- This article is concerned with a particular type of suspension bridge, the suspended-deck type. For an index to the several types see suspension bridge types.
| Suspension bridge | |
|---|---|
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| An early bridge of this type, the Clifton Suspension Bridge | |
| Ancestor | Simple suspension bridge |
| Related | None, but see also cable stayed bridge and compression arch suspended-deck bridge |
| Descendant | Self-anchored suspension bridge |
| Carries | Pedestrians, automobiles, trucks, light rail |
| Span range | Medium to long |
| Material | Steel rope, multiple steel wire strand cables or forged or cast chain links |
| Movable | No |
| Design effort | medium |
| Falsework required | No |
A suspension bridge is a type of bridge that has been created since ancient times as early as 100 AD. Simple suspension bridges, for use by pedestrians and livestock, are still constructed, based upon the ancient Inca rope bridge. One of the oldest of engineering forms, suspension bridges were constructed by primitive peoples using vines for cables and mounting the roadway directly on the cables. A much stronger type was introduced in India about the 4th century AD that used cables of plaited bamboo and later of iron chain.[1] Suspended well from two high locations over a river or canyon, simple suspension bridges follow a shallow downward arc and are not suited for modern roads and railroads. Advances in materials and design led to the development of the suspended-deck suspension bridge, a modern bridge capable of carrying vehicles and light rail. Instead of the deck following the downward arc of the main load-bearing cables (or chains), these cables are suspended between towers, and vertical suspender cables carry the weight of the deck below, upon which traffic crosses. This arrangement allows the deck to be level or to arc slightly upward for additional clearance.
The design of the modern suspended-deck suspension bridge was developed in the early 19th century. Early examples include James Finley's bridge at Jacob's Creek, in Pennsylvania, in 1801, the Menai and Conwy Suspension Bridges (both opened in 1826) in north Wales; and the first Hammersmith Bridge (1827) in west London. This type of bridge is the only practical type suitable for very long spans or when it would be hazardous to maritime traffic to add central supports. One example frequently cited for its aesthetic appeal is the Golden Gate Bridge at the entrance to San Francisco Bay.
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 (An exception is the Royal Albert Bridge (1859) where the anchors are replaced by an arch between the columns.) The roadway is supported by vertical suspender cables or rods. In some circumstances the towers may sit on a bluff or canyon 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 may use a truss bridge to make this connection. In the latter case there will be very little arc in the outboard main cables. Without special design this type is generally not suited for heavy rail applications as the bridge will flex under the concentrated load of a locomotive.
Advantages over other bridge types
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A suspension bridge can be made out of simple materials such as wood and common wire rope.
- The center span may be made long in proportion to the materials required, allowing the bridge to economically span a very wide canyon or waterway.
- It can be built high over water to allow the passage of tall ships.
- Neither temporary central supports nor access from beneath is required for construction, allowing it to span a rift or waterway.
- Being flexible it can flex under wind and seismic conditions, where a more rigid bridge would have to be made stronger and heavier.
- Since they can provide the same strength and stability of other design schemes with less weight and bulk suspension bridges are often less expensive to construct and maintain.
Other bridges
Disadvantages compared with other bridge types
- Lacking stiffness the bridge may become unusable in strong wind conditions and so require closure to traffic.
- Being flexible in response to concentrated loads the structure is generally not used for heavy rail crossings, which concentrate the maximum "live" loading at the location of the locomotives.
- Under severe wind loading, the towers exert a large torque force in the ground, and thus require expensive foundation work when building on soft ground.
Structural analysis
The main forces in a suspension bridge are tension in the main cables and compression in the pillars. Since almost all the force on the pillars is vertically downwards and they are also stabilized by the main cables, they can be made quite slender, as they have been in, for example, the Severn Bridge, near Bristol, England)
Assuming a negligible cable weight compared to the deck and vehicles being supported, a suspension bridge's main cables will form a parabola (very similar to a catenary, the form the unloaded cables take before the deck is added). This can be seen from the cable's constant gradient increase 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, this makes the suspension bridge much simpler to design and analyze than a cable stayed design, where the deck is in compression.
