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A suspension bridge is a type of
bridge A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually someth ...
in which the deck is hung below suspension
cables Cable may refer to: Mechanical * Nautical cable, an assembly of three or more ropes woven against the weave of the ropes, rendering it virtually waterproof * Wire rope, a type of rope that consists of several strands of metal wire laid into a hel ...
on vertical suspenders. The first modern examples of this type of bridge were built in the early 1800s. Simple suspension bridges, which lack vertical suspenders, have a long history in many mountainous parts of the world. Besides the bridge type most commonly called suspension bridges, covered in this article, there are other types of suspension bridges. The type covered here has cables suspended between
tower A tower is a tall structure, taller than it is wide, often by a significant factor. Towers are distinguished from masts by their lack of guy-wires and are therefore, along with tall buildings, self-supporting structures. Towers are specific ...
s, with vertical ''suspender cables'' that transfer the
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and dead loads of the deck below, upon which traffic crosses. This arrangement allows the deck to be level or to arc upward for additional clearance. Like other suspension bridge types, this type often is constructed without the use of
falsework Falsework consists of temporary structures used in construction to support a permanent structure until its construction is sufficiently advanced to support itself. For arches, this is specifically called centering. Falsework includes temporary s ...
. The suspension cables must be anchored at each end of the bridge, since any load applied to the bridge is transformed into a tension in these main cables. The main cables continue beyond the pillars to deck-level supports, and further continue to connections with anchors in the ground. The roadway is supported by vertical suspender cables or rods, called hangers. In some circumstances, the towers may sit on a bluff or
canyon A canyon (from ; archaic British English spelling: ''cañon''), or gorge, is a deep cleft between escarpments or cliffs resulting from weathering and the erosive activity of a river over geologic time scales. Rivers have a natural tendency to cu ...
edge where the road may proceed directly to the main span, otherwise the bridge will usually have two smaller spans, running between either pair of pillars and the highway, which may be supported by suspender cables or their own trusswork. In the latter case, there will be very little arc in the outboard main cables.


History

The earliest suspension bridges were ropes slung across a chasm, with a deck possibly at the same level or hung below the ropes such that the rope had a catenary shape.


Precursor

The
Tibetan Tibetan may mean: * of, from, or related to Tibet * Tibetan people, an ethnic group * Tibetan language: ** Classical Tibetan, the classical language used also as a contemporary written standard ** Standard Tibetan, the most widely used spoken diale ...
siddha and bridge-builder Thangtong Gyalpo originated the use of
iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in ...
chains in his version of simple suspension bridges. In 1433, Gyalpo built eight bridges in eastern
Bhutan Bhutan (; dz, འབྲུག་ཡུལ་, Druk Yul ), officially the Kingdom of Bhutan,), is a landlocked country in South Asia. It is situated in the Eastern Himalayas, between China in the north and India in the south. A mountainou ...
. The last surviving chain-linked bridge of Gyalpo's was the Thangtong Gyalpo Bridge in Duksum en route to
Trashi Yangtse Trashiyangtse or Tashi Yangtse is a small town in Yangtse Gewog, and the district headquarters of the Trashiyangtse District in eastern Bhutan. It lies inside the Bumdeling Wildlife Sanctuary on the eastern tri-junction of Bhutan-India-China and t ...
, which was finally washed away in 2004. Gyalpo's iron chain bridges did not include a suspended-deck bridge, which is the standard on all modern suspension bridges today. Instead, both the railing and the walking layer of Gyalpo's bridges used wires. The stress points that carried the screed were reinforced by the iron chains. Before the use of iron chains it is thought that Gyalpo used ropes from twisted willows or yak skins. He may have also used tightly bound cloth.


