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HISTORY OF BRIDGE DEVELOPMENT
INTRODUCTION
A bridge is a structure which provides passage facilities over an obstacle without
closing the way underneath. The required passage may be for a railway track, road or
pedestrians etc. The obstacle to be crossed may be deep valley full of water, road,
railway etc.
Its origin may have been man’s first attempt to control the forces of nature. A
bridge has always offered man the satisfaction of successfully crossing an
obstruction-be it a primitive of the ancients or a bewildering modern bridge of
immense spans. The concept of bridge is one of the oldest ideas of man brought about
by the requirement of crossing an obstruction. He discovered this much before he
conceived the idea of a wheel.
In this topic, we consider the role of critical analysis played in the history of
bridge building. Throughout history each important structural problem has been
solved by producing a few alternatives and undertaking an investigation to arrive at a
solution. Knowledge of bridge engineering from world practice has great value. For
this reason we begin our topic from a historical perspective. It is not possible to show
all the bridges ever constructed. Here, only those which illustrate the most important
engineering and design developments are being considered.
We know that certain natural bridges were formed, that sustained themselves
by the geometric principles of the arch. We also may reasonably surmise that the first
bridges were such simple structures. There remains evidence of the “clapper” (from
the Latin, claperius, meaning pile of stones) bridges in England, primitive rocks
arranged for passage over rivers. These first beams or stringer bridges were formed
simply by laying a flat stone or log on supports without need for complex
mathematical calculations or resolution of engineering problems.
By the same token, ropes and vines were used for carrying people over ravines
and canyons. Perhaps someone first swung from one point to another, and later kept
the vine or rope attached to two points so that cargo or persons could slide along from
one end to the other. Eventually, these supports would hold another vine or rope over
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which people would walk, ultimately becoming a “roadway” in itself. Such may have
been the origins of the suspension bridge.
The pioneers used empirical methods .They made some intelligent guesses as to the
strength required and built the bridge accordingly
Importance of bridges
The bridges serve as the most useful links connecting big towns and cities, and
hence in case of war or calamities, the destruction of bridges stops the mobility of
army or essential goods. The importance of bridges has been felt from the very
primitive age and cities have sprung up at the bridge head or where they could be
crossed over any time. International trade and travel depend on shipping and air
routes, but efficient distribution networks depend on bridges.
HISTORICAL DEVELOPMENT OF BRIDGES
A Mythological Insight
Valmiki Ramayana provides mythological accounts of bridges constructed from India
to Lanka by the army of Rama in verse 2-22-76. So the first available information in
the development of bridges is during this period. The saying of the verse (translated)
goes like this
“When Rama is about to release a missile presided over by Brahma from his
bow, the sea-god appears in person before him with joined palms and advises him to
get a bridge constructed by Nala across the ocean. The ocean god disappears after
giving this advice to Rama. Nala accordingly constructs a bridge across the sea with
the help of other monkeys “
Another verse from the Ramayana (translated) goes like this
“ That beautiful and lovely bridge constructed by Nala across the ocean the
abode of alligators, shone brightly like a milky way of stars in the sky “
The Ram Sethu also known as Adam's Bridge is a chain of limestone shoals,
between the islands of Rameswaram, off the southeastern coast of Tamil Nadu, India,
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and Mannar, near northwestern Sri Lanka. Geological evidence indicates that this
bridge is a former land connection between India and Sri Lanka
Fig 1. Adam's Bridge (Ram Sethu)
Nala, the son of Viswakarma, was probably the first Indian bridge engineer.
The Arthashastra of Kautilya mentions the construction of dams and bridges. A
Mauryan bridge near Girnar was surveyed by James Princep. The bridge was swept
away during a flood, and later repaired by Puspagupta, the chief architect of Emperor
Chandragupta I. The use of stronger bridges using plaited bamboo and iron chain was
visible in India by about the 4th century. A number of bridges, both for military and
commercial purposes, were constructed by the Mughal administration in India
Ancient Period-Early Developments in Bridge Construction
It is said that the history of bridges is the history of civilization. However
achieving progress in bridge engineering was not an easy task. Bridges, as most other
engineering structures, began with the “cut and try” process. The pioneers used
empirical methods. They made intelligent guesses required and built the bridge
accordingly. Many centuries passed before man created the five basic types of
bridges: the beam, the cantilever, the arch, the suspension and the truss. The first four
types were copied from nature long before recorded history began.