Suspension types
The suspension in older bridges may be made from chain or linked bars, but modern bridge cables are made from multiple strands of wire. This is for greater redundancy; a few flawed strands in the hundreds used pose very little threat, whereas a single bad link or eyebar can eliminate the safety margin or bring down the structure. This was found to be the cause of the collapse of the Silver Bridge over the Ohio river.Deck structure types
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A plate deck suspension bridge over the Yangtze River in China
Other applications
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Cable-suspended footbridge at DFW Terminal D
Construction sequence (wire strand cable type)
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New Little Belt suspension bridge, 1970 Denmark
- Where the towers are founded on underwater piers, caissons are sunk and any soft bottom is excavated for a foundation. If the bedrock 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 earthquake fault, and this has been implemented on the foundations of the cable-stayed Rio-Antirio bridge. The foundation piers are then extended to above water level.
- 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 concrete, stonework, or steel structures. At some elevation there must be a passage for the deck, with the columns extending high above this level.
- Smooth open cable paths called saddles are anchored atop the towers. These allow for slight movements of the cable as the loads change during construction. The top of these saddles may be closed with an additional part after completion of the bridge.
- Anchorages are constructed to resist the tension of the cables. 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.
- A temporary suspended walkway supported by wire rope follows the curve of the cables to be constructed, mathematically described as a catenary arc.
- Another set of wire ropes are suspended above the walkway and are used to support a traveler that has wheels riding atop these cables. There will be one set of wire ropes and a traveler for each cable to be "spun"
- Pulling cables attached to winches are capable of pulling the traveler from one anchorage to the other, traveling in arcs to the tops of the two towers.
- High strength wire, typically less than 10 mm in diameter, is pulled in a loop by pulleys on the traveler, with one end affixed at an anchorage. Workers stationed along the walkway attach the passing cable to a bundle with a temporary binding. When the traveler reaches the opposite anchorage the loop is placed over an open anchor eyebar.
- The traveler is returned to the start point to pick up another loop or it is used to carry a new loop from this side.
- As loops are placed, corrosion proofing may be applied.
- In this way a complete sub-cable is created linking the eyebar (or a set of eyebars) from one anchorage to the other. The sub-cables will have a hexagonal cross section and are held together with the temporary bindings.
- Multiple adjacent sub-cables are placed adjacent to each other. While these are on a hexagonal grid, the general form for the larger cable is circular.
- 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.
- Saddles to carry the suspender cables are clamped to the main cables, each with an appropriate shape to conform to the ultimate slope of the main cables. Each saddle is an equal horizontal distance from the next, with spacing appropriate to the design of the deck.
- Suspender cables engineered and cut to precise lengths and carrying swedged ends are looped over the saddles. In some bridges, where the towers are close to or on the shore, the suspender cables may be applied only to the central span.
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Lions' Gate Bridge under construction
- Special lifting hosts attached to the suspenders or from the main cables are used to lift prefabricated sections of 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 may be used to extend the deck one section at a time. 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, 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.
- With completion of the primary structure various details such as lighting, handrails, finish painting and paving are added.
Details gallery
) Demonstration section of main cable showing component wires | ) Main cable seat at top of tower | ) Suspender cables and saddle on main cable |
The largest suspension bridges in the world
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- Akashi-Kaikyo Bridge (Japan) 1991 m — 1998
- Great Belt Bridge (Denmark) 1624 m — 1998
- Runyang Bridge (China) 1490 m — 2005
- Humber Bridge (England, United Kingdom) 1410 m — 1981 (The largest from 1981 until 1998.)
- Jiangyin Suspension Bridge (China) 1385 m — 1997
- Tsing Ma Bridge (Hong Kong, China) 1377 m — 1997 (largest with both road and metro)
- Verrazano Narrows Bridge (USA) 1298 m — 1964 (The largest from 1964 until 1981.)
- Golden Gate Bridge (USA) 1280 m — 1937 (The largest from 1937 until 1964.)
- Höga Kusten Bridge (Sweden) 1210 m — 1997
- Mackinac Bridge (USA) 1158 m — 1957
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The Humber Bridge, UK
It is also possible to rank suspension bridges by the total length of suspension. Note that some of these bridges have more than two towers, but these are actually multiple bridges. Having more than two towers without a central anchorage could be unstable in some conditions. A modern exception was the design of the proposed Chacao Channel bridge, a project which has been canceled. This innovative bridge was to have two main spans, made possible by the use of a rigid central tower composed of two side-by-side A frames. The stiffness of these frames (as opposed to the flexibility of the usual spar tower) prevents transmission of significant dynamic forces between the mainspans, ensuring dynamic stability in various wind conditions.
