Bridge

Bridge

Overview

A bridge is a structure
Architectural structure
An architectural structure is a free-standing, immobile outdoor constructed element. The structure may be temporary or permanent.Structures include buildings and nonbuilding structures . Examples of building structures include houses, town halls, libraries, and skyscrapers...

 built to span
Span (architecture)
Span is the distance between two intermediate supports for a structure, e.g. a beam or a bridge.A span can be closed by a solid beam or of a rope...

 physical obstacles such as a body of water
Body of water
A body of water or waterbody is any significant accumulation of water, usually covering the Earth or another planet. The term body of water most often refers to large accumulations of water, such as oceans, seas, and lakes, but it may also include smaller pools of water such as ponds, puddles or...

, valley
Valley
In geology, a valley or dale is a depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge.The terms U-shaped and V-shaped are descriptive terms of geography to characterize the form of valleys...

, or road
Road
A road is a thoroughfare, route, or way on land between two places, which typically has been paved or otherwise improved to allow travel by some conveyance, including a horse, cart, or motor vehicle. Roads consist of one, or sometimes two, roadways each with one or more lanes and also any...

, for the purpose of providing passage over the obstacle. Designs of bridges vary depending on the function of the bridge, the nature of the terrain where the bridge is constructed, the material used to make it and the funds available to build it.

The Oxford English Dictionary
Oxford English Dictionary
The Oxford English Dictionary , published by the Oxford University Press, is the self-styled premier dictionary of the English language. Two fully bound print editions of the OED have been published under its current name, in 1928 and 1989. The first edition was published in twelve volumes , and...

 traces the origin of the word bridge to an Old English word brycg, of the same meaning, derived from a hypothetical Proto-Germanic root brugjō.
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Encyclopedia

A bridge is a structure
Architectural structure
An architectural structure is a free-standing, immobile outdoor constructed element. The structure may be temporary or permanent.Structures include buildings and nonbuilding structures . Examples of building structures include houses, town halls, libraries, and skyscrapers...

 built to span
Span (architecture)
Span is the distance between two intermediate supports for a structure, e.g. a beam or a bridge.A span can be closed by a solid beam or of a rope...

 physical obstacles such as a body of water
Body of water
A body of water or waterbody is any significant accumulation of water, usually covering the Earth or another planet. The term body of water most often refers to large accumulations of water, such as oceans, seas, and lakes, but it may also include smaller pools of water such as ponds, puddles or...

, valley
Valley
In geology, a valley or dale is a depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge.The terms U-shaped and V-shaped are descriptive terms of geography to characterize the form of valleys...

, or road
Road
A road is a thoroughfare, route, or way on land between two places, which typically has been paved or otherwise improved to allow travel by some conveyance, including a horse, cart, or motor vehicle. Roads consist of one, or sometimes two, roadways each with one or more lanes and also any...

, for the purpose of providing passage over the obstacle. Designs of bridges vary depending on the function of the bridge, the nature of the terrain where the bridge is constructed, the material used to make it and the funds available to build it.

Etymology


The Oxford English Dictionary
Oxford English Dictionary
The Oxford English Dictionary , published by the Oxford University Press, is the self-styled premier dictionary of the English language. Two fully bound print editions of the OED have been published under its current name, in 1928 and 1989. The first edition was published in twelve volumes , and...

 traces the origin of the word bridge to an Old English word brycg, of the same meaning, derived from a hypothetical Proto-Germanic root brugjō. There are cognate
Cognate
In linguistics, cognates are words that have a common etymological origin. This learned term derives from the Latin cognatus . Cognates within the same language are called doublets. Strictly speaking, loanwords from another language are usually not meant by the term, e.g...

s in other Germanic languages.

History











The first bridges were made by nature itself — as simple as a log fallen across a stream
Stream
A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...

 or stones in the river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

. The first bridges made by humans were probably spans of cut wooden logs or planks and eventually stones, using a simple support and crossbeam arrangement. Some early Americans used trees or bamboo poles to cross small caverns or wells to get from one place to another. A common form of lashing sticks, logs, and deciduous branches together involved the use of long reeds or other harvested fibers woven together to form a connective rope capable of binding and holding together the materials used in early bridges.

The Arkadiko Bridge
Arkadiko Bridge
The Arkadiko Bridge or Kazarma Bridge is a Mycenaean bridge near the modern road from Tiryns to Epidauros on the Peloponnese, Greece. Dating to the Greek Bronze Age, it is one of the oldest arch bridges still in existence and use....

 is one of four Mycenaean corbel arch
Corbel arch
A corbel arch is an arch-like construction method that uses the architectural technique of corbeling to span a space or void in a structure, such as an entranceway in a wall or as the span of a bridge...

 bridges part of a former network of roads, designed to accommodate chariots, between Tiryns
Tiryns
Tiryns is a Mycenaean archaeological site in the prefecture of Argolis in the Peloponnese, some kilometres north of Nauplion.-General information:...

 to Epidauros in the Peloponnese
Peloponnese
The Peloponnese, Peloponnesos or Peloponnesus , is a large peninsula , located in a region of southern Greece, forming the part of the country south of the Gulf of Corinth...

, in Greece
Greece
Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....

. Dating to the Greek Bronze Age
Bronze Age
The Bronze Age is a period characterized by the use of copper and its alloy bronze as the chief hard materials in the manufacture of some implements and weapons. Chronologically, it stands between the Stone Age and Iron Age...

