View source for Bridge

{{Short description|Structure built to span physical obstacles}}
{{good article}}
{{about|the structure|the card game|Contract bridge|other uses|Bridge (disambiguation)|and|Bridges (disambiguation)}}
{{Use dmy dates|date=August 2024}}
{{Use American English|date=August 2025}}
{{Bridge sidebar}}
 
A '''bridge''' is a [[Structure#Load-bearing|structure]] that crosses an obstacle such as a river, lake, railroad, road, or ravine. Its primary function  is to [[transportation|transport]] vehicles, trains, and pedestrians, but bridges may also accommodate pipelines, buildings, wildlife, and canals. [[List of bridge types|Bridge styles]] include [[Arch bridge|arch]], [[Truss bridge|truss]], [[Beam bridge|beam]], [[Cantilever bridge|cantilever]], [[Suspension bridge|suspension]], and [[Cable-stayed bridge|cable-stayed]]. Less common types are [[movable bridge|movable]], double-deck, [[pontoon bridges|pontoon]], and [[military bridges]]. They may also be categorized by their materials, which include wood, brick, stone, iron, steel, and concrete.  

The history of bridges reflects the evolution of humankind's engineering technologies.  The [[Roman Empire|Romans]] and [[History_of_China#Ancient_China|ancient Chinese]] built major bridges of stone and timber. During the [[Renaissance]], advances in science and engineering led to wider bridge spans and more elegant designs. [[Concrete]] was perfected in the early 1800s, and proved to be superior to stone in many regards.  With the [[Industrial Revolution]] came mass-produced steel, which revolutionized bridge design and enabled the creation of  [[suspension bridge|suspension]] and [[cable-stayed bridge]]s that spanned wide obstacles.

The design of a bridge must satisfy many requirements, such as connecting to a transportation network, providing adequate [[Clearance (civil engineering)#Vertical clearance|clearances]], and safely transporting its users. Additional factors include cost, aesthetics, and longevity.  A bridge must be strong enough to support the weight of the bridge itself, as well as the traffic passing over the bridge. It must also tolerate stresses imposed by the environment, such as  wind, snow, earthquakes, water currents, flooding, and [[Thermal expansion|temperature fluctuations]]. To meet all these goals, bridge engineers use analytical methods such as [[limit state design]] and [[finite element method]].

Many bridges are admired for their beauty, and some serve important roles as iconic landmarks that provide a sense of pride and identity to a community.  Bridges are often used as metaphors in art and literature to represent connection or transition.

==History==
{{main|History of bridges}}

===Antiquity===
[[File:Pont_du_Gard_BLS.jpg|thumb|alt=A stone arch bridge passing over a river valley |upright=1.6|The [[Pont du Gard]] [[Aqueduct (bridge)|aqueduct]] in France was built by the [[Roman Empire]] {{circa|40–60 AD}}, and is still standing.{{sfn|Brown|2005|pp=22-23}} ]]

The earliest forms of bridges were simple structures for crossing swamps and creeks, consisting of wooden [[boardwalk]]s or [[Trunk (botany)|logs]].<ref name=early>{{Multiref
|{{harvnb|Bennett|2000|pp=1–3}}.
|{{harvnb|Bennett|1999|pp=9–11}}.
|{{harvnb|Brown|2005|pp=12–13}}.
|{{harvnb|Brunning|2001}}.
}}</ref>{{efn|Examples of early bridges include the [[Sweet Track]] and the [[Post Track]] in England, approximately 6,000 years old.{{sfn|Brunning|2001}} }} [[Pilings]]{{snd}}which are critical elements of bridge construction{{snd}}were used in Switzerland around 4,000 BC to support [[stilt house]]s built over water.{{sfn|Bennett|2000|p=2}}

Several [[corbel arch]] bridges were built {{circa}} 13th century BC by the [[Mycenaean Greece]] culture, including the [[Arkadiko Bridge]], which is still in existence.{{sfn|Cruickshank|2010|p=47}} In the 7th century BC, [[Neo-Assyrian Empire|Assyrian]] king  [[Sennacherib]] constructed stone aqueducts to carry water near the city of [[Ninevah]].{{sfn|Brown|2005|p=18}} One of these aqueducts crossed a small valley at [[Jerwan]] with five corbelled arches, and was {{convert|280|m|ft|sp=us}} long and {{convert|20|m|ft|sp=us}} wide.{{sfn|Brown|2005|p=18}} In [[Babylonia]] in 626 BC, a bridge across the [[Euphrates]] was built with an estimated length of {{convert|120|to|200|m|ft|sp=us}}.{{sfn|Brown|2005|pp=18-19}} In India, the ''[[Arthashastra]]'' treatise by [[Kautilya]] mentions the construction of bridges and dams.{{sfn|Dikshitar |1993|p=332}} Ancient China has an extensive history of bridge construction, including [[cantilever bridge]]s, rope bridges, and bridges built across floating boats.<ref>{{Multiref
|{{harvnb|Cruickshank|2010|p=298}}.
|{{harvnb|Bennett|1999|pp=11–12}}.
}}</ref>

The [[Roman Engineering|ancient Romans]] built many durable bridges using advanced engineering techniques.<ref name=roman>{{Multiref
|{{harvnb|Bennett|1999|pp=14–15}}.
|{{harvnb|Bennett|2000|pp=3–5}}.
|{{harvnb|Brown|2005|pp=20–25}}.
|{{harvnb|Cruickshank|2010|pp=58–80}}.
}}</ref> Many Roman [[aqueduct (bridge)|aqueducts]]{{snd}}some still standing today{{snd}} used a semicircular arch style.<ref name=roman/> An example is the [[Alcántara Bridge]], built over the river [[Tagus]], in Spain.<ref>{{Multiref
|{{harvnb|Brown|2005|p=25}}.
|{{harvnb|Cruickshank|2010|pp=71–73}}.
}}</ref> The Romans used [[cement]] as a construction material, which could be mixed with small rocks to form [[concrete]], or mixed with sand to form [[Mortar (masonry)|mortar]] to join bricks or stones.{{sfn|Delatte|2001}} Some Roman cements, particularly those containing [[Pozzolana|volcanic ash]], could be used in underwater applications.<ref>{{Multiref
|{{harvnb|Brown|2005|pp=20–25,126}}.
|{{harvnb|Bennett|2000|pp=3–5}}.
|{{harvnb|Delatte|2001}}.
}}</ref> The enormous [[Trajan's Bridge]] (105 AD) featured [[Spandrel|open-spandrel]] [[segmental arch]]es made of wood.{{sfn|Bjelić|2022}}

===300 to 1400===
[[File:Anji Bridge, Zhao County, 2020-09-06 05.jpg|thumb|alt=A graceful stone bridge spanning a river, with trees in the background|The [[Anji Bridge]], which uses a shallow [[segmental arch]], was built in China {{circa}} 600 AD.{{sfn|Brown|2005|p=26}}]]
<!-- [[File:Ponte Vecchio from Ponte alle Grazie.jpg|thumb|alt=A bridge with buildings atop it, passing over a river|upright=1.2|During the [[Middle Ages]], bridge builders began employing flatter [[segmental arch]]es{{snd}}such as those seen in the [[Ponte Vecchio]] above{{snd}}which allowed for longer spans compared to the previously used [[semicircular arch]]es.{{sfn|Bennett|2000|pp=6-7}}]]-->

The oldest surviving stone bridge in China is the [[Anji 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.{{sfn|Cruickshank|2010|pp=11-12}}{{efn|The Anji bridge is also called the Zhaozhou Bridge.{{sfn|Cruickshank|2010|pp=11-12}}}} [[Inca rope bridge|Rope bridges]], a simple type of [[suspension bridge]], were used by the [[Inca Empire|Inca]] civilization in the [[Andes]] mountains of South America prior to European colonization in the 16th century.<ref>{{Multiref
|{{harvnb|Brown|2005|p=17}}.
|{{harvnb|Squier|1877 |pp=540–550}}. 
}}</ref>

In [[Middle Ages|Medieval Europe]], bridge design capabilities declined after the [[fall of Rome]], but revived in the [[High Middle Ages]] in France, England, and Italy with the construction of bridges such as the [[Pont d'Avignon]], bridges of the [[Durance#Middle Ages|Durance]] river, the [[Old London Bridge]], and the [[Ponte Vecchio]] in Florence.<ref>{{Multiref
|{{harvnb|Bennett|2000|pp=5–7}}.
|{{harvnb|Brown|2005|pp=28–32}}.
|{{harvnb|Cruickshank|2010|pp=84,86,88–91,96}}.
}}</ref>

===1400 to 1800===

[[File:West Montrose Covered Bridge (Oct. 2018).jpg|thumb|alt=A wooden bridge, covered with a roof, passing over a river|The [[superstructure]] of the [[West Montrose Covered Bridge]] is made of wood.{{sfn|  "West Montrose Covered Bridge". ''Canada's Historic Places'' }}]]

In 15th and 16th century Europe, the [[Renaissance]] brought a new emphasis on science and engineering.{{sfn|Cruickshank|2010|pp=32-33}} Figures such as [[Galileo Galilei]], [[Fausto Veranzio]], and [[Andrea Palladio]] (author of ''[[I quattro libri dell'architettura]]'') wrote treatises that applied a rigorous, analytic approach to architecture and building.{{sfn|Cruickshank|2010|pp=32-33}} Their innovations included [[truss bridge]]s and stone segmental arches, resulting in bridges such as Florence's [[Ponte Santa Trinita]], [[Rialto Bridge]] in Venice, and Paris's [[Pont Neuf]].<ref>{{Multiref
|{{harvnb|Bennett|2000|pp=7–10}}.
|{{harvnb|Brown|2005|pp=36–45}}.
}}</ref> Military and commercial bridges were constructed in India by the [[Mughal Empire|Mughal]] administration.{{sfn| Nath|1982|p=183}} The [[Asante Empire]] in Africa built bridges over [[streams]] and [[rivers]] using tree trunks and beams.<ref>{{Multiref
|{{harvnb|Wilks|1989|p=38}}.
|{{harvnb|Edgerton|2010 |pp=38,62}}.
}}</ref>

In the late 1700s, the design of arch bridges was revolutionized in Europe by [[Jean-Rodolphe Perronet]] and [[John Rennie the Elder|John Rennie]], who designed arches that were flatter than semi-circular Roman arches.{{sfn|Bennett|2000|p=11}} These flatter arches enabled longer spans, fewer piers, and required less material.{{sfn|Bennett|2000|p=11}} These designs were used for bridges such as [[Pont de la Concorde (Paris)|Pont de la Concorde]] and [[New London Bridge]].{{sfn|Bennett|2000|p=11}}

With the advent of the [[Industrial Revolution]], [[cast iron]] became an important construction material for bridges.{{sfn|Brown|2005|pp=45-50}} Although cast iron was strong under [[compression (physics)|compression]], it was brittle, so it was supplanted by [[wrought iron]]{{snd}}which was more ductile and better under [[Tension (physics)|tension]].<ref>{{Multiref
|{{harvnb|Brown|2005|pp=46–51}}.
|{{harvnb|Bennett|2000|pp=16–17}}.
}}</ref> An [[the Iron Bridge|early iron bridge]] was built in Shropshire, England crossing the [[river Severn]].{{sfn|Cruickshank|2010|pp=50-51}}

The abundance of inexpensive [[lumber]] in Canada and the United States caused [[timber bridge]]s to be the most common type of bridge in those countries from the late 1700s to the late 1800s.<ref name="Bennett 2000 12–16">{{Multiref
|{{harvnb|Bennett|2000|pp=12–16}}.
|{{harvnb|Brown|2005|pp=82–84}}.
}}</ref> Many of these timber bridges were [[covered bridges]].<ref name="Bennett 2000 12–16"/> Rail bridges used timber to obtain long spans that utilized strong truss designs, and also tall [[trestle bridge]]s that spanned deep ravines.<ref name="Bennett 2000 12–16"/>

===1800 to present===
[[File:1 Pont de Sidi M'Cid.JPG|thumb|alt=A suspension bridge crossing a deep rocky [[ravine]] |The [[Sidi M'Cid Bridge]] in Algeria was the [[highest bridge]] in the world when it was built in 1912.{{sfn|Sakowski|2014|pp=1259-1261}}  ]]
<!--
[[File:Brooklyn Bridge Manhattan.jpg|thumb|alt=A large suspension bridge, with large towers made of stone| The mass production of steel enabled the construction of large suspension bridges.  The [[Brooklyn Bridge]], built in the 1870s, was the first suspension bridge to use steel for its cables.{{sfn|Bennett|2000|p=22}}]] -->

The mass production of [[steel]] in the late 1800s provided a new material for bridges, enabling lighter, stronger [[truss bridge]]s and cantilever bridges, and producing cables strong enough to make suspension bridges and cable-stayed bridges feasible.<ref>{{Multiref
|{{harvnb|Bennett|2000|pp=18–21}}.
|{{harvnb|Brown|2005|pp=92–104}}.
}}</ref>{{efn|Long before the steel era, people made suspension bridges from vines or ropes. Iron was used in a few early suspension bridges in the form of iron rods or chains (rather than steel wires or cables).{{sfn|Bennett|2000|pp=1,22}}}} <!-- The flexible and dynamic nature of suspension bridges requires special design considerations to safely carry rail traffic.<ref name=SuspRail>{{Multiref
|{{harvnb|Cruickshank|2010|pp= 229–232 }}.
|{{harvnb|Brown|2005|pp=106, 123,147}}.
}}</ref> -->

Concrete{{snd}}which was originally used within the Roman Empire{{snd}}was improved with the invention of [[Portland cement]] in the early 1800s, and replaced stone and masonry as the primary material for bridge [[Foundation (engineering)|foundation]]s. When iron or steel is embedded in the concrete, as in [[reinforced concrete]] or [[prestressed concrete]], it is a strong, inexpensive material that can be used for horizontal elements of [[beam bridge]]s and [[box girder]] bridges.<ref>{{Multiref
|{{harvnb|Bennett|2000|pp=18–26}}.
|{{harvnb|Brown|2005|pp=126–144}}.
}}</ref>

Throughout the 20th century, new bridges by designers such as [[Othmar Ammann]] repeatedly broke records for span distances, enabling transportation networks to cross increasingly wider rivers and valleys.<ref>{{Multiref
|{{harvnb|Bennett|2000|pp=22–24}}.
|{{harvnb|Brown|2005|pp=102, 106-107, 110, 113, 117, 119, 123, 152}}.  Records.
|{{harvnb|Brown|2005|pp= 102, 108, 114, 116, 119}}. Ammann. 
}}</ref> [[Cable-stayed bridges]]{{snd}}which use cable-stays as the exclusive means of support{{snd}}became a popular bridge design following [[World War II]].<ref>{{Multiref
|{{harvnb|Bennett|2000|pp=27–29}}.
|{{harvnb|Brown|2005|pp=146–156}}.
}}</ref>{{efn|Straight, diagonal cables{{snd}}known as ''[[Stay (mechanics)|stays]]''{{snd}}are used to directly connect the  [[Deck (bridge)|bridge deck]] to bridge towers.{{sfn|Bennett|1999|p=61}}    An early cable-stayed bridge was the 1955 [[Strömsund Bridge]] in Norway.{{sfn|Bennett|2000|p=29}} Stays were used  as supplemental supports in some suspension bridges  in the 19th century{{snd}}including the [[Brooklyn Bridge]].{{sfn|Bennett|1999|p=157}} }}

The late 20th century saw several major innovations in bridge design.   [[Extradosed bridge]]s  were introduced and found widespread use, predominantly in Japan.{{sfn|Schlaich|2019|pp=1,6-7}}  In China,  [[Concrete_filled_steel_tube#Bridges|concrete-filled steel tube]]s  were adopted as a new approach to building [[arch bridge]]s.{{sfn| Zheng|Wang|2018}} [[Fiber-reinforced polymer]]s{{snd}}which do not suffer from the rust problems that plague steel{{snd}}were used in bridges for many applications, such as beams, deck slabs, prestressing cables, wraps on the exterior of concrete elements,  and internal reinforcing within concrete.{{sfn|Svecova|2014|pp=371-375, 382, 384-386, 389-392}}{{efn|[[Fiber-reinforced polymer]]s include [[carbon fiber]], [[fiberglass]], and [[aramid]]s.}} In the 21st century a bridge span exceeded  {{convert|2|km|mi|sp=us}} for the first time, with the construction of the [[1915 Çanakkale Bridge]].{{sfn|He|2025}}
<!-- 
===Etymology===
The ''[[Oxford English Dictionary]]'' traces the origin of the word ''bridge'' to the [[Old English]] word ''brycg'', of Germanic origin.{{sfn|"Bridge". ''The Concise Oxford Dictionary''}} There is a possibility that the word can be traced farther back to [[Proto-Indo-European]] ''*bʰrēw-.''{{sfn|"Bridge". ''Oxford English Dictionary''}}
-->

==Uses==
[[File:Magdeburg Kanalbrücke aerial view 13.jpg|thumb|alt=A bridge carrying canal with water, passing over a valley|The [[Magdeburg Water Bridge]] in Germany carries boats across a valley.{{sfn|Denison|2012|p=72}} ]]

[[File:WildlifeCrossingA1IsraelSept202022 01.jpg|thumb|alt=A bridge, topped with soil and vegetation, passing over a highway|This [[Wildlife crossing|wildlife crossing bridge]] is in Israel.{{sfn|  "Why Do Foxes". ''Israel21C''}} ]]

The purpose of any bridge is to traverse  an obstacle. A bridge can provide support and transport for railways, cars, pedestrians,  pipelines, cables, or any  combination of these.{{sfn|Tang|2014|p=1}} [[aqueduct (bridge)|Aqueducts]] were developed early in human history, and carried water to towns and cities.{{sfn|Brown|2005|pp=8,18,20-22}} Canal systems sometimes include [[navigable aqueduct]]s (also called ''canal bridges'') to carry boats across a valley or ravine.{{sfn|Brown|2005|p=53}}

Until the 19th century, the most common use of bridges was to carry pedestrians, horses, and horse drawn carriages.{{sfn|Brown|2005|p=64}} Following the invention of railways, many [[rail bridge]]s were built: in England, the number of bridges doubled during the railway-building boom in the mid 1800s.{{sfn|Brown|2005|p=64}} In the 20th century, the growth of motorway networks required the construction of vast numbers of bridges.{{sfn|Bennett|1999|p=30}} 

Railway bridges have unique requirements because of the heavy loads they carry{{snd}}a single [[locomotive]] can weigh 197 tonnes.{{sfn|Sorgenfrei|2014|p=144}}{{efn|A single locomotive can weigh {{convert|197|tonne|lb|sp=us}}{{sfn|Sorgenfrei|2014|p=144}}}}  Railway bridges are designed to minimize [[Deflection (engineering)|deflection]] (bending under load), to maximize [[Structural robustness|robustness]] (localize the damage caused by accidents), and to tolerate [[Impact (mechanics)|heavy impacts]] (sudden shocks from, for example, rail wheels striking an imperfection in the track).{{sfn|Sorgenfrei|2014|p=144}}  These requirements lead railways to avoid curved bridges, suspension bridges, and cable-stayed bridges;  instead,  straight beam or truss bridges are commonly used.{{sfn|Sorgenfrei|2014|p=146}} 

Some bridges accommodate uses other than transportation. [[Pipeline bridge]]s carry oil pipes or water pipes across valleys or rivers.{{sfn|Tănase|2024}} Many historical bridges supported buildings, such as shrines, factories, shops, restaurants, and houses. Notable examples were the [[Old London Bridge]] and [[Ponte Vecchio]].{{sfn|Cruickshank|2010|pp= 142- 175}} In the modern era, [[bridge-restaurant]]s can be found at some highway [[rest area]]s; these support a restaurant or shops directly above the highway and are accessible to drivers moving in both directions.{{sfn|Greco|2016|pp=89-100}} 
An example is [[Will Rogers Archway]] over the [[Oklahoma Turnpike]].{{sfn|  "Will Rogers Archway". ''Travel Oklahoma''}} The [[Nový Most]] bridge in [[Bratislava]] features a restaurant set atop its single tower.{{sfn|"Bratislava UFO Classed One of the Craziest Places". ''Travel to Slovakia''}}  Conservationists use [[Wildlife crossing|wildlife overpasses]] to reduce [[habitat fragmentation]] and animal-vehicle collisions.<ref>{{Multiref
|{{harvnb|Greenfield|2021}}.
|{{harvnb|  "Why Do Foxes". ''Israel21C''}}.
}}</ref> The first wildlife crossings were built in the 1950s, and these types of bridges are now used worldwide to protect both large and small wildlife.{{sfn|Newer|2012}}
{{clear}}

===Military bridge===
[[File:Slovakia Town Presov 270.jpg|thumb|alt=A military vehicle carrying a bridge on its back, extending the bridge over a creek|This portable [[AM 50]] bridge is being laid over a river in Slovakia.{{sfn| "Bridge Layer AM-50". ''Ministry of Defence and Armed Services of the Czech Republic'' }} 
]]

[[Military bridge]]s are an important type of equipment in the field of [[military engineering]]. They perform a variety of wartime roles, such as quickly traversing obstacles in the midst of battle, or facilitating resupply behind front lines.{{sfn|Tytler|1985|p=198}}{{efn|During wartime, although bridges are sometimes built, they are also destroyed by bombing or by [[combat engineers#Countermobility|combat engineers]].<ref>{{Multiref
|{{harvnb|   Bennett |  1999| pp= 102, 104, 108, 181}}.
|{{harvnb|   Brown |  2005|  pp= 33, 105, 114-115}}.
|{{harvnb|   Cruickshank |2010| pp= 20, 40-41, 43, 91, 327}}.
}}</ref>
}}
<!-- 
{{efn|An example of a portable military bridge is the [[Bailey bridge]].{{sfn|"Army Manual TM 5-277. Panel Bridge, Bailey Type, M2" }}}} 
-->Military bridges can be categorized as ''wet'' bridges that rest on pontoon floats, and ''dry'' bridges that rest on piers, river banks, or anchorages.{{sfn|Tytler|1985|p=198}} A crude mechanism to cross a small ravine is to place a [[fascine]] (a large bundle of pipes or logs) into the ravine to enable vehicles to drive across.{{sfn|Tytler|1985|p=200}}
 
Some military bridges, referred to as [[armoured vehicle-launched bridge]]s (AVLB), are carried on purpose-built vehicles.{{sfn|Tytler|1985|p=200}} These vehicles typically have the same cross-country performance as a tank, and can carry a bridge to an obstacle and deploy ("launch") the bridge.<ref>{{Multiref
|{{harvnb|Tytler|1985|pp=200–203}}.
|{{harvnb| "Close Support Bridging". ''British Army'' }}.
}}</ref> The UK [[Chieftain (tank)|Chieftain AVLB]] could launch a {{convert|23|m|ft|sp=us|adj=on}} bridge{{snd}}capable of supporting 60 ton loads{{snd}} in 3 minutes.{{sfn|Tytler|1985|p=200}}

==Structures==
{{see also|List of bridge types}}

===Basic structures===
<!-- [[File:ScotRail Class 170 Forth Bridge.jpg|thumb| alt=A huge steel bridge passing over a wide body of water|The [[Forth Bridge]] (foreground) uses two kinds of structures: [[truss bridge|trusses]] (left) and [[cantilever bridge|cantilevers]] (right).{{sfn|Cruickshank|2010|pp=292-298}}]]-->
<!--
Bridges can be categorized by their structure (arch, truss, beam, suspension, etc) and their  materials (stone, wood, iron, steel, concrete, etc). For example, a bridge could be identified as a  timber truss bridge, or a reinforced concrete beam bridge, or a stone arch bridge.<ref>{{Multiref
|{{harvnb|Cruickshank|2010|pp=33,36}}.
|{{harvnb|Barker|2007|pp=2–21,87–96}}.  
}}</ref> -->