Primitive man must have built many crossings over shallow streams by
pilling rocks for piers and covering them with slabs of stones, logs, or falling trees so
as to span small rivers.
Early forms of Suspension Bridges: Suspension bridges across the water were built
from the overhanging branches of opposite trees. Thus, it may be seen that the
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evolution of bridge engineering resulted from the evolution of the form of structure,
the materials of construction, and the methods of design, fabrication and erection.
Initially ropes were thrown across a narrow gorge or river, from which people could
hang as they crawled across. This was the earliest suspension bridges. Later, wooden
footways were added between the ropes. The suspension or cable bridge is illustrated
in nature by the swinging vine, utilized by animals and people to pass from one tree to
another over a stream. In its simplest form a suspension bridge consists only of cables
and unstiffened roadway. Many primitive bridges of this kind were built.
Fig 2. Hanging creepers used as monkey trains
Fig 3. A swinging vine
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Bridges made of timber
The natural example of the simple beam bridge is that of a fallen tree spanning a
stream.
Fig 4. Accidentally fallen tree used as bridge
Then the purposefully felled trees/logs and two or more felled logs with
transverse type platform were also used as bridges. A log bridge is a bridge that uses
logs that fall naturally or are intentionally felled and placed across streams. The first
man made bridges with significant span were probably intentionally felled trees. Such
log bridges have a severely limited lifetime due to soil contact and subsequent rot and
wood-eating insect infestation.
Fig 5. A Log Bridge
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Bridges made of stone
The Natural stepping stones
Fig 6. A rough creek crossing
A step-stone bridge is a simple means for a pedestrian to cross a watercourse
during periods of low flow while keeping feet dry. This type, along with the log
bridge is likely the oldest bridge types. Unlike all other bridges, this bridge has no
spans. Water is allowed to course between the stones that form the steps. Step-stone
bridges are often seen in gardens in China and Japan. It is one of several principal
types found in such gardens. Sometimes one will find these as informal crossings of
small streams when hiking, as they are often built by hikers during the drier seasons
and are subject to being swept away (or at least disarranged) during periods of high,
fast water
Clapper bridge is an ancient form of bridge formed by large flat slabs of
granite or schist supported on stone piers (across rivers), or resting on the banks of
streams. Although believed to be of prehistoric origin, most were erected in medieval
times, and some in later centuries. They are often situated close to a ford where carts
could cross. According to the Dartmoor National Park, the word 'clapper' derives from
an Anglo-Saxon word, Cleaca, meaning 'bridging the stepping stones’.
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Fig 7. The Clapper Bridge at Post bridge, Devon-England
Early forms of Arch Bridge: An arch bridge is a bridge with abutments (supports at
either end) at each end shaped as a curved arch. The arch is in compression and
pushes its load out horizontally and vertically into the supporting ground. Natural
bridges of stone have also been formed, where the action of water has worn away rock
until only an arch was left, high above the river bed.
Fig 8. Natural Arch Bridge
Early forms of Cantilever bridges: Quite probably, primitive man discovered the
principle of the cantilever bridge at a very early stage of the development. He made
use of cantilever to construct longer spans than he was able to build with simple
beams. Timber beams or stone slabs projecting out one above the other represented
such bridges.
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Fig 9. A Cantilever Bridge
The earliest bridge of which there is any authentic record was built over the Euphrates
at Babylon at about 780 B.C.
THE ROMAN PERIOD:
The Roman Period dates from 300B.C and covers a period of about 600 years.
The Romans were the first real bridge engineers. The greatest bridge builders of
antiquity were the Romans. They applied a civil engineering repertoire on an
unprecedented grand scale and achieved impressive results .They built bridges in
wood, stone and concrete. They abandoned Timber bridges in favour of stone bridges
which required the arch to be perfected. They solved the complicated engineering
problems of how to rest their massive spans on underwater piers and how to protect
the piers from floods. Today, Roman arches still stand in Italy, Spain and France. The
Greek writer Herodotus in his Histories, records several pontoon bridges. For
Emperor Darius I The Great of Persia (522 BC - 485 BC), the Greek Mandrocles of
Samos once engineered a pontoon bridge that stretched across the Bosporus, linking
Asia to Europe, so that Darius could pursue the fleeing Scythians as well as move his
army into position in the Balkans to overwhelm Macedon
Roman engineering introduced four significant developments to the art of
bridge building that never had been prominent before:
1. The discovery and extensive use of natural cement.
2. Development of the coffer dam.
3. Perfection and widespread application of the semi-circular masonry arch.
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4. The concept of public works.