 (13th century BC), it is one of the oldest arch bridges still in existence and use.
Several intact arched stone bridges from the Hellenistic era can be found in the Peloponnese
Peloponnese
The Peloponnese, Peloponnesos or Peloponnesus , is a large peninsula , located in a region of southern Greece, forming the part of the country south of the Gulf of Corinth...

 in southern Greece
Greece
Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....



The greatest bridge builders of antiquity were the ancient Romans
Roman engineering
Romans are famous for their advanced engineering accomplishments, although some of their own inventions were improvements on older ideas, concepts and inventions. Technology for bringing running water into cities was developed in the east, but transformed by the Romans into a technology...

. The Romans built arch bridges and aqueduct
Aqueduct
An aqueduct is a water supply or navigable channel constructed to convey water. In modern engineering, the term is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose....

s that could stand in conditions that would damage or destroy earlier designs. Some stand today. An example is the Alcántara Bridge
Alcántara Bridge
The Alcántara Bridge is a Roman stone arch bridge built over the Tagus River at Alcántara, Spain between 104 and 106 CE by an order of the Roman Emperor Trajan in 98...

, built over the river Tagus
Tagus
The Tagus is the longest river on the Iberian Peninsula. It is long, in Spain, along the border between Portugal and Spain and in Portugal, where it empties into the Atlantic Ocean at Lisbon. It drains an area of . The Tagus is highly utilized for most of its course...

, in Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...

. The Romans also used cement
Cement
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...

, which reduced the variation of strength found in natural stone. One type of cement, called pozzolana
Pozzolana
Pozzolana, also known as pozzolanic ash , is a fine, sandy volcanic ash. Pozzolanic ash was first discovered and dug in Italy, at Pozzuoli. It was later discovered at a number of other sites as well...

, consisted of water, lime, sand, and volcanic rock
Volcanic rock
Volcanic rock is a rock formed from magma erupted from a volcano. In other words, it is an igneous rock of volcanic origin...

. Brick
Brick
A brick is a block of ceramic material used in masonry construction, usually laid using various kinds of mortar. It has been regarded as one of the longest lasting and strongest building materials used throughout history.-History:...

 and mortar
Mortar (masonry)
Mortar is a workable paste used to bind construction blocks together and fill the gaps between them. The blocks may be stone, brick, cinder blocks, etc. Mortar becomes hard when it sets, resulting in a rigid aggregate structure. Modern mortars are typically made from a mixture of sand, a binder...

 bridges were built after the Roman era, as the technology for cement was lost then later rediscovered.

The Arthashastra
Arthashastra
The Arthashastra is an ancient Indian treatise on statecraft, economic policy and military strategy which identifies its author by the names Kautilya and , who are traditionally identified with The Arthashastra (IAST: Arthaśāstra) is an ancient Indian treatise on statecraft, economic policy and...

of Kautilya mentions the construction of dams and bridges. A Mauryan bridge near Girnar
Girnar
Girnar is a collection of mountains in the Junagadh District of Gujarat, India, situated near Junagadh at a distance of 327 km from Ahmedabad. It is a holy place and an important pilgrimage for both Hindus and Jains. There are a number of temples located here. Amidst the lush green Gir...

 was surveyed by James Princep
James Prinsep
James Prinsep was an Anglo-Indian scholar and antiquary. He was the seventh son of John Prinsep, a wealthy East India merchant and Member of Parliament....

. The bridge was swept away during a flood, and later repaired by Puspagupta, the chief architect of emperor Chandragupta I
Chandragupta I
The Gupta dynasty first seems to be in eminence with the accession of Chandra Gupta I, son of Ghatotkacha to the throne of the ancestral Gupta kingdom. While his two ancestors were given the title of Maharaja , Chandra Gupta I is described in his inscriptions as Maharajadhiraj signifying a rise in...

. The bridge also fell under the care of the Yavana Tushaspa, and the Satrap
Satrap
Satrap was the name given to the governors of the provinces of the ancient Median and Achaemenid Empires and in several of their successors, such as the Sassanid Empire and the Hellenistic empires....

 Rudra Daman. 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
Mughal Empire
The Mughal Empire ,‎ or Mogul Empire in traditional English usage, was an imperial power from the Indian Subcontinent. The Mughal emperors were descendants of the Timurids...

 administration in India.

Although large Chinese bridges of wooden construction existed at the time of the Warring States, the oldest surviving stone bridge in China is the Zhaozhou Bridge
Zhaozhou Bridge
The Anji Bridge is the world's oldest open-spandrel stone segmental arch bridge. Credited to the design of a craftsman named Li Chun, the bridge was constructed in the years 595-605 during the Sui Dynasty...

, built from 595 to 605 AD during the Sui Dynasty
Sui Dynasty
The Sui Dynasty was a powerful, but short-lived Imperial Chinese dynasty. Preceded by the Southern and Northern Dynasties, it ended nearly four centuries of division between rival regimes. It was followed by the Tang Dynasty....

. This bridge is also historically significant as it is the world's oldest open-spandrel
Spandrel
A spandrel, less often spandril or splaundrel, is the space between two arches or between an arch and a rectangular enclosure....

 stone segmental arch bridge. European segmental arch bridges date back to at least the Alconétar Bridge
Alconétar Bridge
The Alconétar Bridge , also known as Puente de Mantible, was a Roman segmental arch bridge in the Extremadura region, Spain. The ancient structure, which featured flattened arches with a span-to-rise ratio of 4–5:1, is one of the earliest of its kind...

