Dr. Jaikrishna Memorial Lecture on Evolution of Bridges

1
SECOND “PROF. JAIKRISHNA
MEMORIAL LECTURE”
“EVOLUTION OF BRIDGES”
Presented By
Er. ASHOK BASA
Past President, The Institution of Engineers, (India)
National Member, Executive Council of World Federation of Engineering
Organization (WFEO)
Member , WFEO – UN ( UNITED NATION ) RELATIONS COMMITTEE ( WURC )
Member , WFEO Committee on Disaster Risk Management(WFEO-DRM)

Bridges are built to satisfy the human need. The
evolution of bridges can be synonymous with the
evolution of civil engineering. It is debatable
“whether bridges have been invented or
evolved”. Moreover it is also believed that bridge
building developed and progressed as an
engineering art, rather than as an engineering
science or from practice to theory, prompted by
the ever-growing transportation needs of the
human race. Therefore, the evolution of bridges
is not only interesting, but also it is stimulating &
inspiring.
2

Right from the beginning, civil engineers deal with
nature. The first concept in bridge building has
been derived from nature. The idea of a slab
bridge might have developed from a tree trunk
that had fallen across a creek or a chasm.
3

The rocks jutting out of the
shallow streams were used as
stepping-stones & these in turn
led to the idea of PIERS. Along
with the rise in the depth of water,
higher & larger rocks were needed
to act as stepping-stones.
Subsequently, people felt, that,
walking was more comfortable
than hopping from stone to stone.
Thus, concept of slab was created.
Slabs of stones were laid across
the stepping-stones, which,
ultimately led to the creation of a
multiple span bridge. These are
known as clapper bridges.
4
Clapper bridges Er.Ashok Basa

For longer spans, vines, where available, were used
to make suspension bridges. Early suspension
bridges consisted of twisted vines tied to tree
trunks on either side of a gorge.
It is quite interesting to note that bridges of three
basic forms – beam, arch & cantilever were used
from the early days of human civilization, even
though methods of structural analysis were
unknown till seventeenth century.
5

Natural Stone Arch Bridge
6Er.Ashok Basa

Stone & Timber are the two materials available in abundance
from the early days of history. The last two centuries have
witnessed the mammoth growth of manufactured materials
like plain, reinforced and pre-stressed concrete, Cast-iron,
wrought iron and steel. These stronger materials led to the
use of longer span. Thus evolutions of bridges have a bearing
on the evolution of materials.
7

The evolution of bridges will be dealt-with by dividing it
into the following periods:
i) The Pre-Christian & Roman Period
ii) The Renaissance & Post-Renaissance Period
iii) The Period during Industrial Revolution
iv) Modern Period
8

The earliest bridges were built from wood. These had the form
of a beam and cantilever as evidenced from bridges in China
and India. The cantilever bridges were built by extending beams
out from the piers on both sides of a stream. A primitive
cantilever bridge over Jhelum in Srinagar is one such example
The Pre-Christian and Roman Periods
Primitive Cantilever Bridge over the Jhelum River at Srinagar,India
9

Although the earliest stone arches, found in the
excavations at Ur in the Middle east and in
Egypt, date back to about 4000 and 3000 B.C.,
respectively, all these arches were parts of
buildings, not bridges. The oldest stone arch
bridge, known as the Caravan Bridge, is said to
be over the Meles River at Smyrna, Turkey, and
is believed to have been built about the ninth
century B.C . Since stones were available in
abundance ,Romans were quite famous for
making stone arch bridges with which exist
even after 2000 years
10

The first known stone arch built in Rome is the Pons Solarus
across the Teverone in the seventh century B.C. However, this
bridge has completely disappeared and little is known about
its origin. One of the most magnificent examples of the
powerful skill of the early Roman engineers is the Pont du
Gard Aqueduct in France built about 19 B.C. This structure is
part bridge and part aqueduct, built to carry water over the
Gard River to the city of Nimes in southern Gaul.
The Pont du Aqueduct, France
11

It consists of three tiers of arches, reaching to a height of 155
ft. above the river. The first, or the bottom, tier consists of six
arches varying in width from 51 to 80 ft, the largest spanning
the river. The second, or middle, tier has eleven arches of the
same dimensions as those of the first, to reach across the
widening valley. The third, or topmost, tier consists of thirty
five 15 ft. arches, extending 885 ft across the river. Amazingly,
mortar was used only in the topmost tier. In the two lower
tiers, no binding material such as mortar or iron clamps was
used to support the blocks of stones.
12

Trajan’s Bridge deserves a special mention as an outstanding
example of vitality and creativity. It was built in the second
century A.D. across River Danube by the Roman emperor
Trajan. The bridge stood on twenty piers of hewn stone, each
150 ft high, 60 ft wide, and 50 ft thick, placed 170 ft apart
(center-to-center). The openings between the piers were
spanned by timber arches 110 ft long.
Trajan’s Bridge ,built over the Danube in 103 AD
13

Trajan’s Bridge was the first to be built across the Danube. It
was also the first bridge for which trusses in any form were
used. Unfortunately, more than a century and a half later, it
was destroyed by another Roman emperor, Aurelian. For well
over twelve hundred years, the 170 ft spans of the Trajan
Bridge remained the longest ever built in the world.
14