Typical characteristics of Roman Bridges
Many are more than 5 meters wide
Most of them slope slightly
Many have rustic work
The stonework has alternating stretcher and header courses ; i.e. one layer of
rectangular stones is laid lengthwise, and the next layer has the ends facing
outwards
Stones linked with dovetail joints or metal bars
Indents in the stones for gripping tools to hold onto
The Romans mixed cement, pozzolana, found near the Italian town of Pozzuoli
(ancient PUTEOLI), with lime, sand, and water to form a mortar that did not
disintegrate when exposed to water. It was used as a binder in piers and arch
spandrels, and mass-formed in foundations.
The oldest roman bridge according to history was the Pons Sublicius,
named for the sublicae, or wooden beams, from which it was built across the river
Tiber in 620B.C. The most celebrated of all the Roman bridges was Caesar’s pile
trestle (55B.C) which was founded on groups of wooden piles. A series of these piles
and cross beams were carried right across the river, and then logs were laid along
them to form the roadbed of the bridge. The Roman’s greatest undertaking was the
large timber arch bridge over Danube in 104A.D. It contained 20 wooden arch spans
resting on cut-stone piers.
Fig 10. Pons Sublicius
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To erect underwater piers, the Romans made use of Coffer dams. They are
temporary enclosures built in river beds to keep the water out while the foundations
were established. They were made by driving timber piles into the river bed,
removing water from the area enclosed, and then excavating the soft ground inside.
Despite the use of coffer dams, Roman bridge foundations typically were not deep
enough to provide sufficient protection against scour. The most well known existing
Roman aqueduct is the Pont Du Gard, near Nimes in France. It is a three tiered bridge,
the lowest of which consists of six large arches and the topmost tier carries the water
channel.
Fig 11. Port de gard near Ninnes, France - A 3-storyed aqueduct
The aqueduct of Segovia of Spain is another example. The Romans abandoned
timber bridges in favour of stone bridges, which required that, the arch to be
perfected. The Romans also used the strong semicircular arch. The Romans, while
certainly not the originators of the arch (credit has been given to the Babylonians for
that), can fairly be said to have perfected its application and principles. Some of the
stone arch bridges built by Roman engineers survive to this day.
Development in China
Following the decline of the Roman Empire with its many engineering
achievements, little developments in beam, arch, suspension, and cantilever bridge
took place in China and other parts of the world. Chinese bridge builders
experimented with forms and materials, perfecting their techniques. China was the
origin of many bridge forms. Marco Polo told of 12,000 bridges built of wood, stone,
and iron near the ancient city of Kin-sai. The first chain-link suspension bridge, the
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Panhogiao or Panho Bridge (206 BC), was built by General Panceng during the Han
Dynasty. Also, one suspension bridge is said to have been built in china about 65
A.D. Another early form of bridge was the cantilever span. The Chinese are believed
to have constructed cantilever bridges many centuries back. The Chinese have
developed the true semicircular arch for ages, although their old spans were always
short. The ancient China, the Zhou Dynasty Chinese text of the Shi Qing (Book of
Odes) records that King Wen of Zhou was the first to create a pontoon bridge in the
11th century BC. However, the historian Joseph Needham has pointed out that in all
likely scenarios, the temporary pontoon bridge was invented during the 9th century
BC - 8th century BC in China. During the Eastern Han Dynasty (25-220 AD), the
Chinese created a very large pontoon bridge that spanned across the width of the
Yellow River.
Post Roman Era
After the fall of the Roman Empire, progress in European bridge building
slowed considerably until the Renaissance. Fine bridges sporadically appeared,
however. Medieval bridges are particularly noted for the Ogival or pointed arch. With
the pointed arch the tendency to sag at the crown is less dangerous, and there is less
horizontal thrust at the abutments. Medieval bridges served many purposes. Chapels
and shops were commonly built on them, and many were fortified with towers and
ramparts. Some featured a drawbridge, a medieval innovation. The most famous
bridge of that age was Old London Bridge, begun in the late 12th century under the
direction of a priest, Peter of Colechurch, and completed in 1209, four years after his
death. London Bridge was designed to have 19 pointed arches, each with a 7.2-metre
(24-foot) span and resting on piers 6 metres (20 feet) wide. There were obstructions
encountered in building the cofferdams, however, so that the arch spans eventually
varied from 4.5 to 10.2 metres (15 to 34 feet). The uneven quality of construction
resulted in a frequent need for repair, but the bridge held a large jumble of houses and
shops and survived more than 600 years before being replaced.
