Bridge and its types 00923006902338

1. Bridge
The first American iron chain suspension bridge was the Jacob's Creek Bridge (1801) in
Westmoreland County, Pennsylvania, designed by inventor James Finley. Finley's bridge was
the first to incorporate all of the necessary components of a Modern suspension bridge,
including a suspended deck which hung by trusses.
A cable-stayed bridge has one or more towers (or pylons), from which cables support the bridge
deck. A distinctive feature are the cables which run directly from the tower to the deck, normally
forming a fan-likepattern or a series of parallellines.This is in contrast to the modern suspension
bridge, where the cables supporting the deck are suspended vertically from the main cable,
anchored at both ends of the bridge and running between the towers. The cable-stayed bridge is
optimal for spans longer than cantilever bridges and shorter than suspension bridges. This is the
range where cantilever bridges would rapidly grow heavier if the span were lengthened, while
suspension bridge cabling would not be more economical if the span were shortened.
Cable-stayed bridges have been known since the 16th century and used widely since the 19th.
Early examples often combined features from both the cable-stayed and suspension designs,
including the famous Brooklyn Bridge. The design fell from favor through the 20th century as
larger gaps were bridged using pure suspension designs, and shorter ones using various systems
built of reinforced concrete. It once again rose to prominence in the later 20th century when the
combination of new materials, larger construction machinery, and the need to replace older
bridges all lowered the relative price of these designs.

2. Suspension bridges
The earliest method of crossing large gaps . Early bridges realised from a walkway suspended
from hanging ropes of vines To walk a lighter bridge of this type at a reasonable pace requires a
particular gliding step, as the more normal walking step will induce travelling waves that can
cause the traveller to pitch (uncomfortably) up and down or side-to-side. Suspension bridge
realised following the simple design of early bridges.
cables (catenaries)
Light deck – hangers suspending the deck on catenaries Lack of stability in high winds Very
flexible under concentrated loads, as the form of the cable will adapt to loading form Improved
behaviour under traffic and wind loads: stiffening trusses at the level of the deck, that distributes
concentrated loads over greater lengths Alternatively: restrain vertical movement of the
catenaries by inclined cables attached to the top of the towers or inclined struts below the
deck.Tacoma Narrows Bridge, USA, collapsed on November 7, 1940 due to wind-induced
vibrations. It had been open for traffic for a few months only before collapsing.
Cable-stayed bridges
A cable-stayed bridge consists of one or more piers, with cables supporting the bridge deck
Basic idea: reduce the span of the beam (deck) several times compared to the clear span
between the piers Steel cable-stayed bridges are regarded as the most economical bridge
design for spans ranging between 200 and 400 m Shorter spans: truss or box girder bridges
Larger spans: suspension bridges.

3. Origins
The origins of the suspension bridge go back a long way in history. Primitive suspension bridges,
or simple crossing devices, were the forebears to today’s modern suspension bridge structures.
Suspension bridges were constructed with iron chain cables over 2000 years ago in China and a
similar record has been left in India. The iron suspension bridge, assumed to have originated in
the Orient, appeared in Europe in the 16th century and was developed in the 18th century.
Although wrought iron chain was used as the main cables in the middle of the 18th century, a
rapid expansion of the center span length took place in the latter half of the 19th century
triggered by the invention of steel. Today, the suspension bridge is most suitable type for very
long-span bridge and actually represents 20 or more of all the longest span bridges in the world.
Structural System
1. Stiffening girders/trusses:
Longitudinal structures which support and distribute moving vehicle loads, act as
chords for the lateral systemand secure the aerodynamic stability of the structure.
2. Main cables:

4. A group of parallel-wire bundled cables which support stiffening girders/trusses by
hanger ropes and transfer loads to towers.
3. Main towers:
Intermediate vertical structures which support main cables and transfer bridge loads to
foundations.
4. Anchorages:
Massive concrete blocks which anchor main cables and act as end supports of a bridge.
Evolution of Modern Suspension Bridges Beginning of the
Modern Suspension Bridge
The modern suspension bridge originated in the 18th century when the development of
the bridge structure and the production of iron started on a full-scale basis. Jacobs Creek
Bridge was constructed by Finley in the United States in 1801, which had a center span of
21.3 m. The bridge’s distinguishing feature was the adoption of a truss stiffening girder
which gave rigidity to the bridge to distribute the load through the hanger ropes and thus
prevent excessive deformation of the cable. The construction of the Clifton Bridge with a
center span of 214 m, the oldest suspension bridge now in service for cars, began in 1831
and was completed in 1864 in the United Kingdom using wrought iron chains. Progress of
the Center Span Length in the First Halfof the 20th Century in the United States The aerial
spinning method (AS method) used for constructing parallel wire cables was invented by
Roebling during the construction of the NiagaraFalls Bridge,which was completed in 1855
with a center span of 246 m. The technology was established in the Brooklyn Bridge,
completed in 1883 with a center span of 486 m, where steel wires were first used. The
Brooklyn Bridge, which is hailed as the first modern suspension bridge, was constructed
across New York’s East River through the self-sacrificing efforts of the Roebling family
father, son, and the daughter-in-law over a period of 14 years. In 1903, the Manhattan
Bridge, with a center span of 448 m, and in 1909 .

5. Description of Humber Suspension Bridge:
The Humber Bridge (Fig. 1) located near Kingston upon Hull, England. It spans between Barton
on the south coast and Hessle on the north coast, connecting the East Riding of Yorkshire and
North Lincolnshire. Construction of the bridge started in 1972 and completed in 1981. The bridge
has a main span of 1410 m and two side spans of 280 m and 530 m on the Hessle and Barton
sides, respectively. The bridge has reinforced concrete towers of 155.5 m high above the
foundation, asteelbox deck and inclined hangers. Theconnection of hangers and deck are hinged
in both directions in the middle of main span.