The basic bridge structures are arch, truss, cantilever, suspension, cable-stayed, and beam.<ref>{{Multiref
|{{harvnb|Shirley-Smith}}.
|{{harvnb|Cruickshank|2010|pp=33,36}}.
|{{harvnb|Barker|2007|pp=2–21,87–96}}. 
}}</ref> The choice of bridge structure to use in a particular situation is based on many factors, including aesthetics, environment, cost, and purpose.{{sfn|Barker|2007|pp=96-108}}{{efn|
Some bridges combine two types of structures. For example, the following bridges (all of which cross the [[ Firth of Forth]]) use simple beam or truss structures on the approach segments, but use another type for the wide central span(s): [[Forth Bridge]] (cantilever central spans), [[Forth Road Bridge]] (suspension central span), and [[Queensferry Crossing]] (cable-stayed central spans).  
}}

====Arch bridge====
{{multiple image
 | header =  [[Arch bridge]]          
<!--  | width = 160  -->
| caption_align=center
 | image1 = Arch bridge.svg
 | alt1= an arched bridge spanning a river, deck resting on top of the arch.
 | caption1 = Deck arch <!-- {{sfn|Denison|2012|p=42}}{{sfn|Shirley-Smith}}{{sfn|Brown|2005|pp=202-203}} -->
 | image2 =  Arch tied bridge.svg
 | alt2= an arched bridge spanning a river, deck suspended below  the arch by vertical lines.
 | caption2 = [[Tied-arch bridge|Tied arch]] <!-- {{sfn|Denison|2012|p=42}}{{sfn|Shirley-Smith}}{{sfn|Brown|2005|pp=202-203}} -->
}}
[[Arch bridge]]s consist of a curved arch, under compression, which supports the [[bridge deck|deck]] either above or below the arch.{{sfn|Bennett|1999|pp=70-75}} The shape of the arch can be a [[semicircle]], [[Ellipse|elliptical]], a [[pointed arch]], or a [[Circular arc|segment of a circle]].<ref>{{Multiref
|{{harvnb|Bennett|1999|p=72}}.
|{{harvnb|Bennett|2000|p=11}}.
|{{harvnb|Brown|2005|p=46}}. 
}}</ref> When the arch is semicircular, as in Roman bridges, the force of the arch is directed vertically downward to the foundation.<ref>{{Multiref
|{{harvnb|Bennett|1999|p=72}}.
|{{harvnb|Bennett|2000|p=4}}.
}}</ref> When the arch is elliptical or a circular segment, the force is directed diagonally, and [[abutment]]s are often required.<ref name=abutDiag/> Deck arch bridges hold the deck above the arch; [[tied-arch bridge]]s suspend the deck below the arch; and [[Through arch bridge|through-arch bridges]] position the deck through the middle of the arch.{{sfn|Bennett|1999|p=75}}

====Truss bridge====
{{multiple image
 | header = [[Truss bridge]]       
<!--  | width = 160  -->
| caption_align=center
 | image1 = Truss bridge.svg
 | alt1= a bridge spanning a river, consisting of several triangles, and the bridge deck is the lower edge of the set of triangles.
 | caption1 = Through truss <!-- {{sfn|Denison|2012|pp=45, 165}}{{sfn|Shirley-Smith}}{{sfn|Brown|2005|pp=202-203}} -->
 | image2 =  Inverted truss bridge.svg
 | alt2= a bridge spanning a river, consisting of several triangles, and the bridge deck is the upper edge of the set of triangles.
 | caption2 = Deck truss<!-- {{sfn|Denison|2012|pp=45, 165}}{{sfn|Shirley-Smith}}{{sfn|Brown|2005|pp=202-203}} -->
}}
A [[truss bridge]] is composed of multiple, connected triangular elements.{{sfn|Bennett|1999|pp=77-79}}{{efn|A truss can be considered as a deep beam, out of which numerous triangular holes have been cut to reduce the weight.{{sfn|Bennett|1999|pp=77-79}}}} The set of triangles form a rigid whole, which rests on the foundation at both ends, applying a vertical force downward.{{sfn|Bennett|1999|pp=77-79}} The deck can be carried on top of the truss ("deck truss") or at the bottom of the truss ("through truss").{{sfn|Wright|2022|pp=7-9,19-20}} Through trusses are useful when more clearance under the bridge is required; deck trusses permit oversized loads and do not interfere with overhead objects, such as electrical lines.{{sfn|Wright|2022|pp=7-9,19-20 }} The individual bars can be made of iron or wood, but most modern truss bridges are made of steel.{{sfn|Bennett|2000|pp=12-16,21}} The horizontal bars along the top are usually in [[Compression (physics)|compression]], and the horizontal bars along the bottom are usually in [[Tension (physics)|tension]].{{sfn|Bennett|1999|pp=77-79}} Other bars in the truss may be in tension or compression, depending on the layout of the triangles.{{sfn|Bennett|1999|pp=68,77-79}} Trusses typically have a span-to-depth ratio (the width of a structure divided by its height) ranging from 10 to 16, compared to beam bridges which typically have a ratio ranging from 20 to 30.{{sfn|Collings|2000|p=413}} Trusses tend to be relatively stiff, and are commonly used for rail bridges which are required to carry very heavy loads.{{sfn|Collings|2000|p=413}}

====Cantilever bridge====
{{multiple image
 | header = [[Cantilever bridge]]        
<!--  | width = 160  -->
| caption_align=center
 | image2 = Cantilever bridge.svg
 | alt2 = a bridge spanning a river, where the bridge is in two disjoint parts: the left part is supported entirely from the leftmost edge where it rests on the ground; and the right part is supported entirely from the rightmost edge where it rests on the ground.
 | caption2 = Two cantilevers extending from anchorages <!-- {{sfn|Denison|2012|p=53,55}}{{sfn|Shirley-Smith}}{{sfn|Brown|2005|pp=202-203}} -->
 | image1 =  Cantilever bridge, balanced.svg
 | alt1= a bridge spanning a river, where there is a solid pier in the middle of the river, and the entire bridge is resting on that pier (and not resting on the banks of the river).
 | caption1 = Balanced cantilever on a single pier  <!-- {{sfn|Denison|2012|p=53,55}}{{sfn|Shirley-Smith}}{{sfn|Brown|2005|pp=202-203}} -->
}}
[[Cantilever bridge]]s consist of beams or trusses that are rigidly attached to a support (pier or anchorage) and extend horizontally from the support without additional supports.<ref>{{Multiref
|{{harvnb|Cruickshank|2010|pp=292-294,361}}.
|{{harvnb|Brown|2005|p=202}}.
}}</ref>  In ancient Asia, cantilever bridges made of large rocks or timber were used to span small obstacles.<ref>{{Multiref
|{{harvnb|Cruickshank|2010|p=298}}.
|{{harvnb|Brown|2005|p=15}}.
|{{harvnb|Bennett|1999|p=12}}.}}</ref> In the 1880s, some early cantilever bridges were built from wrought iron{{sfn|Cruickshank|2010|pp=292-294}} but modern cantilever bridges are generally built from steel.<ref>{{Multiref
|{{harvnb|Cruickshank|2010|pp=292–294}}.
|{{harvnb|Brown|2005|p=78}}.}}</ref>  A balanced cantilever bridge consists of two connected cantilevers extending outward in opposite directions from a single central support.<ref name=balcant>{{Multiref
|{{harvnb|Cruickshank|2010|p=36}}.
|{{harvnb|Bennett|1999|pp=53,94,97,145,223}}.
|{{harvnb|Brown|2005|p=149}}.
}}</ref>  Other cantilever bridges have two cantilevers, anchored at each end of the span, extending toward the center, and meeting in the center.{{sfn|Cruickshank|2010|pp=292-294}} <!--
  Some cantilever bridges have a suspended span (beam or truss) in the center, connecting the two cantilevers where they meet.<ref>{{Multiref
|{{harvnb|Cruickshank|2010|p=296,361}}.
|{{harvnb|Brown|2005|p=202}}.
|{{harvnb|Adams|1909|p=169}}.
}}</ref> 
-->  ''Cantilever construction'' is a method of building a bridge [[superstructure]], which can be utilized for arch and cable-stayed bridges, as well as cantilever bridges. In this technique, construction begins at a support (such as a pier, abutment, or tower) and extends outwards across the obstacle, with no support from below.<ref>{{Multiref
|{{harvnb|Collings|2000|p=433}}.
|{{harvnb|Cruickshank|2010|pp=262–266}}.
|{{harvnb|Bennett|1999|pp=74, 96, 113}}.
|{{harvnb|Brown|2005|pp=89, 105, 141}}.
}}</ref>

====Suspension bridge====
{{multiple image
 | header = [[Suspension bridge]]        
<!--  | width = 160  -->
| caption_align=center
 | image1 = Suspension bridge.svg
 | alt1= a bridge spanning a river, with two tall towers in the river, and a curved cable passing from one river bank to the other, passing over the tops of the towers.  The bridge deck (road) is suspended from the curved cable by vertical lines.
 | caption1 = With anchorages <!-- {{sfn|Denison|2012|pp=57,59}}{{sfn|Shirley-Smith}}{{sfn|Brown|2005|pp=202-203}} -->
 | image2 =Bridge_suspension_self_anchored.svg
 | alt2 = a bridge spanning a river, with a single tall towers in the middle of the river, and a curved cable passing from one river bank to the other, passing over the top of the tower.  The bridge deck (road) is suspended from the curved cable by vertical lines.
 | caption2 = [[Self-anchored suspension bridge|Self-anchored]]<!-- {{sfn|Gimsing|1997|p=193}}  -->
}}
[[Suspension bridges]] have large, curved cables attached to the tops of tall towers,{{efn|name=OneTower}} and suspend the bridge deck from the cables.{{sfn|Brown|2005|p=203}}{{efn|The deck is suspended from the cables by large [[wire rope]]s called ''hangers'', also called ''suspenders''.{{sfn|Bennett|1999|p=84}}}}  In the early 1800s, the first modern suspension bridges{{snd}}such as the [[Jacob's Creek Bridge (Pennsylvania)|Jacob's Creek Bridge]]{{snd}}were [[chain bridge]]s that used iron bars rather than bundled wires for the cables.{{sfn|Brown|2005|p=58}} After steel wire became widely available, longer cables could be built by stringing hundreds of wires between the towers and bundling them,{{sfn|Bennett|1999|pp=84,89-90}} enabling suspension bridges to achieve spans {{convert|2|km|mile|sp=us}} long.<ref>{{Multiref
|{{harvnb|Brown|2005|pp=58–60}}.
|{{harvnb|Bennett|1999|pp=81–90}}.}}</ref>{{efn|The first bridge to achieve a  2 km span was the [[1915 Çanakkale Bridge]].}}  When the bridge crosses a river, stringing  the wires across the large span is a complex process.{{sfn|Bennett|1999|pp=84,89-90}}  The cable of a suspension bridge assumes the shape of a [[catenary]] when initially suspended between the bridge towers; however, once the uniform load of the bridge deck is applied, the cable adopts a [[parabola|parabolic]] shape.{{sfn|Cruickshank|2010|pp=232-233}} Shorter towers require a smaller sag in the cable, which increases the tension in the cable, and thus requires stronger towers and anchorages.{{sfn|Bennett|1999|p=84}}

====Cable-stayed bridge====
{{multiple image
<!--  | width = 160  -->
| caption_align=center
 | header = [[Cable-stayed bridge]]            
 | image1 = Cable-stayed bridge.svg
 | alt1= a bridge spanning a river, with two tall towers in the river,    The bridge deck (road) is suspended from the two towers by numerous straight, diagonal lines.
 | caption1 = Harp pattern, two towers <!-- {{sfn|Denison|2012|p=61,63}}{{sfn|Shirley-Smith}}{{sfn|Brown|2005|pp=202-203}} -->
 | image2 =  Bridge cable stay fan.svg
 | alt2= a bridge spanning a river, with a single tall towers in the middle of the river,    The bridge deck (road) is suspended from the tower  by numerous straight, diagonal lines.
 | caption2 = Fan pattern, single tower <!-- {{sfn|Denison|2012|p=61,63}}{{sfn|Shirley-Smith}} -->
}}
[[Cable-stayed bridge]]s are similar to suspension bridges, but the cables that support the deck connect directly to the towers.{{sfn|Cruickshank| 2010|pp=343-347}}{{efn|name=OneTower|Most suspension bridges and cable-stayed bridges have two or more towers, but some have only one tower. A single-tower cable-stayed bridge is the [[Flehe Bridge]] in Germany,{{sfn|Troyano |2003 |pp= 623, 656, 664 }} and a single-tower suspension bridge is the east span of the [[San Francisco-Oakland Bay Bridge]].{{sfn|Brown|2005|pp=194-195}} }} The cables may be arranged in a fan pattern or a harp pattern.<ref>{{Multiref
|{{harvnb|Vejrum|2014|pp=407-410}}.
|{{harvnb|Cruickshank|2010|p=347}}.
|{{harvnb|Gimsing|1997|pp= 194, 211, 351-352}}.
}}</ref>{{efn|In a harp pattern all the cables are parallel; in a fan pattern the cables all radiate from near the top of the tower.  The [[Severins Bridge]] was the  first cable-stayed bridge that arranged its cables in a fan pattern, rather than a harp pattern.{{sfn|Bennett|2000|p=29}}}} Modern cable-stayed bridges became popular after WWII, when the design was used for many new bridges in Germany.{{sfn|Bennett|2000|pp=27-28}}  When traversing a wide obstacle, designers have a choice of suspension or cable-stayed structures.  Suspension bridges provide a longer span (for comparable materials), and require shorter towers (for a given span size). Cable-stayed bridges use less cable for a given span size; do not require anchorages; and the deck can be readily built by cantilevering outward from the towers.<ref>{{Multiref
|{{harvnb|Bennett|2000|pp=27–28}}.
|{{harvnb|Cruickshank|2010|pp=343–347}}.
}}</ref>

====Beam bridge====
{{multiple image
 | header = [[Beam bridge]] <!-- {{sfn|Denison|2012|pp=37,39}}{{sfn|Shirley-Smith}} -->     
<!--  | width = 160  -->
| caption_align=center
 | image1 =Beam bridge.svg
 | alt1= A flat, straight bridge spanning a river.  There are no towers or piers: the entire  bridge is a flat, wide, rectangular shape.
 | caption1 =
}}
[[Beam bridges]]{{snd}} including [[girder bridges]]{{snd}} are simple structures consisting of one or more parallel, horizontal [[Beam (structure)|beam]]s that span an obstacle. They are the most common type of bridges for both railways and roadways.<ref name=beam>{{multiref
|{{harvnb|Bennett|1999|p=78}}.
|{{harvnb|Bennett|2000|pp=24–26}}.
|{{harvnb|Barker|2007|pp=20–21}}.
}}</ref> Beam bridges are ideal for shorter spans (less than about {{convert|50|m|ft|sp=us}}); for longer spans other structures, such as trusses, are generally more efficient.{{sfn|Barker|2007|pp=20-21}} In many applications, beam bridges can be built rapidly and economically, because the individual beams can be produced offsite and transported to the bridge site.<ref name=beam/> Modern beam bridges are generally made of steel or reinforced concrete, although wood may be suitable for small beam bridges intended for light use.<ref name=beam/> Several different cross-sections may be utilized for beams, including [[I-beam]] (common for steel) or [[Concrete slab|flat slabs]] (sometimes used with concrete).<ref name=beam/>{{efn|The majority of beam bridges have a flat, horizontal bottom; but  some have a bottom that arches upward, called ''haunching''. Haunching looks more graceful than a flat bottom, and can provide greater clearance below the bridge, but it tends to be more costly because flat bottom beams are easier to build.<ref>{{Multiref
|{{harvnb|Zhao| 2017|pp =79, 214-215}}.
|{{harvnb|Troitsky|1994| p =104}}.
}}</ref>}} Beams can traverse longer spans when they are designed as hollow [[box girder]]s; bridges made of box girders are termed [[box girder bridge]]s.<ref name=beam/> The vertical thickness of beam bridges is generally shallower than comparable deck truss bridges, permitting shorter and lower approach roads to cross an obstacle of a given height.<ref name=beam/> Several beam bridges can be chained together, with supports at each juncture, to form [[elevated highway]]s or [[causeway]]s.<ref name=beam/>{{efn|Notable bridges consisting of hundreds of beam bridge elements include  [[Hangzhou Bay Bridge]] and [[Lake Pontchartrain Causeway]].{{sfn|Cruickshank|2010|pp=348-349}}}}

===Other types===

====Movable bridge====
[[File:Tower Bridge (8151690991).jpg|thumb|alt=A tall drawbridge, open, over a river| [[Tower Bridge]] in London is a [[movable bridge]] of the [[Bascule bridge|bascule]] type.{{sfn|Birnstiel|2000|pp=688-690}} ]]

[[Movable bridge]]s are designed so that all or part of the bridge deck can be moved, usually to permit tall traffic{{snd}}that would normally be obstructed by the bridge{{snd}}to pass by.<ref>{{Multiref
|{{harvnb|Brown|2005|p=81}}.
|{{harvnb|Birnstiel|2000|pp=663–665}}.
}}</ref> Early movable bridges include [[drawbridge]]s that pivoted at one end, and required a large amount of work to raise. Adding counterweights on the pivot side of the drawbridge creates a [[bascule bridge]], and makes moving the bridge easier and safer.<ref>{{Multiref
|{{harvnb|Brown|2005|p=81}}.
|{{harvnb|Birnstiel|2000|pp=668–678,684}}.}}</ref> [[Swing bridge]]s pivot horizontally around an anchor point on the bank of a canal, or sometimes from a pier in the middle of the water.<ref>{{Multiref
|{{harvnb|Brown|2005|p=81}}.
|{{harvnb|Birnstiel|2000|pp=665,668,682–683}}.
}}</ref> [[Lift bridge]]s are raised vertically between two towers by cables passing over pulleys at the top of the towers.<ref>{{Multiref
|{{harvnb|Brown|2005|p=81}}.
|{{harvnb|Birnstiel|2000|p=685}}.
}}</ref> Notable movable bridges include [[El Ferdan Railway Bridge]] in Egypt, [[Erasmusbrug]] bascule in Rotterdam, and [[Limehouse Basin#Swing bridge|Limehouse Basin footbridge]] in London.{{sfn|Brown|2005|pp=164-165}} In the modern era, designers sometimes create unusual movable bridges with the intention of establishing signature bridges for a town or locality.{{sfn|Brown|2005|pp=164-165}} Examples include [[Puente de la Mujer]] swing bridge in Buenos Aires, [[Gateshead Millennium Bridge|Gateshead Millennium]]{{snd}}a rare example of a [[tilt bridge]]{{snd}}over the [[River Tyne]], and [[Hörn Bridge]] in Germany.{{sfn|Brown|2005|pp=164-165}}

====Long, multi-span bridge====
{{see also|Viaduct|Causeway|Continuous truss bridge}}
[[File:ViaducdeMillau.jpg|thumb|alt=A large bridge, consisting of multiple tall sections, passing over a wide valley |The [[Millau Viaduct]] crosses the [[Tarn (river)|Tarn river]] valley in France.{{sfn|Brown|2005|pp=192-193}}]]

There are a variety of terms that describe long, multi-span bridges{{snd}}including raised bridge, viaduct, trestle, and causeway. The usage of the terms can overlap, but each has a specific focus.{{sfn|Cruickshank|2010|p=349}} [[Viaduct]]s (carrying vehicles) and [[Aqueduct (bridge)|aqueduct]]s (carrying water) are bridges crossing a valley, supported by multiple arches or piers.<ref>{{Multiref
|{{harvnb|"Aqueduct". ''The Concise Oxford Dictionary''}}.
|{{harvnb|"Viaduct". ''The Concise Oxford Dictionary''}}.
}}</ref> Romans built many aqueducts, some of which are still standing today.{{sfn|Cruickshank|2010|pp=60-61}} Notable viaducts include [[Penponds Viaduct]] in England,{{sfn|Brown|2005|p=69}} [[Garabit Viaduct]] in France,{{sfn|Brown|2005|pp=92-93}} [[Tunkhannock Viaduct]] in Pennsylvania,{{sfn|Brown|2005|pp=130-131}} and [[Millau Viaduct]] in France.{{sfn|Brown|2005||pp=192-193}}

A [[trestle bridge]]{{snd}}commonly used in the 19th century for railway bridges{{snd}} consists of multiple short spans supported by closely spaced structural elements.{{sfn|Cruickshank|2010|pp=46-47}} A trestle is similar to a viaduct, but viaducts typically have taller piers and longer spans.{{sfn|Honan|2018}} A [[continuous truss bridge]] is a long, single truss that rests upon multiple [[Pier (bridge structure)|supports]]. A continuous truss bridge may use less material than a series of simple trusses because a continuous truss distributes live loads across all the spans (in contrast to a series of distinct trusses, where each truss must be capable of supporting the entire live load). Visually, a continuous truss looks similar to a cantilever bridge, but a continuous truss experiences [[Hogging and sagging|hogging]] stresses at the supports and [[Hogging and sagging|sagging]] stresses between the supports.<ref name=contTruss>{{Multiref
|{{harvnb|Denison|2012|p=153}}.
|{{harvnb|Adams|1909|p=168}}.
}}</ref> A [[causeway]] is a low, raised road, usually crossing   a lake or other body of water.<ref name=causeway>{{Multiref
| {{harvnb|"Causeway". ''Merriam-Webster''}}.
| {{harvnb|"Causeway". ''Oxford English Dictionary''}}. 
} {{harvnb|Cruickshank|2010|pp=348-349}}.
}}</ref>   The {{convert|38.4|km|mile|sp=us}} [[Lake Pontchartrain Causeway]] in Louisiana is a bridge, but other causeways are built on earthen embankments.<ref name=causeway/>

====Pontoon bridge====

[[File:Nordhordalandsbrua towards north.jpg|thumb|alt=A concrete bridge over a large body of water|Floating concrete pontoons support the weight of the [[Nordhordland Bridge]] as it crosses a deep [[fjord]] in Norway.{{sfn|Watanabe|2003}}
]]
A [[pontoon bridge]], also known as a floating bridge, uses [[float (nautical)|floats]] or shallow-[[draft (hull)|draft]] boats to support a continuous deck for pedestrian or vehicle travel over water.<ref>{{Multiref
|{{harvnb|Brown|2005|p=203}}.
|{{harvnb|Bennett|1999|p=229}}.
}}</ref> Pontoon bridges are typically used where waters are too deep to build piers, or as a mechanism to implement a movable [[swing bridge]] in a canal.{{sfn|Birnstiel|2000|pp=668,679}} Pontoon bridges were used in ancient China.<ref>{{Multiref
|{{harvnb|Bennett|1999|p=12}}.
|{{harvnb|Brown|2005|pp=8,19}}.
|{{harvnb|Bennett|2000|p=2}}.
}}</ref> During the [[Second Persian invasion of Greece]], Persian ruler [[Xerxes I|Xerxes]] built a [[Xerxes' pontoon bridges|large pontoon bridge]] across the [[Hellespont]], consisting of two parallel rows of 360 boats.<ref>{{Multiref
|{{harvnb|Bennett|1999|p=13}}.
|{{harvnb|Brown|2005|pp=8,19,80}}.
|{{harvnb|Bennett|2000|p=3}}.
}}</ref>

Several pontoon bridges are in use in the modern world. Washington state in the US has several, including [[Hood Canal Bridge]].{{sfn|Holstine|2005|pp=179-182}} In Norway, [[Nordhordland Bridge]] crosses a deep [[fjord]] by resting on floating concrete pontoons.{{sfn|Watanabe|2003}} Many armies have pontoon bridges that can be rapidly deployed, including the [[PMP Floating Bridge]], designed by the [[USSR]].{{sfn|"Handbook on Soviet Ground Forces". ''Department of the Army''|pp=6.79-6.80}}

====Extradosed====

[[File:Shinmeisai Bridge and Akatonbo Bridge.jpg|alt=A concrete bridge over a river|thumb|The Shin Meisei bridge (foreground) in Japan is an example of an [[extradosed bridge]].{{sfn|Hu|2016|p=40}}]]
An [[extradosed bridge]] combines features of a box girder bridge and a cable-stayed bridge.<ref>{{Multiref
|{{harvnb|Vejrum|2014|pp=410-411}}.
|{{harvnb|Schlaich|2019|p=3}}.
|{{harvnb|Hu|2016|pp=i,1,7–13}}.
}}</ref> Visually, extradosed bridges can be distinguished from cable-stayed bridges because the tower height (above the deck) is relatively low: between 7% and 13% of the span width.{{sfn|Schlaich|2019|pp=3-4}}{{efn|Another definition of an extradosed bridge is one where the ''stiffness ratio'' (load carried by stay cables divided by total vertical load) is less than 30%.{{sfn|Hu|2016|p=12}}}} Extradosed bridges are appropriate for spans ranging from {{convert|100|meters|sp=us}} to {{convert|250|meters|sp=us}}.{{sfn|Schlaich|2019|pp=3-4}} Unlike suspension bridges or cable-stayed bridges, the towers of a extradosed bridge rest on the deck, rather than on a footing; and in some implementations, are solidly connected to the deck.{{sfn|Schlaich|2019|p=5}} Because of the relatively flat angle of the cables, the cables of an extradosed bridge compress the deck horizontally, performing a function comparable to prestressing wires that are used within concrete girders.{{sfn|Schlaich|2019|p=3}} Extradosed bridges may be appropriate in applications where the deck must have a shallow depth to maximize clearance under the bridge; or where towers must be relatively short to abide by aviation safety constraints.{{sfn|Schlaich|2019|p=6}}

==Design==
{{main|Bridge design}}

===Design process===
[[File:Sandhill Road overpass.jpg|thumb|alt=A freeway with several cars driving on it, with two concrete bridges passing overhead| Many overpass bridges in the United States [[Interstate Highway System]] are concrete [[box girder bridge]]s, such as these bridges over [[Interstate 280 (California)|Interstate 280]] in California.]]