Bridge building in China is said to have started about
2300 B.C., during the reign of the Emperor Yao. Early
Chinese bridges were often of the pontoon type,
made out of boats called “sampans,” moored a few
feet apart parallel to the stream current. Although
stone was used for piers of wooden spans built in the
Delta, the idea of stone arch bridges is said to have
traveled from Rome to China through Chinese silk
merchants of the Han Dynasty(206 B.C. – A.D. 221).15

No Roman bridges were built after the fourth century.
Engineering practically vanished from Europe for several hundred
years. Consequently, during the Renaissance, when the improved
economy in Europe led to renewed road and bridge construction,
the lost art of building arches had to be relearned and, again, the
proportions of these arches were determined empirically. Robert
Hooke (1635-1703) is credited with defining arch theory in 1670
and with inventing the famous Hooke’s law. Later, the arch theory
was expounded upto by Thomas Young (1773-1829), who, 130
years later, defined the modulus of elasticity, E.
16

It is not known exactly when the first cantilever bridge was
built, but evidence suggests that it was in China, from
where it is said to have traveled to India. The Chinese
cantilever bridge was characterized by stone piers and
timber spans. Originally, wooden caissons were used to
build piers, by filling them with stone rubble to hold the
projecting timbers in place. Later, the piers were built from
masonry, with slots to receive the timber.
17

The cantilevers were built by extending heavy timbers
outwards from the solid stone abutment or the pier. Gies
describes these timbers as “roughly hewn tree trunks,
projecting in pairs, placed with an upward slant, usually in
three or four pairs, with the inner ends held by the weight of
the stone abutment, the outer ends bound together.” In the
valley of Kashmir, India, elaborate cantilever bridges wee
built from deodar logs piled criss-cross and were lined with
shops and houses.
Primitive Cantilever Bridge,
Tibet
18

In their primitive forms, suspension bridges existed in many
distant parts of the world; these are considered to be the
forerunners of the modem suspension bridge. Several of
these primitive bridges have been found in North India,
Burma, and Peru some were hundreds of feet long. As
Prescot described in 1847, in Peru, the cords or cables "were
formed from the tough fibers of the maguey or of the osier of
the country, having an extraordinary tenacity and strength.
19

In northeast India (Assam) and Burma, suspension bridges
consisted of bamboo cables, single and multiple, stretched
across the stream. According to E.C.Barber's 1881 description,
the cables over Brahmaputra River were made of three
strands of bamboo rope, each 1 in. thick, twisted together
and spanning 600 ft. In Sikkim, cables were formed from
canes 3/4 in. thick and 60 to 90 ft long, from a species of cala-
mus, and knotted together; from these, a floor made of loose
bamboo was suspended.
20

21
Primitive Suspension Bridges with Roadway laid directly on cables
During the initial days the suspension bridges were classified into four
types:
(1) The regular roadway type, with the roadway resting directly on the
cables

22
Primitive Hammock –type suspension Bridge
(2) The hammock, or tubular, type, with four cables, in pairs
of two each, all woven together into a web

23Ancient Bridge or the Transporter Bridge
(3)The basket, or transporter, bridge on one cable

24
Primitive Single Cable Suspension Bridge
(4) The suspended roadway, the forerunner of the modem suspension
type. The basket bridge perhaps evolved from a single-cable
suspension bridge. Such bridges, consisting of single bamboo cables,
were stretched across streams in north India

In the regions of the Himalayas, the suspension bridge
builder threw over the chasm two parallel cables; from
these he hung vertical suspenders made of thinner rope
which carried the roadway platform. Here is the principle of
the modem suspension bridge, although executed in cruder
form.
25

Trishuli River Bridge
in Nepal with crude
wire Link
26Er.Ashok Basa

An insight into the bridge-building capability of people in the
region of northern India and the Himalayas is found in the
chronicles of famous Chinese travellers Fa Hsien (A.D. 399), a
Buddhist monk, and Hsuan-Tsang (A.D. 630), a Buddhist
scholar, each of whom made a pilgrimage to India in search of
sacred writings of Buddh. Hsuan Tsang chronicled reports of
crossing "bridges of iron," as clear indication of bridges
suspended from iron chains. Soon the iron-link suspension
bridges appeared in China, an innovation. exported from
India to China, perhaps through the writings of HsuanTsang.
27

28
The Renaissance and Post-Renaissance Periods
The Renaissance period, from the 14th through the 16th
centuries, is known as the age of reason and of the birth of
modern science. Several renowned scientists lived during this
period, including such geniuses as Leonardo da Vinci (1452-
1519), Copernicus (1473-1543), and Galileo Galilei (1564-
1642). Although many new scientific theories were developed
during this period, relatively little advancement was made in
construction. Leonardo da Vinci developed new ideas in the
realms of mechanics and military bridges, and he invented
many devices such as parachutes and flying machines. He
was the first, through his statement of lever, to introduce
the concept of the moment of a force. He also virtually wrote
the principle that is now known as Newton's third law of
motion.