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Fig 12. Old London Bridge
FURTHER DEVELOPMENT OF BRIDGES
Development in Arch Bridges
Stone Arches
Corbelled Arches
Masonry Arch Bridges
R.C.C Arch Bridges
Steel Arch Bridges
The construction of arches began before the days of recorded history. Corbelled stone
arches were used by the Egyptians in the pyramid of Gizeh dating back some 3000-
4000 years ago. The inhabitants of the valleys of Euphrates and Tigris were also
familiar with the arch at a very early period. The Chinese have employed the true
semicircular arch for ages although their spans were always less. But the Romans
pioneered the building of arch bridges, which with their familiar parabolic shape
allowed for longer spans than beam bridges. Because the reach of the beam bridge is
limited, arch bridges provide a natural mechanism for spanning greater distances.
Stone Arches: Stone arch bridges are the oldest of the arch bridges, as early engineers
made use of this available material. However, there is an aesthetic appeal to the use
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of stone, and stone was used in the twentieth century in construction of some very
beautiful and important bridges. Stone as a material handles the massive compressive
forces acting on the bridge. To the extent that concrete is comprised of sand and
gravel, they are included here as "stone" arch bridges, though might be considered
separately.
Fig 13. A Stone Arch Bridge
Corbel Arches
The corbel arch bridge is a masonry, or stone, bridge where each successively higher
course (layer) cantilevers slightly more than the previous course. The steps of the
masonry may be trimmed to make the arch have a rounded shape.
Mayan civilization: Corbelled arches are a distinctive feature of certain pre-
Columbian Meso-american constructions and historical/regional architectural styles,
particularly in that of the Maya civilization. The prevalence of this spanning
technique for entrances and vaults in Maya architecture is attested at a great many
Maya archaeological sites, and is known from structures dating back to the Formative
or Pre classic era.
India: The arches in Indian buildings were trabeate or corbelled. The tomb of
Sultan Ghari is an example of a corbelled arch from 1231 AD, located in New Delhi,
India.
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Fig 14. A corbel arch in Vasant Kunj, New Delhi
In addition to stone, arch bridges were also fabricated from wrought or cast iron as
well as steel
Masonry Arch bridges
The end of the 16th century marked the start of new evolutionary era in the building of
masonry arch bridges. The Renaissance took the structures and forms of construction
of the Romans as its models. Due to its rise/span ratio of 1:2 the semicircular arch
permits only very restricted functionality and is therefore unsuitable for urban
structures in particular. This functional disadvantage gave rise to new arch forms
which were considered shallower than Roman arch.
More than 2000 years certainly passed before the Etruscan’s masonry arch
with specially cut joints appeared. But the span of time from the first masonry arch
theories of the late 17th century to the elastic arch theory is less than 200 years. And
the analysis of masonry arch bridges based on the ultimate load method did not appear
on the scene until the 1960s.
The largest masonry-arch span in the world, 89.9 m (295 ft), is the Syra Bridge at
Plauen, Germany, completed in 1903. No major masonry-arch bridges have been built
in the U.S. in recent years because of their high construction costs.
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Development in Suspension bridges
A simple suspension bridge is an early type of bridge that is supported entirely
from anchors at either end, and has no towers or piers. The simple suspension bridge
is the oldest known type of suspension bridge and there were at least two independent
inventions of the simple suspension bridge, in China and South America. It was also
used in remote ages in Japan, India and Tibet. The cables of these primitive types
were made of wines twisted onto straps of hide and fastened to trees or other
permanent objects on shore. Iron chains for suspension cables were adopted in both
India and Japan more than 500 years ago.
Fig.15. Suspension Bridge in South America
A rope bridge is a bridge constructed chiefly of rope. In its simplest form, it can be
one or two ropes that bridge a river, enabling the traveler to be supported in their
crossing and not be swept away. One rope above another, for feet and hands, may be
referred to as a commando bridge.
More complicated rope bridges can involve the use of multiple ropes, and boards as
footpaths. One of the most complex examples of a culture using these as permanent,
rather than temporary crossings, is the Inca civilization
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Fig.16. A Rope Bridge in China
A Chinese multi-span simple suspension bridge with bamboo cables is
reported at Quan-Xian, documented from 960AD. Simple suspension bridges using
iron chains are also documented in China and the Himalayas, although their earliest
date is unclear. The Luding Bridge dates from 1703, spanning 100 m using eleven
iron chains. Several are attributed to Tibetan monk Thang-stong rGyal-po, who
reportedly built several in Tibet and Bhutan in the 15th century, including one at
Chuka. Claims that more modern suspension bridges with a horizontal deck also
originated in Tibet or China remain largely unsubstantiated.