 (approximately 2nd century AD), while the enormous Roman era Trajan's Bridge
Trajan's bridge
Trajan's Bridge or Bridge of Apollodorus over the Danube was a Roman segmental arch bridge, the first to be built over the lower Danube. For more than a thousand years, it was the longest arch bridge in the world, in terms of both total and span length...

 (105 AD) featured open-spandrel segmental arches in wooden construction.

Rope bridge
Rope bridge
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 traveller 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...

s, a simple type of suspension bridge, were used by the Inca civilization in the Andes
Andes
The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...

 mountains of South America, just prior to European colonization in the 16th century.

During the 18th century there were many innovations in the design of timber bridges by Hans Ulrich, Johannes Grubenmann
Johannes Grubenmann
Johannes Grubenmann was a member of the Swiss family Grubenmann who were famous as joiners and civil engineers in the eighteenth century....

, and others. The first book on bridge engineering was written by Hubert Gautier
Hubert Gautier
Henri Gautier was a French engineer. He was born in Nîmes, France.In 1716, he wrote the first book on building bridges, Traité des ponts. Gautier initially trained as a doctor, turning to mathematics and finally engineering. He served as an engineer for 28 years province of Languedoc.Gautier died...

 in 1716. A major breakthrough in bridge technology came with the erection of the Iron Bridge
The Iron Bridge
The Iron Bridge crosses the River Severn at the Ironbridge Gorge, by the village of Ironbridge, in Shropshire, England. It was the first arch bridge in the world to be made out of cast iron, a material which was previously far too expensive to use for large structures...

 in Coalbrookdale
Coalbrookdale
Coalbrookdale is a village in the Ironbridge Gorge in Shropshire, England, containing a settlement of great significance in the history of iron ore smelting. This is where iron ore was first smelted by Abraham Darby using easily mined "coking coal". The coal was drawn from drift mines in the sides...

, England in 1779. It used cast iron
Cast iron
Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...

 for the first time as arches to cross the river Severn
River Severn
The River Severn is the longest river in Great Britain, at about , but the second longest on the British Isles, behind the River Shannon. It rises at an altitude of on Plynlimon, Ceredigion near Llanidloes, Powys, in the Cambrian Mountains of mid Wales...

.

With the Industrial Revolution
Industrial Revolution
The Industrial Revolution was a period from the 18th to the 19th century where major changes in agriculture, manufacturing, mining, transportation, and technology had a profound effect on the social, economic and cultural conditions of the times...

 in the 19th century, truss
Truss
In architecture and structural engineering, a truss is a structure comprising one or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes. External forces and reactions to those forces are considered to act only at the nodes and result in...

 systems of wrought iron
Wrought iron
thumb|The [[Eiffel tower]] is constructed from [[puddle iron]], a form of wrought ironWrought iron is an iron alloy with a very low carbon...

 were developed for larger bridges, but iron did not have the tensile strength
Tensile strength
Ultimate tensile strength , often shortened to tensile strength or ultimate strength, is the maximum stress that a material can withstand while being stretched or pulled before necking, which is when the specimen's cross-section starts to significantly contract...

 to support large loads. With the advent of steel, which has a high tensile strength, much larger bridges were built, many using the ideas of Gustave Eiffel
Gustave Eiffel
Alexandre Gustave Eiffel was a French structural engineer from the École Centrale Paris, an architect, an entrepreneur and a specialist of metallic structures...

.

In 1927 welding
Welding
Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, with pressure sometimes...

 pioneer Stefan Bryła designed the first welded road bridge in the world, which was later built across the river Słudwia Maurzyce near Łowicz, Poland in 1929. In 1995, the American Welding Society
American Welding Society
The American Welding Society is a nonprofit organization dedicated to advancing the science, technology, and application of welding and allied joining and cutting processes, including brazing, soldering, and thermal spraying...

 presented the Historic Welded Structure Award for the bridge to Poland.

Types of bridges


There are six main types of bridges: beam bridge
Beam bridge
Beam bridges are the most simple of structural forms being supported by an abutment at each end of the deck. No moments are transferred through the support hence their structural type is known as simply supported....

s, cantilever bridge
Cantilever bridge
A cantilever bridge is a bridge built using cantilevers, structures that project horizontally into space, supported on only one end. For small footbridges, the cantilevers may be simple beams; however, large cantilever bridges designed to handle road or rail traffic use trusses built from...

s, arch bridge
Arch bridge
An arch bridge is a bridge with abutments at each end shaped as a curved arch. Arch bridges work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments at either side...

s, suspension bridge
Suspension bridge
A suspension bridge is a type of bridge in which the deck is hung below suspension cables on vertical suspenders. Outside Tibet and Bhutan, where the first examples of this type of bridge were built in the 15th century, this type of bridge dates from the early 19th century...

s, cable-stayed bridge
Cable-stayed bridge
A cable-stayed bridge is a bridge that consists of one or more columns , with cables supporting the bridge deck....

s and truss bridge
Truss bridge
A truss bridge is a bridge composed of connected elements which may be stressed from tension, compression, or sometimes both in response to dynamic loads. Truss bridges are one of the oldest types of modern bridges...

s.