It was Galileo, considered to be the founder of the science of
structural mechanics, who explained scientific theories that
changed the methods of construction. It was his work Two
New Sciences (1638), the first book ever written on the
theory of structural mechanics, that revolutionized
structural engineering and marked the beginning of the
science of strength of materials.
29

The post-renaissance period was also an important period in
the history of bridge building; for during this period lived the
engineer-builder Andrea Palladio (1518-1580) and scientists
such as Robert Hooke (1635-1703) and Isaac Newton (1642-
1727). Other great mathematicians and scientists, such as
James Bernoulli (1654-1705), his brother Johann Bernoulli
(1667-1748), Johann's son Daniel Bernoulli (1700-1782), and
Daniel's friend and colleague Leonard Euler (1707-1783) also
lived during this period. Never before had so many great
thinkers been born in such a short span of time. Their
revolutionary scientific and mathematical discoveries created,
for the first time, the theoretical basis for the construction of
buildings and bridges.
30

GaIileo was the first to indicate the presence of tension in
beams and to correctly calculate that the bending moment
caused by the weight of a uniform beam increased with the
square of its length. However, his stress analysis was
incorrect - he assumed uniform stresses existed throughout
the beam's cross section (similar to the plastic stress
distribution as we know it today). It was Hooke who first gave
the correct linear distribution of both compression and
tension across the cross section of a beam. He aIso implied,
through sketches in his work, that sections that were plane
before bending remained plane after bending, a
fundamental concept in the theory of bending.
31

The most significant contribution of the Renaissance to
construction technology was the development of the truss
as a structural principle. The truss filled the need to span
longer lengths that could not be spanned with timbers, which
were available in the lengths of only 50 ft or so. With trusses,
shorter lengths could be used to build longer bridges.
32

Andrea Palladio (1518-1580), an Italian architect, is credited
with first having developed and used trusses. He built a 108
ft - span truss bridge over the Cismone between Trent and
Bassano, Italy.
The first covered timber bridges were built by two Swiss
carpenters, brothers Hans Ulrich and Johannes Grubenmann
of Switzerland. Hans Ulrich built the first covered timber
bridge in 1757 over the Rhine River. It was a two-span
structure (171 and 193 ft) that proved strong enough to
safely carry carriages weighing up to 25 tons.
33

The first to professionally build bridges in the United States,
and the pioneers of the day, were Timothy Palmer (1751-
1821) of Massachusetts, Louis Wernwag (l770-1843), a
German immigrant, and Theodore Burr (1771-1822) of
Torrington.
34

Palmer built the Permanent Bridge at Philadelphia, a three-
span (150,185, and 150 ft) wood trussed structure With
abutments and wingwalls 750 ft long. After serving for about
fifty years, it was destroyed by fire.
35
Palmer’s Permanent Bridge at Philadelphia

Palmer was among the first to point out the great advantage
obtained by covering wooden bridges to protect them from
rot.
36
Covered Bridge

Burr the most famous of the three pioneers, completed in
1815 a 360-ff arch truss bridge in Pennsylvania. Acclaimed to
be the longest timber truss ever built in America at that
time, it came to be known as Burr's masterpiece. It was
destroyed after two years by an ice jam in the winter of 1817.
Most of these structures were indeterminate combining arch
& truss system.
Burr’s Arch Truss
37

In January 1820, a patent for a double-web lattice truss called
the Town lattice mode was taken out by Ithiel Town, a New
Haven, Connecticut architect. This design was significant
because it could be built cheaply and quickly by a carpenter's
gang in a few days. Although highly indeterminate, it was a
true truss, for, unlike its predecessors, it was free from arch
and horizontal thrust. It was even used for early railroad
bridges.
The Town Lattice Mode
38

Although Town's trusses could serve the railroads, they had a serious weakness, not
in structure, but in material, at the connections. Wood, although strong in
compression, is weak in tension, and can be pulled apart, especially if bolted at the
joints. The problem was solved by William Howe of Spencer, Massachusetts, who,
while retaining the wooden compression members (either single diagonals or Xs),
simply replaced the wood verticals of Long's truss with wrought-iron members
formed of cylindrical rods with screw ends. Patented by Howe in 1840, this system
worked well for many years, until Howe presented his designs for both highway and
railroad bridges. This subjected his bridges and the theoretical problems of bridge
loading to engineering scrutiny for the first time. However, Howe's truss system was
the first and the most popular truss system in America during the first half of the
nineteenth century
39
Howe Truss with Wrought Iron Verticals

Development of the Howe truss was followed by the Pratt truss,
patented in 1844 by brothers Caleb and Thomas Pratt. The Pratt truss
system, although geometrically similar to the Howe truss, differed from
it in one significant aspect: The diagonals (or the Xs) of the Pratt truss,
being tensile members, were made of wrought iron, a stronger
material in tension; thus the Pratt truss provided a much better
arrangement for the emerging all-iron trusses. Both the Howe and the
Pratt trusses were not true timber trusses, however, for they both used
wrought iron for tension members Coincidentally, both the Howe and
Pratt trusses debuted at the beginning of the railroad and automobile
era. After the first metal trusses were built in England in 1845, both
trusses later became all-iron trusses.
The Pratt Truss
40