The process for designing a new bridge typically goes through several iterations, progressively refining the design.{{sfn|Tang|2014|p=2}}  An early step in the design process{{snd}}sometimes called ''conceptual design''{{snd}}is to  consider the multiple requirements that a bridge must satisfy.{{sfn|Tang|2014|p=2}} 

The requirements may be categorized as engineering requirements and non-engineering requirements. Engineering requirements include safety, strength, lifespan, climate, traffic, the size and nature of the obstacle to be traversed, and clearance required for passage underneath.<ref>{{Multiref
|{{harvnb|Tang|2014|p=3}}.
|{{harvnb|Cruickshank|2010|pp=33,38}}.
|{{harvnb|Barker|2007|pp=45–50}}.
|{{harvnb|Hu|2016|pp=106–108}}.
}}</ref> Non-engineering requirements include construction cost, maintenance cost, aesthetics, time available for construction, owner preference, and experience of the builders.<ref>{{Multiref
|{{harvnb|Tang|2014|p=3}}.
|{{harvnb|Barker|2007|pp=45–46, 96–108}}.
|{{harvnb|Barker|2007|p=114}}.
}}</ref> Other factors that may be weighed include impact to environment and wildlife; and the bridge's economic, social, and historic relationship to the local community.{{sfn|Hu|2016|pp=98,106-108}}

After the requirements of a bridge are established, a bridge designer uses [[structural analysis]] methods to identify candidate designs.{{sfn|Barker|2007|pp=283-288}} Several designs may meet the requirements. The [[value engineering]] methodology can be used to select a final design from multiple alternatives.{{sfn|Hu|2016|pp=69-72}} This methodology evaluates candidate designs based on weighted scores assigned to several different criteria, such as: cost, service life, durability, availability of resources, ease of construction, construction time, and maintenance cost.{{sfn|Hu|2016|p=71}} After considering all factors, a bridge designer{{snd}}in consultation with the owner{{snd}} will select a particular design.<ref>{{Multiref
|{{harvnb|Cruickshank|2010|pp=33,38}}.
|{{harvnb|Barker|2007|pp=45–50, 96–108}}.
}}</ref>

===Specifications and standards===
One of the requirements a new bridge must satisfy is compliance with the local bridge design specifications and codes.  In some cases, these are legally binding requirements.{{sfn|Tang|2014|p=3}}  In many countries, the specifications are developed and published by [[standards organizations]]  that define acceptable bridge-building practices and designs.  In Europe, the organization is the [[European Committee for Standardization]], and the standards it publishes are the [[Eurocodes]].{{sfn|"Eurocodes: Building the Future". ''European Commission'' }} In the United States, the [[American Association of State Highway and Transportation Officials]] (AASHTO) publishes the AASHTO LRFD Bridge Design Specifications.{{sfn|"AASHTO LRFD Bridge Design Specifications"}}{{efn|A list of some bridge-related specifications in the US is found in ''[[#CITEREFTroitsky1994|Planning and Design of Bridges]]''.{{sfn|Troitsky|1994|pp=177-179}}}} Canada's bridge standard is the Canadian Highway Bridge Design Code, developed by the non-profit [[CSA Group]].{{sfn| "CSA S6:19, Canadian Highway Bridge Design Code". ''CSA Group'' }}

===Service life===
One of the important requirements  established early in the design process is the [[service life]], which is a specific number of years that the bridge is expected to remain in operation with routine maintenance (and without requiring major repairs).<ref>{{Multiref
|{{harvnb|Hopper|Langlois|2022|pp=2–5}}.
|{{harvnb|Kulicki|2014|p=113}}.
|{{harvnb|Mangus|2014|p=632}}.
}}</ref>{{efn|Routine maintenance includes replacing bridge elements that are designed to be replaced, such as the wearable surface of the deck, or certain cables.{{sfn|Hopper|Langlois|2022|p=5}} }}  For example, wood bridges typically have a service life of 10 to 50 years.{{sfn|Fridley|Duan|2014|pp=348-350}}{{efn|Bridges made from [[glued laminated timber]], if properly designed, can have service lives longer than 50 years.{{sfn|Fridley|Duan|2014|p=350}}}}  Concrete highway bridges typically have service lives of 75 to 150 years.{{sfn|Hopper|Langlois|2022|p=5}} A bridge design methodology incorporates the service life into the design process.{{sfn|Hopper|Langlois|2022|pp=5-20}}

===Aesthetics===
[[File:RhB ABe 4-4 III Kreisviadukt Brusio.jpg|thumb|alt=A train moving atop a stone bridge in an attractive valley|upright=1.4|The [[Brusio spiral viaduct]]{{snd}}a part of the [[Bernina railway]] in Switzerland{{snd}}is designated as a [[World Heritage Site]].{{sfn| "Rhaetian Railway in the Albula". ''UNESCO World Heritage Convention'' }}
]]

The aesthetics of a new bridge are one of the factors considered when designing a bridge.  Attractive bridges can have a positive impact on a community, and some bridges can even be considered as works of art.<ref>{{Multiref
|{{harvnb|Goettemoeller|2014|pp=49-50,52,75}}.
|{{harvnb|Barker|2007|pp=51–66}}.
|{{harvnb|Cruickshank|2010|pp=310–312}}. 
}}</ref>  Bridge designers that are known for emphasizing the visual appeal of their bridges include [[Thomas Telford]], [[Gustave Eiffel]], [[John Roebling]], [[Robert Maillart]], and [[Santiago Calatrava]].<ref>{{Multiref
|{{harvnb|Goettemoeller|2014|pp=52-53}}.
|{{harvnb|Brown|2005|pp= 164, 174-17}}.  Calatrava.
}}</ref> Qualities that influence the perceived attractiveness of a bridge include proportion, order, refinement, environmental integration, texture, and color.{{sfn|Leonhardt|2014|pp=43-46}}

The art historian [[Dan Cruickshank]] notes that bridges are regarded as manifestations of human imagination and ambition, and that many bridges bridge transcend their original utilitarian role and become a work of art.{{sfn|Cruickshank|2010|pp=8-9}} He writes "[a] great bridge has an emotional impact, it has a sublime quality and a heroic beauty that moves even those who are not accustomed to having their senses inflamed by the visual arts."{{sfn|Cruickshank|2010|pp=8-9}}

===Material===
[[File:Ironbridge 6.jpg|thumb|alt= An ornate bridge made of iron, passing over a small, lush valley|[[The Iron Bridge]] in [[Shropshire]], England, completed in 1781, is the first major bridge made entirely of [[cast iron]].{{sfn|Cruickshank|2010|pp=50-51}}]]

[[File:Reinforcing Steel for Stem Wall at South Abutment (September 12, 2016) (29075882214).jpg|thumb|alt=A construction site with a halfway built concrete structure|This concrete bridge support is being prepared for a concrete pour. After the concrete [[Concrete#Curing|cures]], the green [[reinforcing bar]]s will be permanently embedded inside.<ref name=rebar/>]]

{{multiple image       
 | header =  [[Prestressed_concrete]] 
| caption_align=center
 | image1 = Acero postesado.jpg
 | alt1=  A concrete beam with several steel cables emerging from holes in the side of the beam
 | caption1  = These [[Prestressed_concrete#Post-tensioned_concrete|post-tensioned]] cables are tightened with [[Jack_(device)#Hydraulic_jack|hydraulic jacks]] to ensure the concrete stays in [[compression (physics)|compression]].
 | image2 =  DallasHighFiveSegmentalBridge.jpg
 | alt2= A large concrete section of a bridge is suspended above the ground by a large crane
 | caption2 = The small circular holes in this section of [[box girder]] will hold [[Prestressed concrete|prestressing cables]], which run the length of the girder.<ref name=prestress/>
}}  A bridge designer can select from a wide variety of materials, including wood, brick, rope, stone, iron, steel, and concrete.<ref>{{Multiref
|{{harvnb|Collings|2000|pp=407–408}}.
|{{harvnb|Brown|2005|p=6}}.
}}</ref>{{efn|The proportion of bridges made from various materials in one country are: 60% concrete, 30% steel, 3% wood, and 30% other (masonry, aluminum iron, etc.). Data from US, 2018.{{sfn|Nowak|Iatsko|2018}}}}  A bridge made from two or more distinct materials (such as steel and concrete) is known as a composite bridge.{{sfn|Brown|2005|pp=126, 149, 202}} For example, some of the largest arch bridges utilize [[Concrete_filled_steel_tube#Bridges|concrete-filled steel tube]]s.{{sfn| Zheng|Wang|2018}} 

Wood is an inexpensive material that is rarely used for modern roadway bridges.{{sfn|Zhao|2017|pp=84-85}}  Wood is primarily used in beam or truss bridges, and is also used to build large [[trestle bridge]]s for railways.<ref>{{Multiref
|{{harvnb|Cruickshank|2010|pp=39–47}}.
|{{harvnb|Zhao|2017|pp=84–85}}.
}}</ref> When wood is used, it is often in the form of [[glued laminated timber]].{{sfn|Zhao|2017|pp=84-85}}

[[Masonry]] includes stone and brick, and is suitable only for elements of a bridge that are under compression, since masonry will crack if under tension. Therefore, masonry is limited to structures such as arches or foundations.<ref>{{Multiref
|{{harvnb|Cruickshank|2010|pp=47–50}}.
|{{harvnb|Bennett|1999|p=16}}.
}}</ref> In the twentieth century, large masonry bridges {{snd}}although superseded by concrete in the West{{snd}}continued to be built in China.{{sfn|Ou|Chen|2005}}

Iron{{snd}}including [[cast iron]] and [[wrought iron]]{{snd}}was used extensively from the late 1700s to late 1800s, primarily for arch and truss structures. Iron is relatively brittle, and has been replaced by   steel for all but ornamental uses.<ref>{{Multiref
|{{harvnb|Cruickshank|2010|pp=50–52}}.
|{{harvnb|Bennett|1999|pp=29–35}}.
|{{harvnb|Bennett|2000|p=17}}.
}}</ref>

Steel is one of the most common materials used in modern bridges because it is strong in both compression and tension.{{sfn|Bennett|2000|pp=16-19}} Steel was made in small quantities in antiquity, but became widely available in the late 1800s following invention of new [[smelting]] processes by [[Henry Bessemer]] and [[William Siemens]]. Truss bridges and beam bridges are often made of steel, and steel wires are an essential component of virtually all suspension bridges and cable-stayed bridges.<ref>{{Multiref
|{{harvnb|Bennett|1999|pp=36–42}}.
|{{harvnb|Bennett|2000|pp=16–19}}.
|{{harvnb|Brown|2005|pp=92–104}}.
}}</ref> Concrete bridges make extensive use of steel, because all concrete used in bridges contains steel [[reinforcing bars]] or steel [[prestressed]] cables.<ref>{{Multiref
|{{harvnb|Cruickshank|2010|pp=322–327}}.
|{{harvnb|Brown|2005|pp=140–141}}.
|{{harvnb|Bennett|1999|pp=68–69}}.
}}</ref> Steel bridges are more expensive than comparable concrete bridges, but they are much lighter (for the same strength), faster to build, and offer more flexibility during construction and repair.<ref>{{Multiref
|{{harvnb|Bennett|1999|p=70}}.
|{{harvnb|Ellobody|2014|pp=1–2}}.
}}</ref>

Concrete is a strong and inexpensive material, but is brittle and can crack when in tension.{{sfn|Bennett|1999|pp=68-69}} Concrete is useful for bridge elements that are in compression, such as foundations and arches.{{sfn|Bennett|2000|pp=24-27}} Many [[roadway]] bridges are built entirely of concrete using a beam structure, often of the [[box girder]] variety.{{sfn|Bennett|2000|pp=24-27}} Virtually all concrete used in bridges contains steel reinforcing bars, which greatly increase the strength.<ref name=rebar>{{Multiref
|{{harvnb|Bennett|1999|pp=68–69}},
|{{harvnb|Brown|2005|pp=126–134}}.
|{{harvnb|Cruickshank|2010|pp=322–327}}.
}}</ref> Reinforcing bars are set inside the concrete [[formwork|form]], and the concrete is poured into the form, and [[Concrete#Curing|cures]] with the bars inside. If concrete is used in elements that experience tension, [[Prestressed concrete|prestressed cables]] must be embedded within the concrete and tightened.<ref name=prestress>{{Multiref
|{{harvnb|Bennett|1999|pp=68–69}}.
|{{harvnb|Cruickshank|2010|pp=322–327}}.
|{{harvnb|Hewson|2000|pp=241–314}}.
|{{harvnb|Zhao|2017|pp=290–294}}.
}}</ref> The prestressed cables can be pre-tensioned (stretched before{{snd}}and while{{snd}}the concrete cures); or post-tensioned (placed within tubes in the concrete, and tightened after the concrete cures).<ref name="Cruickshank 2010 322–327">{{Multiref
|{{harvnb|Cruickshank|2010|pp=322–327}}.
|{{harvnb|Hewson|2000|pp=241–314}}.
}}</ref> The prestressed cables compress the concrete. When the beam is placed into the bridge and carries a load, the undesirable tension (produced by the tendency of the beam to sag) is counteracted by the compression from the prestressed cables.<ref name="Cruickshank 2010 322–327"/> Concrete beams can be [[Precast concrete|precast offsite]] and transported to the bridge site, or [[Cast-in-place concrete|cast in place]].{{sfn|Bennett|1999|p=53}}  [[High-performance concrete]] is becoming more commonly used in bridges (compared to conventional concrete) because it suffers less damage from heavy traffic and lasts longer.{{sfn|Blank|2014|pp=74, 76-77, 81}}{{efn|Conventional concrete has strength ranging around 25 to 50 MPa, whereas high-performance concrete has strength ranging around 500 to 100 MPa.{{sfn|Blank|2014|pp=74, 76-77, 81}}}}

===Double-deck bridge===
{{See also|List of multi-level bridges}}
[[File:The padma bridge 02.jpg|thumb|alt=A long, straight, flat bridge over a large body of water|The [[Padma Bridge]] in Bangladesh carries rail traffic on the lower deck and vehicular traffic on the upper deck.{{sfn|"Main Bridge Details". ''Padma Multipurpose Bridge Project''}} ]]

Designers may choose to use a double-deck design (also known as double-decked or double-decker), which carries two decks on top of each other. This technique may be used to increase the amount of traffic a bridge can carry, or to build in a location where space is limited.{{sfn|Kumar|2025}} Double-deck bridges permit two different kinds of traffic to be safely carried.  For example,  motor vehicles can be separated from pedestrians or railways.{{sfn|Kumar|2025}}

An early double-deck bridge was [[Niagara Falls Suspension Bridge]], which carried rail on the upper deck, and carriages and pedestrians on the lower deck.{{sfn|Brown|2005|pp=9, 87}} [[George Washington Bridge]] in New York carries 14 motor vehicle lanes (eight above, six below), and is the world's busiest bridge, carrying over 100 million vehicles annually.{{sfn|"2024 Monthly Traffic and Percent of E‐ZPass Usage". ''Port Authority of New York and New Jersey''}} Because of their ability to carry large amounts of motor vehicles, double-deck bridges are often found in large cities, such as [[Tsing Ma Bridge]] in Hong Kong,{{sfn|Brown|2005|p=9}} [[San Francisco–Oakland Bay Bridge]] in California,{{sfn|Brown|2005|p=114}} and [[Great Seto Bridge#Constituent bridges|Shimotsui-Seto Bridge]] in Japan.{{sfn|Brown|2005|p=171}}

===Load analysis===
[[File:East span San Francisco Oakland Bay bridge.jpg|thumb|alt= A very large suspension bridge passing over a large body of water|upright=1.3|The [[San Francisco–Oakland Bay Bridge]] is designed to withstand severe earthquakes. The [[Eastern span replacement of the San Francisco–Oakland Bay Bridge|eastern span]], shown above, is a [[self-anchored suspension bridge]] which can survive a once-in-1,500-year earthquake.{{sfn| "SAS Maintenance Travelers". ''California Department of Transportation'' }}
]]
A bridge design must accommodate all loads and forces that the bridge might reasonably experience. The totality of the forces that the bridge must tolerate is the [[structural load]], which is often divided into three components:  dead load, live load, and environmental load. The [[Structural load#Dead load|dead load]] is the weight of the bridge itself.{{efn|The dead load also includes any permanent fixtures on the bridge, such as light poles, traffic signage, and guardrails;{{sfn|Barker|2007|p=161}}}} The [[Structural load#Live load|live load]] is all forces and vibrations caused by traffic passing over the bridge, including braking and acceleration.  The [[Structural load#Environmental load|environmental load]] encompasses all forces applied by the bridge's surroundings, including weather, earthquakes, mudslides, water currents, flooding, [[Subsidence|soil subsidence]], [[frost heaving]], [[Thermal expansion|temperature fluctuations]], and [[Bridge strike|collisions]] (such as a [[Ship collision|ship striking]] the pier of a bridge).<ref name=load>{{Multiref
|{{harvnb|Cruickshank|2010|p=34}}.
|{{harvnb|Ryall|2000|pp=43-44}}.
|{{harvnb|Huff|2022|pp=23–45}}.
|{{harvnb|Barker|2007|pp=161-162}}.
|{{harvnb|Zhao|2017|pp=100–117}}.
}}</ref>{{efn|There are other ways to classify loads in addition to dead/live/environmental. One is permanent loads (bridge structure) and transient loads (traffic and environment).{{sfn|Barker|2007|p=161}}.  Another is dead (bridge structure) and live (vehicles and environment).{{sfn|Cruickshank|2010|p=34}}  }}

====Return period====
Many load sources vary over time, such as vehicle traffic, wind, and earthquakes. A bridge designer must anticipate the maximum values that those loads are likely to reach during the bridge's lifespan.{{sfn|Barker|2007|p=161}} For sporadic events like floods, earthquakes, collisions, and hurricanes, bridge designers select a maximum severity that the design must accommodate.{{sfn|Barker|2007|pp=197, 201}} The severity is based on the [[return period]], which is average time between events of a given magnitude.  Return periods range from 10 to 2,500 years, depending on type of event and the country in which the bridge is located.<ref>{{Multiref
|{{harvnb|Barker|2007|pp=197, 201}}.
|{{harvnb|Kulicki|2014|p=122}}.
|{{harvnb|Chen|Duan|2014|pp=52, 99, 301,334, 420, 435, 502, 539, 542, 645, 836, 918 }}. Authors discussing international bridge design policies cite return periods of 10, 50, 350, 475, 500, 1000,  2000, and 2500 years.
}}</ref> Longer return periods are used for bridges that are a critical part of the transportation infrastructure. For example, if the bridge is a key lifeline in case of emergencies, the designer may utilize relatively long return period, such as 2,000 years; in this example, the design must endure the strongest storm that is expected to happen once every 2,000 years.{{sfn|Barker|2007|pp=161, 197, 201}}

====Stress and strain====
{{Further|Stress (mechanics)}}
[[File:Software app that performs stress analysis on structures.jpg|thumb|alt=A computer screen running an app that is displaying engineering information| [[Computer-aided design|Software applications]] are used in the bridge design process, such as this app that evaluates [[Stress (mechanics)|stress]] and [[Strain (mechanics)|strain]].{{sfn|Krimotat|2014|p=256}}
]]

[[File:Stress strain ductile.svg|thumb|alt=A two-dimensional graph showing a curved line|Bridge engineers use [[stress–strain curve]]s to assist with the design process.<ref name=stressstrain/>]]

The load forces acting on a bridge cause the components of the bridge to become [[Stress (mechanics)|stressed]]. Stress is a measure of the internal force experienced within a material. Strain is a measure of how much a bridge component bends, stretches, or twists in response to stress. Some strain (bending or twisting) may be acceptable in a bridge component if the material is [[Elasticity (physics)|elastic]]. For example, steel can tolerate some stretching or bending without failing. Other materials, such as concrete, are [[Elasticity (physics)|inelastic]], and their change in shape when stressed is negligible (until the stress becomes excessive and the concrete fails).<ref name=stressstrain>{{Multiref
|{{harvnb|Ellobody|2014|pp=47–54}}.
|{{harvnb|Beer|2017|pp=7–13, 28–34, 55–77, 100–104, 119–122, 237–247}}.
}}</ref>

A bridge designer must calculate the maximum stress that each bridge component will experience, then select an appropriate design and size for the components to ensure they will safely tolerate the loads on the bridge. Stresses are categorized based on the nature of the force that causes the stress, namely: compression, tension, shear, and torsion. [[Compression (physics)|Compression]] forces compact a component by pushing inward (for example, as felt by a bridge foundation when a heavy tower is resting on it). [[Tension (physics)|Tension]] is a stretching force experienced by a component when pulled (for example by the cables of a suspension bridge). [[Shear force|Shear]] is a sliding force experienced by a component when two offset external forces are applied in opposite directions (for example, during an earthquake when the upper part of a structure is pulled north, and the lower part is pulled south). [[Torsion (mechanics)|Torsion]] is a twisting force.<ref name=stress>{{multiref
|{{harvnb|Cruickshank|2010|p=35}}.
|{{harvnb|Brown|2005|pp=14–15}}.
|{{harvnb|Shanmugam|2000|pp=95–123}}.
|{{harvnb|Bennett|1999|pp=67–70}}.
}}
</ref>

==== Traffic====
An important component of the live load carried by a bridge is the vehicle and rail traffic the bridge carries.<ref name=traffic>{{multiref
|{{harvnb|Barker|2007|pp=164–188}}.
|{{harvnb|Ellobody|2014|pp=24, 116–154}}.
}}</ref> In addition to the weight of the vehicle, other forces must be considered, including braking, acceleration, centrifugal forces, and resonant vibrations.<ref name=braking>{{multiref
|{{harvnb|Barker|2007|pp=161–165}}.
|{{harvnb|Cruickshank|2010|p=34}}.
}}</ref> For roadways, the loads imposed by truck traffic far exceed the loads imposed by passenger cars, and so the bridge design process focuses on trucks.{{sfn|Barker|2007|pp=164-165}}

The loads created by trains and vehicles can be determined by modelling, or by relying on data and algorithms contained in engineering specifications published by organizations such as [[Eurocode]] or [[AASHTO]].{{sfn|Ellobody|2014|pp=4-7,24}} Alternatively, [[weigh-in-motion]] technology can measure loads on existing bridges with comparable traffic patterns, providing real-world data which can be used to evaluate a proposed bridge design.{{sfn|O'Brien|2015|pp=41-43}}