Beam bridges


Beam bridge
Beam bridge
Beam bridges are the most simple of structural forms being supported by an abutment at each end of the deck. No moments are transferred through the support hence their structural type is known as simply supported....

s are horizontal beams supported at each end by abutments, hence their structural name of simply supported. When there is more than one span the intermediate supports are known as piers. The earliest beam bridges were simple logs that sat across streams and similar simple structures. In modern times, beam bridges are large box steel girder bridges. Weight on top of the beam pushes straight down on the abutments at either end of the bridge. They are made up mostly of wood or metal. Beam bridge spans typically do not exceed 250 feet (76.2 m) long, as the strength of a span decreases with increased length. However, the main span of the Rio-Niteroi Bridge
Rio-Niterói Bridge
President Costa e Silva Bridge, commonly known as the Rio-Niteroi Bridge, is a box girder bridge located at Guanabara Bay, in the State of Rio de Janeiro in Brazil. It connects the cities of Rio de Janeiro and the municipality of Niterói. It is currently the longest prestressed concrete bridge in...

, a box girder bridge, is 300 metres (984.3 ft). The world's longest beam bridge is Lake Pontchartrain Causeway
Lake Pontchartrain Causeway
The Lake Pontchartrain Causeway, or the Causeway, consists of two parallel bridges crossing Lake Pontchartrain in southern Louisiana, United States. The longer of the two bridges is long...

 in southern Louisiana
Louisiana
Louisiana is a state located in the southern region of the United States of America. Its capital is Baton Rouge and largest city is New Orleans. Louisiana is the only state in the U.S. with political subdivisions termed parishes, which are local governments equivalent to counties...

 in the United States, at 23.83 miles (38.4 km), with individual spans of 56 feet (17.1 m).

Cantilever bridges


Cantilever bridge
Cantilever bridge
A cantilever bridge is a bridge built using cantilevers, structures that project horizontally into space, supported on only one end. For small footbridges, the cantilevers may be simple beams; however, large cantilever bridges designed to handle road or rail traffic use trusses built from...

s are built using cantilever
Cantilever
A cantilever is a beam anchored at only one end. The beam carries the load to the support where it is resisted by moment and shear stress. Cantilever construction allows for overhanging structures without external bracing. Cantilevers can also be constructed with trusses or slabs.This is in...

s—horizontal beams supported on only one end. Most cantilever bridges use a pair of continuous spans that extend from opposite sides of the supporting piers to meet at the center of the obstacle the bridge crosses. Cantilever bridges are constructed using much the same materials & techniques as beam bridges. The difference comes in the action of the forces through the bridge. The largest cantilever bridge is the 549 metres (1,801.2 ft) Quebec Bridge
Quebec Bridge
right|thumb|Lifting the centre span in place was considered to be a major engineering achievement. Photo caption from [[Popular Mechanics]] Magazine, December 1917...

 in Quebec, Canada.

Arch bridges


Arch bridge
Arch bridge
An arch bridge is a bridge with abutments at each end shaped as a curved arch. Arch bridges work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments at either side...

s have abutments at each end. The weight of the bridge is thrust into the abutments at either side. The earliest known arch bridges were built by the Greeks, and include the Arkadiko Bridge
Arkadiko Bridge
The Arkadiko Bridge or Kazarma Bridge is a Mycenaean bridge near the modern road from Tiryns to Epidauros on the Peloponnese, Greece. Dating to the Greek Bronze Age, it is one of the oldest arch bridges still in existence and use....

. Dubai
Dubai
Dubai is a city and emirate in the United Arab Emirates . The emirate is located south of the Persian Gulf on the Arabian Peninsula and has the largest population with the second-largest land territory by area of all the emirates, after Abu Dhabi...

 in the United Arab Emirates
United Arab Emirates
The United Arab Emirates, abbreviated as the UAE, or shortened to "the Emirates", is a state situated in the southeast of the Arabian Peninsula in Western Asia on the Persian Gulf, bordering Oman, and Saudi Arabia, and sharing sea borders with Iraq, Kuwait, Bahrain, Qatar, and Iran.The UAE is a...

 is currently building the Sheikh Rashid bin Saeed Crossing
Sheikh Rashid bin Saeed Crossing
Sheikh Rashid bin Saeed Crossing, also known as Sixth Crossing, is a future bridge in Dubai, United Arab Emirates. Once completed in 2012, it will become the world's longest arch bridge at a length of . The bridge will be wide and will rise above the water. The bridge, designed by FXFOWLE...

, which is scheduled for completion in 2012. When completed, it will be the largest arch bridge in the world.

Tied arch bridges


Tied arch bridge
Tied arch bridge
A tied-arch bridge is an arch bridge in which the outward-directed horizontal forces of the arch, or top chord, are borne as tension by the bottom chord , rather than by the ground or the bridge foundations...

s have an arch-shaped superstructure, but differ from conventional arch bridges. Instead of transferring the weight of the bridge and traffic loads into thrust forces into the abutments, the ends of the arches are restrained by tension in the bottom chord of the structure. They are also called bowstring arches.

