Bridge

A bridge is a structure built to span a physical obstacle, such as a body of water, valley, or road, without closing the way underneath. It is constructed for the purpose of providing passage over the obstacle, usually something that can be detrimental to cross otherwise. There are many different designs that each serve a particular purpose and apply to different situations. Designs of bridges vary depending on the function of the bridge, the nature of the terrain where the bridge is constructed and anchored, the material used to make it, and the funds available to build it.

Most likely the earliest bridges were fallen trees and stepping stones, while Neolithic people built boardwalk bridges across marshland. The Arkadiko Bridge dating from the 13th century BC, in the Peloponnese, in southern Greece is one of the oldest arch bridges still in existence and use.

RhB Ge 4-4 II Wiesener Viadukt
Wiesen Viaduct in Switzerland

Etymology

Akashi-kaikyo bridge3
The Akashi Kaikyō Bridge in Japan, the world's longest suspension span
Sio se pol
The Siosepol bridge over Zayandeh River is an example of Safavid dynasty (1502–1722) bridge design. Isfahan, Iran

The Oxford English Dictionary traces the origin of the word bridge to an Old English word brycg, of the same meaning.[1] The word can be traced directly back to Proto-Indo-European *bʰrēw-. The word for the card game of the same name has a different origin.

History

Pont mycénien de Kazarma 2
The Arkadiko Bridge in Greece (13th century BC), one of the oldest arch bridges in existence

The simplest type of a bridge is stepping stones, so this may have been one of the earliest types. Neolithic people also built a form of boardwalk across marshes, of which the Sweet Track and the Post Track, are examples from England that are around 6000 years old.[2] Undoubtedly ancient peoples would also have used log bridges; that is a timber bridge[3] that fall naturally or are intentionally felled or placed across streams. Some of the first man-made bridges with significant span were probably intentionally felled trees.[4]

Among the oldest timber bridges is the Holzbrücke Rapperswil-Hurden crossing upper Lake Zürich in Switzerland; the prehistoric timber piles discovered to the west of the Seedamm date back to 1523 BC. The first wooden footbridge led across Lake Zürich, followed by several reconstructions at least until the late 2nd century AD, when the Roman Empire built a 6-metre-wide (20 ft) wooden bridge. Between 1358 and 1360, Rudolf IV, Duke of Austria, built a 'new' wooden bridge across the lake that has been used to 1878 – measuring approximately 1,450 metres (4,760 ft) in length and 4 metres (13 ft) wide. On April 6, 2001, the reconstructed wooden footbridge was opened, being the longest wooden bridge in Switzerland.

The Arkadiko Bridge is one of four Mycenaean corbel arch bridges part of a former network of roads, designed to accommodate chariots, between the fort of Tiryns and town of Epidauros in the Peloponnese, in southern Greece. Dating to the Greek Bronze 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.[5]

The greatest bridge builders of antiquity were the ancient Romans.[6] The Romans built arch bridges and aqueducts that could stand in conditions that would damage or destroy earlier designs. Some stand today.[7] An example is the Alcántara Bridge, built over the river Tagus, in Spain. The Romans also used cement, which reduced the variation of strength found in natural stone.[8] One type of cement, called pozzolana, consisted of water, lime, sand, and volcanic rock. Brick and mortar bridges were built after the Roman era, as the technology for cement was lost (then later rediscovered).

In India, the Arthashastra treatise by Kautilya mentions the construction of dams and bridges.[9] A Mauryan bridge near Girnar was surveyed by James Princep.[10] The bridge was swept away during a flood, and later repaired by Puspagupta, the chief architect of emperor Chandragupta I.[10] The use of stronger bridges using plaited bamboo and iron chain was visible in India by about the 4th century.[11] A number of bridges, both for military and commercial purposes, were constructed by the Mughal administration in India.[12]

Although large Chinese bridges of wooden construction existed at the time of the Warring States period, the oldest surviving stone bridge in China is the Zhaozhou Bridge, built from 595 to 605 AD during the Sui dynasty. This bridge is also historically significant as it is the world's oldest open-spandrel stone segmental arch bridge. European segmental arch bridges date back to at least the Alconétar Bridge (approximately 2nd century AD), while the enormous Roman era Trajan's Bridge (105 AD) featured open-spandrel segmental arches in wooden construction.

Rope bridges, a simple type of suspension bridge, were used by the Inca civilization in the Andes 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 Grubenmann, Johannes Grubenmann, and others. The first book on bridge engineering was written by Hubert Gautier in 1716.

A major breakthrough in bridge technology came with the erection of the Iron Bridge in Shropshire, England in 1779. It used cast iron for the first time as arches to cross the river Severn.[13]

With the Industrial Revolution in the 19th century, truss systems of wrought iron were developed for larger bridges, but iron does not have the tensile strength 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.

West Montrose Covered Bridge (Oct. 2018)
The covered bridge in West Montrose, Ontario, Canada

In Canada and the U.S., numerous timber Covered bridges were built in the late 1700s to the late 1800s, reminiscent of earlier designs in Germany and Switzerland. (Some covered bridges were also built in Asia.)[14] In later years, some were partly made of stone or metal but the trusses were usually still made of wood; in the US, there were three styles of trusses, the Queen Post, the Burr Arch and the Town Lattice.[15] Hundreds of these structures still stand in North America. They were brought to the attention of the general public in the 1990s by the novel, movie, and play The Bridges of Madison County.[16][17]

In 1927 welding pioneer Stefan Bryła designed the first welded road bridge in the world, the Maurzyce Bridge which was later built across the river Słudwia at Maurzyce near Łowicz, Poland in 1929. In 1995, the American Welding Society presented the Historic Welded Structure Award for the bridge to Poland.[18]

Types of bridges

Bridges can be categorized in several different ways. Common categories include the type of structural elements used, by what they carry, whether they are fixed or movable, and by the materials used.

Structure type

Bridges may be classified by how the actions of tension, compression, bending, torsion and shear are distributed through their structure. Most bridges will employ all of these to some degree, but only a few will predominate. The separation of forces and moments may be quite clear. In a suspension or cable-stayed bridge, 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.

BeamBridge-diagramBeam bridge
Beam bridges are horizontal beams supported at each end by substructure units and can be either simply supported when the beams only connect across a single span, or continuous when the beams are connected across two or more spans. When there are multiple spans, 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 can range from small, wooden beams to large, steel boxes. The vertical force on the bridge becomes a shear and flexural load on the beam which is transferred down its length to the substructures on either side[19] They are typically made of steel, concrete or wood. Girder bridges and plate girder bridges, usually made from steel, are types of beam bridges. Box girder bridges, made from steel, concrete, or both, are also beam bridges. Beam bridge spans rarely exceed 250 feet (76 m) long, as the flexural stresses increase proportional to the square of the length (and deflection increases proportional to the 4th power of the length).[20] However, the main span of the Rio–Niteroi Bridge, a box girder bridge, is 300 metres (980 ft).