Chain bridges

The first iron chain suspension bridge in the
Western world The Western world, also known as the West, primarily refers to the various nations and states in the regions of Europe, North America, and Oceania.
was the
Jacob's Creek Bridge Jacob's Creek Bridge (1801, demolished 1833) was the first iron-chain suspension bridge built in the United States. Designed by James Finley, a local judge and inventor, it spanned Jacob's Creek, just south of Mount Pleasant, Pennsylvania. Nothi ...
(1801) in Westmoreland County, Pennsylvania, designed by inventor James Finley. Finley's bridge was the first to incorporate all of the necessary components of a modern suspension bridge, including a suspended deck which hung by trusses. Finley patented his design in 1808, and published it in the Philadelphia journal, The Port Folio, in 1810. Early British chain bridges included the
Dryburgh Abbey Bridge Dryburgh Abbey Bridge was a cable-stayed footbridge of significant historical interest erected near Dryburgh Abbey, in the Borders of Scotland. It connected the villages of Dryburgh and St. Boswells (part of a ribbon of settlements, including ...
(1817) and 137 m Union Bridge (1820), with spans rapidly increasing to 176 m with the Menai Bridge (1826), "the first important modern suspension bridge". The first chain bridge on the German speaking territories was the Chain Bridge in
Nuremberg Nuremberg ( ; german: link=no, Nürnberg ; in the local East Franconian dialect: ''Nämberch'' ) is the second-largest city of the German state of Bavaria after its capital Munich, and its 518,370 (2019) inhabitants make it the 14th-largest ...
. The Sagar Iron Suspension Bridge with a 200 feet span (also termed Beose Bridge) was constructed near Sagar, India during 1828-1830 by Duncan Presgrave, Mint and Assay Master. The
Clifton Suspension Bridge The Clifton Suspension Bridge is a suspension bridge spanning the Avon Gorge and the River Avon, linking Clifton in Bristol to Leigh Woods in North Somerset. Since opening in 1864, it has been a toll bridge, the income from which provid ...
(designed in 1831, completed in 1864 with a 214 m central span), is similar to the Sagar bridge. It is one of the longest of the parabolic arc chain type. The current Marlow suspension bridge was designed by
William Tierney Clark William Tierney Clark FRS FRAS (23 August 1783 – 22 September 1852) was an English civil engineer particularly associated with the design and construction of bridges. He was among the earliest designers of suspension bridges. Born in B ...
and was built between 1829 and 1832, replacing a wooden bridge further downstream which collapsed in 1828. It is the only suspension bridge across the non-tidal Thames. The Széchenyi Chain Bridge, (designed in 1840, opened in 1849), spanning the River Danube in Budapest, was also designed by William Clark and it is a larger-scale version of Marlow Bridge. An interesting variation is
Thornewill and Warham Thornewill and Warham Ltd was a metal hardware and industrial metalwork manufacturer, later an engineering company, based in Burton upon Trent, Staffordshire, England. Under different names it traded from 1740 until 1929, becoming a notable produc ...
's Ferry Bridge in Burton-on-Trent,
Staffordshire Staffordshire (; postal abbreviation Staffs.) is a landlocked county in the West Midlands region of England. It borders Cheshire to the northwest, Derbyshire and Leicestershire to the east, Warwickshire to the southeast, the West Midlands C ...
(1889), where the chains are not attached to abutments as is usual, but instead are attached to the main girders, which are thus in compression. Here, the chains are made from flat wrought iron plates, eight inches (203 mm) wide by an inch and a half (38 mm) thick, rivetted together.