Suspension bridges


Suspension bridge
Suspension bridge
A suspension bridge is a type of bridge in which the deck is hung below suspension cables on vertical suspenders. Outside Tibet and Bhutan, where the first examples of this type of bridge were built in the 15th century, this type of bridge dates from the early 19th century...

s are suspended from cables. The earliest suspension bridges were made of ropes or vines covered with pieces of bamboo. In modern bridges, the cables hang from towers that are attached to caissons or cofferdams. The caissons or cofferdams are implanted deep into the floor of a lake or river. The longest suspension bridge in the world is the 12826 feet (3,909.4 m) Akashi Kaikyo Bridge in Japan. See simple suspension bridge
Simple suspension bridge
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. However, it may have saddles...

, stressed ribbon bridge
Stressed ribbon bridge
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...

, underspanned suspension bridge
Underspanned suspension bridge
An underspanned suspension bridge is a rare type of suspension bridge that was developed in the early 19th century. It differs from its ancestor, the simple suspension bridge, in that the deck is raised on posts above the main cables...

, suspended-deck suspension bridge, and self-anchored suspension bridge
Self-anchored suspension bridge
A self-anchored suspension bridge is a suspension bridge in which the main cables attach to the ends of the deck, rather than to the ground via large anchorages...

.

Cable-stayed bridges


Cable-stayed bridge
Cable-stayed bridge
A cable-stayed bridge is a bridge that consists of one or more columns , with cables supporting the bridge deck....

s, like suspension bridges, are held up by cables. However, in a cable-stayed bridge, less cable is required and the towers holding the cables are proportionately shorter. The first known cable-stayed bridge was designed in 1784 by C.T. Loescher. The longest cable-stayed bridge is the Sutong Bridge over the Yangtze River in China.

Movable bridges


Movable bridges are designed to move out of the way of boats or other kinds of traffic, which would otherwise be too tall to fit. These are generally electrically powered.

Double-decked bridges


Double-decked or double-decker bridges have two levels, such as the San Francisco – Oakland Bay Bridge, with two road levels. Tsing Ma Bridge
Tsing Ma Bridge
The Tsing Ma Bridge is a bridge in Hong Kong. It is the world's seventh-longest span suspension bridge, and was the second longest at time of completion. The bridge was named after two of the islands at its ends, namely Tsing Yi and Ma Wan . It has two decks and carries both road and rail...

 and Kap Shui Mun Bridge
Kap Shui Mun Bridge
The Kap Shui Mun Bridge in Hong Kong is one of the longest cable-stayed bridges in the world that transports both road and railway traffic, with the upper deck for motor vehicles, and the lower deck for both vehicles and the MTR. It has a main span of 430 metres and an overall length of 750 metres...

 in Hong Kong
Hong Kong
Hong Kong is one of two Special Administrative Regions of the People's Republic of China , the other being Macau. A city-state situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour...

 have six lanes on their upper decks, and on their lower decks there are two lanes and a pair of tracks for MTR
MTR
Mass Transit Railway is the rapid transit railway system in Hong Kong. Originally opened in 1979, the system now includes 211.6 km of rail with 155 stations, including 86 railway stations and 69 light rail stops...

 metro trains. Some double-decker bridges only use one level for street traffic; the Washington Avenue Bridge
Washington Avenue Bridge (Minneapolis)
The Washington Avenue Bridge carries County Road 122 across the Mississippi River in Minneapolis, Minnesota and connects the East Bank and West Bank portions of the University of Minnesota's main campus...

 in Minneapolis
Minneapolis, Minnesota
Minneapolis , nicknamed "City of Lakes" and the "Mill City," is the county seat of Hennepin County, the largest city in the U.S. state of Minnesota, and the 48th largest in the United States...

 reserves its lower level for automobile traffic and its upper level for pedestrian and bicycle traffic (predominantly students at the University of Minnesota
University of Minnesota
The University of Minnesota, Twin Cities is a public research university located in Minneapolis and St. Paul, Minnesota, United States. It is the oldest and largest part of the University of Minnesota system and has the fourth-largest main campus student body in the United States, with 52,557...

). Likewise, in Toronto
Toronto
Toronto is the provincial capital of Ontario and the largest city in Canada. It is located in Southern Ontario on the northwestern shore of Lake Ontario. A relatively modern city, Toronto's history dates back to the late-18th century, when its land was first purchased by the British monarchy from...

, the Prince Edward Viaduct
Prince Edward Viaduct
The Prince Edward Viaduct System, commonly referred to as the Bloor Viaduct or the viaduct, is the name of a truss arch bridge system in Toronto, Ontario, Canada that connects Bloor Street East, on the west side of the system, with Danforth Avenue on the east...

 has five lanes of motor traffic, bicycle lanes, and sidewalks on its upper deck; and a pair of tracks for the Bloor–Danforth subway line
Toronto subway and RT
The Toronto subway and RT is a rapid transit system in Toronto, Ontario, Canada, consisting of both underground and elevated railway lines, operated by the Toronto Transit Commission . It was Canada's first completed subway system, with the first line being built under Yonge Street, which opened in...

.

Robert Stephenson
Robert Stephenson
Robert Stephenson FRS was an English civil engineer. He was the only son of George Stephenson, the famed locomotive builder and railway engineer; many of the achievements popularly credited to his father were actually the joint efforts of father and son.-Early life :He was born on the 16th of...