In South America, Inca rope bridges predate the arrival of the Spanish in the Andes in
the 16th Century. The oldest known suspension bridge, reported from ruins, dates
from the 7th Century in Central America (see Maya Bridge at Yaxchilan). This bridge
has been proposed as the earliest known suspended-deck suspension bridge, but may
have been a simple suspension bridge. Development of wire cable suspension bridges
dates to the temporary simple suspension bridge at Annonay .
The first chain suspension bridge did not appear in Europe until 1741, when the 70ft
(21m) span Winch Bridge was constructed over a chasm of the River Tees (UK), with
the flooring laid directly on two chains. The grandfather of all great suspension
bridges is the mania straits bridge, England. Built by Thomas Telford in 1825, which
was 60 years ahead of its time. The Menai Bridge was twice rebuilt before the entire
suspension system was replicated in steel in 1940 and the arched openings in the
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towers were widened. Simple suspension bridge designs were made largely obsolete
by the 19th Century.
The inherent tendency of suspension bridges to sway and undulate in wavelike
motions under repeated rhythmic loads such as marching soldiers or the wind was not
completely understood by engineers until the 1940s, following the collapse of the
Tacoma Narrows Bridge. Credit for designing the first suspension bridge rigid enough
to withstand wind loads and the highly concentrated loadings of locomotives belongs
to John Roebling. His first masterpiece was the Niagara Suspension Bridge, with a
span of 821ft (250m) on the Grand Trunk Railway below Niagara Falls
Fig 17. Niagara Bridge (USA)
Iron bridges
Though extremely versatile, wood has one obvious disadvantage - it burns.
There was another material, however, whose use at the end of the 18th century offered
bridge engineers an alternative to the traditional materials of timber, stone, and brick.
The Greeks and Romans had used it to reinforce stone pediments and columns in their
temples and iron links had been forged by the Chinese and used in suspension
bridges.
The successful smelting of iron with coke, rather than charcoal, by English ironmaster
Abraham Darby in 1709 freed iron production from fuel shortage restrictions, made
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large castings possible, and facilitated creation of the arch ribs for the world's first
iron bridge, built seventy years later. Bridges were one of the first structural uses of
iron, preceded only by columns to support the floors of textile mills.
The first successful all-iron bridge in the world was designed by Thomas Farnolls
Pritchard, an architect who suggested using the material as early as 1773. The Iron
Bridge was followed by a succession of cast-iron arches built throughout Europe. One
iron arch, however, merits mention, as it is the oldest iron bridge in America. Dunlaps
Creek Bridge (1839), designed by Captain Richard Delafield of the Army Corps of
Engineers for the National Road in Brownsville, Pennsylvania, survives to this day,
still carrying traffic (Figure 7). Because the material could be moulded into elaborate
shapes, extravagantly decorative iron arches were used for pedestrian bridges on the
grounds of estates and imperial palaces or urban pleasure grounds.
Fig 18. Dunlaps Creek Bridge (1839), Brownsville, Pennsylvania (USA)
Following the construction of the Iron Bridge at Coalbrookdale, Thomas Telford, a
gifted, self-educated Scottish engineer, built a number of cast-iron arches throughout
the British Isles. These included canal aqueducts, which were extraordinarily
innovative arrangements in which the cast iron had real structural value. Telford's
most ambitious notion, however, was his proposal of 1800 for a single cast-iron arch
of 600ft (183m) span over the Thames to replace Old London Bridge.
Today, several collections of cast-iron arches survive in different countries. Rio Cobre
bridge in Jamaica is another example. By 1800, most European engineers were open
to using cast iron.
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Fig 19. RioCobre Bridge ,Jamaica
Steel bridges
Structural steel is strong and supple compared to Cast or Wrought iron, and
allows greater design flexibility. The last thirty years of the 19th century witnessed
the phasing in of steel plates and rolled shapes, leading to the enormous production of
steel trusses and plate-girder spans of ever-increasing lengths throughout the world.
Steel arches and cantilevers were favoured for long spans because they better
withstood the impact, vibration, and concentrated loads of heavy rail traffic.