Wire-cable

The first wire-cable suspension bridge was the Spider Bridge at Falls of Schuylkill (1816), a modest and temporary footbridge built following the collapse of James Finley's nearby
Chain Bridge at Falls of Schuylkill Chain Bridge at Falls of Schuylkill was an 1808 iron-chain suspension bridge built across the Schuylkill River, north of Philadelphia, Pennsylvania. Designed by inventor James Finley, it became the model for his later chain suspension bridges. ...
(1808). The footbridge's span was 124 m, although its deck was only 0.45 m wide. Development of wire-cable suspension bridges dates to the temporary simple suspension bridge at Annonay built by
Marc Seguin Marc Seguin (20 April 1786 – 24 February 1875) was a French engineer, inventor of the wire- cable suspension bridge and the multi-tubular steam-engine boiler. Early life Seguin was born in Annonay, Ardèche to Marc François Seguin, th ...
and his brothers in 1822. It spanned only 18 m. The first permanent wire cable suspension bridge was
Guillaume Henri Dufour Guillaume Henri Dufour (15 September 178714 July 1875) was a Swiss military officer, structural engineer and topographer. He served under Napoleon I and held the Swiss office of General four times in his career, firstly in 1847 when he led the ...
's Saint Antoine Bridge in
Geneva Geneva ( ; french: Genève ) frp, Genèva ; german: link=no, Genf ; it, Ginevra ; rm, Genevra is the second-most populous city in Switzerland (after Zürich) and the most populous city of Romandy, the French-speaking part of Switzerland. Situa ...
of 1823, with two 40 m spans. The first with cables assembled in mid-air in the modern method was Joseph Chaley's Grand Pont Suspendu in Fribourg, in 1834. In the United States, the first major wire-cable suspension bridge was the Wire Bridge at Fairmount in Philadelphia, Pennsylvania. Designed by Charles Ellet Jr. and completed in 1842, it had a span of 109 m. Ellet's Niagara Falls suspension bridge (1847–48) was abandoned before completion. It was used as scaffolding for
John A. Roebling John Augustus Roebling (born Johann August Röbling; June 12, 1806 – July 22, 1869) was a German-born American civil engineer. He designed and built wire rope suspension bridges, in particular the Brooklyn Bridge, which has been designated as ...
's double decker railroad and carriage bridge (1855). The
Otto Beit Bridge The Chirundu Bridge now consists of two road bridges side by side across the Zambezi River between the small town of Chirundu, Zambia and the village of Chirundu, Zimbabwe. At this location around 65 km downstream from the Kariba Dam the r ...
(1938–1939) was the first modern suspension bridge outside the United States built with parallel wire cables. File: Chaksam (Iron Bridge in transliteration from Tibetan to English).png, Drawing of the Tibetan-built Chaksam bridge south of
Lhasa Lhasa (; Lhasa dialect: ; bo, text=ལྷ་ས, translation=Place of Gods) is the urban center of the prefecture-level Lhasa City and the administrative capital of Tibet Autonomous Region in Southwest China. The inner urban area of Lhasa ...
, constructed in 1430, with long chains suspended between towers, and vertical suspender ropes carrying the weight of a planked footway below. File: View of the Chain Bridge The Port Folio June 1810.jpg, "View of the Chain Bridge invented by James Finley Esq." (1810) by William Strickland. Finley's
Chain Bridge at Falls of Schuylkill Chain Bridge at Falls of Schuylkill was an 1808 iron-chain suspension bridge built across the Schuylkill River, north of Philadelphia, Pennsylvania. Designed by inventor James Finley, it became the model for his later chain suspension bridges. ...
(1808) had two spans, 100 feet, and 200 feet. File:Sagar Iron Suspension Bridge.png, Sagar Iron Suspension Bridge, by Major Presgrave, 1828-1830, near Sanodha, Sagar district
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...
constructed using locally produced iron. File: The New Suspension Bridge at Fairmount, Philadelphia by George Lehman circa 1842.jpg, Wire Bridge at Fairmount (1842, replaced 1874).


Structure


Bridge main components

Two towers/pillars, two suspension cables, four suspension cable anchors, multiple suspender cables, the bridge deck.


Structural analysis

The main cables of a suspension bridge will form a catenary; the cables will instead form a
parabola In mathematics, a parabola is a plane curve which is mirror-symmetrical and is approximately U-shaped. It fits several superficially different mathematical descriptions, which can all be proved to define exactly the same curves. One descri ...
if they are assumed to have zero weight. One can see the shape from the constant increase of the gradient of the cable with linear (deck) distance, this increase in gradient at each connection with the deck providing a net upward support force. Combined with the relatively simple constraints placed upon the actual deck, that makes the suspension bridge much simpler to design and analyze than a cable-stayed bridge in which the deck is in compression.


Comparison with cable-stayed bridge

Cable-stayed bridges and suspension bridges may appear to be similar, but are quite different in principle and in their construction. In suspension bridges, large main cables (normally two) hang between the towers and are anchored at each end to the ground. The main cables, which are free to move on bearings in the towers, bear the load of the bridge deck. Before the deck is installed, the cables are under tension from their own weight. Along the main cables smaller cables or rods connect to the bridge deck, which is lifted in sections. As this is done, the tension in the cables increases, as it does with the live load of traffic crossing the bridge. The tension on the main cables is transferred to the ground at the anchorages and by downwards compression on the towers. File:Bridge-suspension.svg, Suspension bridge File:Bridge-fan-cable-stayed.svg, Cable-stayed bridge, fan design In cable-stayed bridges, the towers are the primary load-bearing structures that transmit the bridge loads to the ground. A
cantilever A cantilever is a rigid structural element that extends horizontally and is supported at only one end. Typically it extends from a flat vertical surface such as a wall, to which it must be firmly attached. Like other structural elements, a cant ...
approach is often used to support the bridge deck near the towers, but lengths further from them are supported by cables running directly to the towers. By design, all static horizontal forces of the cable-stayed bridge are balanced so that the supporting towers do not tend to tilt or slide and so must only resist horizontal forces from the live loads.