The world's longest beam bridge is Lake Pontchartrain Causeway in southern Louisiana in the United States, at 23.83 miles (38.35 km), with individual spans of 56 feet (17 m).[21] Beam bridges are the simplest and oldest type of bridge in use today,[22] and are a popular type.[23]

TrussBridge-diagramTruss bridge
A truss bridge is a bridge whose load-bearing superstructure is composed of a truss. This truss is a structure of connected elements forming triangular units. The connected elements (typically straight) 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. The basic types of truss bridges shown in this article have simple designs which could be easily analyzed by nineteenth and early twentieth century engineers. A truss bridge is economical to construct owing to its efficient use of materials.
CantileverBridge-diagramCantilever bridge
Cantilever bridges are built using cantilevers—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 and techniques as beam bridges. The difference comes in the action of the forces through the bridge.

Some cantilever bridges also have a smaller beam connecting the two cantilevers, for extra strength.

The largest cantilever bridge is the 549-metre (1,801 ft) Quebec Bridge in Quebec, Canada.

ArchBridge-diagramArch bridge
Arch bridges 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.

With the span of 220 metres (720 ft), the Solkan Bridge over the Soča River at Solkan in Slovenia is the second-largest stone bridge in the world and the longest railroad stone bridge. It was completed in 1905. Its arch, which was constructed from over 5,000 tonnes (4,900 long tons; 5,500 short tons) of stone blocks in just 18 days, is the second-largest stone arch in the world, surpassed only by the Friedensbrücke (Syratalviadukt) in Plauen, and the largest railroad stone arch. The arch of the Friedensbrücke, which was built in the same year, has the span of 90 m (295 ft) and crosses the valley of the Syrabach River. The difference between the two is that the Solkan Bridge was built from stone blocks, whereas the Friedensbrücke was built from a mixture of crushed stone and cement mortar.[24]

The world's largest arch bridge is the Chaotianmen Bridge over the Yangtze River with a length of 1,741 m (5,712 ft) and a span of 552 m (1,811 ft). The bridge was opened April 29, 2009, in Chongqing, China.[25]

TiedarchBridge-diagramTied arch bridge
Tied arch bridges 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.
SuspensionBridge-diagramSuspension bridge
Suspension bridges 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 bed of the lake, river or sea. Sub-types include the simple suspension bridge, the stressed ribbon bridge, the underspanned suspension bridge, the suspended-deck suspension bridge, and the self-anchored suspension bridge. There is also what is sometimes called a "semi-suspension" bridge, of which the Ferry Bridge in Burton-upon-Trent is the only one of its kind in Europe.[26]

The longest suspension bridge in the world is the 3,909 m (12,825 ft) Akashi Kaikyō Bridge in Japan.[27]

CableStayedBridge-diagramCable-stayed bridge
Cable-stayed bridges, 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 higher.[28] The first known cable-stayed bridge was designed in 1784 by C. T. (or C. J.) Löscher.[29][30]

The longest cable-stayed bridge since 2012 is the 1,104 m (3,622 ft) Russky Bridge in Vladivostok, Russia.[31]

Some Engineers sub-divide 'beam' bridges into slab, beam-and-slab and box girder on the basis of their cross-section.[32] A slab can be solid or voided[33] (though this is no longer favored for inspectability reasons) while beam-and-slab consists of concrete or steel girders connected by a concrete slab.[34] A box-girder cross-section consists of a single-cell or multi-cellular box. In recent years, integral bridge construction[35] has also become popular.

New Champlain Bridge, Montreal, Quebec, Canada
New Champlain Bridge over the St Lawrence river, Montreal, Quebec, Canada. Accommodates cars, bicycles and a light passenger train. Was commissioned in June 2019. The old bridge will be de-constructed

Fixed or movable bridges

Moving a Bloomingdale Trail bridge from Ashland to Western in Chicago.

Most bridges are fixed bridges, meaning they have no moving parts and stay in one place until they fail or are demolished. Temporary bridges, such as Bailey bridges, are designed to be assembled, and taken apart, transported to a different site, and re-used. They are important in military engineering, and are also used to carry traffic while an old bridge is being rebuilt. 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

George Washington Bridge from New Jersey-edit
The double-decked George Washington Bridge, connecting New York City to Bergen County, New Jersey, US, is the world's busiest bridge, carrying 102 million vehicles annually.[36][37]

Double-decked (or double-decker) bridges have two levels, such as the George Washington Bridge, connecting New York City to Bergen County, New Jersey, US, as the world's busiest bridge, carrying 102 million vehicles annually;[36][37] truss work between the roadway levels provided stiffness to the roadways and reduced movement of the upper level when the lower level was installed three decades after the upper level. The Tsing Ma Bridge and Kap Shui Mun Bridge in Hong Kong have six lanes on their upper decks, and on their lower decks there are two lanes and a pair of tracks for MTR metro trains. Some double-decked bridges only use one level for street traffic; the Washington Avenue Bridge in Minneapolis reserves its lower level for automobile and light rail traffic and its upper level for pedestrian and bicycle traffic (predominantly students at the University of Minnesota). Likewise, in Toronto, the Prince Edward Viaduct 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 on its lower deck. The western span of the San Francisco–Oakland Bay Bridge also has two levels.

Robert Stephenson's High Level Bridge across the River Tyne in Newcastle upon Tyne, completed in 1849, is an early example of a double-decked bridge. The upper level carries a railway, and the lower level is used for road traffic. Other examples include Britannia Bridge over the Menai Strait and Craigavon Bridge in Derry, Northern Ireland. The Oresund Bridge between Copenhagen and Malmö consists of a four-lane highway on the upper level and a pair of railway tracks at the lower level. Tower Bridge in London is different example of a double-decked bridge, with the central section consisting of a low-level bascule span and a high-level footbridge.

Viaducts

A viaduct is made up of multiple bridges connected into one longer structure. The longest and some of the highest bridges are viaducts, such as the Lake Pontchartrain Causeway and Millau Viaduct.

Multi-way bridge

Tridge Undercarriage
The Tridge is a type of multi-way bridge

A multi-way bridge has three or more separate spans which meet near the center of the bridge. Multi-way bridges with only three spans appear as a "T" or "Y" when viewed from above. Multi-way bridges bridges are extremely rare. The Tridge, Margaret Bridge, and Zanesville Y-Bridge are examples.

