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Bridge

The Akashi-Kaikyō Bridge in Japan, the world's longest suspension span.

The Si-o-se Pol bridge over Zayandeh River is the epitome of Safavid dynasty(1502–1722) bridge design. Esfahan, Iran

A bridge is a structure built to spanphysical obstacles such as a body ofwater, valley, or road, for the purposeof providing passage over the obstacle.Designs of bridges vary depending onthe function of the bridge, the nature ofthe terrain where the bridge isconstructed, the material used to makeit and the funds available to build it.

Etymology

The Oxford English Dictionary tracesthe origin of the word bridge to an OldEnglish word brycg, of the samemeaning, derived from a hypotheticalProto-Germanic root brugjō. There arecognates in other Germanic languages.

History

Bamboo bridge over the Serayu River in Java, Indonesia (ca.1910-40)

The first bridges were made by nature itself — as simple as alog fallen across a stream or stones in the river. The firstbridges made by humans were probably spans of cut woodenlogs or planks and eventually stones, using a simple supportand crossbeam arrangement. Some early Americans usedtrees or bamboo poles to cross small caverns or wells to getfrom one place to another. A common form of lashing sticks,logs, and deciduous branches together involved the use oflong reeds or other harvested fibers woven together to form aconnective rope capable of binding and holding together thematerials used in early bridges.

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The Arkadiko Bridge in Greece (13th century BC), oneof the oldest arch bridges in existence

An English 18th century example of a bridge in thePalladian style, with shops on the span: Pulteney

Bridge, Bath

Roman bridge of Córdoba, Spain, built in the 1st centuryBC.[1]

The Arkadiko Bridge is one of four Mycenaean corbel archbridges part of a former network of roads, designed toaccommodate chariots, between Tiryns to Epidauros in thePeloponnese, in Greece. Dating to the Greek Bronze Age(13th century BC), it is one of the oldest arch bridges still inexistence and use. Several intact arched stone bridges fromthe Hellenistic era can be found in the Peloponnese insouthern Greece[2]

The greatest bridge builders of antiquity were the ancientRomans.[3] The Romans built arch bridges and aqueductsthat could stand in conditions that would damage or destroyearlier designs. Some stand today.[4] An example is theAlcántara Bridge, built over the river Tagus, in Spain. TheRomans also used cement, which reduced the variation ofstrength found in natural stone.[5] One type of cement, calledpozzolana, consisted of water, lime, sand, and volcanic rock.Brick and mortar bridges were built after the Roman era, asthe technology for cement was lost then later rediscovered.

The Arthashastra of Kautilya mentions the construction ofdams and bridges.[6] A Mauryan bridge near Girnar wassurveyed by James Princep.[7] The bridge was swept awayduring a flood, and later repaired by Puspagupta, the chiefarchitect of emperor Chandragupta I.[7] The bridge also fellunder the care of the Yavana Tushaspa, and the Satrap RudraDaman.[7] The use of stronger bridges using plaited bambooand iron chain was visible in India by about the 4thcentury.[8] A number of bridges, both for military andcommercial purposes, were constructed by the Mughaladministration in India.[9]

Although large Chinese bridges of wooden constructionexisted at the time of the Warring States, the oldest survivingstone bridge in China is the Zhaozhou Bridge, built from 595to 605 AD during the Sui Dynasty. This bridge is alsohistorically significant as it is the world's oldestopen-spandrel stone segmental arch bridge. Europeansegmental arch bridges date back to at least the AlconétarBridge (approximately 2nd century AD), while the enormousRoman era Trajan's Bridge (105 AD) featured open-spandrelsegmental arches in wooden construction.

Rope bridges, a simple type of suspension bridge, were usedby the Inca civilization in the Andes mountains of SouthAmerica, just prior to European colonization in the 16thcentury.

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A log bridge in the French Alps near Vallorcine.

A Han Dynasty (202 BC – 220 AD) Chinese miniature modelof two residential towers joined by a bridge

One of the most famous historical bridges in the world: PonteVecchio

During the 18th century there were many innovations in thedesign of timber bridges by Hans Ulrich, JohannesGrubenmann, and others. The first book on bridgeengineering was written by Hubert Gautier in 1716. A majorbreakthrough in bridge technology came with the erection ofthe Iron Bridge in Coalbrookdale, England in 1779. It usedcast iron for the first time as arches to cross the river Severn.