's High Level Bridge
High Level Bridge
The High Level Bridge is a road and railway bridge spanning the River Tyne between Newcastle upon Tyne and Gateshead in North East England.-Design:...

 across the River Tyne
River Tyne
The River Tyne is a river in North East England in Great Britain. It is formed by the confluence of two rivers: the North Tyne and the South Tyne. These two rivers converge at Warden Rock near Hexham in Northumberland at a place dubbed 'The Meeting of the Waters'.The North Tyne rises on the...

 in Newcastle upon Tyne
Newcastle upon Tyne
Newcastle upon Tyne is a city and metropolitan borough of Tyne and Wear, in North East England. Historically a part of Northumberland, it is situated on the north bank of the River Tyne...

, completed in 1849, is an early example of a double-deck bridge. The upper level carries a railway, and the lower level is used for road traffic. Other examples include Britannia Bridge
Britannia Bridge
Britannia Bridge is a bridge across the Menai Strait between the island of Anglesey and the mainland of Wales. It was originally designed and built by Robert Stephenson as a tubular bridge of wrought iron rectangular box-section spans for carrying rail traffic...

 over the Menai Strait
Menai Strait
The Menai Strait is a narrow stretch of shallow tidal water about long, which separates the island of Anglesey from the mainland of Wales.The strait is bridged in two places - the main A5 road is carried over the strait by Thomas Telford's elegant iron suspension bridge, the first of its kind,...

 and Craigavon Bridge
Craigavon Bridge
The Craigavon Bridge is one of three bridges in Derry, Northern Ireland. It crosses the River Foyle further south than the Foyle Bridge and Peace Bridge. It is one of only a few double-decker road bridges in Europe. It was named after Lord Craigavon, the first Prime Minister of Northern Ireland.The...

 in Derry
Derry
Derry or Londonderry is the second-biggest city in Northern Ireland and the fourth-biggest city on the island of Ireland. The name Derry is an anglicisation of the Irish name Doire or Doire Cholmcille meaning "oak-wood of Colmcille"...

, Northern Ireland
Northern Ireland
Northern Ireland is one of the four countries of the United Kingdom. Situated in the north-east of the island of Ireland, it shares a border with the Republic of Ireland to the south and west...

. The Oresund Bridge
Oresund Bridge
The Øresund or Öresund Bridge is a combined twin-track railway and dual carriageway bridge-tunnel across the Øresund strait.The bridge connects Sweden and Denmark, and it is the longest road and rail bridge in Europe. The Øresund Bridge also connects two major Metropolitan Areas: those of the...

 between Copenhagen
Copenhagen
Copenhagen is the capital and largest city of Denmark, with an urban population of 1,199,224 and a metropolitan population of 1,930,260 . With the completion of the transnational Øresund Bridge in 2000, Copenhagen has become the centre of the increasingly integrating Øresund Region...

 and Malmö
Malmö
Malmö , in the southernmost province of Scania, is the third most populous city in Sweden, after Stockholm and Gothenburg.Malmö is the seat of Malmö Municipality and the capital of Skåne County...

 consists of a four-lane highway on the upper level and a pair of railway tracks at the lower level.

The George Washington Bridge
George Washington Bridge
The George Washington Bridge is a suspension bridge spanning the Hudson River, connecting the Washington Heights neighborhood in the borough of Manhattan in New York City to Fort Lee, Bergen County, New Jersey. Interstate 95 and U.S. Route 1/9 cross the river via the bridge. U.S...

 between New Jersey and New York has two roadway levels. It was built with only the upper roadway as traffic demands did not require more capacity. A truss
Truss
In architecture and structural engineering, a truss is a structure comprising one or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes. External forces and reactions to those forces are considered to act only at the nodes and result in...

 work between the roadway levels provides stiffness to the roadways and reduced movement of the upper level when installed. Tower Bridge
Tower Bridge
Tower Bridge is a combined bascule and suspension bridge in London, England, over the River Thames. It is close to the Tower of London, from which it takes its name...

 is different example of a double-decker bridge, with the central section consisting of a low level bascule span
Bascule bridge
A bascule bridge is a moveable bridge with a counterweight that continuously balances the span, or "leaf," throughout the entire upward swing in providing clearance for boat traffic....

 and a high level footbridge
Footbridge
A footbridge or pedestrian bridge is a bridge designed for pedestrians and in some cases cyclists, animal traffic and horse riders, rather than vehicular traffic. Footbridges complement the landscape and can be used decoratively to visually link two distinct areas or to signal a transaction...

.

Old Yamuna Bridge (Delhi
Delhi
Delhi , officially National Capital Territory of Delhi , is the largest metropolis by area and the second-largest by population in India, next to Mumbai. It is the eighth largest metropolis in the world by population with 16,753,265 inhabitants in the Territory at the 2011 Census...

) or Bridge No. 249 in technical railway parlance, was constructed in 1866 by the East India Railway at a cost of £16,16,335. It was built with a total length of 2640 feet (804.7 m) and consisted of 12 spans of 202.5 feet (61.7 m) each. With the completion of this bridge, two principal cities of North India, Kolkata
Kolkata
Kolkata , formerly known as Calcutta, is the capital of the Indian state of West Bengal. Located on the east bank of the Hooghly River, it was the commercial capital of East India...

 and Delhi, were connected by the railways; this being the last link of the trunk line on this route. In 1913, this was converted into a double line by adding down line girders of 12 spans of 202 feet (61.6 m) each and 2 end spans of 42 feet (12.8 m) to the bridge. For the movement of road traffic, two road bridges were provided below the lines. The entry of trains into Delhi Junction Railway station
Delhi Junction Railway station
Delhi Junction, also known as Old Delhi Railway Station , station code DLI, is the oldest railway station of Delhi city, and a Junction station. It was built by the British in the style of red-coloured fort, in 1903...