Bridge types by use

A bridge can be categorized by what it is designed to carry, such as trains, pedestrian or road traffic (road bridge), a pipeline or waterway for water transport or barge traffic. An aqueduct is a bridge that carries water, resembling a viaduct, which is a bridge that connects points of equal height. A road-rail bridge carries both road and rail traffic. Overway is a term for a bridge that separates incompatible intersecting traffic, especially road and rail.[38] A bridge can carry overhead power lines as does the Storstrøm Bridge.

Some bridges accommodate other purposes, such as the tower of Nový Most Bridge in Bratislava, which features a restaurant, or a bridge-restaurant which is a bridge built to serve as a restaurant. Other suspension bridge towers carry transmission antennas.

Conservationists use wildlife overpasses to stop habitat fragmentation and animal-vehicle collisions. The first animal bridges sprung up in France in the 1950s, and these types of bridges are now used worldwide to protect both large and small wildlife.[39][40][41]

Bridges are subject to unplanned uses as well. The areas underneath some bridges have become makeshift shelters and homes to homeless people, and the undertimbers of bridges all around the world are spots of prevalent graffiti. Some bridges attract people attempting suicide, and become known as suicide bridges.[42]

Bridge types by material

Ironbridge 6
The Iron Bridge completed in 1781 was the first cast iron bridge.
Kraemerbruecke und Aegidienkirche Erfurt 2017
Krämerbrücke in Erfurt, Germany – with half timbered buildings
Stone bridge, Othoni island
Small stone bridge, Othonoi, Greece

The materials used to build the structure are also used to categorize bridges. Until the end of the 18th century, bridges were made out of timber, stone and masonry. Modern bridges are currently built in concrete, steel, fiber reinforced polymers (FRP), stainless steel or combinations of those materials. Living bridges have been constructed of live plants such as Ficus elastica tree roots in India[43] and wisteria vines in Japan.[44]

Bridge type Materials used
Cantilever For small footbridges, the cantilevers may be simple beams; however, large cantilever bridges designed to handle road or rail traffic use trusses built from structural steel, or box girders built from prestressed concrete.[45]
Suspension The cables are usually made of steel cables galvanised with zinc, along with most of the bridge, but some bridges are still made with steel-reinforced concrete.[46]
Arch Stone, brick and other such materials that are strong in compression and somewhat so in shear.
Beam Beam bridges can use pre-stressed concrete, an inexpensive building material, which is then embedded with rebar. The resulting bridge can resist both compression and tension forces.[47]
Truss The triangular pieces of truss bridges are manufactured from straight and steel bars, according to the truss bridge designs.[48]

Analysis and design

Unlike buildings whose design is led by architects, bridges are usually designed by engineers. This follows from the importance of the engineering requirements; namely spanning the obstacle and having the durability to survive, with minimal maintenance, in an aggressive outdoor environment.[34] Bridges are first analysed; the bending moment and shear force distributions are calculated due to the applied loads. For this, the finite element method is the most popular. The analysis can be one, two or three-dimensional. For the majority of bridges, a 2-dimensional plate model (often with stiffening beams) is sufficient or an upstand finite element[49] model. On completion of the analysis, the bridge is designed to resist the applied bending moments and shear forces, i.e., section sizes are selected with sufficient capacity to resist the stresses. Many bridges are made of prestressed concrete which has good durability properties, either by pre-tensioning of beams prior to installation or post-tensioning on site.

In most countries, bridges, like other structures, are designed according to Load and Resistance Factor Design (LRFD) principles. In simple terms, this means that the load is factored up by a factor greater than unity, while the resistance or capacity of the structure is factored down, by a factor less than unity. The effect of the factored load (stress, bending moment, etc.) should be less than the factored resistance to that effect. Both of these factors allow for uncertainty and are greater when the uncertainty is greater.

Aesthetics

Utrecht 'Prins Claus brug'
The Prins Clausbrug across the Amsterdam-Rhine Canal in Utrecht, Netherlands
Stari Most22
The World Heritage Site of Stari Most (Old Bridge) gives its name to the city of Mostar, Bosnia and Herzegovina

Most bridges are utilitarian in appearance, but in some cases, the appearance of the bridge can have great importance.[50] Often, this is the case with a large bridge that serves as an entrance to a city, or crosses over a main harbor entrance. These are sometimes known as signature bridges. Designers of bridges in parks and along parkways often place more importance to aesthetics, as well. Examples include the stone-faced bridges along the Taconic State Parkway in New York.

Bridge to Pier 6, Gatwick North Terminal - geograph.org.uk - 74055
Bridge at Gatwick Airport. The planes can go underneath the bridge

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

Bridge maintenance

Example HiFIT-treated assembly
Highway bridge treated with high-frequency impact treatment

Bridge maintenance consisting of a combination of structural health monitoring and testing. This is regulated in country-specific engineer standards and includes e.g. an ongoing monitoring every three to six months, a simple test or inspection every two to three years and a major inspection every six to ten years. In Europe, the cost of maintenance is considerable[32] and is higher in some countries than spending on new bridges. The lifetime of welded steel bridges can be significantly extended by aftertreatment of the weld transitions . This results in a potential high benefit, using existing bridges far beyond the planned lifetime.

Bridge traffic loading

While the response of a bridge to the applied loading is well understood, the applied traffic loading itself is still the subject of research.[51] This is a statistical problem as loading is highly variable, particularly for road bridges. Load Effects in bridges (stresses, bending moments, etc.) are designed for using the principles of Load and Resistance Factor Design. Before factoring to allow for uncertainty, the load effect is generally considered to be the maximum characteristic value in a specified return period. For example, in Europe, it is the maximum value expected in 1000 years.

Bridge standards generally include a load model, deemed to represent the characteristic maximum load to be expected in the return period. In the past, these load models were agreed by standard drafting committees of experts but today, this situation is changing. It is now possible to measure the components of bridge traffic load, i.e., to weigh trucks, using weigh-in-motion (WIM) technologies. With extensive WIM databases, it is possible to calculate the maximum expected load effect in the specified return period. This is an active area of research, addressing issues of opposing direction lanes,[52][53] side-by-side (same direction) lanes,[54][55] traffic growth,[56] permit/non-permit vehicles[57] and long-span bridges (see below). Rather than repeat this complex process every time a bridge is to be designed, standards authorities specify simplified notional load models, e.g. HL-93,[58][59] intended to give the same load effects as the characteristic maximum values. The Eurocode is an example of a standard for bridge traffic loading that was developed in this way.[60]

Traffic loading on long span bridges

Forth from above
Traffic on Forth Road Bridge, Scotland before it was closed to general traffic. Traffic has now been moved to the Queensferry Crossing, that can be seen on the left.