With the Industrial Revolution in the 19th century, trusssystems of wrought iron were developed for larger bridges,but iron did not have the tensile strength to support largeloads. With the advent of steel, which has a high tensilestrength, much larger bridges were built, many using theideas of Gustave Eiffel.

In 1927 welding pioneer Stefan Bryła designed the firstwelded road bridge in the world, which was later built acrossthe river Słudwia Maurzyce near Łowicz, Poland in 1929. In1995, the American Welding Society presented the HistoricWelded Structure Award for the bridge to Poland.[10]

Types of bridges

There are six main types of bridges: beam bridges, cantileverbridges, arch bridges, suspension bridges, cable-stayedbridges and truss bridges.

Beam bridges

Beam bridges are horizontal beams supported at each end byabutments, hence their structural name of simply supported.When there is more than one span the intermediate supportsare known as piers. The earliest beam bridges were simplelogs that sat across streams and similar simple structures. Inmodern times, beam bridges are large box steel girderbridges. Weight on top of the beam pushes straight down onthe abutments at either end of the bridge.[11] They are madeup mostly of wood or metal. Beam bridge spans typically donot exceed 250 feet (76 m) long, as the strength of a spandecreases with increased length. However, the main span of the Rio-Niteroi Bridge, a box girder bridge, is 300metres (980 ft). The world's longest beam bridge is Lake Pontchartrain Causeway in southern Louisiana in theUnited States, at 23.83 miles (38.35 km), with individual spans of 56 feet (17 m).[12]

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Lomonosov Bridge in St. Petersburg

Stone arch bridge in Shaharah, Yemen

Primitive suspension bridge over the River Astore

Cantilever bridges

Cantilever bridges are built using cantilevers—horizontalbeams supported on only one end. Most cantilever bridgesuse a pair of continuous spans that extend from oppositesides of the supporting piers to meet at the center of theobstacle the bridge crosses. Cantilever bridges areconstructed using much the same materials & techniques asbeam bridges. The difference comes in the action of theforces through the bridge. The largest cantilever bridge is the549-metre (1801 ft) Quebec Bridge in Quebec, Canada.

Arch bridges

Arch bridges have abutments at each end. The weight of thebridge is thrust into the abutments at either side. The earliestknown arch bridges were built by the Greeks, and include theArkadiko Bridge.

With the span of 220 metres (720 ft), the Solkan Bridge overthe Soča River at Solkan in Slovenia is the second largeststone bridge in the world and the longest railroad stonebridge. It was completed in 1905. Its arch, which wasconstructed from over 5000 tonnes (4900 long tons; 5500short tons) of stone blocks in just 18 days, is the secondlargest stone arch in the world, surpassed only by theFriedensbrücke (Syratalviadukt) in Plauen, and the largestrailroad stone arch. The arch of the Friedensbrücke, whichwas built in the same year, has the span of 90 m (300 ft) andcrosses the valley of the Syrabach River. The differencebetween the two is that the Solkan Bridge was built fromstone blocks, whereas the Friedensbrücke was built from amixture of crushed stone and cement mortar.[13]

Dubai in the United Arab Emirates is currently building theSheikh Rashid bin Saeed Crossing, which is scheduled forcompletion in 2012. When completed, it will be the largestarch bridge in the world.[14]

Tied arch bridges

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

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Continuous under-deck truss bridge

Over-deck truss bridge with steel girders and woodencarriageway

"Metrobridge" Vorobyovy Gory (ru:Метромост) double-deckbridge in Moscow carries the Moscow Metro

Suspension bridges

Suspension bridges are suspended from cables. The earliestsuspension bridges were made of ropes or vines covered withpieces of bamboo. In modern bridges, the cables hang fromtowers that are attached to caissons or cofferdams. Thecaissons or cofferdams are implanted deep into the floor of alake or river. The longest suspension bridge in the world isthe 12826 feet (3909 m) Akashi Kaikyo Bridge in Japan.[15]

See simple suspension bridge, stressed ribbon bridge,underspanned suspension bridge, suspended-deck suspensionbridge, and self-anchored suspension bridge.