==== Vibration ====
[[File:Vortex-street-animation.gif|thumb|alt=An animated video showing wind blowing left to right, creating circular vortexes as it passes by a fixed object|Bridge designers must account for forces caused by wind, such as the [[vortex shedding]] shown here.<ref name=flutter_vortex/>]]

[[File:Tacoma Narrows Bridge destruction.ogv|alt=Video shows a large suspension bridge moving and twisting wildly, pushed by the wind, eventually collapsing.|thumb|The [[Tacoma Narrows Bridge (1940)#Collapse|Tacoma Narrows Bridge]] collapsed shortly after opening in 1940 due to failure of the design to properly account for wind forces.<ref name=narrows/>]]

[[File:FEMA - 2816 - Photograph by FEMA News Photo taken on 01-17-1994 in California.jpg|thumb|alt=A collapsed concrete bridge, with a broken support pier.
|This bridge collapsed in the  [[1994 Northridge earthquake]] after the reinforced concrete pier was damaged.<ref>{{Multiref
|{{harvnb|Yashinsky|2014|p=54}}.
|{{harvnb|"Northridge Earthquake Image 2816". ''National Archives''}}.
}}</ref>  ]]

Many loads imposed on a bridge{{snd}}such as wind, earthquakes, and vehicular traffic{{snd}}can cause a bridge to experience irregular or periodic forces, which may cause bridge components to vibrate or [[oscillate]].<ref>{{Multiref
|{{harvnb|Ryall|2000|pp=62–68}}.
|{{harvnb|Barker|2007|pp=178–179,195}}.
|{{harvnb|O'Brien|2015|pp=40,57–58}}.
}}</ref> Some bridge components have inherent [[resonant frequencies]] to which they are particularly susceptible, and vibrations near those frequencies can cause very large stresses.<ref>{{Multiref
|{{harvnb|Ellobody|2014|pp=24,130,142–144}}.
|{{harvnb|Cruickshank|2010|pp=252–253}}.
|{{harvnb|O'Brien|2015|pp=40,57–58}}.
}}</ref>

Winds can produce a variety of vibrational forces on a bridge, including [[Aeroelasticity#Flutter|flutter]], [[galloping (wind)|galloping]], and [[vortex shedding]].<ref name=flutter_vortex>{{Multiref
|{{harvnb|Cai|2014|pp=541-547}}.
|{{harvnb|Ryall|2000|pp=63-66}}.
|{{harvnb|Jones|Howells|2000|pp=641–644}}.
|{{harvnb|Scott|2001|pp=89–93}}.
}}</ref> Considering wind forces during the design process is especially important for long, slender bridges (typically suspension or cable-stayed bridges).<ref>{{Multiref
|{{harvnb|Cai|2014|pp=535-536}}.
|{{harvnb|Ryall|2000|p=63}}.
|{{harvnb|Jones|Howells|2000|pp=641–644}}.
|{{harvnb|O'Brien|2015|pp=40,57–58}}.
}}</ref>  

The Eurocode guideline for bridge design specifies that vibration stress due to moving vehicles should be accounted for by including an additional 10% to 70% of the vehicles' static load; the exact value depends on the span length, the number of traffic lanes, and the type of stress (bending moment or shear force).{{sfn|Dawe |2003 |p=149}}

If resonance issues are identified in the design process, they must be mitigated.  Common techniques to address vibration include  increasing the rigidity of the bridge deck by adding trusses and adding dampers to cables and towers.<ref>{{Multiref
|{{harvnb| O'Brien|2015 |pp=41–46, 57}}.
|{{harvnb|Cruickshank|2010|pp=243–244}}.
|{{harvnb| "Resisting the Twisting". ''Golden Gate Bridge Highway and Transportation District'' }}.
}}</ref> One mechanism used to combat oscillations is a [[tuned mass damper]],  which was first used in the [[Pont de Normandie]] in 1995.<ref>{{Multiref
|{{harvnb|Brown|2005|pp=170,184,203}}.
|{{harvnb|Cai|2014|pp=552-553}}.
|{{harvnb|Farquhar |2000|p=589 }}.
}}</ref> The [[Akashi Kaikyo Bridge]] has twenty tuned mass dampers, weighing nine tonnes each, inside its steel towers.{{sfn|Sangree|Shafer|2003}}

Neglecting to account for vibrations and oscillations can lead to bridge failure. The [[Angers Bridge]] collapsed in 1850, killing over 200 people, partly due to soldiers [[marching]] on the bridge in a manner that increased resonant oscillations.{{sfn|Cruickshank|2010|pp=243-244}}{{efn|In spite of advances in engineering technologies, modern bridges continue to experience severe swaying issues when large numbers of pedestrians are walking on the bridge, even when they are not marching in a synchronized manner.<ref name=millen/>}} The [[Tacoma Narrows Bridge (1940)#Collapse|Tacoma Narrows Bridge]] collapsed in the 1940 in winds of {{convert|68|km/h|mph|abbr=on|sp=us}}, even though the bridge was designed to withstand winds up to {{convert|206|km/h|mph|abbr=on|sp=us}}. Investigations revealed that the designer failed to account for wind effects such as flutter and resonant vibrations.<ref name=narrows>{{Multiref
|{{harvnb|Barker|2007|pp=12–14}}.
|{{harvnb|Cruickshank|2010|pp=252–253}}.
|{{harvnb|"Tacoma Narrows Bridge History". ''Washington Department of Transportation''}}.
}}</ref> The [[Golden Gate Bridge]] was damaged in 1951 due to wind forces, and as a result was reinforced with additional stiffening elements.{{sfn| "Resisting the Twisting". ''Golden Gate Bridge Highway and Transportation District''  }}

[[Earthquake]]s can subject bridges to ground motions that cause severe damage.<ref>{{Multiref
|{{harvnb|Yashinsky|2014|pp=53-55, 61, 77, 83, 94}}.
|{{harvnb|Bennett|1999|p=173}}.
}}</ref>   Following seismic events, [[earthquake engineer]]s study the seismic data to classify and quantify the motions experienced by bridges.{{sfn|Yashinsky|2014|pp=53-54}} These studies are used by governments to create and revise design standards that specify the types of seismic movements that new [[Earthquake-resistant structures|bridges must withstand]].{{sfn|Yashinsky|2014|p=53}} Earthquakes can cause long-period velocity pulses, shear cracks, large ground motions, vertical accelerations, and [[soil liquefaction]].{{sfn|Yashinsky|2014|pp=53-56}}{{
efn|Government agencies that have published earthquake engineering standards for bridges include:   [[Chinese Ministry of Transport]], [[Japan Road Association]], [[Eurocode 8: Design of structures for earthquake resistance| European Committee for Standardization]],  [[American Association of State Highway and Transportation Officials]], and  [[California Department of Transportation]].{{sfn|Yashinsky|2014|p=53}}  
}}

==== Methodologies and tools====
{{Further|Structural analysis|Structural engineering}}
[[File:Puente atirantado CivilFEM.png|thumb|alt=A computer app displaying a bridge with engineering data|Engineers use [[finite element method]] software tools to evaluate a bridge design.<ref>{{Multiref
|{{harvnb|Shanmugam|2000|pp=188,293}}.
|{{harvnb|Jones|Howells|2000|pp=640–641}}.
}}</ref>
]]

The process used to design bridges employs [[structural analysis]] methods and techniques.{{sfn|Barker|2007|pp=283-288}} These methods divide the bridge into smaller components, and analyze the components individually, subject to certain constraints.{{sfn|Barker|2007|pp=283-288}} A proposed bridge design is then [[mathematical model|modeled]] with formulas or computer applications.<ref name=computr>{{Multiref
|{{harvnb|Krimotat|2014|pp=253-257}}.
|{{harvnb|Barker|2007|pp=283-288}}.
}}</ref> The models incorporate the loads and stresses the bridge will experience, as well as the bridge's structure and material. The models calculate the stresses in the bridge and provide data to the designer indicating whether the design meets the required design goals.<ref name=computr/>

Bridge design models include both [[mathematical model]]s and [[numerical model]]s.{{sfn|Barker|2007|pp=283-288}} The mathematical models that assess bridge loads and stresses are complex formulas that typically include differential equations. Solving these formulas directly is virtually impossible, so numerical models are used to provide approximate, but accurate, results.{{sfn|Barker|2007|pp=283-288}} The [[finite element method]] is a numerical model commonly used to perform detailed analysis of stresses and loads of a bridge design.<ref>{{Multiref
|{{harvnb|Shanmugam|2000|pp=177–190, 206, 210, 292–296, 640–641, 713, 940}}.
|{{harvnb|Yamaguchi|2014|pp=225-226,236}}.
|{{harvnb|Ellobody|2014|pp=1–7}}.
|{{harvnb|Reddy|2004|pp=1–23}}.
}}</ref>{{efn|An alternative to the finite element method is the simpler, but less powerful, [[finite strip method]].{{sfn|Barker|2007|p=303}}}} The finite element method models a proposed bridge by dividing it into numerous small, interconnected pieces, and applying a computer algorithm to the pieces. The algorithm simulates the stresses on the bridge that are caused by the loads, and can iterate over time to simulate dynamic movements.{{sfn|Reddy|2004|pp=1-23}}

A bridge designer evaluates the output of the models to determine if the design meets the design goals. Many criteria are evaluated when determining if a bridge design is sufficient, including deflection, cracking, fatigue, [[Bending|flexure]], shear, torsion, buckling, settlement, bearing, and sliding.{{sfn|Barker|2007|pp=114, 124-127}} The criteria, and their allowable values, are termed [[limit state]]s. The set of limit states selected for a design are based on the bridge's structure and purpose.<ref>{{Multiref
|{{harvnb|Barker|2007|pp=114, 124–127}}.
|{{harvnb|Zhao|2017|pp=127–131 }}.
}}</ref>

To ensure that a proposed bridge design is sufficiently strong to endure foreseeable stresses, many bridge designers use methodologies such as [[limit state design]] (used in Europe and China) or [[Load and Resistance Factor Design]] (LRFD) (used in US).<ref>{{Multiref
|{{harvnb|Barker|2007|pp=113–118}}.
|{{harvnb|Zhao|2017|pp=125–131, 341–349}}.
|{{harvnb|Du|Au|2005}}.
}}</ref> These methodologies add a margin of safety to the bridge design by incorporating [[safety factor]]s into the design process.{{sfn|Barker|2007|pp=114-120,134-137,142, 157-158}} The safety factors are applied two ways: (a) increasing the assumed loads and stresses the bridge will experience; and (b) decreasing the assumed strength of the bridge's structure.{{sfn|Barker|2007|pp=117-128}}{{efn|The strength of a bridge component is referred to as ''resistance'' in the context of LRFD.{{sfn|Barker|2007|pp=113-114}}}} The magnitude of the safety factors are based on several considerations, including the bridge's own dead weight, vehicle traffic, earthquakes, water or ice flows (from rivers or ocean currents) impacting the bridge foundations, rain or snow on the bridge, wind, settling into the soil, and collisions.{{sfn|Barker|2007|pp=113-114,161-162, 463}}{{efn|Collisions include vehicles on the deck striking a bridge structure; or a ship striking a bridge foundation.{{sfn|Barker|2007|p=463}}}}

==Construction==
{{Further|Bridge design}}

[[File:Schematic diagram showing some structural elements of a bridge.svg|thumb|alt=A schematic diagram identifying the various parts of a Hypothetical bridge|right|upright=1.2|Some elements of a fictional bridge. 1 Approach, 2 Arch, 3 Truss, 4 Abutment, 5 Bearing, 6 Deck and beams, 7 Pier Cap, 8 Pier, 9 Piling, 10 Footing, 11 Caisson, 12 Subsoil.<ref>{{Multiref
|{{harvnb|Zhao|2017|pp=2–6}}.
|{{harvnb|"Tacoma Narrows Bridge History". ''Washington Department of Transportation''}}.
}}</ref>]]

The structural elements of a bridge are generally divided into the  [[Substructure (engineering)|substructure]] and the [[superstructure#Bridges|superstructure]].{{sfn|Zhao|2017|pp=4-7}}  The substructure consists of the lower portions of the bridge, including the [[foundation (engineering)|footing]]s,{{efn|The term ''[[foundation (engineering)|foundation]]'' is sometimes used to represent footings, but in most contexts ''foundation'' means all or most of the substructure.{{sfn|Elnashai|2000|pp=530-531}}}} [[abutment]]s, [[Pier (bridge structure)|pier]]s, [[piling]]s, anchorages, and [[bridge bearing|bearing]]s.{{sfn|Zhao|2017|pp=6,7}}  The superstructure rests upon the substructure, and consists of the [[Deck (bridge)|deck]],   trusses, arches, towers, cables, beams, and girders.<ref>{{Multiref
|{{harvnb|Zhao|2017|pp=4–5}}.
|{{harvnb|"Tacoma Narrows Bridge History". ''Washington Department of Transportation''}}.
}}</ref>

===Construction process===

Construction of a bridge is typically managed by [[construction engineer]]s, who are responsible for planning and supervising the construction process.   Important aspects of this role include budgeting, scheduling, periodically conducting formal [[design review]]s, and communicating with the bridge designers to interpret and update the [[Engineering drawing|design plans]].<ref>{{Multiref
|{{harvnb|Durkee|2014|pp=24-25}}.
|{{harvnb|Blank|2014|pp=67-71}}.
}}</ref>{{efn|An example schedule for design reviews is to hold them at 33%, 65%, 95%, and 100% of bridge completion.{{sfn|Blank|2014|p=70}}}}

The forces experienced by a bridge during construction can be larger or have a different nature than the forces it will experience after completion. The bridge design process typically focuses on the strength of the fully completed bridge, but it should also consider the unusual stresses that individual elements will experience during construction. Special  techniques may be required during construction to avoid excessive stresses, such as temporary supports under the bridge, temporary reinforcement, or bracing of specific elements.<ref>{{Multiref
|{{harvnb|Durkee|2014|pp=3-4}}.
|{{harvnb|Kulicki|2014a|pp=307-308 }}.
}}</ref>

When an existing bridge is being replaced or refurbished, the impact on traffic flow can have a detrimental effect on residents and services. [[Accelerated bridge construction]] processes{{snd}}that focus on using pre-fabricated components and a rapid timetable{{snd}}may be used to mitigate the impacts.{{sfn|Tang|2014a|pp=175-179}}

===Substructure ===
[[File:Bridge abutment diagram side-by-side.svg|alt=Two schematic diagrams showing how force is transmitted in a flat bridge compared to an arched bridge|thumb|upright=1.2|Abutments are an important element of a substructure. Beam bridges (left) direct force vertically into the abutments; some arch bridges (right) direct forces diagonally. 1 Deck, 2 Abutments, 3 Subsoil, 4 Load on bridge, 5 Force from abutment into subsoil.<ref name=abutDiag/>]] 

Construction of all bridge types begins by creating the substructure. The first elements built are typically the footings and abutments, which are typically large blocks of reinforced concrete, entirely or partially buried underground.  The footings and abutments support the entire weight of the bridge, and transfer the weight to the [[subsoil]].<ref name=foundation>{{Multiref
|{{harvnb|Zhao|2017|pp=6,7}}.
|{{harvnb|Islam|Malek|2014|pp=181-182}}.
|{{harvnb|Ma|2014|pp=239-240}}.
}}</ref> Based on their height-to-width ratio, footings are categorized as: [[shallow foundations|shallow]] (height is less than width) or [[deep foundations|deep]] (height is greater than width).<ref name=deep>{{Multiref
|{{harvnb|Islam|Malek|2014|pp=181-182}}.
|{{harvnb|Ma|2014|pp=239-240}}.
}}</ref>   If the subsoil cannot support the load placed on the footings, [[piling]]s must first be driven below the footings: pilings are long structures{{snd}}made of wood, steel, or concrete{{snd}}placed vertically below footings.<ref name=piles>{{Multiref
|{{harvnb|Gerwick|2014|pp=138-147}}.
|{{harvnb|Ma|2014|pp=239-244, 247, 272}}.
|{{harvnb|Denison|2012|pp=233–234, 246,248}}.
|{{harvnb|Cruickshank|2010|p=206}}.
}}</ref>  Some pilings reach down and rest on [[bedrock]]; others rely on friction to prevent the footing from sinking lower.<ref name=piles/>

Abutments are usually located at the ends of a bridge deck, where it reaches the subsoil.{{sfn|Zhao|2017|pp=6,23, 356-362}} They direct the weight into the subsoil, either vertically or diagonally.<ref name=abutDiag>{{Multiref
|{{harvnb|Bennett|1999|pp=72, 228}}.
|{{harvnb|Cruickshank|2010|pp=35, 64, 162, 207, 364–365}}.
}}</ref> Abutments may also act as retaining walls, keeping the subsoil under the approach road from eroding.{{sfn|Zhao|2017|pp=6,23, 356-362}} After footings for the piers have been created, the piers and pier caps are built to complete the substructure.<ref>{{Multiref
|{{harvnb|Rookhuyzen|2018 }}.
|{{harvnb|Zhao|2017|pp= 395–403}}.
|{{harvnb|Shirley-Smith}}.
}}</ref>{{efn|A pier cap is a block of concrete at the top of a pier, upon which rests the deck.{{sfn|Zhao|2017|pp=33,67,397}} }} Suspension bridges usually require anchorages, which are large reinforced concrete blocks solidly anchored into the earth{{snd}}they must be exceptionally heavy and tied into the subsoil because they must withstand the lateral pull of the large cables that hold the entire deck and live load.<ref name=anchor>{{Multiref
|{{harvnb|Cruickshank|2010|pp= 227, 249–250, 343,  360}}.
|{{harvnb| Brown|2005|pp= 107–108, 110,  113, 202}}.
|{{harvnb|Bennett|1999 |pp= 84,118, 228}}.
}}</ref>{{efn|[[Self-anchored suspension bridge]]s do not require anchorages.{{sfn|Brown|2005|p=107}}}}

====Building supports in water====
{{multiple image
<!--  | width = 160  -->
| caption_align=center
 | header =           
 | image1 = Abernethy Bridge Project June 2023 (52956248522), enclosed column.jpg
 | alt1= A large concrete structure in the middle of a river, kept dry by a steel wall surrounding it
 | caption1 = This concrete bridge pier is being built within a [[cofferdam]] (the rusted, vertical steel walls).{{sfn|"I-205 Abernethy Bridge". ''Oregon Department of Transportation''}}
 | image2 = Caisson Schematic diagram.svg
 | alt2 = A schematic diagram showing the cross section of a structure used to excavate bridge foundations under water
 | caption2 = To build a bridge pier in water, [[Caisson (engineering)|caissons]] may be used to hold workers and machinery during excavation.{{sfn|Bennett|1999|pp=111-112}}
}}

When bridge supports (such as piers or towers) are built in a river, lake, or ocean, special technologies must be utilized.{{sfn|Gerwick|2014|pp=137-138}} [[Caisson (engineering)|Caissons]] can be used to provide a workspace while constructing the submerged portion of the supports. A caisson is a large, watertight, hollow structure, open on the bottom. It is usually sunk to the bottom of the water and workers can work inside, preparing the ground for the footings. When excavation is complete, a caisson is typically filled with concrete to create all or part of the footing.<ref name=caisson>{{multiref
|{{harvnb|Gerwick|2014|pp=156, 161-162}}.
|{{harvnb|Cruickshank|2010|p= 285}}.
|{{harvnb|Brown|2005|pp=77-78, 92-93}}.
|{{harvnb|Bennett|1999|pp=111–112}}.
}}</ref>  Air pressure inside a sealed caisson must be kept high to prevent water from seeping in.{{sfn|Cruickshank|2010|p=53}} Workers, if they do not properly [[Decompression (diving)|decompress]] when exiting the caisson, can get [[decompression sickness]].<ref name=bends/> Early bridge builders did not understand decompression, and deaths were common: thirteen workers died from decompression sickness when building the [[Eads Bridge]] (completed in 1874).<ref name=bends>{{multiref
|{{harvnb|Brown|2005|p=89}}.
|{{harvnb|Bennett|1999|pp=111–112 }}.
}}</ref> 

An alternative to a caisson is a [[cofferdam]], which is a temporary dam surrounding the support location, open on top, where workers may work while constructing the footings.<ref name=coffer>{{Multiref
|{{harvnb|Gerwick|2014|pp=148-155}}.
|{{harvnb|Bennett|1999|p=228}}.
}}</ref> Another approach for constructing foundations in water was employed for the [[Akashi Kaikyo Bridge|Akashi Kaikyo suspension bridge]]: the two foundations for its towers are {{convert|70|m|ft|sp=us}} tall and {{convert|80|m|ft|sp=us}} in diameter. The foundations were partially built on land, then towed by tugboats to the bridge site. They were sunk to the bottom in water {{convert|60|m|ft|sp=us}} deep, and each was filled with 355,000 cubic meters of concrete. The foundations rest directly on the ocean bottom, without pilings or footings.<ref>{{Multiref
|{{harvnb|Sangree|Shafer|2003}}.
|{{harvnb|Kashima|Sakamoto|1998|pp=71–72}}.
}}</ref>

====Bearings====
{{main|Bridge bearing}}
[[File:Bajai hid 06.jpg|thumb|upright=0.9|alt=Two cylinders of steel, supporting a large steel bridge, and resting on a concrete support|<!-- The superstructure of this bridge can accommodate slight movements without damage, --> This bridge superstructure rests on [[bridge bearing|bearings]].{{sfn|Zhao|2017|pp=424–434}}]]
[[Bridge bearing|Bearings]] are often placed between the superstructure and the substructure at the points of contact. Bearings are mechanical devices that enable small movements{{snd}}which may result from 
[[thermal expansion|thermal expansion and contraction]], [[Creep (deformation)|material creep]], or minor [[seismic event]]s. Without bearings, the bridge structure may be damaged when such movements occur. Bearings can be selected to permit small rotational or slipping movements in a specific direction, without permitting movements in other directions. Types of bearings used on bridges include hinge bearings, roller bearings, rocker bearings, sliding bearings, spring bearings, and [[Elastomeric bridge bearing|elastomeric bearings]].<ref name=bearing>{{Multiref
|{{harvnb|Dornsife|2014|pp=1-9}}.
|{{harvnb|Shanmugam|2000|p=96}}.
|{{harvnb|Zhao|2017|pp=424–434}}.
}}</ref>

===Superstructure ===
[[File:Golden Horn Metro Bridge Mars 2013.jpg|thumb|alt=A bridge being constructed, with two large cranes on top|[[Gantry crane|Gantries]] are one technique used to gradually assemble a bridge deck.{{sfn|Bennett|1999|pp=79-80, 97, 226}}]]

[[File:Gewoelbebruecke A73.jpg|thumb|alt=A huge wooden arch structure, over which an arch bridge is being built|This temporary [[falsework]] will be removed after an arch is built over it.<ref name=falsework/>]] 
 
After the substructure is complete, the superstructure is built, resting on the substructure. [[Beam bridge]] superstructures may be fabricated off-site (common for steel beams) or cast-in-place (for many concrete beams).<ref>{{Multiref
|{{harvnb| Bennett| 1999  | p=78  }}.  
|{{harvnb| Bennett| 2000 | pp=24–26  }}.  
|{{harvnb| Barker | 2007| pp=20–21  }}.  
}}</ref> The beams may be laid across the piers by a crane or [[Gantry crane|gantry]].<ref>{{Multiref
|{{harvnb|Hewson|2000|p=286}}.
|{{harvnb|Brown|2005|p=141}}.
}}</ref> If the span crosses a deep ravine, a technique known as [[incremental launching|launching]] may be used: the beams and deck are assembled on the approach road, then pushed horizontally across the obstacle.<ref name=launch/>{{efn|[[Incremental launching]] may be employed for several types of bridges: beam bridges, deck arch bridges, and cable-stay bridges with short spans. In all cases, the substructure is completed first, then the deck is pushed horizontally across the top of the substructure.<ref name=launch/>}}