Most bridge standards are only applicable for short and medium spans[61] - for example, the Eurocode is only applicable for loaded lengths up to 200 m. Longer spans are dealt with on a case by case basis. It is generally accepted that the intensity of load reduces as span increases because the probability of many trucks being closely spaced and extremely heavy reduces as the number of trucks involved increases. It is also generally assumed that short spans are governed by a small number of trucks traveling at high speed, with an allowance for dynamics. Longer spans on the other hand, are governed by congested traffic and no allowance for dynamics is needed. Calculating the loading due to congested traffic remains a challenge as there is a paucity of data on inter-vehicle gaps, both within-lane and inter-lane, in congested conditions. Weigh-in-Motion (WIM) systems provide data on inter-vehicle gaps but only operate well in free flowing traffic conditions. Some authors have used cameras to measure gaps and vehicle lengths in jammed situations and have inferred weights from lengths using WIM data.[62] Others have used microsimulation to generate typical clusters of vehicles on the bridge.[63][64][65]

Bridge vibration

Bridges vibrate under load and this contributes, to a greater or lesser extent, to the stresses.[34] Vibration and dynamics are generally more significant for slender structures such as pedestrian bridges and long-span road or rail bridges. One of the most famous examples is the Tacoma Narrows Bridge that collapsed shortly after being constructed due to excessive vibration. More recently, the Millenium Bridge in London vibrated excessively under pedestrian loading and was closed and retrofitted with a system of dampers. For smaller bridges, dynamics is not catastrophic but can contribute an added amplification to the stresses due to static effects. For example, the Eurocode for bridge loading specifies amplifications of between 10% and 70%, depending on the span, the number of traffic lanes and the type of stress (bending moment or shear force).[66]

Vehicle-bridge dynamic interaction

There have been many studies of the dynamic interaction between vehicles and bridges during vehicle crossing events. Fryba[67] did pioneering work on the interaction of a moving load and an Euler-Bernoulli beam. With increased computing power, vehicle-bridge interaction (VBI) models have become ever more sophisticated.[68][69][70][71] The concern is that one of the many natural frequencies associated with the vehicle will resonate with the bridge first natural frequency.[72] The vehicle-related frequencies include body bounce and axle hop but there are also pseudo-frequencies associated with the vehicle's speed of crossing[73] and there are many frequencies associated with the surface profile.[51] Given the wide variety of heavy vehicles on road bridges, a statistical approach has been suggested, with VBI analyses carried out for many statically extreme loading events.[74]

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

In the United States, the National Bridge Inventory tracks the structural evaluations of all bridges, including designations such as "structurally deficient" and "functionally obsolete".

Bridge monitoring

There are several methods used to monitor the condition of large structures like bridges. Many long-span bridges are now routinely monitored with a range of sensors. Many types of sensors are used, including strain transducers, accelerometers,[75] tiltmeters, and GPS. Accelerometers have the advantage that they are inertial, i.e., they do not require a reference point to measure from. This is often a problem for distance or deflection measurement, especially if the bridge is over water.

An option for structural-integrity monitoring is "non-contact monitoring", which uses the Doppler effect (Doppler shift). A laser beam from a Laser Doppler Vibrometer is directed at the point of interest, and the vibration amplitude and frequency are extracted from the Doppler shift of the laser beam frequency due to the motion of the surface.[76] The advantage of this method is that the setup time for the equipment is faster and, unlike an accelerometer, this makes measurements possible on multiple structures in as short a time as possible. Additionally, this method can measure specific points on a bridge that might be difficult to access. However, vibrometers are relatively expensive and have the disadvantage that a reference point is needed to measure from.

Snapshots in time of the external condition of a bridge can be recorded using Lidar to aid bridge inspection.[77] This can provide measurement of the bridge geometry (to facilitate the building of a computer model) but the accuracy is generally insufficient to measure bridge deflections under load.

While larger modern bridges are routinely monitored electronically, smaller bridges are generally inspected visually by trained inspectors. There is considerable research interest in the challenge of smaller bridges as they are often remote and do not have electrical power on site. Possible solutions are the installation of sensors on a specialist inspection vehicle and the use of its measurements as it drives over the bridge to infer information about the bridge condition.[78][79][80] These vehicles can be equipped with accelerometers, gyrometers, Laser Doppler Vibrometers[81][82] and some even have the capability to apply a resonant force to the road surface in order to dynamically excite the bridge at its resonant frequency.

See also

References

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Further reading

  • Brown, David J. Bridges: Three Thousand Years of Defying Nature. Richmond Hill, Ont: Firefly Books, 2005. ISBN 1-55407-099-6.
  • Sandak, Cass R. Bridges. An Easy-read modern wonders book. New York: F. Watts, 1983. ISBN 0-531-04624-9.
  • Whitney, Charles S. Bridges of the World: Their Design and Construction. Mineola, NY: Dover Publications, 2003. ISBN 0-486-42995-4 (Unabridged republication of Bridges : a study in their art, science, and evolution. 1929.)

External links

Bridge over Troubled Water (song)

"Bridge over Troubled Water" is a song by American music duo Simon & Garfunkel. Produced by the duo and Roy Halee, the song was released as the follow-up single to "The Boxer" in January 1970. The song is featured on their fifth studio album, Bridge over Troubled Water (1970). Composed by singer-songwriter Paul Simon, the song is performed on piano and carries the influence of gospel music. The original studio recording employs elements of Phil Spector's "Wall of Sound" technique using L.A. session musicians from the Wrecking Crew.It was the last song recorded for their fifth and final album, but the first fully completed. The song's instrumentation was recorded in California while the duo's vocals were cut in New York. Simon felt his partner, Art Garfunkel, should sing the song solo, an invitation Garfunkel initially declined but later accepted. Session musician Larry Knechtel performs piano on the song, with Joe Osborn playing bass guitar and Hal Blaine closing out the song with drums. The song won five awards at the 13th Annual Grammy Awards in 1971, including Grammy Award for Record of the Year and Song of the Year.

The song became Simon & Garfunkel's biggest hit single, and it is often considered their signature song. It was a number one hit on the Billboard Hot 100 for six weeks, and it also topped the charts in the United Kingdom, Canada, France, and New Zealand. It was a top five hit in eight other countries as well, eventually selling over six million copies worldwide, making it among the best-selling singles. It became one of the most performed songs of the twentieth century, with over 50 artists, among them Elvis Presley and Aretha Franklin, covering the song. It was ranked number 48 on Rolling Stone's 500 Greatest Songs of All Time.