Interestingly, none of the designers or builders of the timber bridges
were engineers - they were all highly skilled carpenters (Howe was a
carpenter-mechanic). They had built thousands of bridges that carried
loads and stood the test of time, but none were based on any rational
design principles. These bridges first came under engineering scrutiny
when the first American treatise on bridge building appeared in 1847 –
A Work on Bridge-Building, by Squire Whipple (1797-1886) of Utica,
New York. This book presented the stress analysis of an articulated
truss, and it emphasized the fact that cast iron, being weak in tension
but strong in compression, was unsuitable and uneconomical for tension
members; it was more logical to use cast iron for compression
members in a truss, in combination with wrought-iron tension
members.
41

Independently of Whipple, American engineer Colonel
Herman Haupt published a theoretical treatise titled The
General Theory of Bridge Construction in 1851. These two
books are considered the foundation of modem framed
structures. They were followed by Whipple's more
exhaustive textbook in 1873, An Elementary and Practical
Treatise on Bridge Building.
42

Whipple's, initial form was a bowstring truss whose upper
chords, being compression members, were made from cast
iron, and whose lower chords and intermediate members,
being tensile members, were made from wrought iron.
Whipple did not invent this truss form, however; it had been
developed some years earlier in France. Whipple also
developed a trapezoidal truss with heavy cast-iron verticals
and an empirical arrangement of wrought-iron diagonals.43
Whipple’s Arch Truss Bridge
Whipple’s Trapezoidal Bridge

Compounding the weakness of wood truss joints in tension
was the problem of the heavier load-carrying requirement
of bridges built for the developing railroads. Timber bridge
builders could not produce a satisfactory answer to these
problems. Notwithstanding their remarkable functionality,
the timber bridges were doomed to retirement. The end of
their usefulness was initiated by the collapse on March 4,
1840, of the High Rock Bridge, a Town lattice bridge, over the
Catskill Creek, New York, dropping a train of boxcars in the
water and killing one man. This marked the first American
railroad bridge fatality.
44

Europe was the hub of bridge-building activity during the
Renaissance; Italy, France, and England were great
commercial centers, and many famous bridges were built
during that time in those countries. These included Ponte di
Rialto (the Rialto Bridge) over the Grand Canal at Venice,
designed by Antonia da Ponte in 1587 and it is hailed as the
most painted bridge in the art world
45
The Ponte di Rialto (Rialto Bridge)

One of the most outstanding bridge designers of the post-
Renaissance period was Jean Randolphe Perronet (1708-
1794). Born in Paris, Perronet was a friend of King Louis XV of
France. His first bridge was the Pont de Neuilly over the Seine
River. A five-arch bridge, each arch spanning 128 ft over piers
only 13 ft thick, it had the slimmest piers ever used for an
arch bridge and was hailed as the most graceful stone arch
ever built. Perronet was the first to reduce the proportion of
bridge piers with the principle of equilibrated thrust, and is
said to be the father of modern bridge building.
46

The first segmental arch is said to have been built by Taddeo
Gaddi in 1345 in Florence, Italy, over the 300-ft-wide Arno
River. This arch profile was significant from the engineering
standpoint: whereas its predecessor, the semicircular arch,
transmitted all loads in the downward vertical direction, the
segmental arch introduced the element of horizontal thrust.
47

The Period during Industrial Revolution
Heralded by the invention of the steam engine, the
industrial revolution brought about a revolutionary change
in the practice of bridge building in the nineteenth century.
Iron was not a new discovery of this period - it had been
known ever since the period of the pyramids, and the Persian
kings are said to have obtained iron from India as early as
1500 B.C. But iron had not been developed into a structural
material until now because people lacked the technology to
produce it in sufficient bulk.
48

The invention of the railroad brought new engineering
challenges that forced bridge builders to think a new. As a
test, on July 25, 1814, George Stephenson placed his
locomotive, the "Blucher," on the Killingworth Railway,
England. On a slightly ascending grade, the engine drew
eight loaded wagons carrying thirty tons at a speed of four
miles an hour, the best record yet made by any steam
engine. With an improved locomotive, patented by him on
February 28, 1815, George Stephenson made history on
September 27, 1825, when he drove the first engine from
Darlington to Stocton, England, pulling a train of wagons
carrying 450 passengers at a speed of 15 miles an hour.
49

With the arrival of the railroad, however, for the first time
bridges were required to carry significantly heavier live
loads. In industrial England, the need for transporting large
quantities of coal and pig iron required many loaded wagons,
resulting in a high live load-to-dead load ratio. Also, because
railroads covered increasingly longer distances and a greater
number of streams, rivers, and valleys, bridges were needed
in larger numbers and with longer span.
50

51
The First Iron Bridge at Coalbrookdale, England

The world's first cast-iron bridge was built in 1777-1779 by
Abraham Darby III (1750-1791), in Coalbrookdale, England,
over the Severn River. It was designed by the young Darby
himself. Regarded a milestone in the history of bridge
building, this 100-ft-span semicircular arch bridge is made up
of five arch ribs, each cast in two 70-ft halves at the
Coalbrookdale Iron Works. More than 200 years later, it is still
in service, although restricted to pedestrian traffic only, and
preserved by the British government as a national mon-
ument. The first Iron Arch in the United States was built in
1836, spanning 80 ft over Dunrap’s Creep at Brownsville, in
Pennsylvania
52