The earliest known use of steel in bridge construction was the 334ft (102m)
suspension span across the Danube Canal (1828) near Vienna (Austria). Steel halved
the weight of wrought iron, but remained prohibitively expensive for another forty
years before steelmaking processes such as the Bessemer and the Open-hearth were
perfected. The first major bridge utilizing true steel was the Eads Bridge (1874), one
of the Mississippi River crossings in the USA. The crowning achievement of the
material during the 19th century was the mighty Forth Railway Bridge in Scotland
(1890). Its design was motivated by the Tay Bridge disaster. Steel arches of enormous
span were built during the first few decades of the 20th century.
In India, for example, the British built several long-span railway bridges, such as the
Hooghly and the Sukkur bridges called Howrah Bridge which exceeded 1000ft
(300m) in span and are interesting because they were constructed using the simplest
equipment and armies of unskilled labour.
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Fig.20. Howrah Bridge, Calcutta
Railroads and Viaducts
Railroads, the transportation mode that revolutionized the 19th century, generated a
bridge type that merits special attention. The limited traction of locomotives forced
the railroad engineer to design the line with easy gradients. Viaducts and trestles were
the engineering solution for maintaining a nearly straight and horizontal line where
the depth and width of the valley or gorge rendered embankments impracticable.
These massive, elevated structures were first built in Roman style of multiple-stone
arches and piers. Later, when wrought iron and steel became available, engineers built
viaducts and trestles of great length and height on a series of truss spans or girders
borne by individual framed towers composed of two or more bents braced together.
Fig 21. Kinzua Viaduct,Pennsylvania (USA)
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Development in Cantilever bridges
To solve the problem of increasing the span distance, other alternatives to
beam and arch bridges included suspension and cantilever bridges. Cantilever bridges
are a modified form of Beam Bridge, with the support being placed not at the end, but
somewhere in the middle of the span. Engineers in the nineteenth century understood
that a bridge which was continuous across multiple supports would distribute the
loads among them. This would result in lower stresses in the girder or truss and meant
that longer spans could be built. The use of a hinge in the multi-span system presented
the advantages of a statically determinate system and of a bridge that could handle
differential settlement of the foundations. Engineers could more easily calculate the
forces and stresses with a hinge in the girder.
Heinrich Gerber was one of the engineers to obtain a patent for a hinged girder
(1866) and is recognized as the first to build one. The Hassfurt Bridge over the Maine
river in Germany with a central span of 124 feet (38 meters) was completed in 1867
and is recognized as the first modern cantilever bridge.
The Kentucky River Bridge by C. Shaler Smith (1877), the Niagara Cantilever
Bridge by Charles Conrad Schneider (1883) and the Poughkeepsie Bridge by John
Francis O'Rourke and Pomeroy P. Dickinson (1889) were all important early uses of
the cantilever design. The Kentucky River Bridge spanned a gorge that was 275 feet
(84 meters) deep.
The most famous early cantilever bridge is the Forth Rail Bridge. This bridge
held the record for longest span in the world for seventeen years
Fig 22. Forth Rail Bridge -Scotland
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Scientific analysis of bridge design during the 19th century
It took the worst bridge disasters of the century in the USA, Great Britain, and
France to usher in the development of standards, specifications, and enough
regulation to protect the travelling public. The loss of 83 lives caused by the collapse
of a cast- and wrought-iron truss in Ashtabula prompted an investigation by the
American Society of Civil Engineers. The loss of 80 lives by failure of a section of
the two-mile-long Tay Bridge resulted in similar inquiries in Britain.
The reasons for these major failures were similar: ignorance of metallurgy resulted in
uneven manufacturing methods and defective castings, and inadequate inspection and
maintenance were inherent at both bridges. For the Tay Bridge, exceptionally strong
vibrations due to dynamic wind stresses under a moving load created a lack of
aerostatic stability and eventual failure. It took engineers another quarter-century to
perfect bridge design according to advanced theories of stress analysis, understanding
of material properties, and renewed respect for the forces of nature. A definitive
understanding of the physical oscillations and vibrations of structures did not occur
until the middle of the 20th century after the Tacoma Bridge collapse in the USA
in1940
Truss bridges and Girder bridges
Advances in design theory, graphic statics, and knowledge of the strength of
materials by engineers such as Karl Culmann and Squire Whipple were achieved in
the second half of the 19th century, but the factor that most influenced the scientific
design of bridges was the railroads. Engineers had to know the precise amount of
stresses in bridge members to accommodate the thundering impact of locomotives.