Brooklyn Bridge

The Brooklyn Bridge is a hybrid cable-stayed/suspension bridge in New York City. It connects the boroughs of Manhattan and Brooklyn, spanning the East River. The Brooklyn Bridge has a main span of 1,595.5 feet (486.3 m) and a height of 133 ft (40.5 m) above Mean High Water. It is one of the oldest roadway bridges in the United States and was the world's first steel-wire suspension bridge, as well as the first fixed crossing across the East River.

The Brooklyn Bridge started construction in 1869 and was completed fourteen years later in 1883. It was originally called the New York and Brooklyn Bridge and the East River Bridge, but it was later dubbed the Brooklyn Bridge. However, it was not named as such until the city government passed a law to that effect in 1915. Over the years, the Brooklyn Bridge has undergone several reconfigurations; it formerly carried horse-drawn vehicles and elevated railway lines, but now carries vehicular, pedestrian, and bicycle traffic. Commercial vehicles are banned from the bridge.

Since opening, the Brooklyn Bridge has become an icon of New York City. It was designated a National Historic Landmark in 1964 and a National Historic Civil Engineering Landmark by the American Society of Civil Engineers in 1972. The Brooklyn Bridge is also a New York City designated landmark.

Chelsea F.C.

Chelsea Football Club is an English professional football club. Founded in 1905, they compete in the Premier League, the top division of English football. Chelsea are among England's most successful clubs, having won over thirty competitive honours, including 6 top-flight titles, 8 FA Cups, 5 League Cups, 2 UEFA Europa Leagues, 2 UEFA Cup Winners' Cups, 1 UEFA Champions League, and 1 UEFA Super Cup. Their home ground is Stamford Bridge in Fulham, London.Chelsea won their first major honour, the League Championship, in 1955. They won the FA Cup for the first time in 1970 and their first European honour, the UEFA Cup Winners' Cup, in 1971. After a period of decline in the late 1970s and 1980s, the club enjoyed a revival in the 1990s and had more success in cup competitions. The past two decades have been the most successful in Chelsea's history, winning five of their six league titles and the UEFA Champions League. Chelsea are one of five clubs to have won all three of UEFA's main club competitions, and the only London club to have won the Champions League.

Chelsea's home kit colours are royal blue shirts and shorts with white socks. The club's crest features a ceremonial lion rampant regardant holding a staff. The club have rivalries with neighbouring teams Arsenal and Tottenham Hotspur, and a historic rivalry with Leeds United. Based on attendance figures, the club have the sixth-largest fanbase in England. In terms of club value, Chelsea are the sixth most valuable football club in the world, worth £2.13 billion ($2.576 billion), and are the eighth highest-earning football club in the world, with earnings of over €428 million in the 2017–18 season. Since 2003, Chelsea have been owned by Russian billionaire Roman Abramovich.

Contract bridge

Contract bridge, or simply bridge, is a trick-taking card game using a standard 52-card deck. In its basic format, it is played by four players in two competing partnerships, with partners sitting opposite each other around a table. Millions of people play bridge worldwide in clubs, tournaments, online and with friends at home, making it one of the world's most popular card games, particularly among seniors. The World Bridge Federation (WBF) is the governing body for international competitive bridge, with numerous other bodies governing bridge at the regional level.

The game consists of several deals, each progressing through four phases. The cards are dealt to the players, and then the players ‘’call’’ (or ‘’bid’’) in an auction to take the contract, specifying how many tricks the partnership receiving the contract (the declaring side) needs to take to receive points for the deal. During the auction, partners communicate information about their hand, including its overall strength and the length of its suits, although conventions for use during play also exist. The cards are then played, the declaring side trying to fulfill the contract, and the defenders trying to stop the declaring side from achieving its goal. The deal is scored based on the number of tricks taken, the contract, and various other factors which depend to some extent on the variation of the game being played.Rubber bridge is the most popular variation for casual play, but most club and tournament play involves some variant of duplicate bridge, in which the cards are not re-dealt on each occasion, but the same deal is played by two or more sets of players (or "tables") to enable comparative scoring. For competition level, so called IMP score is of high significance.

George Washington Bridge

The George Washington Bridge is a double-decked suspension bridge spanning the Hudson River, connecting the Washington Heights neighborhood of Manhattan in New York City with the borough of Fort Lee in New Jersey. The bridge is named after George Washington, the first President of the United States. The George Washington Bridge is the world's busiest motor vehicle bridge, carrying over 103 million vehicles per year in 2016. It is owned by the Port Authority of New York and New Jersey, a bi-state government agency that operates infrastructure in the Port of New York and New Jersey. The George Washington Bridge is also informally known as the GW Bridge, the GWB, the GW, or the George, and was known as the Fort Lee Bridge or Hudson River Bridge during construction.

The idea of a bridge across the Hudson River was first proposed in 1906, but it was not until 1925 that the state legislatures of New York and New Jersey voted to allow for the planning and construction of such a bridge. Construction on the George Washington Bridge started in October 1927; the bridge was ceremonially dedicated on October 24, 1931, and opened to traffic the next day. The opening of the George Washington Bridge contributed to the development of Bergen County, New Jersey, in which Fort Lee is located. The current upper deck was widened from six to eight lanes in 1946. The six-lane lower deck was constructed beneath the existing span from 1958 to 1962 because of increasing traffic flow.

The George Washington Bridge is an important travel corridor within the New York metropolitan area. It has an upper level that carries four lanes in each direction and a lower level with three lanes in each direction, for a total of 14 lanes of travel. The speed limit on the bridge is 45 mph (72 km/h). The bridge's upper level also carries pedestrian and bicycle traffic. Interstate 95 (I-95) and U.S. Route 1/9 (US 1/9, composed of US 1 and US 9) cross the river via the bridge. US 46, which lies entirely within New Jersey, terminates halfway across the bridge at the state border with New York. At its eastern terminus in New York City, the bridge continues onto the Trans-Manhattan Expressway (part of I-95, connecting to the Cross Bronx Expressway).

The George Washington Bridge measures 4,760 feet (1,450 m) long and has a main span of 3,500 feet (1,100 m). It had the longest main bridge span in the world at the time of its opening and held this distinction until the opening of the Golden Gate Bridge in 1937.

Golden Gate Bridge

The Golden Gate Bridge is a suspension bridge spanning the Golden Gate, the one-mile-wide (1.6 km) strait connecting San Francisco Bay and the Pacific Ocean. The structure links the American city of San Francisco, California—the northern tip of the San Francisco Peninsula—to Marin County, carrying both U.S. Route 101 and California State Route 1 across the strait. The bridge is one of the most internationally recognized symbols of San Francisco, California, and the United States. It has been declared one of the Wonders of the Modern World by the American Society of Civil Engineers.The Frommer's travel guide describes the Golden Gate Bridge as "possibly the most beautiful, certainly the most photographed, bridge in the world." At the time of its opening in 1937, it was both the longest and the tallest suspension bridge in the world, with a main span of 4,200 feet (1,280 m) and a total height of 746 feet (227 m).