Iron was first used in European bridge construction in 1841. It was used
in the chain cables of a suspension bridge, a 70-ft span over the Tees
River in England. The first metal trusses in England were built in 1845.
In 1846, the multiple - system triangular truss, called the Warren truss
was introduced. Relatively simple in form and devoid of any vertical
members, the Warren truss consisted of top and bottom chords and
diagonal members only. In contrast to the initial versions of the Howe
and Pratt trusses, which consisted of verticals and Xs and were statically
indeterminate, the Warren truss was statically determinate and
therefore simple to analyze. The diagonals of a Warren truss are
alternately in compression and tension. Because of its analytical
determinacy, the Warren truss gained wide popularity among bridge
engineers. In 1852, the all-iron Pratt truss was introduced. Its form was
modified by replacing the Xs in panels with single diagonals, making it
a statically determinate truss, which enhanced its popularity.
53

54
Warren Truss
Double Warren Truss
Howe Truss
Curved Chord Pratt Truss
Baltimore Truss
PetitTruss
K Truss

In addition to the use of iron as a new material for bridge
building, advances were also made in the mechanics of bridge
engineering. In stone arches, the dead weight is so large that
the horizontal thrust is greater than that required to resist
the active earth pressure of the embankments on the
abutments. The cast-iron superstructure of the
Coalbrookdale bridge was rather light, and hence its
horizontal thrust was too small to balance the active
pressure on the abutments from the embankments.
Consequently, the abutments tilted inward, pushing the arch
up a little at its crown. This is the reason for its upward
pointing appearance. This behavior was noted by Telford,
who corrected the problem in his designs.
55

In England, John Smeaton (1724-1792) was the first engineer
to use cast iron to any great extent and is credited with
introducing its systematic use in bridges. He used it in
constructing windmills, water wheels, and pumps. He also
was the first to use cast-iron girders in buildings, in 1755, for
the floor of a factory. As an outstanding civil engineer,
Smeaton came to be known as the father of civil engineering
in England, and he was the first to call himself a consulting
engineer.
56

In bridge trusses, compression members were made from
cast iron, whereas the tensile members were made from
wrought iron, a common practice at the time. The Newark
Dyke Bridge over the River Trent, near Newark, England, the
earliest example of a Warren truss bridge, is an example of
this practice. Having a clear span of 246 ft 6 in., and built
between 1851 and 1853, the top chords (compression
members) of this bridge consisted of cast-iron flanged pipes
butting end-to-end. The bottom chords (tension members)
were made of wrought-iron links. The diagonals, alternately
compression and tension members, were made from cast
iron and wrought iron, respectively.
57

The advent of railroads required sturdier bridges to control
deflections and vibrations. In England, as a possible solution,
tubular bridges were tried in the construction of the London-
Chester-Holyhead Railroad. These bridges were to span the
400-ftwide Conway River and the Menai Straits. The familiar
arch form was ruled out for the Menai Straits by navigational
considerations
58

59
Transverse Section though
middle of the tube
Longitudinal Section though
middle of the tube

These tubular bridges through which trains could pass were
suggested in 1845 by Robert Stephenson (1803-1859) and
designed by William Fairbairn (1789-1874). They consisted of
wrought-iron plates with side plates stiffened by vertical
T-stiffeners. Figure shows the Britannia Bridge spanning the
Menai Straits, built not too far from Thomas Telford's historic
suspension bridge and completed in 1850. It consists of two
1511-ft, 4680-ton continuous hollow tubes, placed side-by-
side, supported on two abutments and three towers (212,
230 and 212 ft high), resulting in a four-span (230, 460, 460,
and 230 ft) continuous bridge.
60

61
The construction of the Conway and the Britannia Bridges
marked a significant breakthrough in the knowledge of the
strength of engineering structures. It was for these bridges
that general strength was - established by model tests; the
strength of iron plates and riveted joints was investigated;
for thin-walled structures, the buckling phenomenon was
discovered; and the effects of lateral wind pressure and non-
uniform solar heating were studied. Several bridges of this
type were later built in England and elsewhere by Robert
Stephenson.

62
Eventually, however, this type of construction was abandoned
in favor of more economical and efficient bridge construction.
For bridges of shorter spans, thin-walled plate girders were
introduced by I.K. Brunnel (1806-1859). Some of, Brunnel's
plate girder bridges were discussed by Fairbairn in his book,
The Application of Cast and Wrought Iron to Building
Purposes. This book drew heavily on bridge-building
experience and "quickly became the gospel in the British
construction industry

63
In 1842, D.J.Jourawski designed and built several bridges in
Russia; one of the most important was the 180-ft, 9-span
bridge built 170 ft above the waters of River Werebia for the
St. Petersburg-Moscow railroad. For this bridge, he often
used wooden beams of great depth as well as built-up
wooden beams. While building timber bridges for the St.
Petersburg-Moscow railroad in 1844-1850, he developed the
theory of shearing stresses in rectangular beams that is still
in use. During this period, the theorem of three moments
was developed by B. P. E. Clapeyron (1799-1864), a French
mathematician, as he analyzed continuous-beam bridges.
This theorem was later modified by Otto Mohr (1835-1918)
for bridge supports that have settlement.