Founded on the pioneering work of the American Squire Whipple and other European
engineers as Collignon, the last quarter of the 19th century witnessed broad
application of both analytical and graphical analysis, testing of full-size members,
comprehensive stress tables, standardized structural sections, metallurgical analysis,
precision manufacturing and fabrication in bridge shops, publication of industry-wide
standards, plans, and specifications, inspections, and systematic cooperation between
engineers, contractors, manufacturers, and workers. The combined experience of the
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railroads, bridge manufacturing companies, and the engineering communities enabled
the railroads successfully to tackle long-span iron and steel bridges and long-span
trussed-roof train sheds , the two engineering icons of the 19th century.
The metal truss bridge features a network of metal beams arranged in a pattern based
on triangles that work to support the bridge. The metal truss bridge was essentially the
result of the transition from wood to metal for use in bridge building. Although
experiments in metal bridges had been going on for many years, it was not until the
1870s that metal bridges began to take off and began to be the preferred material over
wood.
Steel-truss construction has been used extensively in bridge building because
of its low cost. Modern developments have increased the attainable length of span,
and continuous trusses are increasingly employed. A notable example of this type is
Lindenthal’s Sciotoville Bridge (1917), over the Ohio River, with a truss 472.4 m
(1550 ft) long in two spans of 236.2 m (775 ft) each. The Astoria Bridge (1966) over
the Columbia River in Oregon is the longest continuous truss bridge, with a 375.5-m
(1232-ft) span.
Fig.23.A Truss Bridge
A girder bridge, in general, is a bridge built of girders placed on bridge abutments and
foundation piers. In turn, a bridge deck is built on top of the girders in order to carry
traffic. The girder is the simple form of Beam Bridge. Originally wood, girders then
were made from iron or steel, or even reinforced concrete. Following World War II
and the expansion of highways, steel and concrete girder bridges became
commonplace.
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Fig 24. Girder bridge
Modern developments
Reinforced concrete Bridges
Prestressed Concrete Bridges
Movable(swing or bascule)bridges
Cable stayed superstructure
Reinforced concrete bridges
Soon after the turn of the 20th century, the development of reinforced concrete
brought about great progress in concrete bridge construction. Just when the masonry
arch bridge was reaching its peak around the beginning of the 20th Century,
reinforced concrete arrived on the scene. Since then, it has become the major
construction material for bridges as it has for most structural and civil engineering
applications, with its intrinsic versatility, design flexibility and, above all, natural
durability.
The Esla Bridge over the Esla River, Spain, with a 196.6-m (645-ft) span, was
completed in 1940 and The Gladesville Bridge (1964) at Sydney, Australia, rises 45.7
m (150 ft) above the Parramatta River on a 304.8-m (1000-ft) are the few examples
of reinforced concrete arch span in recent times.
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Fig 25.RCC Bridge over NH-9 in Andhra Pradesh
Prestressed concrete bridges
The most important innovation in the history of reinforced concrete
technology was the development of prestressed concrete. It had also been used to a
limited extent in masonry construction. Its application to reinforced concrete
revolutionized bridge construction. In prestressed concrete, a prestress force is applied
to a concrete member and this induces an axial compression that counteracts all, or
part of, the tensile stresses set up in the member by applied loading. In the field of
bridge engineering, the introduction of prestressed concrete has aided the construction
of long-span concrete bridges. These often comprise precast units, lifted into position
and then tensioned against the units already in place, the process being continued until
the span is complete. For smaller bridges, the use of simply supported precast
prestressed concrete beams has proved an economical form of construction. The
introduction of ranges of standard beam section has simplified the design and
construction of these bridges.
The earliest investigations of prestressed concrete beams were conducted in
the nineteenth century. Further application in construction was made during the first
three decades of the 20th century. Dischinger was the person who built the world’s
first prestressed concrete bridge in Aue, Germany, which was completed in 1937.
Further developments were the Mass River Bridge built in 1949 by Gustave Magnel,
which was the world’s first prestressed continuous girder bridge.
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A stressed ribbon bridge is a tension structure. The suspension cables are
embedded in the deck which follows a catenary arc between supports. Unlike the
simple span the ribbon is stressed in compression, which adds to the stiffness of the
structure. Such bridges are typically made from concrete reinforced by steel
tensioning cables. Where such bridges carry vehicle traffic a certain degree of
stiffness is required to prevent excessive flexure of the structure, obtained by stressing
the concrete in compression. The Maldonado Bridge, located in Maldonado, Uruguay
is an example for stressed ribbon bridge which is a modern development in
prestressed concrete bridges.