Cable-stayed bridges

Cable-stayed bridges, like suspension bridges, are held up bycables. However, in a cable-stayed bridge, less cable isrequired and the towers holding the cables areproportionately shorter.[16] The first known cable-stayedbridge was designed in 1784 by C.T. Loescher.[17] Thelongest cable-stayed bridge is the Sutong Bridge over theYangtze River in China.

Movable bridges

Movable bridges are designed to move out of the way ofboats or other kinds of traffic, which would otherwise be tootall 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 tworoad levels. Tsing Ma Bridge and Kap Shui Mun Bridge inHong Kong have six lanes on their upper decks, and on theirlower decks there are two lanes and a pair of tracks for MTRmetro trains. Some double-decker bridges only use one levelfor street traffic; the Washington Avenue Bridge inMinneapolis reserves its lower level for automobile trafficand 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 itsupper deck; and a pair of tracks for the Bloor–Danforth subway line on its lower deck.

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Old Bridge in Mostar, Bosnia and Herzegovina

Mehmed Paša Sokolović Bridge in Višegrad, Bosnia andHerzegovina

Robert Stephenson's High Level Bridge across the RiverTyne in Newcastle upon Tyne, completed in 1849, is an earlyexample of a double-deck bridge. The upper level carries arailway, and the lower level is used for road traffic. Otherexamples include Britannia Bridge over the Menai Strait andCraigavon Bridge in Derry, Northern Ireland. The OresundBridge between Copenhagen and Malmö consists of afour-lane highway on the upper level and a pair of railwaytracks at the lower level.

The George Washington Bridge between New Jersey andNew York has two roadway levels. It was built with only theupper roadway as traffic demands did not require morecapacity. A truss work between the roadway levels providesstiffness to the roadways and reduced movement of the upperlevel when installed. Tower Bridge is different example of adouble-decker bridge, with the central section consisting of alow level bascule span and a high level footbridge.

Old Yamuna Bridge (Delhi) or Bridge No. 249 in technicalrailway parlance, was constructed in 1866 by the East IndiaRailway at a cost of £16,16,335. It was built with a totallength of 2640 feet (800 m) and consisted of 12 spans of202.5 feet (61.7 m) each. With the completion of this bridge,two principal cities of North India, Kolkata and Delhi, wereconnected by the railways; this being the last link of thetrunk line on this route. In 1913, this was converted into adouble line by adding down line girders of 12 spans of 202feet (62 m) each and 2 end spans of 42 feet (13 m) to the bridge. For the movement of road traffic, two road bridgeswere provided below the lines. The entry of trains into Delhi Junction Railway station, in such close proximity to theRed Fort, never ceases to impress the rail traveler, reminding all that after the Uprising of 1857, Delhi was a fortifiedcity. The old Yamuna Bridge has an identical twin, a bridge further downstream at Naini on the Allahabad —Mughalsarai 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 is a bridge that carries water, resembling a viaduct, which is a bridge that connects points of equalheight. 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 sheltersand homes to homeless people, and the undersides of bridges all around the world are spots of prevalent graffiti.Some bridges attract people attempting suicide, and become known as suicide bridges.

To create a beautiful image, some bridges are built much taller than necessary. This type, often found in east-Asianstyle gardens, is called a Moon bridge, evoking a rising full moon. Other garden bridges may cross only a dry bed ofstream washed pebbles, intended only to convey an impression of a stream. Often in palaces a bridge will be builtover an artificial waterway as symbolic of a passage to an important place or state of mind. A set of five bridgescross a sinuous waterway in an important courtyard of the Forbidden City in Beijing, China. The central bridge wasreserved exclusively for the use of the Emperor, Empress, and their attendants.