64
Modern Period
Certain properties of iron had been known for centuries.
When it was remelted and cooled in the mould, it became
hard and brittle cast iron. When most of the impurities were
removed in the liquid state, it gained considerably in tensile
strength and became wrought iron. Upon further remelting
and reintroducing some of the removed carbon, a much
stronger metal-steel-resulted. This latter part of the process
was very difficult, and consequently, steel was rare and costly.

During the mid-nineteenth century, with the
widespread growth of the railroads in the
United States, the failures of cast-iron bridges
occurred at an alarming rate. Then the tests of
Hodgkinson and Fairbairn (in England) revealed
the poor tensile strength of cast iron. As a result,
after 1850, the use of cast iron was abandoned
in favor of wrought iron. By the end of the
nineteenth century, the use of wrought iron in
bridges was in turn replaced by steel
65

66
EADS BRIDGE (1868-
1874)over River
Mississipi in St
Louis, Missouri

67
James Eads (1820-1887), a businessman in St. Louis was
the first, in 1867, to use steel for bridge construction-in
spite of its unproven performance, lack of research. Eads
himself was not an engineer and had never before built a
bridge. But as one of the great calculated risks of
engineering history, in 1868-1874 he masterminded and
built the triple-arch (502, 520, and 502 ft) double-decked
Eads Bridge over the Mississippi at St. Louis. Completed
in 1874, the Eads Bridge is still in service, carrying two
railroad tracks on the lower deck and highway traffic on
the upper deck.

68
The Eads Bridge was a milestone in the history of bridge building, with
several pioneering features. The largest and boldest of its day, the Eads
Bridge marked the first extensive use of steel in bridge building. Its arches
were the first use of hollow tubular chord members, and its arches were
the first ever to span a distance of over 500 ft. Eads used the arch form in
spite of great opposition by such experienced bridge builders as John
Roebling, the builder of the Brooklyn Bridge, and Robert Stephenson;
being fixed-ended and indeterminate, the arches involved problems of
stress analysis and erection adjustment that had not been experienced
before. Construction of the Eads Bridge involved the first significant use of
compressed air in America. And the compressed air was used at the
greatest depth used anywhere up to that time; the caisson sunk for the
east abutment foundation of the bridge remains to this day one of the
deepest in which compressed-air workers have ever worked. Finally, the
three great arches were built without any falsework, by cantilevering the
arches out from the piers toward the span centers; this was the first
extensive use of the modern-day cantilever method of bridge
construction, previously proposed by Robert Stephenson and I.K. Brunel.

69
Eads had to convince the public of the strength and safety of
the bridge. For this he gave an impressive demonstration on
July 2, 1874. First, fourteen heavy locomotives, in two
divisions of seven each, were moved out on two tracks and
stopped over the center of each arch, side by side. Then all
fourteen, seven on each track, crossed side-by-side. And
finally, all fourteen crossed the bridge in single file. Their
tenders were filled with coal and water during all these cross-
ings. (Eads wanted to load the bridge with more locomotives,
but none were available). The bridge was formally opened
July 4, 1874, amid fireworks and fanfare.

70
The advent of steel and its successful use for the Eads Bridge
heralded a new era in bridge building. Beginning from the
mid-nineteenth century, some of the world’s greatest
bridges were built: cantilever bridges, arch bridges,
suspension bridges, and cable-stayed bridges.
An important discovery during the development of railroads
was the phenomenon of fartigue of metal caused by a
repeated cycle of stress. This phenomenon was first
described in 1839 by Poncelet in his book Industrial
Mechanics [Poncelet, 1870]. He stated that, under the
action of alternating tension and compression, the most
perfect spring may fail in fatigue.

71
Theoretical treatment of moving loads was another
important contribution of engineers in the latter part of
the nineteenth century. In 1867, E.Winkler (1835-1888)
introduced the concept of influence line while working
on problems of bridge engineering and prepared tables
of the most unfavorable position of the live load for a
beam with four spans.
Carl Von Ruppert, a German engineer, is reported to
have been the first to design a cantilever bridge. The
first modern cast-iron truss cantilever bridge was built
by Heinrich Gerber in 1867 over the Main River at
Hassfurt, Germany, with a central span of 425 ft, it was
known as the Gerber Bridge for some year.

72
Human Cantilever adopted by Sir Benjamin Baker to demonstrate principles of the
Firth of Forth Bridge

Forth Bridge Scotland (1882-90)
73Er.Ashok Basa

Erection of Forth Bridge in progress
74Er.Ashok Basa

Forth Bridge Scotland (1882-90)
75Er.Ashok Basa

76
The first great cantilever bridge, the longest at the time, was
built over the Firth of Forth, in England. Designed by Sir John
Fowler and Sir Benjamin Baker, it was opened to traffic on
March 4, 1890. A significant design consideration for this
bridge was the allowance for wind pressure-56Ib/ft2. One
Ib/ft2 more than the 550 Lb/ft2 used by the French in their
bridge designs, it was the maximum allowance used
anywhere for a bridge design. This was significant because
the disaster of the contemporary Tay Bridge was blamed, in
part, on its low-wind-pressure design (10-15 Ib/ft2). Figure
shows the brilliant method adopted by Sir Benjamin Baker to
illustrate the principle of the cantilever bridge.