Fig.26.The Maldonado Bridge, located in Maldonado, Uruguay,
Movable or Transporter Bridges (Bascule or Swing)
The bascule or draw span was developed by Europeans during the middle Ages. This
is the descendent of Beam Bridge. There was a resurgence of moveable bridges
during the late 19th century. Reliable electric motors and techniques for
counterbalancing the massive weights of the bascule lift, or swing spans marked the
beginning of modern moveable-bridge construction. They are usually found in flat
terrain, where the cost of approaches to gain high-level crossings is prohibitive, and
their characteristics include rapidity of operation, the ability to vary the openings
depending on the size of vessels, and the facility to build in congested areas adjacent
to other bridges. This type of bridge also reaches back into history, integrating ancient
technology such as the rope ferry with new structural forms and materials such as the
iron beam and the strongest steel cables.
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Fig.27.Bascule (Movable Bridge)
Cable-Stayed type Superstructure
A cable-stayed bridge is a bridge that consists of one or more columns (normally
referred to as towers or pylons), with cables supporting the bridge deck. This is the
descendent of Suspension-type bridges.
Cable-stayed bridges can be dated back to the 1784 design of a timber bridge by
German carpenter C.T. Loescher. Many early suspension bridges were of hybrid
suspension and cable-stayed construction, including the 1817 footbridge at Dryburgh
Abbey, and the later Albert Bridge (1872) and Brooklyn Bridge (1883). Their
designers found that the combination of technologies created a stiffer bridge, and John
A. Roebling took particular advantage of this to limit deformations due to railway
loads in the Niagara Falls Suspension Bridge.
Fig 28. Cable-Stayed Bridge
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FACTORS THAT AFFECTED THE DEVELOPMENT OF BRIDGES:
The factors which are mainly responsible for this are as follows:
1. Advancement of construction material
Bridge is a massive structure, which needs sufficient quantity of construction
material. In olden days, the means of transport was not as quick as that of today;
hence the difficulty of transport of materials gave rise to the practice of using local
available materials. Thus in places where good quality timber was available in
abundance, wooden bridges flourished and where timber was scarce and stones was
available in plenty, stone were developed. In tropics, the existence of strong creepers
led to the evolution of suspension bridges.
2. Advent of new materials
With advent of new materials, new ideas came to light in the bridge
engineering. The invention of cast iron replaced timber and stone or trussed bridges
by cast iron bridges. Later on cast iron was replaced by wrought iron and wrought
iron by steel. In the beginning of 20th century, much headway was made in the
production of good quality concrete and a new horizon was opened. By the thirties of
the 20th century R.C.C bridges took the place of steel bridges. Further advancement in
the production of high tensile steel and high strength concrete gave rise to the
development of prestressed concrete bridges. Now a day’s big span bridge are
constructed of prestressed concrete as it is economical in material and has longer life.
3. Advancement in theory and scientific research
The design of the bridges was empirically based on past experience gained by
success or failure of the bridges constructed. The well known Hook’s law came into
existence in the middle of 17th century and Euler’s formula for columns and struts was
published in 18th century. The theory of bending was put forth in 1826. All these
theories led to the theoretical analysis of bridge engineering which enabled modern
bridges design and construction. The development of plastic theory and prestressed
concrete technique further advanced the knowledge of bridge engineering.
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4. Improvement of constructional methods
The improvement in constructional methods has contributed very much to the
advancement of bridge engineering science. The use of compressed air has helped to a
great extent in the construction of bridge piers foundation waters which otherwise
would have been impossible.
5. Advancements in other branches of science
The research work in hydraulics, structural engineering, highway engineering
has considerably contributed to the development of bridge engineering and are closely
related to it.
CONCLUSION
The developments of bridges in the early stage took place in different countries
independently more or less at the same time. Of course the pace of development could
not be kept at par due to many factors. Developments in different countries could not
travel fast to benefit each other by mutual exchange of knowledge and the progress
made in each country remained of local nature. Along with development of other
branches of science, the science of bridge engineering also has been progressed and
very rapidly in the 19th century.
It is certain that technological advancement will continue to influence the type of
bridges in future. New structural concepts in connection with engineered materials
offer a wide range of possibilities for future bridges.
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