keeping step
-h
mors at Niagara Falls. The
Although special diagon­
either SIde of and near the
but
was
0'45
mm.
=
heaviest vibrations were on
inch.
Horseshoe Fall.
al bracing may be strong
en
0
ugh
statically,
soft shales below the lime­
greater changes of length
by
stone, although they were
tension and compres­
evident in the harder lime­
sion in such special brac­
stone and sandstones that
ings, which are, of course,
weaker
than
the
c r0s s
beams, increases the later·
They dis­
appeared in places in the
the
ELECTRIC
SELF·LOADING
CAR
FOR
STREET
SWEEPING.
occur amid t.hese.
Passmg
down aloug the gorge, the
vibrations decreased in in­
for sweeping up and carrying off the tensity, becoming too faint to be perceived between the
The car is 8 feet wide by 25 feet long suspension bridges, but increasing again on nearing the
that cryp­
viction gaining ground rapidly that horizontal vibra­ and 11 feet high. It is carried on two a xles, and is fitted rapids. Persons living near the falls believe
than elsewhere,
tions are as inJurious to dmability as vertical ones are. with the usual equipment of a trolley car. The brakes tats are more common in the rocks therc
the
(5) Loaded levers to counteract the push of an arch and the motor are placed above the wheels. The motor the texture having been attected by the jar ot
al flexure and hence the os-
cillation period. The matter of oscillation of bridges is of an electric
more appreciated ot late years than tormerly, the con­ street refuse.
car,
s
were applied to the s treet girder of the bridge over the is connected by cha.iD and sprocket gear to the driving cataract, but Prof. Brewer finds no eVIdence of thi .
© 1896 SCIENTIFIC AMERICAN, INC.