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

EfficiencyA bridge's structural efficiency is the ratio of load carried to bridge mass, given a specific set of material types. Inone common challenge students are divided into groups and given a quantity of wood sticks, a distance to span, andglue, and then asked to construct a bridge that will be tested to destruction by the progressive addition of load at thecenter of the span. The bridge taking the greatest load is by this test the most structurally efficient. A more refinedmeasure for this exercise is to weigh the completed bridge rather than measure against a fixed quantity of materialsprovided and determine the multiple of this weight that the bridge can carry, a test that emphasizes economy ofmaterials and efficient glue joints (see balsa wood bridge).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 andassociated disposal, recycling, and replacement, less the value of scrap and reuse of components. Bridges employingonly compression are relatively inefficient structurally, but may be highly cost efficient where suitable materials areavailable near the site and the cost of labor is low. For medium spans, trusses or box beams are usually mosteconomical, while in some cases, the appearance of the bridge may be more important than its cost efficiency. Thelongest spans usually require suspension bridges.

Juscelino Kubitschek bridge in Brasília, Brazil

Other functions

Some bridges accommodate otherpurposes, such as the tower of NovýMost bridge in Bratislava, whichfeatures a restaurant. Other suspensionbridge towers carry transmissionantennas.

A bridge can carry overhead powerlines as does the Storstrøm Bridge.

Costs and cost overruns frequentlyoccur in bridge construction. Flyvbjerg et al. (2003) found the average cost overrun in bridge building is 34%.[18]

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

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Bridge failuresThe 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 whenmany new designs were being built, often using new materials.In the United States, the National Bridge Inventory tracks the structural evaluations of all bridges, includingdesignation as "structurally deficient" and "functionally obsolete".

Bridge monitoringThere are several methods to monitor the stress on large structures like bridges. The most common method is the useof accelerometer, which are integrated into the bridge while it is build. This technology is used for long-termsurveillance of the bridge.[19]

Another option for structural health monitoring is non-contact which uses the Doppler effect (Doppler shift). A laserbeam from a Laser Doppler Vibrometer is directed at the point of interest, and the vibration amplitude and frequencyare extracted from the Doppler shift of the laser beam frequency due to the motion of the surface.[20] The advantageof this method is that the setup for the equipment is faster and unlike accelerometer this makes measurements onmultiple structures in a short time possible, also this method can measure specific points on a bridge that might bedifficult to access.

ReferencesNotes[1] "Roman Bridge in Cordoba ( 1st century B.C.)" (http:/ / en. structurae. de/ structures/ data/ index. cfm?id=s0001269) (in (German)).

En.structurae.de. . Retrieved 2012-01-04.[2] T.H. Nielsen and J. Roy. Defining ancient Arkadia: symposium April 1–4, 1998. Kgl. Danske Videnskabernes Selska, 1998. p. 253. (http:/ /

books. google. com/ books?id=Aa9IFGkrhi8C& pg=PA253& dq=Hellenistic+ Bridge+ Xerokampi& ei=96aQS9L2FaSclQT5m6SpDQ&cd=2#v=onepage& q=Hellenistic Bridge Xerokampi& f=false)

[3] "Context for World Heritage Bridges" (http:/ / www. icomos. org/ studies/ bridges. htm). Icomos.org. 1941-07-01. . Retrieved 2012-01-04.[4] "History of BRIDGES" (http:/ / www. historyworld. net/ wrldhis/ PlainTextHistories. asp?historyid=ab97). Historyworld.net. . Retrieved

2012-01-04.[5] "Lessons from Roman Cement and Concrete" (http:/ / www. pubs. asce. org/ WWWdisplay. cgi?0103045). Pubs.asce.org. . Retrieved

2012-01-04.[6][6] Dikshitar, pg. 332[7][7] Dutt, pg 46[8][8] "suspension bridge" in Encyclopædia Britannica (2008). 2008 Encyclopædia Britannica, Inc.[9][9] Nath, pg. 213[10] Sapp, Mark E. (February 22, 2008). "Welding Timeline 1900-1950" (http:/ / www. weldinghistory. org/ whistoryfolder/ welding/

wh_1900-1950. html). WeldingHistory.org. . Retrieved 2008-04-29.[11] "Beam bridges" (http:/ / www. design-technology. org/ beambridges. htm). Design Technology. . Retrieved 2008-05-14.[12] "A big prefabricated bridge". Life 40 (22): 53–60. 28 May 1956.[13] Gorazd Humar (September 2001). "World Famous Arch Bridges in Slovenia" (http:/ / books. google. com/ books?id=E7ywmb24EQMC&

lpg=PA121& dq="world famous arch bridges in slovenia"& pg=PA121#v=onepage& q="world famous arch bridges in slovenia"& f=false).In Charles Abdunur (in English, French). Arch'01: troisième Conférence internationale sur les ponts en arc Paris:. Paris: Presses des Ponts.pp. 121-124. ISBN 2-85978-347-4. .

