Cable Suspended Bridges

8/8/2019 Cable Suspended Bridges

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CABLE-SUSPENDED

BRIDGESENGLISH CLASS


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Few structures are as universally appealing as cable-

supported bridges. The origin of the concept of bridging

large spans with cables, exerting their strength in tension,

is lost in antiquity and undoubtedly dates back to a time

before recorded history. Perhaps primitive humans,

wanting to cross natural obstructions such as deep

gorges and large streams, observed a spider spinning a

web or monkeys traveling along hanging vines.


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EVOLUTION

Early cable-suspended bridges were footbridges consisting of cables

formed from twisted vines or hide drawn tightly to reduce sag. The

cable ends were attached to trees or other permanent objects located

on the banks of rivers or at the edges of gorges or other natural

obstructions to travel. The deck, probably of rough-hewn plank, was

laid directly on the cable. This type of construction was used in

remote ages in China, Japan, India, and Tibet. It was used by the

Aztecs of Mexico, the Incas of Peru, and by natives in other parts of

South America. It can still be found in remote areas of the world.


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The first metal suspension bridge in North

America was the Jacobs Creek Bridge in

Pennsylvania, designed and erected by James Finley

in 1801. Supported by two suspended chains of

wrought-iron links, its 70-ft span was stiffened by

substantial trussed railing and timber planks.


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A major milestone in progress with wire cable was

passed with erection of the 1,010-ft suspended span

of the Ohio River Bridge at Wheeling, Va. (later

W.Va.), by Charles Ellet, Jr., in 1849. A second

important milestone was the opening in 1883 of the

1,595.5-ft wirecable- supported span of the

Brooklyn Bridge, built by the Roeblings.


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The first use of a pure stayed bridge is credited to

Loscher, who

built a timber-stayed bridge in 1784 with a span of 105 ft


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The pure-stayed-bridge concept was apparently not used again

until 1817 when two British engineers, Redpath and Brown,

constructed the Kings Meadow Footbridge with a span of about 110

ft.


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DespiteNaviers adverse criticism of stayed bridges, a few more

were built shortly after the fatal collapses of the bridges in England

and Germany, for example, the Gischlard- Arnodin cable bridge (Fig.

15.2c) with multiple sloping cables hung from two masonry towers.


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In 1840, Hatley, an Englishman, used chain stays in a parallel

configuration resembling harp strings (Fig. 15.2d). He maintained the

parallel spacing of the main stays by using a closely spaced subsystem

anchored to the deck and perpendicular to the principal loadcarrying

cables.


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The principle of using stays to support a bridge superstructure did

not die completely in the minds of engineers. John Roebling

incorporated the concept in his suspension bridges, such as his

Niagara Falls Bridge (Fig. 15.3);


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Rebirth of stayed bridges appears to have begun in 1938 with the

work of the German engineer Franz Dischinger. While designing a

suspension bridge to cross the Elbe River near Hamburg (Fig. 15.5),

Dischinger determined that the vertical deflection of the bridge under

railroad loading could be reduced considerably by incorporating cable

stays in the suspension system.


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AKASHI KAIKO JAPANAKASHI KAIKO JAPAN 1990M1990M


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STOREBELTSTOREBELT ZEALANDZEALAND--SPRAGOSPRAGO,,

DENMARKDENMARK 1624M1624M


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HUMBERHUMBER RIVERRIVER HULL,HULL, ENGLANDENGLAND

1410M1410M


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THANX

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Cable Suspended Bridges

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