[[Arch bridge]] superstructure construction methods depend on the material. Concrete or stone arches use a temporary wood structure known as [[falsework]] or [[centering]] to support the arch while it is built.<ref name=falsework>{{Multiref
|{{harvnb|Zhao|2017|p=16}}.
|{{harvnb|Cruickshank| 2010|pp = 64, 97,  334, 362 }}.
|{{harvnb|Brown | 2005|pp=21, 44, 54, 101, 140, 202}}.
|{{harvnb|Bennett|1999|pp=16, 70, 228}}.
|{{harvnb|Shirley-Smith}}.
}}</ref> Some steel arch bridges are constructed without falsework: both sides are built in a cantilever fashion from the abutments, and when they reach the middle, they are jacked slightly apart for the final section to be inserted.<ref>{{Multiref
|{{harvnb|Brown | 2005|pp=101, 140}}.
|{{harvnb|Shirley-Smith}}
}}</ref>

[[Cantilever bridge]] superstructures are usually built incrementally by proceeding outward from anchorages or piers. Most cantilever superstructures can be built without temporary support piers, as the bridge can support itself as it extends outward. A similar process is used for steel or concrete cantilevers: prefabricated sections may be positioned at ground (or water) level and hoisted into place with a gantry, or may be transported horizontally along the previously completed portion of the cantilever. Concrete cantilevers require steel prestressing cables to be passed through tubes within each section and tightened, which will put the concrete into compression.<ref>{{Multiref
|{{harvnb|Cruickshank|2010|pp=292–297}}.
|{{harvnb|Brown | 2005|pp=78,79}}.
|{{harvnb|Shirley-Smith}}.
|{{harvnb|Theryo|2014|pp=97-101 }}.
|{{harvnb|Kulicki|2014a|pp= 283-287,293-301 }}.
}}</ref>  [[Truss bridge]]s are built using a variety of methods, including piece-by-piece,  cantilevering, or falsework.{{sfn|Kulicki|2014a|pp=307-308 }}

[[Cable-stayed bridge]] superstructures begin with the construction of one or more towers, which rest directly on footings that are part of the substructure. The deck is constructed in pieces beginning at the towers{{efn|name=OneTower}} and moving outward. As each piece of the deck is added, it is connected to towers with steel cables, and the cables are tightened to take the load of the deck. The deck proceeds outwards in both directions at the same rate, to ensure the forces applied to the tower are balanced. If the deck is made of concrete, steel prestressing cables are inserted through tubes inside each deck section, and tightened to put the concrete into compression.<ref>{{Multiref
|{{harvnb|Cruickshank|2010|pp=340–355}}.
|{{harvnb|Shirley-Smith}}.
|{{harvnb|Gimsing |1997|pp=438-444}}.
}}</ref>

[[Suspension bridge]] superstructure construction usually begins with the towers.{{sfn|Gimsing |1997|pp=434-436}}{{efn|name=OneTower}} The towers may be steel or concrete, and rest directly on footings. The large cables are created by hauling a large pulley back and forth across the span, stringing multiple wires between the anchorages in each pass, in a process termed ''spinning''. After the wires are spun, they are bundled together to form the cables.{{efn|Spinning the wires took 209 days for the [[George Washington Bridge]].{{sfn|Bennett|1999|p=118}}}} The cables are securely fastened to the anchorages at both ends.{{efn|Some suspension bridges, called [[self-anchored suspension bridges]], do not use anchorages.{{sfn|Gimsing |1997|pp=192-193}}}} Vertical wires called ''hangers'' are suspended from the cables, then small sections of the deck are attached to the hangers, and the sections are attached to each other.<ref>{{Multiref
|{{harvnb|Bennett|1999|pp=84,89–90, 118}}. 
|{{harvnb|Shirley-Smith}}.
|{{harvnb|Brown|2005|pp=8,87,91,106,109,202}}.
|{{harvnb|Gimsing |1997|pp=434-436}}. 
}}</ref>

====Towers====

[[File:Bridge cable saddle vs anchor.svg |upright=1.3|alt=A diagram showing a curved line passing over a curved object on top of a tower; and another diagram showing two lines that each of which end inside a tower.|thumb| A cable transfers its load to a tower by either (a) passing over a curved saddle (left image); or (b) the end of the cable is anchored into the tower (right image). Key: 1 Cable, 2 Saddle, 3 Anchor, 4 Tower.{{sfn| Gimsing|1997| pp= 395-406}}{{efn|When cables are anchored to a tower (as in the right diagram) the anchors are placed in pairs at the same height, so the horizontal forces of the two cables cancel each other out.  For clarity, this diagram shows anchors from pairs at different heights.}}]]
 
Towers are an important component of the superstructure of cable-stayed bridges and suspension bridges.{{efn|The term ''pylon'' is interchangeable with the word ''tower'' in the context of bridges.{{sfn|Gimsing |1997|p=345}}}} Towers are made of either concrete or steel. Steel towers are much lighter than concrete towers (of the same height). Concrete is generally suitable only for towers up to about {{convert|250|meters}} tall, whereas steel towers can be much taller.{{sfn|Gimsing |1997|p=345}}{{efn|Most towers are rigidly attached to the footings below them, but some relatively short towers have bearings at their base which permit pivoting.{{sfn|Gimsing |1997|p=347}}}}

Towers support the bridge cables, which{{snd}}in turn{{snd}} hold the weight of the bridge deck and the vehicular traffic. Most of the load imposed on a tower is applied vertically downward on the tower, rather than sideways.{{sfn|Gimsing |1997|pp=345-347}}  Towers experience a [[compression (physics)|compression stress]], in contrast to cables, which experience a [[tension (physics)|tension stress]].{{sfn|Bennett|1999|p=84}}  There are two mechanisms used to attach a cable to a tower: saddles or anchors. Saddles are curved structures which allow a cable to pass through (or over the top of) a tower. An anchor holds the end of a cable. Saddles are often used in suspension bridges, and anchors are often used in cable-stayed bridges.{{sfn|Gimsing |1997|pp=377-383,395-406}}

====Cables====
{{Further|Wire rope}}

{{multiple image
<!--  | width = 160  -->
| caption_align=center
 | image1 =  Suspension bridge cable cross section strands wires.svg
 | alt1= A circular cross section, showing 37 smaller circles inside a large circle; and a small dot inside one of the small circles.
 | caption1 = This cross-section of a cable shows 37 strands, where each strand consists of multiple small wires..<ref>{{Multiref
|{{harvnb| Gimsing|1997| pp=87-94}}.  Wires within a strand.
|{{harvnb| Gimsing|1997| pp= 95-100}}.  Strands within a cable.
}}</ref>

 | image2 = Verrazano-Narrows Bridge- The Beginning (15694087186).jpg
 | alt2= Two men are standing high in the air on a walkway, and a wheel is above them, suspended by wires.
 | caption2 =This wheel is spinning a pair of wires across the [[Verrazano-Narrows Bridge]] to build a cable.{{sfn|Talese|2014|pp=65-77}}
}}
 
{{multiple image
|image1                 =  Tacoma Narrows bridge cable saddle.jpg 
 |width1=200
 |alt1=Thick cables, composed of hundreds of small steel wires, inside a dark room.
|caption1=This suspension bridge cable transfers its heavy load to the tower by resting on a curved saddle.  
<!--
|image2                 = Verazanno Narrows bridge cable anchorage.jpg  
 |width2=200
 |alt2= Many parallel steel wires, attached at one end to a large concrete block.
|caption2=A large concrete anchorage (right)  holds the end of a suspension bridge cable, visible here as multiple wire strands (left).-->
}}
Steel cables are an element of both  cable-stayed bridges and suspension bridges.  Cables are made of one or more strands, and each strand consists of multiple wires. A wire is a thin, flexible piece of solid steel, of higher tensile strength than normal steel, and with a diameter of 3mm to 7mm.{{sfn|Gimsing |1997|pp=87-88}}{{efn|The number of wires in a strand is typically 37 to 127  (for PPWS construction) and 200 to 500 (for air-spinning contruction).{{sfn|Jones|Howells|2000|pp=602-604}}}} 
Cables are typically constructed at the bridge site by unspooling wires or strands from large [[reel]]s.{{sfn|Jones| Howells |2000|pp=650-653}}{{efn|Some cables consist of a single strand.  In that situation, if the strand is delivered to the bridge site on a reel, there is no need to construct the cable at the bridge site.}} Large suspension bridges may use cables that are over {{convert|1|meter|sp=us}} in diameter and weigh over 20,000 tonnes.<ref>{{Multiref
|{{harvnb|Gimsing |1997|p=56}}.  Diameter over 1m.
|{{harvnb|Sangree |Shafer|2003}}.  290 strands per cable.
|{{harvnb|Jones| Howells |2000|pp=599–603}}.  94 tonnes per strand.
}}</ref>  

Before building the cables of a suspension bridge, temporary [[Footbridge#Catwalk|catwalk]]s must be constructed to support the wires while they are drawn across the span and over the tops of the towers.{{sfn|Gimsing|1997|pp=419-421}} There are two approaches to pulling the wires across the span: the air spinning method where the individual wires are carried across by pulleys; and the prefabricated parallel-wire strand (PPWS) method where entire strands are individually pulled across.<ref>{{Multiref
|{{harvnb|Jones| Howells|2000|pp= 602-605}}.
|{{harvnb|Gimsing |1997|pp=98-99}}.
}}</ref>{{efn|For large suspension bridges, the length of wire or strand on a reel may not reach across the full span, so when a reel reaches its end, the wires (or strands) must be spliced to the wires (or strands) of a new reel.{{sfn|Gimsing|1997|pp=422-423}}}}

The air spinning method was used for all suspension bridges until the PPWS method was invented in the 1960s.{{sfn|Gimsing|1997|pp=37-38}} The air spinning method is slower because it requires the spinning pulley to cross the span thousands of times, pulling a pair of wires each time.<ref name=AS_PPWS/> After 300 to 500 wires are pulled, aluminum bands are used to bundle them into strands.{{sfn|Gimsing|1997|pp=424-425}}. The PPWS method permits strands to be built away from the bridge site, but the process of pulling the heavy strands across the full span of the bridge is more difficult.<ref name=AS_PPWS>{{Multiref
|{{harvnb|Jones| Howells|2000|pp= 602-603}}.
|{{harvnb|Gimsing |1997|pp= 37-38, 88, 98}}.
|{{harvnb|Bennett|1999|pp=84-85}}.
}}</ref>{{efn|The PPWS method  was used for the Akashi Kaikyo Bridge, where each strand weighed 94 tonnes and was {{convert|4|km|sp=us}} long.{{sfn|Jones| Howells|2000|pp= 599-603}} }}

The wires within a strand may be parallel, or they may wrap around each other in a twisted (spiral) pattern.{{sfn|Jones| Howells|2000|pp= 599-601}} Air spinning always produces strands that contain parallel wires. The PPWS method can utilize strands with parallel or twisted wires.{{sfn|Jones| Howells|2000|pp= 599-602}} 

After all the wires have been drawn across the full span and are connected to the towers, they are compacted into a tight bundle by an hydraulic device that moves along the cable and compresses the wires together.<ref>{{Multiref
|{{harvnb|Gimsing |1997|pp=99, 429-430}}.
|{{harvnb|Jones| Howells|2000|p=604}}
}}</ref> Then a wire is usually wrapped around the cable in a helical manner, to provide protection against water intrusion.{{sfn|Gimsing |1997|pp= 430-431}} The deck is suspended from the cable with vertical strands called hangers. Each hanger is attached to the main cable by a bracket called a ''cable band''.{{sfn|Gimsing |1997|pp=392-394}}

====Deck====
{{main|Deck (bridge)}}
{{Easy CSS image crop
|image                 =Fahrbahn Agnes Bernauer Brücke Straubing.JPG
|desired_width         = 260
|crop_left_perc        = 0
|crop_right_perc       = 0
|crop_top_perc         = 0
|crop_bottom_perc      = 20
|align = right
 |alt=The underside of a green bridge, consisting of many parallel pieces of steel
|caption=The [[:de:Agnes-Bernauer-Brücke (Straubing)|Agnes Bernauer Bridge]] in Germany has an [[orthotropic deck]], visible as numerous small, parallel steel ribs on its underside.
}}

[[File:Ilmtalbruecke-April2009b.jpg|thumb|alt=A large concrete arch bridge being constructed|The deck of this arch bridge is being [[incremental launching|horizontally pushed]] onto the substructure with [[Jack (device)|jacks]].<ref name=launch>{{Multiref
|{{harvnb|Hewson|2000|pp=302–306, 432–433}}.
|{{harvnb|Brown|2005|p=193}}
|{{harvnb|Shirley-Smith}}.
}}</ref>]]

The [[Deck (bridge)|deck]] of a bridge is the horizontal, continuous surface that extends across the full span of a bridge, and  upon which vehicles or pedestrians travel.  Decks generally rest on beams or box girders.  When a deck is rigidly attached to its supporting beams or girders they function together as a single structure.<ref>{{Multiref
|{{harvnb|Chavel|2022|p=1}}.
|{{harvnb|Vejrum|2014|p=413}}.
|{{harvnb|Mangus|2014|pp=592,594,596}}.
}}</ref>{{efn|The beams or box girders (that the deck rests upon) may be steel or concrete.  The top surface of a concrete box girder bridge may act as a deck, in which case, the deck is not a separate element of the bridge.  The usage of the word ''deck'' sometimes includes its supporting beams and girders.}}

The two most common types of decks are concrete decks and [[orthotropic steel deck]]s.<ref>{{Multiref
|{{harvnb|Mangus|2014|p=590}}.
|{{harvnb|Shen|2014|pp=573-575}}.
}}</ref>{{efn|Some bridges use both types of deck: concrete in some parts of the bridge, and orthotropic steel in other parts.{{sfn|Mangus|2014|p=604}}  Other materials (in addition to concrete and steel plates) used to build decks include wood planks and open steel [[grating]]s.{{sfn|Chavel|2022|pp=20,31-32}}}}   Concrete decks are flat [[Concrete slab|slabs]] of [[reinforced concrete]].  The slabs may [[Precast concrete|precast]]  off-site, or [[Cast-in-place concrete|cast-in-place]] by pouring concrete into [[formwork|forms]] on the bridge superstructure.<ref>{{Multiref
|{{harvnb|Chavel|2022|pp=5-6, 11-13}}.
|{{harvnb|Shen|2014|pp=573-575}}.
}}</ref>{{efn|An advantage of pre-cast slabs is that{{snd}}after bridge construction{{snd}}they do not shrink or [[Creep (deformation)|creep]] as much as cast-in-place slabs.{{sfn|Vejrum|2014|p=413}}}}  Orthotropic steel decks are built of numerous small [[wiktionary:rib|ribs]] of steel,  running in the direction of the bridge roadway.{{efn|''Orthotropic'' means (a) the ribs are perpendicular to the crosswise  floor beams (''ortho''gonal); and (b) the ribs are more closely spaced than the crosswise floor  beams  (aniso''tropic'').{{sfn|Dahlberg|2022|p=2 }}
}} On top of the ribs is a flat steel plate, coated with a [[wearing surface]].<ref>{{Multiref
|{{harvnb|Mangus|2014|pp=590,602}}.
|{{harvnb|Chavel|2022|pp=26-28}}.
}}</ref>  Below the ribs are floor [[Beam (structure)|beams]], placed crosswise to the ribs.{{sfn|Mangus|2014|pp=590,592}}{{efn|Floor beams are small beams that cross the width of the bridge, and rest on larger beams that run lengthwise and span the full distance between bridge supports.{{sfn|Mangus|2014|pp=590,592}}}}  Orthotropic  steel decks are more  expensive than concrete steel decks, but weigh less. They are useful in applications where weight is critical, a thin deck is required, or the environment is subject to earthquakes or extreme cold weather.{{sfn|Mangus|2014|pp=590, 604}}

Many decks have a wearing surface on top, which is a layer of material  designed to be periodically replaced after it is worn away by vehicular traffic.  Wearing surfaces are typically made of [[Construction aggregate|aggregate]] (small rocks) mixed with a [[Binder (material)|binder]] such as [[asphalt concrete|asphalt]], [[polyurethane]], [[epoxy resins]], or [[polyester]].<ref>{{Multiref
|{{harvnb|Mangus|2014|pp=625-628}}.
|{{harvnb|Chavel|2022|pp=29,32}}.
}}</ref>{{efn|[[Wearing surface]]s are essential for steel decks, but a concrete deck often acts as its own wearing surface. Concrete decks must be designed to accommodate the weight of a future addition of a wearing surface,  which will be applied when the concrete wears down due to vehicular traffic.{{sfn|Shen|2014|pp=279-280}}}} Railway bridge decks are categorized as open decks (the [[Railroad tie|ties]] rest directly  on beams or girders, with air gaps between) and [[Track ballast|ballast]] decks (the ties rest on ballast rocks, and the ballast rests on a deck slab).{{sfn|Sorgenfrei|2014|pp=147-148}}

Constructing the deck (and its supporting beams or girders) can be difficult when the bridge is over water or a deep valley.  A variety of techniques are available, and the choice depends on factors such as  the topography of the site, the deck material (concrete or steel), traffic or obstacles under the bridge, and whether sections can be built off-site and transported to the bridge.  Methods of deck construction include  building atop [[Falsework#In_bridge_construction|temporary supports]], [[Jack (device)|jacking up]] from the ground, [[incremental launching]] (building the entire deck on the approach road and pushing it horizontally),  lifting from below with a [[Hoist (device)|hoist]] mounted on the bridge, [[Cantilever#In_bridges,_towers,_and_buildings|cantilevering]] (incrementally extending the deck, starting from towers or abutments),   and lifting with a [[Crane vessel|floating crane]].<ref name=constrMethod>{{Multiref
| {{harvnb|Bakhoum|2014|pp=568-578}}.
| {{harvnb|Shi|2014|pp=86-87}}.
}}</ref>

===Protection===
[[File:Peeling paint.jpg|alt=A thick, old wire cable, with paint that is partially worn off|thumb|Paint can be used to reduce deterioration of steel components. Steel bridges need to be repainted periodically, as seen in this wire hanger from the [[Golden Gate Bridge]], which is painted [[International orange#Golden Gate Bridge|international orange]].{{sfn|"Painting The Golden Gate Bridge". ''Golden Gate Bridge, Highway and Transportation District''}}  ]]

To achieve a longer lifespan, a bridge is protected from deterioration by incorporating certain features into the design. Bridges can deteriorate due to a variety of causes, including rust, corrosion, chemical actions, and mechanical abrasion. Deterioration is sometimes visible as rust on steel components, or cracks and [[spall#Spalling in refractory concrete|spalling]] in concrete.{{sfn|Mulheron|2000|pp=805-807}}

Deterioration can be slowed with various measures, primarily aimed at excluding water and oxygen from the bridge elements.{{sfn|Mulheron|2000|pp=807-808}} Techniques to prevent water-based damage include drainage systems, waterproofing membranes (such as polymer films), and eliminating [[expansion joints]].{{sfn|Mulheron|2000|pp=810-815}}{{efn|Expansion joints relieve stress due to thermal expansion and contraction, but permit water to seep into vulnerable bridge elements, which can lead to corrosion and degradation. [[Integral bridge]] concepts are an alternative to expansion joints.{{sfn|Mulheron|2000|pp=815-816}} }}

Concrete bridge elements can be protected with waterproof seals and coatings.{{sfn|Mulheron|2000|pp=816-822}}{{efn|Concrete can deteriorate by  the process of [[carbonatation]], or by penetration of [[chloride ion]]s, typically from salt.  The salt may come from ocean water, or from [[road salt]] applied during winter de-icing procedures.{{sfn|Mulheron|2000|pp=806-808, 817-819, 821, 824 }}}} Reinforcing steel within concrete can be protected by using high-quality concrete and increasing the thickness of the concrete surrounding the steel.{{sfn|Mulheron|2000|pp=822-830}} Steel elements of a bridge can be protected by paints or by [[galvanizing]] with zinc.<ref>{{Multiref
|{{harvnb|Mulheron|2000|pp= 822–826, 830–837}}.
|{{harvnb|Zhao|2017|pp=252–268}}.
}}</ref> Paint can be avoided entirely for steel members by using certain steel alloys, such as [[stainless steel]] or [[weathering steel]] (a steel alloy that eliminates the need for paint, by forming a protective outer layer of rust).<ref>{{Multiref
|{{harvnb|Mulheron|2000|pp=837–840}}.
|{{harvnb|Zhao|2017|pp=279–284}}.
}}</ref>

[[Bridge scour]] is a potentially serious problem when bridge footings are located in water. Currents in the water can cause the sand and rocks around and below the footings to wash-away over time. This effect can be mitigated by placing a [[cofferdam]] around the footings, or surrounding the footings with [[rip-rap]].<ref>{{Multiref
|{{harvnb|Mulheron|2000|pp=842–844}}.
|{{harvnb|Kashima|Sakamoto|1998|pp=72–73}}.
}}</ref>{{efn|As an example of measures taken to  combat scour: the underwater foundations of the [[Akashi Kaikyo Bridge]] are surrounded with  [[rip rap]] {{convert|8|m|ft|sp=us}} thick.{{sfn|Kashima|Sakamoto|1998|pp=72}}}}
 
Suspension bridges and cable-stayed bridges have large cables containing hundreds of steel wires. Several techniques are used to minimize corrosion inside the cables, such as wrapping the cables with galvanized wire, injecting the cables with grout or epoxy, using interlocking S-profile wires, and circulating dry air through the interior of the cable.{{sfn|Gimsing|1997|pp=557-559,604-605}}

==Operation==

===Management===
After a bridge is completed and becomes operational, management processes are employed to ensure that it remains open to traffic, avoids safety incidents, and achieves its intended lifespan. These processes{{snd}}collectively referred to as ''bridge management''{{snd}} include technical activities such as maintenance, inspection, [[Structural health monitoring|monitoring]], and testing.{{sfn|Vassie|2000|pp=849-859}}  In addition to technical tasks, management encompasses planning, budgeting, and prioritization of maintenance activities.{{sfn|Vassie|2000|pp=849-859}} Bridge managers use methodologies such as [[bridge management system]]s and  [[Life-cycle cost analysis|Life-Cycle Cost Analysis]] to manage a bridge and estimate the maintenance costs of a bridge throughout its lifetime.<ref>{{Multiref
|{{harvnb|Hu|2016|pp=66-69}}.
|{{harvnb|Fu|Devaraj |2014|pp=233-234}}.
}}</ref> Annual maintenance costs increase as the bridge ages and degrades.{{sfn|Hu|2016|p=66}}

===Maintenance===
{{Easy CSS image crop
|image                 = Bridge maintenance - geograph.org.uk - 7061609.jpg
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 |alt=A small, movable cage with two persons standing in it, is hanging below a large white suspension bridge
|caption=A crew of workers are using a maintenance  traveler (the mobile cage structure) to inspect the [[Clifton Suspension Bridge]].
}}

Maintenance activities seek to prolong the life of the bridge, reduce lifecycle costs, and ensure the safety of the community.{{sfn|Alampalli|2014|pp=269-272}}   Maintenance tasks can be categorized as corrective tasks and  preventive tasks.{{sfn|Alampalli|2014|pp=276,282}}   Corrective tasks are implemented in response to unexpected issues that arise, such as repairing structural elements (piers, beams, girders, towers, or cables) and replacing bearings.{{sfn|Alampalli|2014|pp=288-292}}

Preventive tasks include washing, painting, lubricating bearings, sealing the deck, filling cracks,  removing snow, filling potholes, and repairing minor issues with  structures and electrical fixtures.{{sfn|Alampalli|2014|pp=282-288}}   Some preventive tasks are performed on a periodic schedule. Example intervals for periodic bridge maintenance tasks include:  
washing entire structure (1–2 years);  
sealing deck surface (4–6 years);
lubricating bearings (4  years); 
painting steel bridge components (12–15  years); 
replacing the deck's wearing surface (12  years); 
sealing  sidewalks (5  years);  
filling cracks (4  years); 
and cleaning drains (2  years).<ref>{{harvnb|Alampalli|2014|pp=285-286}}. Maintenance periods shown are from the [[New York City Department of Transportation]].</ref>

===Inspection and monitoring===
[[File:Korrosion Lieserschluchtbrücke.jpg|thumb|alt=A large block of concrete, partially crumbling, with internal steel bars exposed|This pier of a bridge in Germany is degrading, and the internal steel [[rebar|reinforcing bars]] are exposed and rusting.]]