[14] Glass, Amy. "Dubai to build world's longest arch bridge" (http:/ / www. arabianbusiness. com/509621-worlds-longest-arch-bridge-for-dubai?ln=en). Arabian Business. . Retrieved 2008-05-14.

[15] Sigmund, Pete (2007-02-07). "The Mighty Mac: A Sublime Engineering Feat" (http:/ / www. constructionequipmentguide. com/ story.asp?story=8153& headline=The Mighty Mac: A Sublime Engineering Feat). Construction Equipment Guide. . Retrieved 2008-05-14.

[16] Johnson, Andy. "Cable Stay vs Suspension Bridges" (http:/ / www. newton. dep. anl. gov/ askasci/ eng99/ eng99373. htm). U.S. Departmentof Energy. .

[17] "Bridges" (http:/ / www. nyc. gov/ html/ dot/ html/ bridges/ bridges. shtml). NYCDOT. . Retrieved 2008-05-14.[18] "Flyvbjerg, Bent, Nils Bruzelius, and Werner Rothengatter, 2003. ''Megaprojects and Risk: An Anatomy of Ambition'' (Cambridge:

Cambridge University Press)" (http:/ / books. google. com/ books?vid=ISBN0521009464& id=RAV5P-50UjEC& printsec=frontcover&dq=megaprojects+ and+ Risk:+ An+ Anatomy+ of+ Ambition). Books.google.com. . Retrieved 2012-01-04.

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[19] "The new Minnesota smart bridge" (http:/ / www. mnme. com/ pdf/ smartbridge. pdf). . Retrieved 2012-01-30.[20] "Basic Principles of Vibrometry" (http:/ / http:/ / www. polytec. com/ us/ solutions/ vibration-measurement/ basic-principles-of-vibrometry/

). . Retrieved 2012-01-25.

Bibliography• 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.)

• Dikshitar, V. R. R. Dikshitar (1993). The Mauryan Polity. Motilal Banarsidass. ISBN 81-208-1023-6.• Dutt, Romesh Chunder (2000). A History of Civilisation in Ancient India: Vol II. Routledge. ISBN

0-415-23188-4.• Nath, R. (1982). History of Mughal Architecture. Abhinav Publications. ISBN 81-7017-159-8.• Kinney, A. R.; el al. (2003). Worshiping Siva and Buddha: The Temple Art of East Java. University of Hawaii

Press. ISBN 0-8248-2779-1.• Buck, William; el al. (2000). Ramayana. University of California Press. ISBN 0-520-22703-4

External links• Digital Bridge: Bridges of the Nineteenth Century (http:/ / bridges. lib. lehigh. edu/ ), a collection of digitized

books at Lehigh University• Structurae (http:/ / en. structurae. de/ ) - International Database and Gallery of Engineerings Structures with over

10000 Bridges.• U.S. Federal Highway Administration Bridge Technology (http:/ / www. fhwa. dot. gov/ bridge/ )• Bridge enthusiast site (http:/ / www. nireland. com/ bridgeman/ index. htm)• Video on how bridges are made (http:/ / www. webcastgroup. com/ client/ start. asp?wid=0670524062530)

(Grade school level educational film by National Association of Manufactures.)• The Museum of Japanese Timber Bridges (http:/ / tbl. tec. fukuoka-u. ac. jp/ index-en. shtml) Fukuoka University• "en.Broer.no": site for bridges (http:/ / www. en. broer. no)• (http:/ / www. cnngo. com/ explorations/ none/ 24-worlds-most-amazing-bridges-062644) (CNN) 24 of the