Advantages

*Longer main spans are achievable than with any other type of bridge. *Less material may be required than other bridge types, even at spans they can achieve, leading to a reduced construction cost. *Except for installation of the initial temporary cables, little or no access from below is required during construction and so a waterway can remain open while the bridge is built above. *They may be better able to withstand earthquake movements than heavier and more rigid bridges. *Bridge decks can have deck sections replaced in order to widen traffic lanes for larger vehicles or add additional width for separated cycling/pedestrian paths.


Disadvantages

*Considerable stiffness or aerodynamic profiling may be required to prevent the bridge deck vibrating under high winds. *The relatively low deck stiffness compared to other (non-suspension) types of bridges makes it more difficult to carry
heavy rail Various terms are used for passenger railway lines and equipment; the usage of these terms differs substantially between areas: Rapid transit A rapid transit system is an electric railway characterized by high speed (~) and rapid accelerat ...
traffic in which high concentrated
live loads A structural load or structural action is a force, deformation, or acceleration applied to structural elements. A load causes stress, deformation, and displacement in a structure. Structural analysis, a discipline in engineering, analyzes the ef ...
occur. *Some access below may be required during construction to lift the initial cables or to lift deck units. That access can often be avoided in cable-stayed bridge construction.


Variations


Underspanned

In an underspanned suspension bridge, also called under-deck cable-stayed bridge, the main cables hang entirely below the bridge deck, but are still anchored into the ground in a similar way to the conventional type. Very few bridges of this nature have been built, as the deck is inherently less stable than when suspended below the cables. Examples include the Pont des Bergues of 1834 designed by
Guillaume Henri Dufour Guillaume Henri Dufour (15 September 178714 July 1875) was a Swiss military officer, structural engineer and topographer. He served under Napoleon I and held the Swiss office of General four times in his career, firstly in 1847 when he led the ...
; James Smith's Micklewood Bridge; and a proposal by
Robert Stevenson Robert Stevenson may refer to: * Robert Stevenson (actor and politician) (1915–1975), American actor and politician * Robert Stevenson (civil engineer) (1772–1850), Scottish lighthouse engineer * Robert Stevenson (director) (1905–1986), Engli ...
for a bridge over the River Almond near
Edinburgh Edinburgh ( ; gd, Dùn Èideann ) is the capital city of Scotland and one of its 32 Council areas of Scotland, council areas. Historically part of the county of Midlothian (interchangeably Edinburghshire before 1921), it is located in Lothian ...
.
Roebling's Delaware Aqueduct Roebling's Delaware Aqueduct, also known as the Roebling Bridge, is the oldest existing wire suspension bridge in the United States. It runs over the Delaware River, from Minisink Ford, New York, to Lackawaxen, Pennsylvania. Opened in 1849 as ...
(begun 1847) consists of three sections supported by cables. The timber structure essentially hides the cables; and from a quick view, it is not immediately apparent that it is even a suspension bridge.


Suspension cable types

The main suspension cables in older bridges were often made from a chain or linked bars, but modern bridge cables are made from multiple strands of wire. This not only adds strength but improves reliability (often called redundancy in engineering terms) because the failure of a few flawed strands in the hundreds used pose very little threat of failure, whereas a single bad link or
eyebar In structural engineering and construction, an eyebar is a straight bar, usually of metal, with a hole ("eye") at each end for fixing to other components. Eyebars are used in structures such as bridges, in settings in which only tension, and ...
can cause failure of an entire bridge. (The failure of a single eyebar was found to be the cause of the collapse of the Silver Bridge over the
Ohio River The Ohio River is a long river in the United States. It is located at the boundary of the Midwestern and Southern United States, flowing southwesterly from western Pennsylvania to its mouth on the Mississippi River at the southern tip of ...
.) Another reason is that as spans increased, engineers were unable to lift larger chains into position, whereas wire strand cables can be formulated one by one in mid-air from a temporary walkway.