London Bridge

Several bridges named London Bridge have spanned the River Thames between the City of London and Southwark, in central London. The current crossing, which opened to traffic in 1973, is a box girder bridge built from concrete and steel. It replaced a 19th-century stone-arched bridge, which in turn superseded a 600-year-old stone-built medieval structure. This was preceded by a succession of timber bridges, the first of which was built by the Roman founders of London.

The current bridge stands at the western end of the Pool of London and is positioned 30 metres (98 ft) upstream from previous alignments. The approaches to the medieval bridge were marked by the church of St Magnus-the-Martyr on the northern bank and by Southwark Cathedral on the southern shore. Until Putney Bridge opened in 1729, London Bridge was the only road-crossing of the Thames downstream of Kingston upon Thames. London Bridge has been depicted in its several forms, in art, literature, and songs, including the nursery rhyme "London Bridge Is Falling Down".

The modern bridge is owned and maintained by Bridge House Estates, an independent charity of medieval origin overseen by the City of London Corporation. It carries the A3 road, which is maintained by the Greater London Authority. The crossing also delineates an area along the southern bank of the River Thames, between London Bridge and Tower Bridge, that has been designated as a business improvement district.

Mississippi River

The Mississippi River is the second-longest river and chief river of the second-largest drainage system on the North American continent, second only to the Hudson Bay drainage system. Its source is Lake Itasca in northern Minnesota and it flows generally south for 2,320 miles (3,730 km) to the Mississippi River Delta in the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains all or parts of 32 U.S. states and two Canadian provinces between the Rocky and Appalachian mountains. The main stem is entirely within the United States; the total drainage basin is 1,151,000 sq mi (2,980,000 km2), of which only about one percent is in Canada. The Mississippi ranks as the fourth-longest and fifteenth-largest river by discharge in the world. The river either borders or passes through the states of Minnesota, Wisconsin, Iowa, Illinois, Missouri, Kentucky, Tennessee, Arkansas, Mississippi, and Louisiana.Native Americans have lived along the Mississippi River and its tributaries for thousands of years. Most were hunter-gatherers, but some, such as the Mound Builders, formed prolific agricultural societies. The arrival of Europeans in the 16th century changed the native way of life as first explorers, then settlers, ventured into the basin in increasing numbers. The river served first as a barrier, forming borders for New Spain, New France, and the early United States, and then as a vital transportation artery and communications link. In the 19th century, during the height of the ideology of manifest destiny, the Mississippi and several western tributaries, most notably the Missouri, formed pathways for the western expansion of the United States.

Formed from thick layers of the river's silt deposits, the Mississippi embayment is one of the most fertile regions of the United States; steamboats were widely used in the 19th and early 20th centuries to ship agricultural and industrial goods. During the American Civil War, the Mississippi's capture by Union forces marked a turning point towards victory, due to the river's strategic importance to the Confederate war effort. Because of substantial growth of cities and the larger ships and barges that replaced steamboats, the first decades of the 20th century saw the construction of massive engineering works such as levees, locks and dams, often built in combination. A major focus of this work has been to prevent the lower Mississippi from shifting into the channel of the Atchafalaya River and bypassing New Orleans.

Since the 20th century, the Mississippi River has also experienced major pollution and environmental problems – most notably elevated nutrient and chemical levels from agricultural runoff, the primary contributor to the Gulf of Mexico dead zone.

Nile

The Nile (Arabic: النيل‎, written as al-Nīl; pronounced as an-Nīl) is a major north-flowing river in northeastern Africa, and is the longest river in Africa and the disputed longest river in the world, as the Brazilian government claims that the Amazon River is longer than the Nile. The Nile, which is about 6,650 km (4,130 mi) long, is an "international" river as its drainage basin covers eleven countries, namely, Tanzania, Uganda, Rwanda, Burundi, the Democratic Republic of the Congo, Kenya, Ethiopia, Eritrea, South Sudan, Republic of the Sudan and Egypt. In particular, the Nile is the primary water source of Egypt and Sudan.The Nile has two major tributaries, the White Nile and Blue Nile. The White Nile is considered to be the headwaters and primary stream of the Nile itself. The Blue Nile, however, is the source of most of the water and silt. The White Nile is longer and rises in the Great Lakes region of central Africa, with the most distant source still undetermined but located in either Rwanda or Burundi. It flows north through Tanzania, Lake Victoria, Uganda and South Sudan. The Blue Nile begins at Lake Tana in Ethiopia and flows into Sudan from the southeast. The two rivers meet just north of the Sudanese capital of Khartoum.The northern section of the river flows north almost entirely through the Sudanese desert to Egypt, then ends in a large delta and flows into the Mediterranean Sea. Egyptian civilization and Sudanese kingdoms have depended on the river since ancient times. Most of the population and cities of Egypt lie along those parts of the Nile valley north of Aswan, and nearly all the cultural and historical sites of Ancient Egypt are found along river banks.

Operation Market Garden

Operation Market Garden was a failed World War II military operation fought in the Netherlands from 17 to 25 September 1944. It was the brainchild of Field Marshal Sir Bernard Law Montgomery, planned primarily by Generals Brereton and Williams of the USAAF. The airborne part of the operation was undertaken by the First Allied Airborne Army with the land operation by XXX Corps of the British Second Army. The objective was to create a 64 mi (103 km) salient into German territory with a foothold over the River Rhine, creating an Allied invasion route into northern Germany. This was to be achieved by seizing a series of nine bridges by Airborne forces with land forces swiftly following moving over the bridges. The operation succeeded in liberating the Dutch cities of Eindhoven and Nijmegen along with many towns, creating a 60 mi (97 km) salient into German-held territory limiting V-2 rocket launching sites. It failed, however, to secure a foothold over the Rhine, halting at the river.

Market Garden consisted of two sub operations:

Market - an airborne assault to seize key bridges; laying a carpet of airborne troops.