World's Most Amazing Bridges -retrieved 30 Apr 2011• Amazing footage of strangler figs made into "living bridges." (http:/ / www. youtube. com/

watch?v=apBO9pujP5E)

Article Sources and Contributors 10

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Image Sources, Licenses and ContributorsImage:Akashi-kaikyo bridge3.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Akashi-kaikyo_bridge3.jpg  License: GNU Free Documentation License  Contributors: Originaluploader was Sam at en.wikipediaImage:Sio se pol.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Sio_se_pol.jpg  License: Creative Commons Attribution-Sharealike 2.5  Contributors: Alexander.stohr, Shahab.mg,2 anonymous editsFile:COLLECTIE TROPENMUSEUM Brug van bamboe over de Kali Serayu bij Wonosobo TMnr 10026487.jpg  Source:http://en.wikipedia.org/w/index.php?title=File:COLLECTIE_TROPENMUSEUM_Brug_van_bamboe_over_de_Kali_Serayu_bij_Wonosobo_TMnr_10026487.jpg  License: unknown Contributors: Docu, Elekhh, HumboldtFile:Pont mycénien de Kazarma 2.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Pont_mycénien_de_Kazarma_2.jpg  License: Creative Commons Attribution-ShareAlike 3.0Unported  Contributors: PtyxImage:Pulteney Bridge, Bath 2.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Pulteney_Bridge,_Bath_2.jpg  License: Creative Commons Attribution-Sharealike 2.5  Contributors:MichaelMaggsImage:Puente Romano Panoramica 1.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Puente_Romano_Panoramica_1.jpg  License: GNU Free Documentation License Contributors: HamerykoImage:Vallorcine footpath bridge 2003-12-13.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Vallorcine_footpath_bridge_2003-12-13.jpg  License: GNU Free DocumentationLicense  Contributors: Klaus with K, Man vyi, Olivier2, Snommoc, TCY, ThryduulfImage:Pottery tower 6.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Pottery_tower_6.JPG  License: Creative Commons Attribution-Share Alike  Contributors: Gary Lee ToddFile:Ponte Vecchio.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Ponte_Vecchio.jpg  License: Creative Commons Attribution 3.0  Contributors: Mfiskum. Marius Fiskum.www.fototopia.noFile:Sankt Petersburg 2005 i.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Sankt_Petersburg_2005_i.jpg  License: GNU Free Documentation License  Contributors: User:HeidasImage:Shehara 02.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Shehara_02.jpg  License: Creative Commons Attribution-Sharealike 3.0,2.5,2.0,1.0  Contributors: Bernard Gagnon

Image Sources, Licenses and Contributors 11

Image:Bridge Astore.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Bridge_Astore.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors: ShakeelgilgityImage:Kingston-Rhinecliff Bridge2.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Kingston-Rhinecliff_Bridge2.JPG  License: Creative Commons Attribution-Sharealike 3.0 Contributors: David Hermeyer and SamFile:Elbbrücke1990Tangermünde.png  Source: http://en.wikipedia.org/w/index.php?title=File:Elbbrücke1990Tangermünde.png  License: Creative Commons Attribution 3.0  Contributors:UlammImage:Vorobyovy Gory metro station in Moscow (09-05-2006 at night).jpg  Source:http://en.wikipedia.org/w/index.php?title=File:Vorobyovy_Gory_metro_station_in_Moscow_(09-05-2006_at_night).jpg  License: GNU Free Documentation License  Contributors: Serguei S.DukachevImage:Stari Most22.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Stari_Most22.jpg  License: Creative Commons Attribution-Sharealike 2.5  Contributors: Apalsola, Mhare,Ronaldino, 1 anonymous editsImage:Visegrad Drina Bridge 1.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Visegrad_Drina_Bridge_1.jpg  License: Creative Commons Attribution-ShareAlike 3.0 Unported Contributors: Julian NitzscheImage:BSB Ponte JK Panorama 05 2007 266.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:BSB_Ponte_JK_Panorama_05_2007_266.jpg  License: Public Domain  Contributors:Mario Roberto Duran Ortiz

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