Suspender-cable terminations

Poured sockets are used to make a high strength, permanent cable termination. They are created by inserting the suspender wire rope (at the bridge deck supports) into the narrow end of a conical cavity which is oriented in-line with the intended direction of strain. The individual wires are splayed out inside the cone or 'capel', and the cone is then filled with molten lead-antimony-tin (Pb80Sb15Sn5) solder.


Deck structure types

Most suspension bridges have open truss structures to support the roadbed, particularly owing to the unfavorable effects of using plate girders, discovered from the Tacoma Narrows Bridge (1940) bridge collapse. In the 1960s, developments in bridge aerodynamics allowed the re-introduction of plate structures as shallow box girders, first seen on the Severn bridge, built 1961–1966. In the picture of the
Yichang Bridge The Yichang Yangtze River Highway Bridge () is a suspension bridge that crosses the Yangtze River some 20 km downstream from the center city of Yichang, China. It is located within the prefecture-level city of Yichang, and carries the G50 Sh ...
, note the very sharp entry edge and sloping undergirders in the suspension bridge shown. This enables this type of construction to be used without the danger of vortex shedding and consequent aeroelastic effects, such as those that destroyed the original Tacoma Narrows bridge.


Forces

Three kinds of forces operate on any bridge: the dead load, the
live Live may refer to: Arts, entertainment, and media Films * ''Live!'' (2007 film), 2007 American film * ''Live'' (2014 film), a 2014 Japanese film *'' ''Live'' (Apocalyptica DVD) Music * Live (band), American alternative rock band * List of album ...
load, and the
dynamic Dynamics (from Greek δυναμικός ''dynamikos'' "powerful", from δύναμις ''dynamis'' "power") or dynamic may refer to: Physics and engineering * Dynamics (mechanics) ** Aerodynamics, the study of the motion of air ** Analytical dyn ...
load. Dead load refers to the weight of the bridge itself. Like any other structure, a bridge has a tendency to collapse simply because of the gravitational forces acting on the materials of which the bridge is made. Live load refers to traffic that moves across the bridge as well as normal environmental factors such as changes in temperature, precipitation, and winds. Dynamic load refers to environmental factors that go beyond normal weather conditions, factors such as sudden gusts of wind and earthquakes. All three factors must be taken into consideration when building a bridge.


Use other than road and rail

The principles of suspension used on a large scale also appear in contexts less dramatic than road or rail bridges. Light cable suspension may prove less expensive and seem more elegant for a cycle or footbridge than strong girder supports. An example of this is the
Nescio Bridge The Nescio Bridge (or ''Nesciobrug'' in Dutch) is a cycle and footbridge in the Netherlands. This curved, steel suspension bridge, located in Amsterdam, is the country's first suspension bridge that carries only a cycle track and footway, and at ...
in the Netherlands, and the Roebling designed 1904 Riegelsville suspension pedestrian bridge across the Delaware River in Pennsylvania. The longest pedestrian suspension bridge, which spans the River Paiva, Arouca
Geopark A geopark is a protected area with internationally significant geology within which sustainable development is sought and which includes tourism, conservation, education and research concerning not just geology but other relevant sciences. In 20 ...
, Portugal, opened in April 2021. The 516 metres bridge hangs 175 meters above the river. Where such a bridge spans a gap between two buildings, there is no need to construct special towers, as the buildings can anchor the cables. Cable suspension may also be augmented by the inherent stiffness of a structure that has much in common with a tubular bridge.