- Akashi-Kaikyo Bridge (Japan) 3909 m
- Kurushima-Kaikyo Bridge (Japan) 3260 m (suspended sections are not all contiguous)
- Great Seto Bridge (Japan) 3186 m (two bridges with common anchorage)
- San Francisco-Oakland Bay Bridge (USA) 2822 m (two bridges with common central anchorage)
- Great Belt Bridge (Denmark) 2719 m
- Mackinac Bridge (USA) 2625 m
The Strait of Messina Bridge, with a center span of 3300 m, was planned to connect Italy and Sicily but was cancelled shortly before construction was set to begin. Bridges have also been suggested for the Strait of Gibraltar and the Sunda Strait with longest spans of several kilometres. The suspension cables for these longest bridges are suspended from the ends of cable-stayed ties extending diagonally from tall pylons, also called towers.
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Other famous suspension bridges
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Brooklyn Bridge with Manhattan Bridge in background
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Golden Gate Bridge, California, USA
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Western portion of the San Francisco-Oakland Bay Bridge — two bridges with a common central anchorage
- Union Bridge (England/Scotland) 137 m - 1820. The largest suspension bridge from 1820 to 1826. The oldest in the world still in use today.
- Menai Suspension Bridge (north Wales) 176 m - 1826, The largest suspension bridge from 1826 until 1834.
- Zähringen Bridge (Switzerland) 271 m - 1834. The largest suspension bridge from 1834 until 1849. The bridge was removed in the 1920s.
- Wheeling Suspension Bridge (USA) 308 m - 1849. The largest suspension bridge from 1849 until 1851 and from 1864 to 1866
- Lewiston-Queenston Bridge (USA and Canada) 316 m - 1851. The largest suspension bridge from 1851 until it was destroyed by wind in 1864.
- John A. Roebling Suspension Bridge (USA) 322 m - 1866. The largest suspension bridge from 1866 - 1869
- Niagara Clifton Bridge 384 m - 1869. The largest suspension bridge from 1869 to 1883. Replaced in 1899.
- Brooklyn Bridge (USA) 486 m - 1883. The largest suspension bridge from 1883 until 1903.
- Williamsburg Bridge (USA) 488 m - 1903. The largest suspension bridge from 1903 until 1924.
- Bear Mountain Bridge (USA) 497 m - 1924. The largest suspension bridge 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 (USA) 533 m - 1926. The largest suspension bridge from 1926 until 1929.
- Ambassador Bridge (Michigan-Ontario, USA-Canada) 564 m - 1929. The largest suspension bridge from 1929 to 1931.
- Royal Gorge Bridge (USA) 1929 The highest (384 m) suspension bridge in the world.
- San Francisco-Oakland Bay Bridge (California, USA) 704 m -1936 The western portion is two complete two tower bridges end-to-end with a central anchorage, required to avoid dynamic interactions between three main spans between the four towers. Until recently, this was the longest steel high-level bridge in the world. http://www.sfmuseum.org/hist9/mcgloin.html The eastern portion (a cantilever bridge) is currently being replaced with a self-anchored suspension bridge which will be the longest of its type in the world.
- Tacoma Narrows Bridge (USA) 853 m - 1950 & 2007. The largest twin suspension bridge in the world.
- Hercilio Luz Bridge (Florianopolis, Brazil) 820 m long - 1926. The oldest suspension bridge ever built for automobiles. It was closed in 1991, and the city is working on its restoration.
Infamous suspension bridges
- The Bridge of San Luis Rey (Fictional)
- Silver Bridge, a 1928 eyebar chain bridge that collapsed in 1967, killing forty-eight people.
- Tacoma Narrows Bridge, (USA) 853 m - 1940 The Tacoma Narrows are prone to sustained and moderately strong winds, with which the bridge had a tendency to resonate (owing to its unique plate-girder deck structure). This led to its collapse only months after completion. The collapse was captured on film.