, in such close proximity to the Red Fort, never ceases to impress the rail traveler, reminding all that after the Uprising of 1857
Indian Rebellion of 1857
The Indian Rebellion of 1857 began as a mutiny of sepoys of the British East India Company's army on 10 May 1857, in the town of Meerut, and soon escalated into other mutinies and civilian rebellions largely in the upper Gangetic plain and central India, with the major hostilities confined to...

, Delhi was a fortified city. The old Yamuna Bridge has an identical twin, a bridge further downstream at Naini
Naini
Naini is a satellite locality/township of the city of Allahabad, Uttar Pradesh, India in the south-east.-History:Naini was infamous for its prison, Naini Jail, where many freedom fighters—including Pt...

 on the Allahabad
Allahabad
Allahabad , or Settled by God in Persian, is a major city of India and is one of the main holy cities of Hinduism. It was renamed by the Mughals from the ancient name of Prayaga , and is by some accounts the second-oldest city in India. It is located in the north Indian state of Uttar Pradesh,...

 — Mughalsarai
Mughalsarai
Mughalsarai is a city and a municipal board in Chandauli district in the Indian state of Uttar Pradesh. Located around 10 km from Varanasi, it is an important railway junction of the Indian Railways. Once, it enjoyed the position of the largest railway marshalling yard of Asia...

 section of the now North Central Railways.

By use


A bridge is designed for trains, pedestrian or road traffic, a pipeline or waterway for water transport or barge traffic. An aqueduct
Aqueduct
An aqueduct is a water supply or navigable channel constructed to convey water. In modern engineering, the term is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose....

 is a bridge that carries water, resembling a viaduct
Viaduct
A viaduct is a bridge composed of several small spans. The term viaduct is derived from the Latin via for road and ducere to lead something. However, the Ancient Romans did not use that term per se; it is a modern derivation from an analogy with aqueduct. Like the Roman aqueducts, many early...

, which is a bridge that connects points of equal height. A road-rail bridge carries both road and rail traffic.

Bridges are subject to unplanned uses as well. The areas underneath some bridges have become makeshift shelters and homes to homeless people, and the undersides of bridges all around the world are spots of prevalent graffiti. Some bridges attract people attempting suicide
Suicide
Suicide is the act of intentionally causing one's own death. Suicide is often committed out of despair or attributed to some underlying mental disorder, such as depression, bipolar disorder, schizophrenia, alcoholism, or drug abuse...

, and become known as suicide bridge
Suicide bridge
A suicide bridge is a bridge used frequently to die by suicide, most typically by jumping off and into the water below ....

s.

To create a beautiful image, some bridges are built much taller than necessary. This type, often found in east-Asian style gardens, is called a Moon bridge
Moon bridge
A moon bridge is a highly arched pedestrian bridge, which in its wooden form may require the walker to initially climb and also when descending. This type is associated with gardens in China and Japan...

, evoking a rising full moon. Other garden bridges may cross only a dry bed of stream washed pebbles, intended only to convey an impression of a stream. Often in palaces a bridge will be built over an artificial waterway as symbolic of a passage to an important place or state of mind. A set of five bridges cross a sinuous waterway in an important courtyard of the Forbidden City
Forbidden City
The Forbidden City was the Chinese imperial palace from the Ming Dynasty to the end of the Qing Dynasty. It is located in the middle of Beijing, China, and now houses the Palace Museum...

 in Beijing
Beijing
Beijing , also known as Peking , is the capital of the People's Republic of China and one of the most populous cities in the world, with a population of 19,612,368 as of 2010. The city is the country's political, cultural, and educational center, and home to the headquarters for most of China's...

, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

. The central bridge was reserved exclusively for the use of the Emperor, Empress, and their attendants.

Structure


Bridges may be classified by how the forces of tension
Tension (mechanics)
In physics, tension is the magnitude of the pulling force exerted by a string, cable, chain, or similar object on another object. It is the opposite of compression. As tension is the magnitude of a force, it is measured in newtons and is always measured parallel to the string on which it applies...

, compression, bending
Bending
In engineering mechanics, bending characterizes the behavior of a slender structural element subjected to an external load applied perpendicularly to a longitudinal axis of the element. The structural element is assumed to be such that at least one of its dimensions is a small fraction, typically...

, torsion
Torsion (mechanics)
In solid mechanics, torsion is the twisting of an object due to an applied torque. In sections perpendicular to the torque axis, the resultant shear stress in this section is perpendicular to the radius....

 and shear
Shear stress
A shear stress, denoted \tau\, , is defined as the component of stress coplanar with a material cross section. Shear stress arises from the force vector component parallel to the cross section...

 are distributed through their structure. Most bridges will employ all of the principal forces to some degree, but only a few will predominate. The separation of forces may be quite clear. In a suspension or cable-stayed span, the elements in tension are distinct in shape and placement. In other cases the forces may be distributed among a large number of members, as in a truss, or not clearly discernible to a casual observer as in a box beam. Bridges can also be classified by their lineage, which is shown as the vertical axis on the diagram.