Construction sequence (wire strand cable type)

Typical suspension bridges are constructed using a sequence generally described as follows. Depending on length and size, construction may take anywhere between a year and a half (construction on the original Tacoma Narrows Bridge took only 19 months) up to as long as a decade (the Akashi-Kaikyō Bridge's construction began in May 1986 and was opened in May 1998 – a total of twelve years). #Where the towers are founded on underwater piers, '' caissons'' are sunk and any soft bottom is excavated for a foundation. If the
bedrock In geology, bedrock is solid rock that lies under loose material ( regolith) within the crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface material. An exposed portion of be ...
is too deep to be exposed by excavation or the sinking of a caisson, pilings are driven to the bedrock or into overlying hard soil, or a large concrete pad to distribute the weight over less resistant soil may be constructed, first preparing the surface with a bed of compacted gravel. (Such a pad footing can also accommodate the movements of an active fault, and this has been implemented on the foundations of the cable-stayed Rio-Antirio bridge.) The piers are then extended above water level, where they are capped with pedestal bases for the towers. #Where the towers are founded on dry land, deep foundation excavation or pilings are used. #From the tower foundation, towers of single or multiple columns are erected using high-strength reinforced concrete, stonework, or steel. Concrete is used most frequently in modern suspension bridge construction due to the high cost of steel. #Large devices called ''saddles'', which will carry the main suspension cables, are positioned atop the towers. Typically of cast steel, they can also be manufactured using riveted forms, and are equipped with rollers to allow the main cables to shift under construction and normal loads. #'' Anchorages'' are constructed, usually in tandem with the towers, to resist the tension of the cables and form as the main anchor system for the entire structure. These are usually anchored in good quality rock but may consist of massive reinforced concrete deadweights within an excavation. The anchorage structure will have multiple protruding open ''eyebolts'' enclosed within a secure space. #Temporary suspended walkways, called ''catwalks'', are then erected using a set of guide wires hoisted into place via winches positioned atop the towers. These catwalks follow the curve set by bridge designers for the main cables, in a path mathematically described as a catenary arc. Typical catwalks are usually between eight and ten feet wide and are constructed using wire grate and wood slats. #Gantries are placed upon the catwalks, which will support the main cable spinning reels. Then, cables attached to winches are installed, and in turn, the main cable spinning devices are installed. #High strength wire (typically 4 or 6 gauge galvanized steel wire), is pulled in a loop by pulleys on the traveler, with one end affixed at an anchorage. When the traveler reaches the opposite anchorage the loop is placed over an open anchor
eyebar In structural engineering and construction, an eyebar is a straight bar, usually of metal, with a hole ("eye") at each end for fixing to other components. Eyebars are used in structures such as bridges, in settings in which only tension, and ...
. Along the catwalk, workers also pull the cable wires to their desired tension. This continues until a bundle, called a "cable strand" is completed, and temporarily bundled using stainless steel wire. This process is repeated until the final cable strand is completed. Workers then remove the individual wraps on the cable strands (during the spinning process, the shape of the main cable closely resembles a hexagon), and then the entire cable is then compressed by a traveling hydraulic press into a closely packed cylinder and tightly wrapped with additional wire to form the final circular cross-section. The wire used in suspension bridge construction is a galvanized steel wire that has been coated with corrosion inhibitors. #At specific points along the main cable (each being the exact distance horizontally in relation to the next) devices called "cable bands" are installed to carry steel wire ropes called ''Suspender cables.'' Each suspender cable is engineered and cut to precise lengths, and are looped over the cable bands. In some bridges, where the towers are close to or on the shore, the suspender cables may be applied only to the central span. Early suspender cables were fitted with zinc jewels and a set of steel washers, which formed the support for the deck. Modern suspender cables carry a shackle-type fitting. #Special lifting hoists attached to the suspenders or from the main cables are used to lift prefabricated sections of the bridge deck to the proper level, provided that the local conditions allow the sections to be carried below the bridge by barge or other means. Otherwise, a traveling
cantilever A cantilever is a rigid structural element that extends horizontally and is supported at only one end. Typically it extends from a flat vertical surface such as a wall, to which it must be firmly attached. Like other structural elements, a cant ...
derrick may be used to extend the deck one section at a time starting from the towers and working outward. If the addition of the deck structure extends from the towers the finished portions of the deck will pitch upward rather sharply, as there is no downward force in the center of the span. Upon completion of the deck, the added load will pull the main cables into an arc mathematically described as a
parabola In mathematics, a parabola is a plane curve which is mirror-symmetrical and is approximately U-shaped. It fits several superficially different mathematical descriptions, which can all be proved to define exactly the same curves. One descri ...
, while the arc of the deck will be as the designer intended – usually a gentle upward arc for added clearance if over a shipping channel, or flat in other cases such as a span over a canyon. Arched suspension spans also give the structure more rigidity and strength. #With the completion of the primary structure various details such as lighting, handrails, finish painting and paving is installed or completed.