Picture Gallery
Akashi-Kaikyo Bridge at night | 25 de Abril Bridge in Lisbon, Portugal | A suspension bridge falls: Tacoma Narrows Bridge collapses | ) The Ambassador Bridge- Longest suspension bridge from 1929-1931 |
) New York's famous Brooklyn Bridge | ) San Francisco-Oakland Bay Bridge under construction | ) Driving on the 2nd largest suspension bridge, Denmark's Great Belt Bridge (Storebæltsbroen). | ) Busan, the Republic of Korea's Gwangan Grand Bridge, with a suspension section of around 500 meters but with an overall length of 7,420 meters |
) The famous Golden Gate Bridge in San Francisco |
Notes
1. ^ Suspension bridge. (2007). In Encyclopedia Britannica. Retrieved April 5, 2007, from Encyclopedia Britannica Online
See also
- - for all the articles about specific suspension bridges.
- List of largest suspension bridges - ordered by the length of the main span.
- Cable-stayed bridge - superficially similar to a suspension bridge, but cables from the towers directly support the roadway, rather than the road being suspended indirect by additional cables from the main cables connecting two towers.
- Inca rope bridge - which have many 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-supporting 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.
Bridge-related articles | ||
|---|---|---|
| Types of bridges | Moveable bridge Beam bridge Cantilever bridge Arch bridge Suspension bridge Cable-stayed bridge Truss bridge Visual index to various types | ) |
| Lists of Bridges | Notable bridges By length Longest suspension bridge spans Largest cable-stayed bridges Largest cantilever bridges Arch bridges Bridge disasters | |
External links
- New Brunswick Canada Suspension FootBridges
- Structurae: Suspension Bridges
- American Society of Civil Engineers History and Heritage of Civil Engineering - Bridges
- Bridgemeister: Mostly Suspension Bridges
There are several types of suspension bridge:
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- Simple suspension bridge, a foundational type for pedestrians based upon the ancient Inca rope bridge.
- Stressed ribbon bridge, similar to the simple suspension bridge but more stable and usable for vehicles.
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Clifton Suspension Bridge is a suspension bridge, spanning the Avon Gorge and linking Clifton in Bristol to Leigh Woods in North Somerset, England. Designed by Isambard Kingdom Brunel, it is a distinctive landmark that is used as a symbol of Bristol. It is a grade I listed building.
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simple suspension bridge is an early bridge type and is still formed from native materials, chiefly grass rope, in some areas of South America. These rope bridges must be periodically renewed owing to the limited lifetime of the materials, and rope components are made and
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A cable-stayed bridge is a bridge that consists of one or more columns (normally referred to as towers or pylons), with cables supporting the bridge deck. There are two major classes of cable-stayed bridges, differentiated by how the cables are connected to the
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A compression arch suspended-deck bridge, or through arch bridge, is a bridge made from modern materials such as steel or reinforced concrete in which a compression arch rises above the deck. Cables connect the deck to the arch.
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A self-anchored suspension bridge is a suspension bridge in which the main cables do not attach to the ground via large anchorages; instead, the main cables attach to the ends of the road deck, which experiences compression equal to the tension in the cables.
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pedestrian is a person travelling on foot, whether walking or running. In modern times, the term mostly refers to someone walking on a road or footpath, but this was not the case historically.
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History
Walking is the primary means of human locomotion...... Click the link for more information.
automobile (from Greek auto, self and Latin mobile moving, a vehicle that moves itself rather than being moved by another vehicle or animal) or motor car (usually shortened to just car) is a wheeled passenger vehicle that carries its own motor.
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truck is a vehicle usually used for transporting bulk goods, materials, or equipment. The word "truck" comes from the Greek "trochos", meaning "wheel". In America, the big wheels of wagons were called trucks.
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Light rail or light rail transit[1] (LRT) is a form of rail transport system that generally uses electric rail cars[2] on private rights-of-way or sometimes in streets. Light rail is a step below rapid transit, which is fully grade-separated.
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Wire rope consists of several strands laid (or 'twisted') together like a helix. Each strand is likewise made of metal wires laid together like a helix. Initially wrought iron wires were used, but today steel is the main material used for wire ropes.
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Falsework refers to temporary structures used in construction to support spanning or arched structures in order to hold the component in place until its construction is sufficiently advanced to support itself.
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bridge is a structure built to span a gorge, valley, road, railroad track, river, body of water, or any other physical obstacle. Designs of bridges will vary depending on the function of the bridge and the nature of the terrain where the bridge is to be constructed.
