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A suspension bridge is a type of Bridge that has been made since ancient times. Simple Suspension Bridge s, for use by Pedestrian s and livestock, are still constructed in some places worldwide, based upon the ancient Inca Rope Bridge . Suspended 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. Over centuries, 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 Cable s (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 the Menai and Conwy Suspension Bridges (both opened in 1826 ) in north Wales , and the first Hammersmith Bridge ( 1827 ) in west London . Since then, suspension bridges have been built all over the world. This type of bridge is the only practical type useful for very long spans limited by topography, or when it would be hazardous to maritime traffic to add temporary or permanent central supports. Many people find this kind of bridge to be particularly pleasing visually. 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 securely 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 Regional Rail applications as the bridge will flex under the concentrated load of a Locomotive . ADVANTAGES OVER OTHER BRIDGE TYPES
DISADVANTAGES OVER OTHER BRIDGE TYPES
STRUCTURAL ANALYSIS The main Force s 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 fairly 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 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 analyse 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 outright. DECK STRUCTURE TYPES (Chang Jiang) in China ]] Most suspension bridges have used open truss structures to support the roadbed (particularly owing to the unfavorable effects of using plate girders, discovered accidentally). Recent developments in bridge aerodynamics have allowed the re-introduction of plate structures. In the illustration to the right, 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 Tacoma Narrows Bridge . OTHER APPLICATIONS Terminal D]] The principles of suspension used on the large scale may also appear in contexts less dramatic than road or rail bridges. Light cable suspension may prove less expensive and seem more elegant for a footbridge than strong girder supports. 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 suspension bridge, 1970 Denmark ]]
, Istanbul ]]
THE LARGEST SUSPENSION BRIDGES IN THE WORLD between Akashi and Awaji Island , Japan]] main article: List Of Largest Suspension Bridges When a suspension bridge is called "the largest", it typically means that the length of the main span is the longest. The record is currently held by the Akashi-Kaikyo Bridge in Japan. Ranking by the largest span does not mean that a bridge is longer from end to end or even more massive, but it is a reasonably good indicator of the overall engineering achievement. The following is a list of the 15 largest suspension bridges ranked by length of center span. # Akashi-Kaikyo Bridge ( Japan ) 1991 M - 1998 # Great Belt Bridge ( Denmark ) 1624 m - 1998 # Runyang Bridge ( China ) 1490 m - 2005 # Humber Bridge ( England ) 1410 m - 1981 (The largest from 1981 until 1998.) # Jiangyin Suspension Bridge (China) 1385 m - 1997 # Tsing Ma Bridge ( Hong Kong ) 1377 m - 1997 (with 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 - 1958 # Minami Bisan-Seto Bridge (Great Seto Bridge) (Japan) 1118 m - 1988 # Fatih Sultan Mehmet Bridge (Turkey) 1090 m - 1988 # Bosphorus Bridge (Turkey) 1074 m - 1973 # George Washington Bridge (USA) 1067 m - 1931 (The largest from 1931 until 1937.) , UK , formerly the longest suspension bridge in the world]] 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 to this is the Chacao Channel Bridge , currently under construction. This innovative bridge will 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 , Hong Kong ]] The Strait Of Messina Bridge , with a center span of 3300 m, is planned to connect Italy and Sicily but construction has not yet begun. 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 struts extending diagonally from tall pylons. OTHER FAMOUS SUSPENSION BRIDGES , California, USA]] ]] , Florianopolis , Brazil ]]
INFAMOUS SUSPENSION BRIDGES
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