Longest spans

Suspension bridges are typically ranked by the length of their main span. These are the ten bridges with the longest spans, followed by the length of the span and the year the bridge opened for traffic:


Other examples

(Chronological) * Union Bridge (England/Scotland, 1820), the longest span (137 m) from 1820 to 1826. The oldest suspension bridge in the world still carrying road traffic. *
Roebling's Delaware Aqueduct Roebling's Delaware Aqueduct, also known as the Roebling Bridge, is the oldest existing wire suspension bridge in the United States. It runs over the Delaware River, from Minisink Ford, New York, to Lackawaxen, Pennsylvania. Opened in 1849 as ...
(USA, 1847), the oldest wire suspension bridge still in service in the United States. *
John A. Roebling Suspension Bridge The John A. Roebling Suspension Bridge (formerly the Cincinnati-Covington Bridge) is a suspension bridge that spans the Ohio River between Cincinnati, Ohio, and Covington, Kentucky. When opened on December 1, 1866, it was the longest suspensio ...
(USA, 1866), then the longest wire suspension bridge in the world at 1,057 feet (322 m) main span. *
Brooklyn Bridge The Brooklyn Bridge is a hybrid cable-stayed/ suspension bridge in New York City, spanning the East River between the boroughs of Manhattan and Brooklyn. Opened on May 24, 1883, the Brooklyn Bridge was the first fixed crossing of the East Rive ...
(USA, 1883), the first steel-wire suspension bridge. * Bear Mountain Bridge (USA, 1924), the longest suspension span (497 m) from 1924 to 1926. The first suspension bridge to have a concrete deck. The construction methods pioneered in building it would make possible several much larger projects to follow. *
Benjamin Franklin Bridge The Benjamin Franklin Bridge, originally named the Delaware River Bridge and known locally as the Ben Franklin Bridge, is a suspension bridge across the Delaware River connecting Philadelphia, Pennsylvania, and Camden, New Jersey. Owned and ...
(USA, 1926), replaced Bear Mountain Bridge as the longest span at 1,750 feet between the towers. Includes an active subway line and never-used trolley stations on the span. *
San Francisco–Oakland Bay Bridge The San Francisco–Oakland Bay Bridge, known locally as the Bay Bridge, is a complex of bridges spanning San Francisco Bay in California. As part of Interstate 80 and the direct road between San Francisco and Oakland, it carries about 260,000 ...
(USA, 1936). This was once the longest steel high-level bridge in the world (704 m). The eastern portion (a cantilever bridge) has been replaced with a self-anchored suspension bridge which is the longest of its type in the world. It is also the world's widest bridge. *
Golden Gate Bridge The Golden Gate Bridge is a suspension bridge spanning the Golden Gate, the strait connecting San Francisco Bay and the Pacific Ocean. The structure links the U.S. city of San Francisco, California—the northern tip of the San Francisco Pen ...
(USA, 1937), the longest suspension bridge from 1937 to 1964. It was also the world's tallest bridge from 1937 to 1993, and remains the tallest bridge in the United States. * Mackinac Bridge (USA, 1957), the longest suspension bridge between anchorages in the Western hemisphere. *
Si Du River Bridge The Sidu River Bridge (Siduhe Bridge, 四渡河特大桥) is a suspension bridge crossing the valley of the Sidu River near Yesanguan in Badong County of the Hubei Province of the People's Republic of China. The bridge was designed by CCSHCC Se ...
(China, 2009), the highest bridge in the world, with its deck around 500 meters above the surface of the river. *
Rod El Farag Bridge Rod El Farag ( ar, روض الفرج, ; also spelled Road El Farag, Road Elfarag or Road Alfarag) is an administrative region forming about one third of Shobra in Cairo, Egypt. Rod El Farag neighbours the River Nile to the west, Boulaq to the south ...
(Egypt, 2019), a modern Egyptian steel wire-cables based suspension bridge crossing the river
Nile The Nile, , Bohairic , lg, Kiira , Nobiin: Áman Dawū is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa and has historically been considered the longest riv ...
, which was completed in 2019 and holds the
Guinness World Record ''Guinness World Records'', known from its inception in 1955 until 1999 as ''The Guinness Book of Records'' and in previous United States editions as ''The Guinness Book of World Records'', is a reference book published annually, listing world ...
for the widest suspension bridge in the world with a width of 67.3 meters, and with a span of 540 meters.