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simple suspension bridge is an early bridge type and is still formed from native materials, chiefly grass rope, in some areas of South America. These rope bridges must be periodically renewed owing to the limited lifetime of the materials, and rope components are made and
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pedestrian is a person travelling on foot, whether walking or running. In modern times, the term mostly refers to someone walking on a road or footpath, but this was not the case historically.
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History
Walking is the primary means of human locomotion...... Click the link for more information.
Inca rope bridges were simple suspension bridges over canyons and gorges (pongos) to provide access for the Inca Empire. Bridges of this type were suitable for use since the Inca people did not use wheeled transport - traffic was limited to pedestrians and
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Engineering is the applied science of acquiring and applying knowledge to design, analysis, and/or construction of works for practical purposes. The American Engineers' Council for Professional Development, also known as ECPD,[1] (later ABET [2]
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vine is any plant of genus Vitis (the grape plants) or, by extension, any similar climbing or trailing plant. The word, derived from Latin vīnea, referred to the grape-bearing variety.
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cable is one or more wires or optical fibers bound together, typically in a common protective jacket or sheath. The individual wires or fibers inside the jacket may be covered or insulated. Combination cables may contain both electrical wires and optical fibers.
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This page is currently protected from editing until disputes have been resolved.
Protection is not an endorsement of the current [ version] ([ protection log]).
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Bambuseae
Kunth ex Dumort.
Diversity
Around 91 genera and 1,000 species
Subtribes
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Kunth ex Dumort.
Diversity
Around 91 genera and 1,000 species
Subtribes
- Arthrostylidiinae
- Arundinariinae
- Bambusinae
- Chusqueinae
- Guaduinae
- Melocanninae
- Nastinae
- Racemobambodinae
- Shibataeinae
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3, 4, 6
(amphoteric oxide)
Electronegativity 1.83 (Pauling scale)
Ionization energies
(more) 1st: 762.5 kJmol−1
2nd: 1561.9 kJmol−1
3rd: 2957 kJmol−1
Atomic radius 140 pm
Atomic radius (calc.
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(amphoteric oxide)
Electronegativity 1.83 (Pauling scale)
Ionization energies
(more) 1st: 762.5 kJmol−1
2nd: 1561.9 kJmol−1
3rd: 2957 kJmol−1
Atomic radius 140 pm
Atomic radius (calc.
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Vehicles are non-living means of transport. They are most often man-made (e.g. bicycles, cars, motorcycles, trains, ships, and aircraft), although some other means of transport which are not made by man can also be called vehicles; examples include icebergs and floating tree trunks.
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Light rail or light rail transit[1] (LRT) is a form of rail transport system that generally uses electric rail cars[2] on private rights-of-way or sometimes in streets. Light rail is a step below rapid transit, which is fully grade-separated.
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cable is one or more wires or optical fibers bound together, typically in a common protective jacket or sheath. The individual wires or fibers inside the jacket may be covered or insulated. Combination cables may contain both electrical wires and optical fibers.
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James Finley (1756 - 1828), also known as Judge James Finley, is widely recognised as the the first designer and builder of the modern suspension bridge.
His Jacob's Creek Bridge, built in 1801 and demolished in 1833, was an early example of a suspension bridge using
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His Jacob's Creek Bridge, built in 1801 and demolished in 1833, was an early example of a suspension bridge using
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Menai Suspension Bridge, or Pont Grog y Borth in Welsh, is a suspension bridge between the island of Anglesey and the mainland of Wales. Designed by Thomas Telford and completed in 1826, it is considered the first modern suspension bridge in the world.
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Conwy Suspension Bridge was one of the first road suspension bridges in the world. Located in the medieval town of Conwy in the traditional county of Caernarfonshire, North Wales, it is now only passable on foot. The bridge is now in the care of the National Trust.
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Motto
Cymru am byth (Welsh)
"Wales forever"
Anthem
"Hen Wlad Fy Nhadau"
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Cymru am byth (Welsh)
"Wales forever"
Anthem
"Hen Wlad Fy Nhadau"
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Hammersmith Bridge is a crossing of the River Thames in west London, just south of the Hammersmith town centre area of the London Borough of Hammersmith and Fulham on the north side of the river.
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