77
In addition to providing the rigidity required for long-span
railway bridges, two very important factors contributed to the
popularity of cantilever bridges: They were statically
determinate analytically, and they did not require falsework
that would obstruct a river or a waterway during
construction.
The evolution of modem suspension bridges occurred in the
United States and in Europe, most notably in England.

78
The first suspension bridges capable of withstanding the
rigors of modern times were erected in the United States.
According to Charles Bender [Bender, 1872], suspension
bridges were first introduced to North America by Judge
James Finley. Finley was also the first to develop stiffened
suspension bridges. Thomas Pope, a shipbuilder turned
bridge builder who wrote the first American Treatise on
Bridge Architecture [Pope, 1811], spread Finley's "ingenious
invention" throughout the world.
Finley built his first suspension bridge, the Jacob's Creek
Bridge in Pennsylvania in 1801.

79
British engineers followed the Americans, and many
suspension bridges were built in England during the first
quarter of the nineteenth century. In England, the first
suspension bridge to carry loaded carriages, the Union
Bridge at Norham Ford, was built in 1820 by Samuel
Brown over the Tweed River Consisting of 12 chains, 6 on
each side, its suspension span 449 ft.

80
The first great suspension bridge, and the world's first bridge
over the ocean, was built by Thomas Telford (1757-1834)
over the Menai Strait, England. Its 580-ft span was a world
record at that time. It used 2000 tons of wrought iron to
build 16 cable chains and was opened to traffic on January
30, 1826. One week after it opened, the bridge was
observed to be suffering from aerodynamic vibrations
during a gale in the strait. This problem was rectified by
installing transverse bracings that fastened the chain cables
to each other at intervals

81
The major suspension bridge was the 1595.5-ft Brooklyn
Bridge designed by John Augustus Roebling (1806-1869),
who is considered to be the inventor of modem suspension
bridges. Started by John Roebling in 1867 and completed in
1883 by his son Washington Roebling, it was the first
suspension bridge to use cables of steel wire, and it was
heralded as "the Eighth Wonder of the World". Built over the
East River in New York State, it remained the longest
suspension bridge for the next 20 years. It was surpassed in
1903 by the second East River bridge, the Williamsburg
Bridge, designed by Leffert L. Buck.

82
With a 1600-ft main span (4-1/2 ft longer than the Brooklyn
Bridge), the Williamsburg was the first large suspension bridge
with steel towers. Preceding the construction of the Brooklyn
Bridge, John Roebling had built six suspension structures of
modest spans in the years 1844-1850, five of which were
aqueducts. He made history by building an 821-ft suspension
bridge 245 ft above the rapids of Niagara River, New York, the
world's first successful railway suspension bridge, opened to
traffic on March 6, 1855. Suspended from four 10-1/4 in-
diameter cables, each having 3640 ungalvanized wrought-iron
wires, it had an upper deck for railroad tracks and a lower deck
for pedestrians and carriages [Roebling, 1846, 1855]. In the
Niagara Bridge, Roebling was the first to incorporate inclined
stays in conjunction with stiffening trusses to provide additional
stiffness to minimize vertical undulations in a major suspension
bridge.

83
From Telford's Menai Strait Bridge (built in 1826) to Roebling's
Brooklyn Bridge (built in 1869-1883) was a period of evolution of
suspension bridges. Beginning with Brooklyn Bridge, the building of
suspension bridges became an American enterprise. After World War II,
the use of suspension bridge for long-span construction grew rapidly.
The Brooklyn Bridge span (930, 1595-1/2, and 930 ft), although modest
in terms of modem records, was an epoch-making span that heralded
the era of suspension bridges in the United States. It was followed by
many notable suspension bridges-George Washington (1931), San
Francisco-Oakland Bay (1936), Golden Gate (1937), Bronx-Whitestone
(1939), Tacoma Narrows 1 (1940), Tacoma Narrows II (1950), Delaware
Memorial (1951), Mackinac Straits (1957), Walt Whitman (1957),
Verazzano Narrows (1964), and others, each with a record-breaking
span and a history of its own, all built in the twentieth century

84
While the cast-iron, wrought-iron, and steel bridges were
being built during the nineteenth century, another
construction material was being developed in both England
and the United States. The art of producing reliable lime
mortar, known to the Romans, was lost for many centuries in
the Middle Ages. The real breakthrough in reliable mortar
came about in the early 1820s. Joseph Adspin, a bricklayer of
Leeds, England, invented the first artificial cement, called
Portland cement. It was so named because its color and
texture resembled a limestone found in the Isle of Portland
off the southern coast of England, which is still a popular
source of building stone in England.

85
In the 1860s, a Parisian gardener named Joseph Monier (1823-1906)
was using the newly developed building material, concrete, to make
tubs for large plants. Finding that concrete by itself had to be used in
inconvenient bulk to achieve adequate strength, he hit on the idea of
embedding a web of iron wire in the material during its preparation.
Monier was not the first to think of combining concrete with iron or
steel; the idea had been patented earlier in both France and America.
However, his wire netting was the first such arrangement to work. He
obtained his first patent on July 16, 1867, for the construction of
basins, tubs, and reservoirs of cement in which iron netting was
embedded. Within a few years, reinforced concrete was being used for
dozens of structural purposes. Realizing the importance of his work,
Monier secured patents in 1877 that covered floors, buildings, bridges,
arches, railway sleepers, and other types of construction. His first
bridge, built in 1875, was 13 ft wide and spanned 50 ft

86
Early in the history of reinforced concrete, in 1888, an
American named P.H. Jackson of San Francisco had an even
better idea. He theorized that if steel wire were used in
reinforcing concrete and if the wire were stretched tight to
begin with, the result would be a much stronger kind of
reinforced concrete that could be used in much smaller
quantities. Jackson's experiments were never successful,
probably because the steel wire of his day could not
withstand enough tension. It was not until about 1930,
when Eugene Freyssinet of France began using high-strength
steel wire, that another new concept in building-prestressed
concrete-evolved.