An important part of maintenance is inspecting a bridge for damage or degradation, and taking steps to mitigate any issues detected. Degradation can come from a variety of sources: expansion/contraction from freeze/thaw cycles, rain and snow, oxidation of steel, saltwater spray, [[carbonatation]] of concrete, vehicular traffic, corrosion, mechanical abrasion, poor bridge design, and improper repair procedures.<ref>{{Multiref
|{{harvnb|Abdunur|2000|pp=883–895}}.
|{{harvnb|Mulheron|2000|pp=805–807}}.
}}</ref>  Some countries mandate periodic inspection schedules, for example, routine inspections every 24 months, or inspecting underwater foundations for scouring every 60 months.{{sfn|Copelan|2014|p=338}}

Relying solely on visual inspection to assess  degradation of a bridge can be unreliable, so inspectors use a variety of [[nondestructive testing]] techqniques.{{sfn|Washer|2014|pp=303-305}}  These techniques include [[Schmidt hammer|hammer strike]] tests, [[Ultrasonic testing|ultrasonic pulse velocity]] tests, [[seismic tomography]], and [[ground penetrating radar]].<ref>{{Multiref
|{{harvnb|Abdunur|2000|pp=898-906 }}.
|{{harvnb|Washer|2014|pp=305-306,317-318}}.
|{{harvnb|Alampalli|2014|p=295 }}.
}}</ref>  [[Magnetometer]]s can be used to detect the location of reinforcing steel within concrete.{{sfn|Abdunur|2000|pp=898-906 }} Various electrical tests, such as [[permeability (electromagnetism)|permeability]] and [[electrical resistance|resistance]], can give insight into the condition of surface concrete.{{sfn|Abdunur|2000|pp=898-906 }} X-rays can be passed through concrete to obtain data about concrete density and condition.{{sfn|Abdunur|2000|pp=908-909 }} Videography using slender probes can be used where access is available.{{sfn|Abdunur|2000|pp=910-912 }}
[[File:SOB Sitterviadukt über die Sitter, St. Gallen SG - Herisau AR 20190720-jag9889.jpg|thumb |alt=A tall bridge covered in temporary scaffolding|[[Scaffolding]] is erected under the ''[[:de:Sitterviadukt (Südostbahn)|Sitterviadukt]]'' rail bridge in Switzerland while maintenance on the deck truss is performed.{{sfn|Quirchmair|2022}}]]  

Measurements of the state of a bridge may be made automatically and periodically using [[structural health monitoring]] (SHM) technologies.{{sfn|Frangopol |2014|pp= 247-248 }} SHM places permanent sensors at critical locations in the bridge, which may be sampled at any time to obtain data about stresses and chemical degradation.{{sfn|Abdunur|2000|p=906}}  The sensors may be placed in the bridge during construction, or while it is in operation{{snd}}for example, to monitor the quality of a repair.<ref>{{Multiref
|{{harvnb|Abdunur|2000|p=906}}.
|{{harvnb|Frangopol |2014|pp= 248-249 }}.
}}</ref>    Many long-span bridges are routinely monitored with a range of sensors, including [[Strain gauge|strain transducers]], [[sodar]], [[accelerometer]]s, [[tiltmeter]]s, and [[GPS]].{{sfn|Xu|2011|pp=41-42, 45-46, 62-64, 68-69, 110-111, 216-217, 252}}

To evaluate the condition of large steel cables, electrical coils are moved along the cable, measuring the induction of the cable, which can reveal corrosion issues.{{sfn|Abdunur|2000|pp=912-914}} Detailed measurements of the external surface of a bridge can be recorded using [[lidar]] technology. Comparing measurements taken at multiple points in time can reveal long-term changes.{{sfn|Omer|2018 }}

A variety of [[Structural testing|structural tests]] may be performed to evaluate a bridge's condition. One test involves placing loads in selected locations on the bridge, and measuring the resulting deflections: sensitive instruments measure how much the bridge elements bend or twist, and the results can reveal if the element is not performing within expected limits. Another test involves jacking the bridge deck off its supports slightly, and measuring the force required. Cables can be evaluated by vibrating them and measuring their dynamic response.{{sfn|Abdunur|2000|pp=915-934}} 

Some testing{{snd}}termed [[destructive testing]]{{snd}}requires removing samples from the bridge and taking them to a laboratory for analysis with microscopes, sonic devices, or X-ray diffraction.{{sfn|Abdunur|2000|pp=896-898, 955}} Destructive testing is performed on samples such as [[Core sample|cores drilled]] from concrete, or a small piece of steel wire cut from a cable.{{sfn|Abdunur|2000|pp=896-898, 955}}{{efn|1=The process of cutting-out a small piece of wire from a large cable of a heavily trafficked suspension bridge is seen in [https://www.youtube.com/watch?v=XMbiq5aleOc&t=74 this video].}}

===Failures===
{{see also|List of bridge failures}}{{Anchor|Bridge failures}}
[[File:Nanfangao Bridge Collapse 20191003d.jpg|thumb
 |alt=A broken bridge, which has fallen into the water over which it used to pass
 |The [[Nanfang'ao Bridge]] in Taiwan collapsed because of excessive corrosion that went undetected.{{sfn| "TTSB Details Reasons for Nanfang'ao Bridge Collapse". ''Focus Taiwan''}} ]]
Bridge failures are of special importance to [[structural engineers]], because the [[failure analysis|analyses of the failures]] provide [[lessons learned]] that serve to improve design and construction processes.<ref>{{Multiref
|{{harvnb|Petroski |1994|pp=169–171}}.
|{{harvnb| "Bridge Failure". ''United Nations'' }}.
|{{harvnb|Barker|2007|pp=21–39}}.
}}</ref> Bridge failures are caused by a variety of factors, which can be categorized as   natural factors (flood, scour, earthquake, landslide, and wind) and human factors
(improper design and construction method, collision, overloading, fire, corrosion, and lack of inspection and
maintenance).{{sfn|Choudhury|Hasnat|2015|pp=26-28}}  Over time, bridge failures have led to significant improvements in bridge design, construction, and maintenance practices.<ref>{{Multiref
|{{harvnb|Barker|2007|pp=23–25}}.
|{{harvnb|Petroski |1994|pp=158–171}}.
}}</ref> 

Before the advent of bridge engineering procedures based on rigorous, scientific principles, bridges frequently failed. Failures were most common in the mid 1800s, when the rapidly expanding railway networks were building hundreds of new bridges every year around the globe.{{sfn|Barker|2007|p=22}}  In the United States, 40 bridges per year failed in the 1870s, amounting to 25% of all bridges built in that decade.<ref>{{Multiref
|{{harvnb|Barker|2007|p=22}}.
|{{harvnb|Bennett|1999|p=31}}.
}}</ref> 

In the modern era, in spite of advances in bridge engineering methodologies, bridge failures continue to be a global issue.  In Australia, the [[King Street Bridge (Melbourne)|King Street Bridge]] collapsed in 1962, a year after opening, due to improper welding techniques.{{sfn|Choudhury|Hasnat|2015|pp=30-31}}  In Palau, the [[Koror–Babeldaob Bridge]] collapsed in 1996, three months after a repair operation made major changes to the bridge.{{sfn|Burgoyne |Scantlebury |2008}}  In 1998, the [[Turag-Bhakurta Bridge]] in Bangladesh collapsed due to river waters scouring away the soil around the bridge supports.{{sfn|Choudhury|Hasnat|2015|p=32}} The [[Millennium Bridge, London|Millennium Bridge]] in London opened in 2000, but closed two days later due to excessive swaying.{{efn|The Millennium Bridge received the nickname "Wobbly Bridge" as a result of the swaying.{{sfn|Warren|2025}}}}  It did not open until two years later{{snd}}after dampers were installed.<ref name=millen>{{Multiref
|{{harvnb|Dallard|2001}}.
|{{harvnb|Warren|2025}}.
}}</ref>   About half of all bridge failures in the early 21st century in the US were due to water-related causes, such as flood damage or scouring (water currents undermining the  bridge supports).<ref>{{Multiref
| {{harvnb|Cook|2014}}.
| {{harvnb|Nowak|Iatsko|2018}}.
| {{harvnb|Wardhana |Hadipriono|2003}}.
}}</ref>
{{clear}}

==Society and culture==

=== Economic and environmental impact===

Bridges can have a significant impacts{{snd}}both positive and negative{{snd}} on a community's environment, society, and economy.   Positive effects can include shorter transport times, employment opportunities, improvements to social equity, improved productivity, and increases to  the [[gross domestic product]].  Negative impacts of bridges can include contributions to global warming,  increased traffic accidents, workplace injuries, corruption, and increased pollution (during construction, from maintenance work, and from vehicular traffic).  During the bridge design process, these effects may be modeled with [[sustainability]] methodologies such as [[Life-cycle assessment|life cycle sustainability assessment]] or  [[Building information modeling in green building |building information modeling]], and the results can be used to improve the bridge's sustainability.<ref name=sustain>{{Multiref
|{{harvnb| Ahmad|2025}}.
|{{harvnb| Zhou |2021}}.
}}</ref>

In underdeveloped regions with mountainous topography, construction of bridges that cross deep valleys can bring major benefits to  the communities they connect.  Without bridges, such areas often have a core region that is more prosperous, surrounded by less developed peripheral regions.    Building bridges over deep valleys can  reduce developmental disparities between areas, as well as generate economic development, and improve accessibility to goods and services.{{sfn|Cai|Deng|2024}}

===Metaphor and symbol===
{{Further|Bridges in art}}

{{Easy CSS image crop
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 |alt==A man blowing a trumpet, with a rainbow in the background
|caption=In [[Norse mythology]], the [[Bifröst]] rainbow bridge connects earth with [[Asgard]].{{sfn|Watson|1937|p=1}} 
}}
<!--
[[File:BridgeOfSanLuisRey.JPG|thumb|alt= The cover of a book, which has an illustration of a Catholic priest standing before a mountain and a bridge | upright=0.7|The [[Pulitzer Prize]] winning novel ''[[The Bridge of San Luis Rey]] ''revolves around a bridge failure that killed five people.{{sfn|Cruickshank|2010|pp=17-19}}]]-->
{{Quote box
 |qalign = center
| align = right
| quote = <poem>
Reaching for the world, as our lives do,
As all lives do, reaching that we may give
The best of what we are and hold as true:
Always it is by bridges that we live.</poem>
| source =  [[Philip Larkin]] "Bridge for the Living" (1981)<ref>{{Multiref
|{{harvnb| Cruickshank| 2010| pp= 13–14}}.
|{{harvnb|French|1993}}.
}}</ref> 
}}
Bridges occur extensively in art, legend, and literature, often employed in a metaphorical manner.<ref>{{Multiref
|{{harvnb|Cruickshank|2010|pp=8–20}}.
|{{harvnb|Watson|1937|pp=vii-viii,231–233 }}.
}}</ref> In [[Norse mythology]], the home of the gods{{snd}}[[Asgard]]{{snd}}is connected to the earth by [[Bifröst]], a rainbow bridge.{{sfn|Watson|1937|p=1}} Many bridges in Europe are named ''Devil's Bridge'', and sometimes have folkloric stories that explain why the bridge is associated with the devil.{{sfn|Watson|1937|pp=33, 35-39}} Christian legend holds that [[St. Bénézet]] lifted a huge boulder to begin construction of the [[Pont Saint-Bénézet]] bridge, and went on to found the apocryphal [[Bridge-Building Brotherhood]].{{sfn|Watson|1937|pp=43-48}} Stories and poems often employ a bridge as a metaphor of the human lifespan, or human experiences.{{sfn|Watson|1937|pp=65-66,71-74}} Bridges are often the setting for pageants, celebrations, and processions.{{sfn|Watson|1937|pp=103-106}} <!-- The [[Peace Bridge]] is one of several examples of bridges that were built or named to honor peace and harmony.{{sfn|Watson|1937|p=147}} --> Some nations have chosen to designate bridges that connect them as friendship bridges or peace bridges.{{sfn|Brown|2005|p=6}}{{efn|See this [[Friendship Bridge (disambiguation)|list of bridges with "friendship" in the name]],  and this [[ Peace Bridge (disambiguation)|list of bridges with "peace" in the name]].}} In 1996, the European Commission held a competition to select art for the [[euro banknotes]]. [[Robert Kalina]], an Austrian designer, won with a set of illustrations of bridges, chosen because they symbolize links between states in the union and with the future.<ref name=euro>{{Multiref
|{{harvnb|"Money Talks". ''BBC News''}}.
|{{harvnb|Schmid|2001}}.
|{{harvnb| "Design Elements". ''European Central Bank'' }}.
}}</ref>
 
Bridges are often venerated as symbols of humankind's heroism and accomplishments.{{sfn|Cruickshank|2010|pp=11,13}} The inspirational nature of bridges has led them to be featured in the works of poets, painters and writers.{{sfn|Cruickshank|2010|p=13}} Bridges feature prominently in paintings{{snd}}often in the background{{snd}}as in the ''[[Mona Lisa]]''.{{sfn|Cruickshank|2010|pp=14-16}} Authors have used bridges as the centerpiece of novels, such as ''[[The Bridge on the Drina]]'' by [[Ivo Andrić]] and [[Thornton Wilder]]'s ''[[The Bridge of San Luis Rey]]''.{{sfn|Cruickshank|2010|pp=17-19}}  British poet [[Philip Larkin]], inspired by the construction of the [[Humber Bridge]] near his home, wrote "Bridge for the Living" in 1981.{{sfn|Cruickshank|2010|pp=13-14}}

===Signature bridges===
[[File:炫彩津门35大沽桥.jpg|thumb|alt=A large bridge crossing a river, in nighttime,  with skyscrapers in the background|The [[Dagu Bridge]] in China was designed to be a signature bridge.{{sfn|Tang|2014|pp=19-20}}]]
<!-- [[File:Bristol Balloon Fiesta - panoramio (1).jpg|thumb|alt=A large bridge, and about thirty large, colorful balloons in the sky above the bridge|left| upright=1.2|The [[Clifton Suspension Bridge]] is a landmark associated with the city of [[Bristol]] in England.{{sfn|Cruickshank|2010|p=233}}]] -->
Many bridges{{snd}}known as ''signature bridges''{{snd}}are strongly identified with a particular community.<ref>{{Multiref
|{{harvnb|Brown|2005|pp=130,164-165,168,186 }}.
|{{harvnb|Cruickshank|2010|pp=23,233 }}.  
}}</ref>{{efn|Most signature bridges are roadway bridges or pedestrian bridges; railways  rarely construct signature bridges.{{sfn|Sorgenfrei|2014|p=144}}
}} Some visually impressive bridges, such as the [[Dagu Bridge]] in China, are designed with the express goal of creating a landmark for the host city.<ref>{{Multiref
|{{harvnb|Cruickshank|2010|pp=8–9}}.
|{{harvnb|Hu|2016|pp=103–112}}.
|{{harvnb|Tang|2014|pp=19-20}}.   Dagu bridge.
}}</ref> The art historian Dan Cruickshank notes that some bridges have the ability to "transform a place a community and ... can make its mark on the landscape and in men's minds, capture the imagination, engender pride and sense of identity and define a time and place."{{sfn|Cruickshank|2010|pp=8-9}} Large suspension bridges, in particular, are often regarded as iconic landmarks that symbolize the cities in which they are located. Notable examples include the [[Brooklyn Bridge]] in New York; the [[Golden Gate Bridge]] in [[San Francisco]]; the [[Clifton Suspension Bridge]] in [[Bristol]]; and the [[Széchenyi Chain Bridge]] in [[Budapest]].{{sfn|Cruickshank|2010|p=233}}{{efn|Some large cable-stayed bridges also have iconic designs.{{sfn|Vejrum|2014|pp=405-407}}}}

===Profession and regulation===
{{Further|Regulation and licensure in engineering}}
[[File:The Institution of Civil Engineers porch 2025-10-03.jpg|thumb|The [[Institution of Civil Engineers]], located in London, is the world's oldest professional civil engineering association.{{sfn|Watson|1988|pp=viii,14-16,53}}]]
The profession of [[civil engineering]]{{snd}}which includes the discipline of bridge building{{snd}} began to be formalized in the 1700s when a school of engineering was created in France within the [[Corps des Ponts et Chaussées]] at the [[École de Paris (engineering)|École de Paris]], under the direction of [[Jacques Gabriel]].{{sfn|Bennett|1999|p=24}} In 1747 the first school dedicated to bridge building was founded, also in France: the [[École Nationale des Ponts et Chaussées]]{{efn|Originally named '' Bureau des dessinateurs du Roi'', it was given its current name in 1775.}} led by engineers [[Daniel-Charles Trudaine]] and [[Jean-Rodolphe Perronet]].{{sfn|Bennett|1999|p=24}} The first professional organization focused on civil engineering was the [[Institution of Civil Engineers]] founded in 1818 in the UK, initially led by [[Thomas Telford]].{{sfn|Watson|1988|pp=viii,14-16,53}}

In the modern era, bridge engineering is regulated by national organizations, such as the [[National Council of Examiners for Engineering and Surveying]] (US), the [[Canadian Council of Professional Engineers]] (Canada), and the [[Engineering Council]] (UK).{{sfn|"The History of the National Council". ''NCEES''|pp=1,161, 366}} In many countries, bridge engineers must be licensed or meet minimal educational requirements.{{sfn|"Engineering: Issues Challenges and Opportunities". ''UNESCO''|pp=27-28, 135-136, 358-365 }} Some countries require engineers to pass qualification examinations, for example, in the US engineers must pass the [[Fundamentals of Engineering exam]] followed by the [[Principles and Practice of Engineering exam]].{{sfn|"Occupational Outlook Handbook". ''Department of Labor''|p=148}}  In Poland, bridge engineers are required to obtain certification by accumulating several years of experience under a senior engineer, and passing an exam administered by the  Polish Chamber of Civil Engineers (''[[:pl:Polska_Izba_In%C5%BCynier%C3%B3w_Budownictwa]]'').{{sfn|Biliszczuk|2014|p=632}}  International cooperation in the field of engineering is facilitated by the [[World Federation of Engineering Organizations]].{{sfn|"The History of the National Council". ''NCEES'' |pp=70-71,88,123-125,366,377 }}

===Suicide===
[[Suicide]]s are sometimes committed by [[Suicide bridge|jumping off bridges]].  This method can account for 20% to 70% of suicides in urban areas with access to tall bridges.{{efn|In general, less than 10% of suicides are from jumping.{{sfn|Merli |Costanza |2024}}}}  In some regions, suicide by jumping  disproportionately affects young adults, who tend to have lower [[inhibitory control]].  Specific bridges can gain notoriety and attract persons experiencing a [[suicidal crisis]],  which creates a [[feedback loop]]. High-risk bridges often have [[Suicide barrier|suicide prevention barriers]] installed,{{efn|Arguments against installing suicide prevention measures include cost, aesthetics, and questions of effectiveness.{{sfn|Merli |Costanza |2024}}}} which   dramatically decrease the suicide rate on the bridge.{{efn|Barriers should be at least 2m tall, and extend the full length of the bridge.{{sfn|Merli |Costanza |2024}}}}  Installing barriers on a high-risk bridge generally reduces the jumping suicide rate in a region,  although in some instances, other bridges become substitutes.{{sfn|Merli |Costanza |2024}}
<!-- ===Numismatics===
[[File:EUR 500 reverse (2002 issue).jpg|alt=A colorful 500 euro bank note illustrated with a bridge and a map of Europe|thumb|The 500 [[euro]] banknote displays a cable-stayed bridge.<ref name=euro/>]]
Bridges have been featured on coins since antiquity.{{sfn|Markowitz |2016}} In 1996, the European Commission held a competition to select art for the [[euro banknotes]]. [[Robert Kalina]], an Austrian designer, won with a set of illustrations of bridges, chosen because they symbolize links between states in the union and with the future. The designs were supposed to be devoid of any identifiable characteristics, so as to not show favoritism to specific countries. But the initial designs by Kalina were discovered to be of specific bridges, including the [[Rialto]] and the [[Pont de Neuilly]], and so were changed to be more generic. Each banknote denomination depicts a bridge design representative of a certain architectural era.<ref name=euro>{{Multiref
|{{harvnb|"Money Talks". ''BBC News''}}.
|{{harvnb|Schmid|2001}}.
|{{harvnb| "Design Elements". ''European Central Bank'' }}.
}}</ref>{{efn|
The eras utilized for bridge images on Euro banknotes are:  
Classical (€5),
Romanesque (€10),
Gothic (€20), 
Renaissance (€50), 
Baroque and Rococo (€100),
19th century iron and glass (€200), and  20th century (€500).<ref name=euro/>}}-->
{{clear}}
<!-- 
==See also==

* [[International Association for Bridge and Structural Engineering]]
* [[European Engineer]]
* [[World Federation of Engineering Organizations]] 
* [[Regulation and licensure in engineering]]
* [[National Council of Examiners for Engineering and Surveying]] USA
* [[Canadian Council of Professional Engineers]] 
* [[Chartered Engineer (UK)]]  
* [[Engineering Council]] UK
* [[Civil engineer]]
* [[American Society of Civil Engineers]]
* [[Institution of Civil Engineers]] UK?
* [[ Canadian Society for Civil Engineering]]
-->

==References==

===Footnotes===
{{notelist}}

===Citations===
{{reflist}}

===Sources===

====Books====
{{refbegin}}

<!-- {{sfn|Abdunur|2000|p=?}}  --> 
* {{cite book
 | last=Abdunur
 | first=Charles
 | chapter = Inspection, Monitoring, and Assessment
 | title=The Manual of Bridge Engineering
 | editor-last=Ryall
 | editor-first= Michael 
 | isbn= 0727727745 
 | chapter-url=https://archive.org/details/manualofbridgeen0000unse/page/883
 | access-date=1 September 2025
 | year=2000
 | publisher=[[Thomas Telford (publisher)|Thomas Telford]]
 | pages= 883–942
}}

<!-- {{sfn|Adams |1909|p=?}}  --> 
*  {{cite book 
| last=Adams 
| first=Charles Kendall
| author-link = Charles Kendall Adams
 |title=Universal Cyclopædia and Atlas 
|date=1909 
|oclc=707041389
|publisher=D. Appleton and Company   
|pages=161–174
|url=https://books.google.com/books?id=TttTAAAAYAAJ
 |access-date=September 1, 2022
 |language=en 
|chapter=Bridges
}}

<!-- {{sfn|Alampalli|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 5. Construction and Maintenance
 | edition = Second
 | first= Sreenivas 
 | last= Alampalli
 | chapter = Bridge Maintenance
 | pages = 269–298
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852330
 | url= https://books.google.com/books?id=BCeOAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}
 
<!-- {{sfn|Bakhoum|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 5. Construction and Maintenance
 | edition = Second
 | first= Mourad 
 | last= Bakhoum
 | chapter = Bridge Construction Methods
 | pages = 567–627
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852330
 | url= https://books.google.com/books?id=BCeOAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Barker|2007|p=?}}  --> 
* {{Cite book
 | title=Design of Highway Bridges: An LRFD Approach
 | last =Barker
 | first= Richard M. 
 | isbn=9781119646310
 | url=https://archive.org/details/designofhighwayb0000bark_s2n4 
 | access-date=1 September 2025
 | year=2007
 | publisher=Wiley
}}

<!-- {{sfn|Beer|2017|p=?}}  --> 
* {{Cite book
 | title=Mechanics of Materials
 | last=Beer
 | first=Ferdinand 
 | author-link = Ferdinand P. Beer
 | isbn=   9789339217624
 | url=https://archive.org/details/mechanicsofmater0000beer_a6t7
 | access-date=17 September 2025
 | year=2017 
 | publisher=[[McGraw Hill]]
}}