Efficiency


A bridge's structural efficiency is the ratio of load carried to bridge mass, given a specific set of material types. In one common challenge students are divided into groups and given a quantity of wood sticks, a distance to span, and glue, and then asked to construct a bridge that will be tested to destruction by the progressive addition of load at the center of the span. The bridge taking the greatest load is by this test the most structurally efficient. A more refined measure for this exercise is to weigh the completed bridge rather than measure against a fixed quantity of materials provided and determine the multiple of this weight that the bridge can carry, a test that emphasizes economy of materials and efficient glue joints (see balsa wood bridge
Balsa wood bridge
The building of balsa-wood bridges is very often used as an educational technology. It may be accompanied by a larger project involving varying areas of study....

).

A bridge's economic efficiency will be site and traffic dependent, the ratio of savings by having a bridge (instead of, for example, a ferry, or a longer road route) compared to its cost. The lifetime cost is composed of materials, labor, machinery, engineering, cost of money, insurance, maintenance, refurbishment, and ultimately, demolition and associated disposal, recycling, and replacement, less the value of scrap and reuse of components. Bridges employing only compression are relatively inefficient structurally, but may be highly cost efficient where suitable materials are available near the site and the cost of labor is low. For medium spans, trusses or box beams are usually most economical, while in some cases, the appearance of the bridge may be more important than its cost efficiency. The longest spans usually require suspension bridges.


Other functions


Some bridges accommodate other purposes, such as the tower of Nový Most
Nový Most
Nový Most is a road bridge over the Danube in Bratislava, the capital of Slovakia. It is the 32nd-tallest, and thus shortest, member of the World Federation of Great Towers, and is the only bridge to be a member...

 bridge in Bratislava
Bratislava
Bratislava is the capital of Slovakia and, with a population of about 431,000, also the country's largest city. Bratislava is in southwestern Slovakia on both banks of the Danube River. Bordering Austria and Hungary, it is the only national capital that borders two independent countries.Bratislava...

, which features a restaurant. Other suspension bridge towers carry transmission antennas.

A bridge can carry overhead power lines as does the Storstrøm Bridge
Storstrøm Bridge
Storstrøm Bridge is a road and railway arch bridge that crosses Storstrømmen between the islands of Falster and Masnedø in Denmark....

.

Costs and cost overrun
Cost overrun
A cost overrun, also known as a cost increase or budget overrun, is an unexpected cost incurred in excess of a budgeted amount due to an under-estimation of the actual cost during budgeting...

s frequently occur in bridge construction. Flyvbjerg et al. (2003) found the average cost overrun in bridge building is 34%.

In railway parlance, an overbridge is a bridge crossing over the course of the railway. In contrast, an underbridge allows passage under the line.

Bridge failures


The failure of bridges is of special concern for structural engineers in trying to learn lessons vital to bridge design, construction and maintenance. The failure of bridges first assumed national interest during the Victorian era
Victorian era
The Victorian era of British history was the period of Queen Victoria's reign from 20 June 1837 until her death on 22 January 1901. It was a long period of peace, prosperity, refined sensibilities and national self-confidence...

 when many new designs were being built, often using new materials.

In the United States, the National Bridge Inventory
National Bridge Inventory
The National Bridge Inventory is a database, compiled by the Federal Highway Administration, with information on all bridges and tunnels in the United States that have roads passing above or below. This is similar to the grade crossing identifier number database compiled by the Federal Railroad...

 tracks the structural evaluations of all bridges, including designation as "structurally deficient" and "functionally obsolete".

See also


  • Architectural structure
    Architectural structure
    An architectural structure is a free-standing, immobile outdoor constructed element. The structure may be temporary or permanent.Structures include buildings and nonbuilding structures . Examples of building structures include houses, town halls, libraries, and skyscrapers...

  • Bridge to Nowhere (disambiguation)
  • Cost overrun
    Cost overrun
    A cost overrun, also known as a cost increase or budget overrun, is an unexpected cost incurred in excess of a budgeted amount due to an under-estimation of the actual cost during budgeting...

     in bridge construction
  • Footbridge
    Footbridge
    A footbridge or pedestrian bridge is a bridge designed for pedestrians and in some cases cyclists, animal traffic and horse riders, rather than vehicular traffic. Footbridges complement the landscape and can be used decoratively to visually link two distinct areas or to signal a transaction...

  • Landscape architecture
    Landscape architecture
    Landscape architecture is the design of outdoor and public spaces to achieve environmental, socio-behavioral, or aesthetic outcomes. It involves the systematic investigation of existing social, ecological, and geological conditions and processes in the landscape, and the design of interventions...

  • Megaproject
    Megaproject
    A megaproject is an extremely large-scale investment project. Megaprojects are typically defined as costing more than US$1 billion and attracting a lot of public attention because of substantial impacts on communities, environment, and budgets. Megaprojects can also be defined as "initiatives that...

  • Overpass
    Overpass
    An overpass is a bridge, road, railway or similar structure that crosses over another road or railway...

  • Oxford BT Centre for Major Programme Management
  • Sea bridge
  • BS 5400
    BS 5400
    BS 5400 is a British Standard for design and construction of steel, concrete and composite bridges use in highway and railway.The standard specifies the requirements and the code of practice on design of steel, concrete and composite bridges that use steel sections as well as the materials and...

    , a British Standard for steel, concrete and composite bridges
  • contrast with tunnel
    Tunnel
    A tunnel is an underground passageway, completely enclosed except for openings for egress, commonly at each end.A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal. Some tunnels are aqueducts to supply water for consumption or for hydroelectric stations or are sewers...



External links