87
Prestressed concrete, although it was used widely for bridge
construction in Europe during the first half of the twentieth
century, had a rather slow start in the United States. The
first major prestressed concrete bridge built in the United
States is the Walnut Lane Bridge in Philadelphia,
Pennsylvania, built in 1956. Since then, the use of
prestressed Concrete in bridge construction has steadily
increased throughout the world. With the advent of the
cantilever, or the segmental, method of construction,
prestressed concrete bridges have become economically
feasible for medium spans, and even spans in the 800-ft
range have been built in Japan. Today, prestressed concrete
bridges have almost become the preferred type for short
and medium spans, outbidding steel bridges.

88
Name: Mahatma Gandhi Setu, Location: Patna, India
Main Span: 397.19 Ft Construction : 1972 to 1982

93
Because of past failures, cable-stayed bridges were
condemned and forgotten; almost no cable-stayed bridges
were built for more than a century. They were rediscovered
in 1938 by the German engineer Prof. Franz Dischinger
(1887-1953) as he tried, to design a two-track railway
suspension bridge spanning 2460 ft (750 m) across the river
Elbe near Hamburg, Germany.

94
His goal was to incorporate stays into railroad suspension
bridges to reduce deflections. This technique, of course, was
not new. Stay ropes had been used in some older suspension
bridges, mainly in Roebling's Niagara Bridge (1855), the
Cincinnati Bridge (1866), and in the Brooklyn Bridge (1883).
But these ropes were too slack and too weak to play any
significant role. However, without realizing that this was the
drawback, builders omitted these stays in later suspension
bridges. It is noteworthy that, although the resurgence of
Cable-stayed Bridges is lauded as a great innovation of the
twentieth century, the concepts of using stays is hardly new.
The basic idea of supporting and/or stabilizing a beam by
ropes from a vertical support began perhaps with the booms,
rigging, and masts of ancient Egyptian sailing ships.

95
After World War II Germany was the pioneer in
building cable-stayed bridges. But subsequently
it is now adopted in many countries including
India.

Name: Sutong Bridge , Location: Suzhou, Nantong, China
Main Span : 3570 Ft 96

Name: Stonecutters Bridge , Location: Rambler Channel Hong
Kong(PRC) Main Span : 3340 Ft 97

Name: E’dong Bridge , Location: Huangshi,China
Main Span : 3038 Ft 98

Name: Storebælt Bridge , Location: Halsskov-Sprogø,Denmark
Main Span : 1624m (5328 Ft) 99

Name: Xihoumen Bridge , Location: Zhoushan Archipelago,China
Main Span : 1650m (5414 Ft)
100

101
Name: Brooklyn Bridge , Location: Newyork ,, USA
Main Span: 1595 Ft Constuction 1869 to 1883

102
Name: Tower Bridge , Location: London
Main Span: 270 Ft Constuction 1886 to 1894

103
Name: Sydney Harbour Bridge , Location: Sydney, Australia
Main Span: 1650 Ft Construction : 1923 to 1932

104
Name: Golden Gate Bridge , Location: San Francisco , USA

105
Name: Howrah Bridge , Location: Kolkatta, India

106
Name: Vidyasagar Setu , Location: Kolkatta, India

107
Name: Bandra-Worli Sea link Bridge , Location: Mumbai, India

Name: Akashi Kaikyō Bridge , Location: Kobe-Awaji Route, Japan
Main Span : 1991m (6532 Ft)
108

“ Desire , not necessity, is the mother of invention ” From the
presentations what we shared today , it is quite clear that “
the ideas for things come from dissatisfaction with what there
is and from the want of a satisfactory thing for doing what we
want done “. Therefore it is aptly said that ’’ Man is more a
dissatisfied Socrates than a satisfied pig “. Because of this
unique quality , man has always been aware , not to be
overwhelmed with success leading to complacency , over
confidence and unwarranted optimism , but to listen to the
lessons from failure and the urge to achieve better. It is
because of this , along with passage of time and development
of materials , we have seen how from simple wooden bridge
to today’s magnificent long span bridges have been evolved .
I congratulate all the civil engineers including all present here
, to be privileged to be a part of the process of this great
evolution . Finally I conclude with a prayer to the almighty on
behalf of all of us.
“ Oh God “ Please give us the courage to change things we can’’,
the serenity to accept this we can not change , and the
wisdom to know the difference between the two.
110

All the sources are acknowledged
with thanks
111

Dr. Jaikrishna Memorial Lecture on Evolution of Bridges

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Dr. Jaikrishna Memorial Lecture on Evolution of Bridges