<!-- {{sfn|Bennett|1999|p=?}}  --> 
* {{Cite book
 | title=The Creation of Bridges: From Vision to Reality - the Ultimate Challenge of Architecture, Design and Distance
 | last=Bennett 
 | first=David
 | isbn=  1550415522
 | url=https://archive.org/details/creationofbridge0000davi
 | access-date=1 September 2025
 | year=1999
 | publisher=[[Aurum]]
}}

<!-- {{sfn|Bennett|2000|p=?}}  --> 
* {{cite book
 |last=Bennett
 | first=David 
 | chapter = The History and Aesthetic Development of Bridges
 | title=The Manual of Bridge Engineering
 | editor-last=Ryall
 | editor-first= Michael 
 | isbn= 0727727745 
 | chapter-url=https://archive.org/details/manualofbridgeen0000unse/page/1
 | access-date=1 September 2025
 | year=2000
 | publisher=[[Thomas Telford (publisher)|Thomas Telford]]
 | pages= 1–42
}}
 
 <!-- {{sfn|Biliszczuk|2014|p=?}}  --> 
* {{cite book
 | title=Handbook of International Bridge Engineering
 | last=Biliszczuk
 | first=Jan
 | display-authors=etal
 | chapter = Bridge Engineering in Poland
 | pages = 593–634
 | editor-last1 =Chen
 | editor-first1=  Wai-Fah
 | editor-last2 = Duan
 | editor-first2=  Lian
 | isbn=9781439810293
 | url=https://archive.org/details/handbookofintern0000unse_j3m6  
 | access-date= 1 September 2025
 | year=2014
 | publisher=Taylor & Francis
}}

<!-- {{sfn|Birnstiel|2000|p=?}}  --> 
* {{cite book
 | last=Birnstiel
 | first=Charles
 | chapter = Moveable Bridges
 | title=The Manual of Bridge Engineering
 | editor-last=Ryall
 | editor-first= Michael 
 | isbn= 0727727745 
 | chapter-url=https://archive.org/details/manualofbridgeen0000unse/page/663
 | access-date=1 September 2025
 | year=2000
 | publisher=[[Thomas Telford (publisher)|Thomas Telford]]
 | pages= 663–698
}}

<!-- {{sfn|Blank|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 5. Construction and Maintenance
 | edition = Second
 | first= Simon 
 | last= Blank
 | display-authors=etal
 | chapter =  Concrete Bridge Construction 
 | pages = 67–84
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852330
 | url= https://books.google.com/books?id=BCeOAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Brown|2005 |p=?}}  --> 
* {{Cite book
 | last=Brown
 | first=David 
 | title=Bridges: Three Thousand Years of Defying Nature
 | date=2005 
 | publisher=[[Mitchell Beazley]]
 | isbn=1845330803
 | url=https://archive.org/details/bridgesthreethou0000davi
 | access-date=1 September 2025
}}
 
<!-- {{sfn|Cai|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 1. Fundamentals
 | edition = Second
 | first= Steve
 | last= Cai
 | display-authors=etal
 | chapter = Wind Effects on Long-Span Bridges
 | pages = 535–554
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852347
 | url= https://books.google.com/books?id=WaONAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Chavel|2022|p=?}}  --> 
* {{cite book
 | last=Chavel
 | first=Brandon
 | chapter =Bridge Deck Design
 | title=Steel Bridge Design Handbook
 | publisher= [[American Institute of Steel Construction]]
 | isbn=  
 | chapter-url=https://www.aisc.org/globalassets/nsba/design-resources/steel-bridge-design-handbook/b917_sbdh_chapter17.pdf
 | access-date=4 November 2025
 | year=2022
}}

 <!-- {{sfn|Chen|Lian|2014|p=?}}  --> 
* {{cite book
 | title=Handbook of International Bridge Engineering
 | editor-last1 =Chen
 | editor-first1=  Wai-Fah
 | editor-last2 = Duan
 | editor-first2=  Lian
 | isbn=9781439810293
 | url=https://archive.org/details/handbookofintern0000unse_j3m6  
 | access-date= 1 September 2025
 | year=2014
 | publisher=Taylor & Francis
}}
 
<!-- {{sfn|Choudhury|Hasnat|2015}}  --> 
* {{cite book
 | last1=Choudhury
 | first1=Jamilur  
 | last2=Hasnat
 | first2=Ariful 
 | title = IABSE-JSCE Joint Conference on Advances in Bridge Engineering-III
 | chapter =Bridge Collapses Around the World: Causes and Mechanisms
 | isbn= 9789843393135
 | chapter-url =  https://www.iabse-bd.org/session/k2.pdf
 | access-date=4 November 2025
 | year=2015
 | publisher=[[International Association for Bridge and Structural Engineering]]
 | pages= 26–34
}}

<!-- {{sfn|Collings|2000|p=?}}  --> 
* {{cite book
 | last=Collings
 | first=David
 | chapter =Composite Construction
 | title=The Manual of Bridge Engineering
 | editor-last=Ryall
 | editor-first= Michael 
 | isbn= 0727727745 
 | chapter-url=https://archive.org/details/manualofbridgeen0000unse/page/407
 | access-date=1 September 2025
 | year=2000
 | publisher=[[Thomas Telford (publisher)|Thomas Telford]]
 | pages= 407–448
}}

<!-- {{sfn|Copelan|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 5. Construction and Maintenance
 | edition = Second
 | first= Joyce 
 | last= Copelan
 | chapter = Bridge Maintenance
 | pages = 337–350
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852330
 | url= https://books.google.com/books?id=BCeOAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

 <!-- {{sfn|Cruickshank|2010|p=?}}  --> 
* {{cite book
 | title=Bridges: Heroic Designs that Changed the World
 | last= Cruickshank  
 | first= Dan
 | author-link=Dan Cruickshank
 | isbn= 9780007881086
 | url = https://archive.org/details/isbn_9780007881086   
 | access-date= 1 September 2025
 | year=2010
 | publisher=[[Harper Collins ]]
}}

 <!-- {{sfn|Dawe |2003 |p=?}}  --> 
* {{Cite book
 |title=Research Perspectives: Traffic Loading on Highway Bridges
| url=https://archive.org/details/researchperspect0000dawe 
 |access-date=15 September 2025
 |first=Peter
|last=Dawe
|date=2003
 |publisher=[[Thomas Telford (publisher)|Thomas Telford]]
|isbn=0727732412
}}

<!-- {{sfn|Denison|2012|p=?}}  --> 
* {{cite book
 | title=How to Read Bridges: A Crash Course In Engineering and Architecture
 | last=Denison
 | first= Edward
 | isbn= 9781408171769
 | url=https://archive.org/details/howtoreadbridges0000deni 
 | access-date= 1 September 2025
 | year=2012
 | publisher=[[Rizzoli]]
}}

<!-- {{sfn|Dikshitar |1993|p=?}}  --> 
* {{cite book
 | title=The Mauryan Polity
 | last= Dikshitar 
 | first= V.R.R.
 | isbn= 8120810236
 |orig-year=1932
 | year=1993
 | publisher=[[Motilal Banarsidass]]
 | url=https://archive.org/details/in.ernet.dli.2015.78927/page/n340/mode/1up?q=bridge
 |access-date = 20 September 2025
}} Reprinted in 1993.

<!-- {{sfn|Dornsife|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 3. Substructure Design
 | edition = Second
 | first= Ralph
 | last= Dornsife
 | chapter = Bearings 
 | pages =  1–34
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852309
 | url= https://books.google.com/books?id=Q6iNAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Durkee|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 5. Construction and Maintenance
 | edition = Second
 | first= Jackson 
 | last= Durkee
 | chapter =  Steel Bridge Construction
 | pages =  1–50
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852330
 | url= https://books.google.com/books?id=BCeOAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Edgerton|2010 |p=?}}  --> 
* {{cite book 
|url=https://books.google.com/books?id=Tkm5UZJz8z0C&q=Bridges+constructed+by+pounding
|last=Edgerton
 |first=Robert B. 
|year=2010 
|title=The Fall of the Asante Empire: The Hundred-Year War For Africa's Gold Coast
 |publisher=[[Simon and Schuster]]
 |isbn=9781451603736 
}}

<!-- {{sfn|Ellobody|2014|p=?}}  --> 
* {{cite book
 | title=Finite Element Analysis and Design of Steel and Steel–Concrete Composite Bridges
 | last =Ellobody
 | first= Ehab
 | isbn= 9780124172470
 | year=2014
 | publisher=[[Butterworth-Heinemann]]
 | url = https://archive.org/details/finiteelementana0000ello
 | access-date= 1 September 2025
}}
 
<!-- {{sfn|Elnashai|2000|p=?}}  --> 
* {{cite book
 | last=Elnashai
 | first= Amr
 | chapter = Seismic Response and Design
 | title=The Manual of Bridge Engineering
 | editor-last=Ryall
 | editor-first= Michael 
 | isbn= 0727727745 
 | chapter-url=https://archive.org/details/manualofbridgeen0000unse/page/519
 | access-date=1 September 2025
 | year=2000
 | publisher=[[Thomas Telford (publisher)|Thomas Telford]]
 | pages= 519–548
}}

<!-- {{sfn|Farquhar |2000|p=?}}  --> 
* {{cite book
 | last=Farquhar 
 | first=  Daniel
 | chapter = Cable-Stay Bridges
 | title=The Manual of Bridge Engineering
 | editor-last=Ryall
 | editor-first= Michael 
 | isbn= 0727727745 
 | chapter-url=https://archive.org/details/manualofbridgeen0000unse/page/549
 | access-date=1 September 2025
 | year=2000
 | publisher=[[Thomas Telford (publisher)|Thomas Telford]]
 | pages= 549–594
}}

<!-- {{sfn|Frangopol |2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 5. Construction and Maintenance
 | edition = Second
 | first= Dan
 | last= Frangopol
 | display-authors=etal 
 | chapter = Bridge Health Monitoring
 | pages =  247–268
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852330
 | url= https://books.google.com/books?id=BCeOAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Fridley|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 1. Fundamentals
 | edition = Second
 | first1= Kenneth
 | last1= Fridley 
 | first2 = Lian
 | last2= Duan
 | chapter = Timber Design
 | pages = 341–369
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852347
 | url= https://books.google.com/books?id=WaONAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Alampalli|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 5. Construction and Maintenance
 | edition = Second
 | first1 = Gongkang 
 | last1 = Fu
 | first2 = Dinesh 
 | last2 = Devaraj 
 | chapter = Bridge Management Using Pontis and Improved Concepts
 | pages = 233–245
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852330
 | url= https://books.google.com/books?id=BCeOAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Gerwick|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 5. Construction and Maintenance
 | edition = Second
 | first= Ben
 | last= Gerwick
 | chapter = Substructures of Major Overwater Bridges
 | pages = 137–174
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852330
 | url= https://books.google.com/books?id=BCeOAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

 <!-- {{sfn|Gimsing |2011|p=?}}  --> 
* {{cite book
 | title=Cable Supported Bridges: Concept and Design
 | last=Gimsing 
 | first=Niels J.
 | isbn=9781119951872
 | url=https://archive.org/details/cablesupportedbr0000gims
 | access-date=1 September 2025
 | year=1997
 | edition= Second
 | publisher=Wiley
}}

<!-- {{sfn|Goettemoeller|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 1. Fundamentals
 | edition = Second
 | first= Frederick
 | last= Goettemoeller
 | chapter = Bridge Aesthetics: Achieving Structural Art in Bridge Design 
 | pages = 49–76
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852347
 | url= https://books.google.com/books?id=WaONAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Greco|2016|p=?}}  --> 
* {{cite book
 | title=Architetture Autostradali in Italia
 | last =Greco
 | first= Laura
 | isbn= 9788849292121
 | year=2016
 |language =Italian
 | publisher=[[:it:Gangemi Editore]]
 | url = https://books.google.com/books?id=_fZTCwAAQBAJ
 | access-date= 1 September 2025
}}

<!-- {{sfn|Hewson|2000|p=?}}  --> 
* {{cite book
 | last= Hewson
 | first= Nigel 
 | chapter = Design of Prestressed Concrete Beams
 | title=The Manual of Bridge Engineering
 | editor-last=Ryall
 | editor-first= Michael 
 | isbn= 0727727745 
 | chapter-url=https://archive.org/details/manualofbridgeen0000unse/page/241
 | access-date=1 September 2025
 | year=2000
 | publisher=[[Thomas Telford (publisher)|Thomas Telford]]
 |pages= 241–314
}}

<!--  {{sfn|Holstine|2005|p=??}} --> 
* {{cite book
 | title=Spanning Washington: Historic Highway Bridges of the Evergreen State
 | last=Holstine
 | first=Craig
 | isbn=9780874222814
 | url=https://books.google.com/books?id=NDJSAAAAMAAJ
 | access-date=15 September 2025
 | year=2005
 | publisher=[[Washington State University Press]]
}}

<!--  {{sfn|Huff|2022|p=??}} --> 
* {{cite book
 | title=LRFD Bridge Design: Fundamentals and Applications
 | last=Huff
 | first=T.
 | isbn=9781000543377
 | url=https://books.google.com/books?id=MCtaEAAAQBAJ
 | access-date=10 September 2025
 | year=2022
 | publisher=[[CRC Press]]
}}

<!-- {{sfn|Islam|Malek2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 3. Substructure Design
 | edition = Second
 | first1= Mohammed 
 | last1 = Islam 
 | first2= Amir
 | last2= Malek
 | chapter = Shallow Foundations
 | pages = 181–238
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852309 
 | url= https://books.google.com/books?id=Q6iNAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Jones|Howells|2000|p=?}}  --> 
* {{cite book
 | last1=Jones
 | first1=Vardiman
 | last2 = Howells
 | first2= John
 | chapter = Suspension Bridges
 | title=The Manual of Bridge Engineering
 | editor-last=Ryall
 | editor-first= Michael 
 | isbn= 0727727745 
 | chapter-url=https://archive.org/details/manualofbridgeen0000unse/page/595
 | access-date=1 September 2025
 | year=2000
 | publisher=[[Thomas Telford (publisher)|Thomas Telford]]
 | pages= 595–662
}}

<!-- {{sfn|Krimotat|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 1. Fundamentals
 | edition = Second
 | first1= Alexander 
 | last1 = Krimotat
 | chapter = Structural Modeling
 | pages = 253–269
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852309 
 | url= https://books.google.com/books?id=WaONAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn| Kulicki|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 1 Fundamentals
 | edition = Second
 | first= John
 | last= Kulicki
 | chapter = Highway Bridge Design Specifications
 | pages = 113–130
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852309 
 | url= https://books.google.com/books?id=WaONAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}
 
<!-- {{sfn| Kulicki|2014a|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 2. Superstructure Design
 | edition = Second
 | first= John
 | last= Kulicki
 | chapter =  Highway Truss Bridges
 | pages = 283–308
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852293
 | url= https://books.google.com/books?id=JpClAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014a
 | publisher=[[CRC Press]] 
}}
 
<!-- {{sfn|Leonhardt|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 1. Fundamentals
 | edition = Second
 | first= Fritz
 | last= Leonhardt
 | chapter = Aesthetics: Basics
 | pages = 29–48
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852347
 | url= https://books.google.com/books?id=WaONAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Ma|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 3. Substructure Design
 | edition = Second
 | first= Youzhi
 | last= Ma
 | chapter =Deep Foundations
 | pages = 238–278
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852309 
 | url= https://books.google.com/books?id=Q6iNAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Mangus |2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 2. Superstructure Design
 | edition = Second
 | first= Alfred
 | last= Mangus 
 | chapter =  Orthotropic Steel Decks 
 | pages = 589–646
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852293 
 | url= https://books.google.com/books?id=JpClAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Mulheron|2000|p=?}}  --> 
* {{cite book
 | last=Mulheron
 | first=Mike
 | chapter = Protection
 | title=The Manual of Bridge Engineering
 | editor-last=Ryall
 | editor-first= Michael 
 | isbn= 0727727745 
 | chapter-url=https://archive.org/details/manualofbridgeen0000unse/page/805
 | access-date=1 September 2025
 | year=2000
 | publisher=[[Thomas Telford (publisher)|Thomas Telford]]
 | pages= 805–848
}}
 
<!-- {{sfn| Nath|1982|p=?}}  --> 
* {{cite book
 | last= Nath
 | first=Ram
 | author-link =Ram Nath
 | title=History of Mughal Architecture
 |volume=3
 | year=1982
 | isbn= 8170172977
 | publisher= [[Abhinav Publications]]
 | url= https://books.google.com/books?id=ha5fG13V3XcC
 |access-date= 17 September 2025
}}
 
<!-- {{sfn| O'Brien|2014 |p=?}}  --> 
* {{cite book
 | last= O'Brien
 | first=Eugene
 | title= Bridge Deck Analysis
 | url=https://archive.org/details/bridgedeckanalys0000obri_m0m0
 | access-date=12 September 2025
 | year=2015
 | edition=Second
 | isbn= 9781482227239
 | publisher=[[CRC Press]]
}}
 
<!-- {{sfn|Petroski |1994|p=?}}  --> 
* {{cite book
 | last=Petroski 
 | first= Henry
 | author-link=Henry Petroski
 | title=To Engineer Is Human: The Role of Failure in Successful Design
 | url=https://archive.org/details/toengineerishuma0000henr 
 | access-date=20 September 2025
 | year=1994
 | isbn=1566195020 
 | publisher=Barnes & Noble
}}

<!-- {{sfn|Reddy|2004|p=?}}  --> 
* {{cite book
 | last=Reddy
 | first=J. N. 
 | author-link = J. N. Reddy (engineer)
 | title=An Introduction to the Finite Element Method
 | url=https://archive.org/details/introductiontofi0000jnre 
 | access-date=10 September 2025
 | edition=Third
 | year=2004
 | isbn=9780070607415
 | publisher=[[McGraw Hill]]
}}

<!-- {{sfn|Ryall|2000|p=?}}  --> 
* {{cite book
 | last=Ryall
 | first=Michael 
 | chapter = Loads and Load Distribution
 | title=The Manual of Bridge Engineering
 | editor-last=Ryall
 | editor-first= Michael 
 | isbn= 0727727745 
 | chapter-url=https://archive.org/details/manualofbridgeen0000unse/page/43
 | access-date=1 September 2025
 | year=2000
 | publisher=[[Thomas Telford (publisher)|Thomas Telford]]
 | pages= 43–94
}}
 
 <!-- {{sfn|Sakowski|2014|p=?}}  --> 
* {{cite book
 | title=Handbook of International Bridge Engineering
 | last=Sakowski
 | first=Eric
 | chapter = Highest Bridges
 | pages = 1251–1306
 | editor-last1 =Chen
 | editor-first1=  Wai-Fah
 | editor-last2 = Duan
 | editor-first2=  Lian
 | isbn=9781439810293
 | url=https://archive.org/details/handbookofintern0000unse_j3m6  
 | access-date= 1 September 2025
 | year=2014
 | publisher=[[Taylor & Francis]]
}}

<!-- {{sfn|Scott|2001|p=?}}  --> 
* {{cite book
 | title=In the Wake of Tacoma: Suspension Bridges and the Quest for Aerodynamic Stability
 | last=Scott
 | first= Richard
 | isbn= 0784405425
 | url=https://archive.org/details/inwakeoftacomasu0000scot
 | access-date=1 September 2025
 | year=2001
 | publisher=[[American_Society_of_Civil_Engineers#Publications|ASCE Press]]
}}
 
<!-- {{sfn|Schlaich|2019|p=?}}  --> 
* {{cite book
 |url=https://concrete.ethz.ch/assets/sed17.pdf
 |access-date=16 October 2025
 |author-last=Schlaich
 |author-first=Mike
 |editor-last1=Schlaich
 |editor-first1=Mike 
 |year=2019
 |title=Extradosed Bridges
 |chapter=General
 | pages=3–8
 |isbn=9783857481680
 | publisher =[[International Association for Bridge and Structural Engineering]]
}}

<!-- {{sfn|Shanmugam|2000|p=?}}  --> 
* {{cite book
 | last=Shanmugam
 | first=N. E. 
 | chapter = Structural Analysis
 | title=The Manual of Bridge Engineering
 | editor-last=Ryall
 | editor-first= Michael 
 | isbn= 0727727745 
 | chapter-url=https://archive.org/details/manualofbridgeen0000unse/page/95
 | access-date=1 September 2025
 | year=2000
 | publisher=[[Thomas Telford (publisher)|Thomas Telford]]
 | pages= 95–224
}}

<!-- {{sfn|Shi|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 5. Construction and Maintenance
 | edition = Second
 | first= Junfeng 
 | last= Shi
 | display-authors=etal
 | chapter = Cable-Supported Bridge Construction
 | pages = 85–112
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852330
 | url= https://books.google.com/books?id=BCeOAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Shen|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 2. Superstructure Design
 | edition = Second
 | first= John
 | last= Shen
 | chapter =  Concrete Decks 
 | pages = 573–588
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852293 
 | url= https://books.google.com/books?id=JpClAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Sorgenfrei|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 1. Fundamentals
 | edition = Second
 | first= Donald 
 | last= Sorgenfrei
 | display-authors=etal
 | chapter = Railroad Bridge Design Specifications
 | pages = 143–158
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852347
 | url= https://books.google.com/books?id=WaONAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Squier|1877 |p=?}}  --> 
* {{cite book
 | last=Squier
 | first=Ephraim George
 | author-link=E. G. Squier
 | title=Peru; Incidents of Travel and Exploration in the Land of the Incas
 | oclc = 2396588
 | url=https://archive.org/details/peruincidentsoft00squi
 | access-date=13 September 2025
 | year=1877 
 | publisher=[[Harper & Brothers ]]
}}

<!-- {{sfn|Svecova|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 1. Fundamentals
 | edition = Second
 | first= Dagmar 
 | last= Svecova
 | display-authors=etal
 | chapter = Application of Fiber Reinforced Polymers in Bridges
 | pages = 371–404
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852347
 | url= https://books.google.com/books?id=WaONAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Talese|2014|p=?}}  --> 
*{{cite book
|last=Talese
|first=Gay
|author-link=Gay Talese
|title=The Bridge: The Building of the Verrazano–Narrows Bridge
|url=https://books.google.com/books?id=cK-pBAAAQBAJ
|isbn=9781620409114
|publisher=[[Harper & Row]]
|orig-year=1964
|year=2014
}} 

<!-- {{sfn|Tang|2014a|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 5. Construction and Maintenance
 | edition = Second
 | first= Benjamin 
 | last= Tang
 | chapter = Accelerated Bridge Development
 | pages = 175–206
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852330
 | url= https://books.google.com/books?id=BCeOAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014a
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Tang|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 1. Fundamentals
 | edition = Second
 | first= Man-Chung
 | last= Tang
 | chapter = Conceptual Design
 | pages =  1–34
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852347
 | url= https://books.google.com/books?id=WaONAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Theryo|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 2. Superstructure Design
 | edition = Second
 | first= Teddy
 | last= Theryo
 | chapter = Segmental Concrete Bridges
 | pages = 91–170
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn=  9781439852293 
 | url= https://books.google.com/books?id=JpClAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Troitsky|1994|p=?}}  --> 
* {{cite book
 | title=Planning and Design of Bridges
 | author=Troitsky
 | first=  M.S.
 | isbn= 0471028533
 | url= https://archive.org/details/planningdesignof0000troi
 | access-date=1 September 2025
 | year=1994
 | publisher=[[Wiley (publisher)|Wiley]]
}}
  
<!-- {{sfn|Troyano |2003 |pp= 623, 656, 664 }}  --> 
* {{cite book
 | last=Troyano
 | first=L.F.
| title=Bridge Engineering: A Global Perspective
 | publisher=[[Thomas Telford (publisher)|Thomas Telford]]
 | year=2003
 | isbn=9780727732156
 | url=https://books.google.com/books?id=0u5G8E3uPUAC 
 | access-date= 25 October 2025
}}