Garden - a ground attack moving over the seized bridges creating the salient.The attack was the largest airborne operation up to that point in World War II.Supreme Commander General Eisenhower's strategic goal was to encircle the heart of German industry, the Ruhr Area, in a pincer movement. The northern end of the pincer would circumvent the northern end of the Siegfried Line, giving easier access into Germany across the north German plains enabling mobile warfare. The prime aim of Operation Market Garden was to establish the northern end of a pincer ready to project deeper into Germany. Allied forces would project north from Belgium, 60 miles (97 km) through the Netherlands, across the Rhine and consolidate north of Arnhem on the Dutch/German border, ready to close the pincer.The operation made massive use of airborne forces, whose tactical objectives were to secure the bridges and to allow a rapid advance by armored ground units to consolidate north of Arnhem. The operation required the seizure of the bridges by airborne troops across the Meuse River, two arms of the Rhine (the Waal River and the Lower Rhine), together with crossings over several smaller canals and tributaries. However, this large airborne force contrasted with the ground forces being light with only one corps moving north of Eindhoven, XXX Corps. XXX Corps took along 5,000 vehicles full of bridging equipment and 9,000 sappers.The Allies captured several bridges between Eindhoven and Nijmegen at the beginning of the operation. Lieutenant-General Brian Horrocks' XXX Corps ground force advance was delayed by the initial failure of the airborne units to secure bridges at Son en Breugel and Nijmegen. German forces demolished the bridge over the Wilhelmina Canal at Son before it could be captured by the US 101st Airborne Division, although a Bailey bridge was then built over the canal by British sappers. This delayed XXX Corps' advance by 12 hours, however they made up the time, reaching Nijmegen on schedule. The US 82nd Airborne Division's failure to capture the main highway bridge over the Waal River at Nijmegen before 20 September delayed the advance by 36 hours. XXX Corps had to seize the bridge themselves instead of speeding over a captured bridge onwards to Arnhem, where the British paratroopers were still holding the north end of the bridge.At the northern point of the airborne operation, the British 1st Airborne Division initially encountered strong resistance. The delays in capturing the bridge at Nijmegen and constructing a Bailey bridge at Son gave time for German forces (the 9th SS panzer infantry and 10th SS panzer infantry Divisions, which were in the Arnhem area at the start of the jump) to organise their counterattack. A small British force managed to capture the north end of the Arnhem road bridge, denying use of the intact bridge to German forces. After the ground forces failed to relieve the paratroopers on time, they were overrun on 21 September. At the same time that XXX Corps' tanks moved over the Nijmegen bridge, 36 hours late, after seizing it from the Germans, the British paratroopers at the Arnhem bridge were capitulating, unable to hold on any longer. The remainder of the British 1st Airborne Division was trapped in a small pocket west of the Arnhem bridge, which was evacuated on 25 September after sustaining heavy casualties.

The Allies had failed to cross the Rhine. The river remained a barrier to their advance into Germany until offensives at Remagen, Oppenheim, Rees and Wesel in March 1945. The failure of Operation Market Garden to form a foothold over the Rhine ended Allied hopes of finishing the war by Christmas 1944.

River Thames

The River Thames ( (listen) TEMZ), known alternatively in parts as the Isis, is a river that flows through southern England including London. At 215 miles (346 km), it is the longest river entirely in England and the second-longest in the United Kingdom, after the River Severn.

It flows through Oxford (where it is called the Isis), Reading, Henley-on-Thames and Windsor. The lower reaches of the river are called the Tideway, derived from its long tidal reach up to Teddington Lock. It rises at Thames Head in Gloucestershire, and flows into the North Sea via the Thames Estuary. The Thames drains the whole of Greater London.Its tidal section, reaching up to Teddington Lock, includes most of its London stretch and has a rise and fall of 23 feet (7 m). Running through some of the driest parts of mainland Britain and heavily abstracted for drinking water, the Thames' discharge is low considering its length and breadth: the Severn has a discharge almost twice as large on average despite having a smaller drainage basin. In Scotland, the Tay achieves more than double the Thames' average discharge from a drainage basin that is 60% smaller.

Along its course are 45 navigation locks with accompanying weirs. Its catchment area covers a large part of south-eastern and a small part of western England; the river is fed by at least 50 named tributaries. The river contains over 80 islands. With its waters varying from freshwater to almost seawater, the Thames supports a variety of wildlife and has a number of adjoining Sites of Special Scientific Interest, with the largest being in the remaining parts of the North Kent Marshes and covering 5,449 hectares (13,460 acres).

San Francisco–Oakland Bay Bridge

The San Francisco–Oakland Bay Bridge, known locally as the Bay Bridge or as the Emperor Norton Bridge, is a complex of bridges spanning San Francisco Bay in California. As part of Interstate 80 and the direct road between San Francisco and Oakland, it carries about 260,000 vehicles a day on its two decks. It has one of the longest spans in the United States.

The toll bridge was conceived as early as the gold rush days, but construction did not begin until 1933. Designed by Charles H. Purcell, and built by American Bridge Company, it opened on November 12, 1936, six months before the Golden Gate Bridge. It originally carried automobile traffic on its upper deck, and trucks and commuter trains on the lower, but after the Key System abandoned rail service, the lower deck was converted to all-road traffic as well. In 1986 the bridge was unofficially dedicated to James Rolph.The bridge has two sections of roughly equal length; the older western section, officially known as the Willie L. Brown Jr. Bridge (after former San Francisco Mayor and California State Assembly Speaker Willie L. Brown Jr.), connects downtown San Francisco to Yerba Buena Island, and the newer unnamed eastern section connects the island to Oakland. The western section is a double suspension bridge with two decks, westbound traffic being carried on the upper deck while eastbound is carried on the lower one. The largest span of the original eastern section was a cantilever bridge. During the 1989 Loma Prieta earthquake, a portion of the eastern section's upper deck collapsed onto the lower deck and the bridge was closed for a month. Reconstruction of the eastern section of the bridge as a causeway connected to a self-anchored suspension bridge began in 2002; the new eastern section opened September 2, 2013, at a reported cost of over $6.5 billion, a 2,500% cost overrun from the original estimate of $250 million. Unlike the western section and the original eastern section of the bridge, the new eastern section is a single deck with the eastbound and westbound lanes on each side making it the world's widest bridge, according to Guinness World Records, as of 2014. Demolition of the old east span was completed on September 8, 2018.

Stamford Bridge (stadium)

Stamford Bridge () is a football stadium in Fulham, adjacent to the borough of Chelsea in South West London, commonly referred to as The Bridge. It is the home of Chelsea Football Club, which competes in the Premier League.

The capacity of the stadium is 40,834, making it the ninth largest venue of the 2019–20 Premier League season. The club has plans to expand capacity to 63,000 by the 2023–24 season. When expansion starts, Chelsea intend to play at Wembley Stadium until they return in 2024.Opened in 1877, the stadium was used by the London Athletic Club until 1905, when new owner Gus Mears founded Chelsea Football Club to occupy the ground; Chelsea have played their home games there ever since. It has undergone major changes over the years, most recently in the 1990s when it was renovated into a modern, all-seater stadium.