Notable collapses

*
Broughton Suspension Bridge Broughton Suspension Bridge was an iron chain suspension bridge built in 1826 to span the River Irwell between Broughton and Pendleton, now in Salford, Greater Manchester, England. One of Europe's first suspension bridges, it has been attrib ...
(England) – Iron chain bridge built in 1826. One of Europe's first suspension bridges, it collapsed in 1831 due to mechanical resonance induced by troops marching in step. As a result of the incident, the British Army issued an order that troops should "break step" when crossing a bridge. * Silver Bridge (USA) – Eyebar chain highway bridge, built in 1928, that collapsed in late 1967, killing forty-six people. The bridge had a low-redundancy design that was difficult to inspect. The collapse inspired legislation to ensure that older bridges were regularly inspected and maintained. Following the collapse a bridge of similar design was immediately closed and eventually demolished. A second similarly-designed bridge had been built with a higher margin of safety and remained in service until 1991. * Tacoma Narrows Bridge, (USA), 853 m – 1940. The Tacoma Narrows bridge was vulnerable to structural vibration in sustained and moderately strong winds due to its plate-girder deck structure. Wind caused a phenomenon called aeroelastic fluttering that led to its collapse only months after completion. The collapse was captured on film. There were no human deaths in the collapse; several drivers escaped their cars on foot and reached the anchorages before the span dropped. * Yarmouth suspension bridge (England) – Built in 1829 and collapsed in 1845, killing 79 people. * Peace River Suspension Bridge (Canada) The north anchor's soil support for the suspension bridge, which was completed in 1943, failed over a few days in October 1957, and the entire bridge subsequently collapsed. * On 30 October 2022, Jhulto Pul, a pedestrian suspension bridge over the
Machchhu River Machchhu River ( gu, મચ્છુ નદી, translit=Machchhu nadi) is a river in Gujarat, India, with its origin in the Madla hills. Its basin has a maximum length of . The total catchment area of the basin is . The river is also occasional ...
in the city of Morbi, Gujarat, India collapsed, leading to the deaths of at least 141 people.


See also

* : Suspension bridges — for articles about specific suspension bridges. * List of longest suspension bridge spans * Timeline of three longest spans whether bridge,
aerial tramway An aerial tramway, sky tram, cable car, ropeway, aerial tram, telepherique, or seilbahn is a type of aerial lift which uses one or two stationary ropes for support while a third moving rope provides propulsion. With this form of lift, the grip ...
, powerline, ceiling or
dome A dome () is an architectural element similar to the hollow upper half of a sphere. There is significant overlap with the term cupola, which may also refer to a dome or a structure on top of a dome. The precise definition of a dome has been a m ...
etc. * Cable-stayed bridge — superficially similar to a suspension bridge, but cables from the towers directly support the roadway, rather than the road being suspended indirectly by additional cables from the main cables connecting two towers. *
Inca rope bridge Incana rope bridges are simple suspension bridges over canyons , gorges and rivers ('' pongos'') constructed by the Inca Empire. The bridges were an integral part of the Inca road system and exemplify Inca innovation in engineering. Bridges of ...
— has features in common with a suspension bridge and predates them by at least three hundred years. However, in a rope bridge the deck itself is suspended from the anchored piers and the guardrails are non-structural. * Self-anchored suspension bridge — combining elements of a suspension bridge and a cable-stayed bridge. * Simple suspension bridge — a modern implementation of the rope bridge using steel cables, although either the upper guardrail or lower footboard cables may be the main structural cables. *
Floating suspension bridge A floating suspension bridge is a type of suspension bridge supported by towers built on floating pontoons which are tethered to the seabed. The design is intended to overcome the difficulties of building suspension towers in locations where th ...


References


External links

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New Brunswick Canada suspension footbridgesStructurae: suspension bridges
History and heritage of civil engineering – bridges
Bridgemeister: Mostly suspension bridges
* {{DEFAULTSORT:Suspension Bridge Bridges by structural type Structural engineering