<!-- {{sfn|Tytler|1985 |p=?}}  --> 
* {{cite book
 | last=Tytler
 | first= I.F.B.
 | title=Vehicles and Bridging
 | isbn =   0080283225 
 | url=https://archive.org/details/vehiclesbridging0000unse
 | access-date=13 September 2025
 | year=1985 
 | series = Battlefield Weapons Systems and Technology
 | publisher=Brasey's Defense Publishers
}}

<!-- {{sfn|Vassie|2000|p=?}}  --> 
* {{cite book
 | last=Vassie
 | first=Perry
 | chapter = Bridge Management
 | title=The Manual of Bridge Engineering
 | editor-last=Ryall
 | editor-first= Michael 
 | isbn= 0727727745 
 | chapter-url=https://archive.org/details/manualofbridgeen0000unse/page/849
 | access-date=1 September 2025
 | year=2000
 | publisher=[[Thomas Telford (publisher)|Thomas Telford]]
 | pages= 849–882
}}

<!-- {{sfn| Vejrum|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 2. Superstructure Design
 | edition = Second
 | first= Tina
 | last= Vejrum
 | chapter = Cable-Stayed Bridges
 | pages = 399–434
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852293
 | url= https://books.google.com/books?id=JpClAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}
 
<!-- {{sfn|Washer|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 5. Construction and Maintenance
 | edition = Second
 | first= Glenn 
 | last= Washer
 | chapter =  Nondestructive Evaluation Methods for Bridge Elements
 | pages = 301–336 
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852330
 | url= https://books.google.com/books?id=BCeOAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Watson|1937|p=?}}  --> 
* {{cite book
 |  title=Bridges in History and Legend
 | last=Watson
 |  first= Wilbur J.
 | oclc=1393531
 | url=https://archive.org/details/bridgesinhistory0000wilb
 | access-date=1 September 2025
 | year=1937
 | publisher=[[J. H. Jansen]]
}}

 <!-- {{sfn|Watson|1988|p=?}}  --> 
* {{cite book
 |  title=The Civils: The Story of the Institution of Civil Engineers
 |  author=Watson
 |  first= Garth
 |  isbn=9780727703927
 |  url=https://archive.org/details/civilsstoryofins0000wats 
 | access-date= 31 October 2025
 |  year=1988
 |  publisher=[[Thomas Telford (publisher)|Thomas Telford]]
}}

<!-- {{sfn|Wilks|1989|p=?}}  --> 
* {{cite book 
| url= https://books.google.com/books?id=NSs4AAAAIAAJ
 | title= Asante in the Nineteenth Century: The Structure and Evolution of a Political Order
| first=Ivor
|last= Wilks 
|author-link=Ivor Wilks
| publisher= [[CUP Archive]]
 |via = Books.google.com
 |access-date= 29 December 2020
|isbn= 9780521379946
|date= 1989
}}

<!-- {{sfn| Wright|2022|p=?? }} --> 
* {{Cite book
|first=William J. 
|last=Wright
| chapter-url=https://www.aisc.org/globalassets/nsba/design-resources/steel-bridge-design-handbook/b905_sbdh_chapter5.pdf
| url=https://www.aisc.org/nsba/design-and-estimation-resources/steel-bridge-design-handbook/
|access-date=18 September 2025
|chapter=Selecting the Right Bridge Type
|title= Steel Bridge Design Handbook
|year=2022
|publisher=[[American Institute of Steel Construction]]
}}

<!-- {{sfn|Xu|2011|p=?}}  --> 
* {{cite book
 |  title=Structural Health Monitoring of Long-Span Suspension Bridges
  |  last=Xu
 | first=  You Lin
 |display-authors = etal
  |  isbn=9780415597937
  |  url=https://books.google.com/books?id=9F9pNdAk4WAC
  |  year=2011
 |   publisher=[[Taylor & Francis]]
}}

<!-- {{sfn|Yamaguchi|2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 1. Fundamentals
 | edition = Second
 | first= Eiki
 | last= Yamaguchi
 | chapter = Finite Element Method
 | pages = 225–251
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852309 
 | url= https://books.google.com/books?id=WaONAgAAQBAJ
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}
 
<!-- {{sfn|Yashinsky |2014|p=?}}  --> 
* {{cite book
 | title=Bridge Engineering Handbook. Vol 4. Seismic Design
 | edition = Second
 | first= Mark 
 | last= Yashinsky 
 | display-authors=etal
 | chapter = Earthquake Damage to Bridges
 | pages = 53– 98
 | editor-last1=Chen  
 | editor-first1= Wai-Fah
 | editor-last2  = Duan
 | editor-first2 = Lian
 | isbn= 9781439852323  
 | url= https://books.google.com/books?id=EqSNAgAAQBAJ 
 | access-date= 31 October 2025
 | year=2014
 | publisher=[[CRC Press]] 
}}

<!-- {{sfn|Zhao|2017|p=?}}  --> 
* {{cite book
 |  title=Bridge Engineering: Design, Rehabilitation, and Maintenance of Modern Highway Bridges
 | last=Zhao
 |  first= Jim
 |display-authors = etal
 | edition=Fourth
 | isbn=9781259643101
 | url= https://books.google.com/books?id=Ii1zDgAAQBAJ
 | access-date=16 September 2025
 | year=2017
 | publisher=McGraw Hill
}}
{{refend}}

====Journals and websites====
{{refbegin}}

<!--  {{sfn|Ahmad |2025}} -->
* {{Cite journal 
|last=Ahmad 
|first=DM
 |date=2025 
|title=  A Risk-Informed BIM-LCSA Framework for Lifecycle Sustainability Optimization of Bridge Infrastructure
|journal=  Buildings 
|publisher=[[MDPI]]
|volume=15
|issue =16
 |article-number= 2853
|doi= 10.3390/buildings15162853
 |doi-access=free
 |issn= 2075-5309 
}}

<!--  {{sfn|Bjelić |2022 }} -->
* {{Cite journal 
|last=Bjelić 
|first=Igor
 |date=2022 
|title=Use of Building Materials During the Construction of Trajan's Bridge on the Danube 
|journal=Arheologija I Prirodne Nauke 
|publisher= [[Institute of Archaeology, Belgrade]]
|volume=18
 |pages=45–58 
|doi=10.18485/arhe_apn.2022.18.4
 |issn=1452-7448
|url= https://doi.fil.bg.ac.rs/pdf/journals/arhe_apn/2022/arhe_apn-2022-18-4.pdf
|access-date=3 October 2025
}}

<!--  {{sfn|Brunning|2001}} -->
* {{cite journal
 |last=Brunning 
|first=Richard
 |year=2001
 |title=The Somerset Levels
 |journal=[[Current Archaeology]]
|publisher=[[Current Publishing]]
 |volume=XV (4) 
|issue=172  
|pages=139–143
|issn = 0011-3212
}}

<!--  {{sfn|Burgoyne |Scantlebury |2008}} -->
* {{cite web 
 |last1=Burgoyne 
|first1= C
 |last2=Scantlebury 
|first2= R
 |year=2008
 |title=Lessons Learned from the Bridge Collapse in Palau
 |website = [[University of Cambridge]]
 |publisher =  [[Institution_of_Civil_Engineers#Publishing|Institution of Civil Engineers]]
 |volume= 161
|issue= 6
|article-number=700038
|issn = 1751-7672
 | url=https://cjb.emma.cam.ac.uk/cjbpubs/p62.pdf
 |access-date= 14 November 2025
}}
 
<!--  {{sfn|Cai|Deng|2024}} -->
* {{cite journal
 |last1= Cai
|first1=  J.
|last2= Deng
|first2= Z.
 |year=2024
 |title= The Spatial Impact of High Bridges on Travel Accessibility and Economic Integration in Guizhou, China 
 |journal=  [[Humanities and Social Sciences Communications]]
|publisher= [[Nature Portfolio]]
 |volume= 11
|issue= 
|article-number= 1565  
|issn =  	2662-9992
|url= https://www.nature.com/articles/s41599-024-04106-x 
| doi=  10.1057/s41599-024-04106-x
|access-date= 14 November 2025
}}

<!--  {{sfn|Capka|2005}} 
* {{cite web
 |url=https://www.transportation.gov/testimony/rebuilding-highway-and-transit-infrastructure-gulf-coast-following-hurricane-katrina-0
 |access-date=21 September 2025
 |last=Capka
 |first=J. Richard
 |author-link =J. Richard Capka
 |year=2005
 |title=Rebuilding Highway and Transit Infrastructure on the Gulf Coast Following Hurricane Katrina
 |website=[[U.S. Department of Transportation]]
}}
-->
<!--  {{sfn|Cook|2014}} -->
* {{cite thesis
 |url=https://digitalcommons.usu.edu/etd/2163 
 |access-date=2 October 2025
 |last=Cook
 |first= Wesley
 |year=2014
 |publisher= [[Utah State University]]
 | degree = PhD
 |title=Bridge Failure Rates, Consequences, and Predictive Trends
}}

<!--  {{sfn|Dahlberg|2022|p= ?? }} -->
*  {{cite web 
 |last = Dahlberg
 | first=Justin
 | display-authors=etal
 | title=Guide for Orthotropic Steel Deck Level 1 Design
 | access-date= 10 November 2025
 | year= 2022
 | url= https://www.fhwa.dot.gov/bridge/pubs/hif22056.pdf#:~:text=Orthotropic%20steel%20deck:%20A%20system%20where%20a,to%20the%20deck%20directly%20supporting%20live%20loads
 | publisher = U. S. [[Federal Highway Administration]]
}}

<!--  {{sfn|Dallard|2001}} -->
* {{cite journal
|last=Dallard
|first= P.
|display-authors=etal
|title=London Millennium Bridge: Pedestrian-Induced Lateral Vibration
|journal= [[Journal of Bridge Engineering]]
|volume= 6
|issue=6
|pages= 412–417f
|date=2001
|url=http://ascelibrary.org/doi/pdf/10.1061/(ASCE)1084-0702(2001)6:6(412)
 |doi= 10.1061/(ASCE)1084-0702(2001)6:6(412)
|access-date= 5 November 2025
|issn=1084-0702 
}}

<!--  {{sfn|Delatte|2001}} -->
* {{cite journal
|journal=Journal of Professional Issues in Engineering Education and Practice
|publisher= [[American Society of Civil Engineers]]
|issn=1052-3928
|volume=127
|issue=3
|date= July 2001
|pages= 109–115
|last=Delatte
|first= Norbert
|url=https://engagedscholarship.csuohio.edu/cgi/viewcontent.cgi?article=1039&context=encee_facpub
|title=Lessons from Roman Cement and Concrete 
 |doi= 10.1061/(ASCE)1052-3928(2001)127:3(109)
|access-date=3 October 2025
}}

<!--  {{sfn|Du|Au|2005}} -->
* {{cite journal
|journal=Structural Safety
|publisher=[[Elsevier ]]
|issn=0167-4730
|volume=27
|issue=3
|date= July 2005
|pages=230–245
|last1=Du
|first1= Jin Sheng
|last2= Au
|first2= Francis T.K. 
|url=https://www.sciencedirect.com/science/article/abs/pii/S0167473004000505
|title=Deterministic and Reliability Analysis of Prestressed Concrete Bridge Girders: Comparison of the Chinese, Hong Kong and AASHTO LRFD Codes
 |doi=10.1016/j.strusafe.2004.10.004 
|access-date= 9 October 2025
}}

<!--  {{sfn|French|1993}} -->
* {{cite journal
|last= French
|first= Patricia Ross
|date=  January 1993
|title=Living by Bridges: Philip Larkin's Resisting Subtext
 |journal= [[South Atlantic Review]]
|issn=	0277-335X
|volume= 58
|issue=1
|pages= 85–100
 |doi=10.2307/3201102
|jstor= 3201102
}}

<!--  {{sfn|Greenfield|2021}} -->
* {{Cite news
|last=Greenfield
|first=Patrick
|date=23 January 2021|title=How Creating Wildlife Crossings Can Help Reindeer, Bears – and Even Crabs|url=http://www.theguardian.com/environment/2021/jan/23/how-wildlife-crossings-are-helping-reindeer-bears-and-even-crabs-aoe
|url-status=live
|archive-url=https://web.archive.org/web/20210123083528/https://www.theguardian.com/environment/2021/jan/23/how-wildlife-crossings-are-helping-reindeer-bears-and-even-crabs-aoe 
|archive-date=23 January 2021
 |access-date=2021-01-26
|newspaper=[[The Guardian]]
|language=en
|issn = 1756-3224  
}}

<!--  {{sfn|He|2025}} -->
* {{cite journal
|last =He
|first= Dongsheng 
|display-authors=etal
|title=A Novel Analytical Model for Structural Analysis of Long-Span Hybrid Cable-Stayed Suspension Bridges
|journal=Applied Sciences  
|issn=2076-3417
|volume=15
|number= 3 
|date=February 2025
|article-number= 1187
| doi=10.3390/app15031187
|doi-access=free
}}

<!--  {{sfn|Honan|2018}} -->
* {{Cite magazine
|last=Honan
|first=David
|year= 2018
|title=Railroad Bridges, Viaducts, and Trestles
|magazine=Trains Magazine
|issn = 0041-0934
|url=https://www.trains.com/trn/train-basics/ask-trains/bridges-viaducts-and-trestles/
|access-date=2020-09-11
}}

<!--  {{sfn|Hopper|Langlois|2022 |pp=?? }} -->
* {{cite web
|url=https://www.fhwa.dot.gov/bridge/preservation/docs/hif22052.pdf
|access-date=2 October 2025
|title=Service Life Design Reference Guide
|date=November 2022 
|first1=Travis 
|last1=Hopper
|first2=Anne-Marie
|last2=Langlois
 |display-authors = etal
|website=Federal Highway Administration
}}

<!--  {{sfn|Hu|2016|pp=??}} -->
* {{cite web
|url=https://static.tti.tamu.edu/tti.tamu.edu/documents/0-6729-1.pdf
|access-date=17 September 2025
|title=Synthesis on Cost-Effectiveness of Extradosed Bridges
|series=Technical Report
|date=March 2016
|first=Jiong 
|last=Hu 
|display-authors = etal
|website=Texas A&M Transportation Institute
}}

<!--  {{sfn|Kashima|Sakamoto|1998}} -->
* {{Cite journal
|first1=Satoshi
|last1= Kashima
|first2= Mitsushige 
|last2=Sakamoto <!-- |others= Yukihiro Sano, Kozoo Higuchi -->
|title=Construction of Akashi Kaikyo Bridge Foundation
|url=https://dx.doi.org/10.5169/seals-59833
|access-date=2 October 2025
|website= IABSE Symposium (Kobe): Long-Span and High-Rise Structures
| publisher=[[IABSE]]
 |year=1998
|volume=79 
|pages=69–74
|doi= 10.5169/seals-59833
}}  [https://www.e-periodica.ch/cntmng?pid=bse-re-003%3A1998%3A79%3A%3A84  PDF version]

<!--  {{sfn|Kumar|2025}} -->
* {{cite journal
 | url =  https://link.springer.com/article/10.1007/s42417-024-01562-2 
   | last = Kumar
 |  first=  Saket
 |display-authors = etal
 |  title = Dynamic Response of Double Deck Cable-Stayed Bridge Subjected to Train Load on Lower Deck.
 |  journal =   Journal of Vibration Engineering & Technologies 
 |publisher= [[Springer Nature]]
 |  volume =  13
 |  number = 20 
 |  year = 2025
 | article-number = 20
 | issn = 2523-3939
  |  doi = 10.1007/s42417-024-01562-2
 | bibcode = 2025JVET...13...20K
 | access-date = 12 September 2025 
}}

<!--  {{sfn|Merli |Costanza |2024}} -->
* {{cite journal
 | url =   https://pmc.ncbi.nlm.nih.gov/articles/PMC11077020/
   | last1 =  Merli 
 |  first1=   Roberto
   | last2 =  Costanza 
 |  first2=   Alessandra
 |  title = Effectiveness of Physical Barriers to Prevent Suicide by Jumping from High-Risk Bridges
 |  journal =   Preventive Medicine Reports
 |publisher=  [[Preventive Medicine (journal)|Preventive Medicine]]
 |  volume =    42
 |  number = 
 |  year = 2024
 | article-number =  102745 
 | issn =  2211-3355
  |  doi =  10.1016/j.pmedr.2024.102745
 | access-date = 14 November 2025 
}}

<!-- {{sfn|Newer|2012}}  --> 
*  {{cite magazine
|title=World's Coolest Animal Bridges
|first=Rachel 
|last=Newer
|date=23 July 2012
|magazine=Smithsonian.com
|access-date=21 February 2019
|url=https://www.smithsonianmag.com/smart-news/worlds-coolest-animal-bridges-5774855/
|issn= 1930-5508
}}

<!-- {{sfn|Nowak |Iatsko |2018 }}  --> 
* {{cite magazine
| last1 = Nowak 
|first1= Andrzej 
| last2 = Iatsko 
|first2= Olga 
| date = June 2018
|volume = 48
|issue = 2
|magazine = The Bridge
|issn= 0737-6278
| title =  Are Our Bridges Safe?
 | url = https://www.nae.edu/183130/Are-Our-Bridges-Safe 
|access-date= 17 November 2025
|publisher= [[National Academy of Engineering]]
}}

<!-- {{sfn|Omer|2018 }}  --> 
* {{cite web
| last1 = Omer 
|first1= Muhammad 
|  display-authors = etal 
| year = 2018 
| title = Performance Evaluation of Bridges Using Virtual Reality
 | url = https://pure.manchester.ac.uk/ws/files/69286920/Omer_et_al_ECCM_2018_submitted.pdf
|access-date= 17 November 2025
| website = [[The University of Manchester]]
|publisher= [[6th European Conference on Computational Mechanics  ]]
}}

<!-- {{sfn|Ou|Chen|2005 }}  --> 
*  {{Cite web 
|last1=Ou 
|first1=Z.
 |last2=Chen
 |first2=B.
 |date=2005 
|title=Stone Arch Bridges in Fujian, China 
|url=https://arch-bridges.fzu.edu.cn/__local/D/17/E4/2A8621F70E7AC7ABD0302341CA7_8367E69E_14B74D.pdf?e=.pdf
 |access-date=10 September 2025 
 |website=[[Fuzhou University]]
}}

<!-- {{sfn|Quirchmair|2022}}  --> 
*  {{Cite web 
 |last1=Quirchmair
 |first1=Martin
 |date=2022
 |website=Railway Gazette International
 | issn =0373-5346
 |title=Track Maintenance: Sittertobel Renovation Improves Track Forces
 |url=https://www.railwaygazette.com/in-depth/track-maintenance-sittertobel-renovation-improves-track-forces/61622.article
 |access-date=21 September 2025 
}}

<!-- {{sfn|Rookhuyzen|2018 }}  --> 
*  {{Cite web 
 |last1=Rookhuyzen 
 |first1=David
 |date=2018
 |publisher= [[Arizona Department of Transportation]]
 |title=Transportation Defined: Pier Caps  
 |url=https://azdot.gov/adot-blog/transportation-defined-pier-caps-cap-piers
 |access-date=20 September 2025 
}}

<!-- {{sfn|Sangree|Schafer|2003}}  --> 
*  {{Cite web 
 |last1=Sangree
 |first1=Rachel
 |last2=Shafer
 |first2=Ben
|  display-authors = etal
 |date=2003
 |website=Perceptions on the Evolution of Structures
 |title=The Structural Art of the Akashi Kaikyo Bridge  
 |url=https://www.ce.jhu.edu/perspectives/handouts_unprotected/akashi.pdf
 |access-date=2 October 2025 
}}

<!-- {{sfn|Schmid|2001 }}  --> 
* {{cite news
|last=Schmid
 |first=John 
|url=https://www.nytimes.com/2001/08/03/news/03iht-euro_ed3_.html 
|title=Etching the Notes of a New European Identity
|newspaper=[[International Herald Tribune]] 
|issn=0294-8052
|date=3 August 2001 
|access-date=23 September 2025
}}

<!-- {{sfn|Shirley-Smith}}  --> 
*  {{Cite encyclopedia
|last1=Shirley-Smith
|first1=Hubert
|author-link=Hubert Shirley-Smith
|title=Bridge
|encyclopedia=Britannica
|url=https://www.britannica.com/technology/bridge-engineering
 |access-date=19 September 2025 
}}

<!-- {{sfn|Tănase|2024}}  --> 
* {{cite journal
 | last = Tănase
 | first= Maria 
 |  display-authors = etal
 |  title = Optimizing Pipeline Bridge Components Through FEA Technical Validation
 | journal = Buildings
 | volume = 14
 | year = 2024
 |  number = 12
 | article-number = 3935
 | doi= 10.3390/buildings14123935 
 | doi-access= free 
 |  issn = 2075-5309
}}
 
<!-- {{sfn|Wardhana |Hadipriono|2003}}  --> 
* {{cite journal
 |  first1= Kumalasari 
 | last1 =  Wardhana 
 |  first2= Fabian 
 | last2 =  Hadipriono
 | title =Analysis of Recent Bridge Failures in the United States
 | journal = Journal of Performance of Constructed Facilities
 | publisher=[[ American Society of Civil Engineers]]
 | issn = 1943-5509
 | volume = 17
 | number = 3
 | pages = 144
 | year = 2003
 | doi = 10.1061/(ASCE)0887-3828(2003)17:3(144)
     |  url=   https://doi.org/10.1061/(ASCE)0887-3828(2003)17:3(144)
  |access-date = 2 October 2025
}}

<!-- {{sfn|Warren|2025}}  --> 
* {{cite news
|url = https://www.bbc.com/news/articles/c787gy21w6po
|  first= Jess 
 | last =  Warren
 | title = 'Wobbly' Millennium Bridge marks 25th anniversary
 | newspaper = [[BBC]]
 | date = 10 June 2025
  |access-date = 6 November 2025
}}

<!-- {{sfn|Watanabe|2003}}  --> 
* {{cite journal
 |  first= Eiichi
 | last =  Watanabe
 | title = Floating Bridges: Past and Present
 | journal = Structural Engineering International
 | publisher = [[Taylor & Francis]]
 | issn = 1016-8664
 | volume = 13
 | number = 2
 | pages = 128–132
 | year = 2003
 | doi = 10.2749/101686603777964810
     |  url=   https://doi.org/10.2749/101686603777964810
  |access-date = 13 September 2025
| url-access = subscription
 }}

<!-- {{sfn| Zheng|Wang|2018}} -->
* {{cite journal
 | title = Concrete-Filled Steel Tube Arch Bridges in China
 |  journal = Engineering
 | volume = 4
 | number = 1
 | pages = 143–155
 | year = 2018
 |  issn = 2095-8099
 |  doi = 10.1016/j.eng.2017.12.003
 |   url = https://www.sciencedirect.com/science/article/pii/S2095809917303491
 | access-date=31 October 2025
 |  first1=Jielian
 |  last1= Zheng 
|first2=Jianjun
|last2= Wang
| bibcode = 2018Engin...4..143Z
 }}

<!-- {{sfn| Zhou |2021}} -->
* {{cite journal
 | title =  Environmental, Economic and Social Impact Assessment: Study of Bridges in China's Five Major Economic Regions
 |  journal =  [[International Journal of Environmental Research and Public Health]]  
 | volume = 18
 | number = 1
 | pages = 122
 | year = 2021
 | article-number  =  2021
 |  issn = 	1660-4601 
 |  doi =  10.3390/ijerph18010122
 |  first1= ZhiWu
 |  last1= Zhou 
  |display-authors=etal
| pmid = 33375382 
 | pmc = 7795641 
 | doi-access = free 
 }}
{{refend}}

====Unknown author====
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}}
{{refend}}
 
{{Bridge footer}}
{{Construction overview}}
{{Infrastructure}}
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[[Category:Bridges| ]]
[[Category:Civil engineering]]
[[Category:Infrastructure]]
[[Category:Structural engineering]]
[[Category:Transport buildings and structures]]