Stamford Bridge has been a venue for England international matches, FA Cup Finals, FA Cup semi-finals and Charity Shield games. It has also hosted numerous other sports, such as cricket, rugby union, speedway, greyhound racing, baseball and American football. The stadium's highest official attendance is 82,905, for a league match between Chelsea and Arsenal on 12 October 1935.

Sydney Harbour Bridge

The Sydney Harbour Bridge is a heritage-listed steel through arch bridge across Sydney Harbour that carries rail, vehicular, bicycle, and pedestrian traffic between the Sydney central business district (CBD) and the North Shore. The dramatic view of the bridge, the harbour, and the nearby Sydney Opera House is an iconic image of Sydney, and Australia itself. The bridge is nicknamed "The Coathanger" because of its arch-based design.Under the direction of Dr John Bradfield of the NSW Department of Public Works, the bridge was designed and built by British firm Dorman Long and Co Ltd of Middlesbrough and opened in 1932. The bridge's design was influenced by the Hell Gate Bridge in New York City. It is the sixth longest spanning-arch bridge in the world and the tallest steel arch bridge, measuring 134 m (440 ft) from top to water level. It was also the world's widest long-span bridge, at 48.8 m (160 ft) wide, until construction of the new Port Mann Bridge in Vancouver was completed in 2012.The Sydney Harbour Bridge was added to the Australian National Heritage List on 19 March 2007 and to the New South Wales State Heritage Register on 25 June 1999.

The Bridge on the River Kwai

The Bridge on the River Kwai is a 1957 British-American epic war film directed by David Lean and based on the novel Le Pont de la Rivière Kwaï (1952) by Pierre Boulle. The film uses the historical setting of the construction of the Burma Railway in 1942–1943. The cast included William Holden, Jack Hawkins, Alec Guinness, and Sessue Hayakawa.

It was initially scripted by screenwriter Carl Foreman, who was later replaced by Michael Wilson. Both writers had to work in secret, as they were on the Hollywood blacklist and had fled to the UK in order to continue working. As a result, Boulle, who did not speak English, was credited and received the Academy Award for Best Adapted Screenplay; many years later, Foreman and Wilson posthumously received the Academy Award.The film was widely praised, winning seven Academy Awards (including Best Picture) at the 30th Academy Awards. In 1997, the film was deemed "culturally, historically, or aesthetically significant" and selected for preservation in the National Film Registry by the United States Library of Congress. It has been included on the American Film Institute's list of best American films ever made. In 1999, the British Film Institute voted The Bridge on the River Kwai the 11th greatest British film of the 20th century.

The Shard

The Shard, also referred to as the Shard of Glass, Shard London Bridge and formerly London Bridge Tower, is a 95-storey supertall skyscraper, designed by the Italian architect Renzo Piano, in Southwark, London, that forms part of the Shard Quarter development. Standing 309.6 metres (1,016 ft) high, the Shard is the tallest building in the United Kingdom, the tallest building in the European Union, and the sixth-tallest building in Europe. It is also the second-tallest free-standing structure in the United Kingdom, after the concrete tower of the Emley Moor transmitting station. It replaced Southwark Towers, a 24-storey office block built on the site in 1975.

The Shard's construction began in March 2009; it was topped out on 30 March 2012 and inaugurated on 5 July 2012. Practical completion was achieved in November 2012. The tower's privately operated observation deck, The View from The Shard, was opened to the public on 1 February 2013. The glass-clad pyramidal tower has 72 habitable floors, with a viewing gallery and open-air observation deck on the 72nd floor, at a height of 244 metres (801 ft). The Shard was developed by Sellar Property Group on behalf of LBQ Ltd and is jointly owned by Sellar Property (5%) and the State of Qatar (95%). The Shard is managed by Real Estate Management (UK) Limited on behalf of the owners.

Tower Bridge

Tower Bridge is a combined bascule and suspension bridge in London, built between 1886 and 1894. The bridge crosses the River Thames close to the Tower of London and has become an iconic symbol of London. Because of this, Tower Bridge is sometimes confused with London Bridge, situated some 0.5 mi (0.80 km) upstream. Tower Bridge is one of five London bridges now owned and maintained by the Bridge House Estates, a charitable trust overseen by the City of London Corporation. It is the only one of the Trust's bridges not to connect the City of London directly to the Southwark bank, as its northern landfall is in Tower Hamlets.

The bridge consists of two bridge towers tied together at the upper level by two horizontal walkways, designed to withstand the horizontal tension forces exerted by the suspended sections of the bridge on the landward sides of the towers. The vertical components of the forces in the suspended sections and the vertical reactions of the two walkways are carried by the two robust towers. The bascule pivots and operating machinery are housed in the base of each tower. Before its restoration in the 2010s, the bridge's colour scheme dated from 1977, when it was painted red, white and blue for Queen Elizabeth II's Silver Jubilee. Its colours were subsequently restored to blue and white.The bridge deck is freely accessible to both vehicles and pedestrians, whereas the bridge's twin towers, high-level walkways and Victorian engine rooms form part of the Tower Bridge Exhibition, for which an admission charge is made. The nearest London Underground tube stations are Tower Hill on the Circle and District lines, London Bridge on the Jubilee and Northern lines and Bermondsey on the Jubilee line, and the nearest Docklands Light Railway station is Tower Gateway. The nearest National Rail stations are at Fenchurch Street and London Bridge.

Truss bridge

A truss bridge is a bridge whose load-bearing superstructure is composed of a truss, a structure of connected elements usually forming triangular units. The connected elements (typically straight) may be stressed from tension, compression, or sometimes both in response to dynamic loads. The basic types of truss bridges shown in this article have simple designs which could be easily analyzed by 19th and early 20th-century engineers. A truss bridge is economical to construct because it uses materials efficiently.

Wormhole

A wormhole (or Einstein–Rosen bridge) is a speculative structure linking disparate points in spacetime, and is based on a special solution of the Einstein field equations solved using a Jacobian matrix and determinant. A wormhole can be visualized as a tunnel with two ends, each at separate points in spacetime (i.e., different locations or different points of time). More precisely it is a transcendental bijection of the spacetime continuum, an asymptotic projection of the Calabi–Yau manifold manifesting itself in Anti-de Sitter space.

Wormholes are consistent with the general theory of relativity, but whether wormholes actually exist remains to be seen. Many scientists postulate wormholes are merely a projection of the 5th dimension, analogous to how a 2D being could only experience part of a 3D object.A wormhole could connect extremely long distances such as a billion light years or more, short distances such as a few meters, different universes, or different points in time.

Structural types
Lists of bridges by type
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