A hanging bridge is a type of bridge where the deck (load section) is suspended under the suspension cable on the vertical suspender. The first modern example of this type of bridge was built in the early 1800s. Simple suspension bridges, which have no vertical suspenders, have a long history in many parts of the mountains of the world.
This type of bridge has a suspended cable between the towers, plus a vertical suspension cable that carries the deck load below, where traffic passes. This arrangement allows the deck to be aligned or curved upwards for additional permissions. Like other types of suspension bridges, this type is often built without counterfeiting.
The suspension cable must be anchored at each end of the bridge, since any load applied to the bridge is converted into a voltage across this main cable. The main cable continues beyond the pillar to support the deck level, and further continues the connection with the anchor on the ground. The highway is supported by a vertical suspension cable or rod, called a hanger. In some circumstances, the tower may sit on a cliff or rim of the canyon where the road can go directly to the main landscape, otherwise the bridge will typically have two smaller spans, running between a pair of pillars and a highway, which may be supported by a suspender cable or use the frame bridge to make this connection. In the latter case there will be very few arcs in the outboard main cable.
Video Suspension bridge
Histori
The earliest suspension bridge is a rope clamped across a ravine, with a deck probably on the same level or hanging below the rope so that the rope has a catenary shape.
Precursors
The Tibetan saint and bridge builder Thangtong Gyalpo started the use of an iron chain in his version of a simple suspension bridge. In 1433, Gyalpo built eight bridges in eastern Bhutan. Gyalpo's last chain-linked bridge is the Thangtong Gyalpo Bridge in Duksum on the way to Trashi Yangtse, which was finally swept away in 2004. The Gyalpo iron chain bridge does not include the hanging deck bridge which is standard on all modern suspension bridges. today. Instead, the two hedges and walks of the Gyalpo bridge are wired. Stress points that are done screed reinforced by iron chains. Before using the iron chain, there is the assumption that Gyalpo uses a rope from a crooked willow tree or yak skin. She may also use tightly tied fabrics.
Bridge Chain
The first iron chain hanging bridge in the Western world is the Jacob's Creek Bridge (1801) in Westmoreland County, Pennsylvania, designed by inventor James Finley. The Finley Bridge is the first to incorporate all the necessary components of a modern hanging bridge, including a hanging deck that is hung with a roll. Finley patented the design in 1808, and published it in the Philadelphia journal, The Port Folio, in 1810.
The earliest British chain bridges include the Dryburgh Abbey Bridge (1817) and the 137 m Union Bridge (1820), with rapid spans rising to 176 m with the Menai Bridge (1826), "the first important modern hanging bridge". The first chain bridge on the continent of Europe is the Chain Bridge in Nuremberg, Germany. The Clifton Suspension Bridge (designed in 1831, completed in 1864 with a 214 m middle range) is one of the longest types of parabolic arc chains. The Marlow suspension bridge is currently designed by William Tierney Clark and was built between 1829 and 1832, replacing a wooden bridge further downstream that collapsed in 1828. It is the only suspension bridge across the non-tidal Thames River. The SzÃÆ' Â © chenyi Chain Bridge, which stretches the Danube River in Budapest, is also designed by William Clark and it is a larger scale version of the Marlow bridge.
Interesting variants are Thornewill and Warham's Ferry Bridge at Burton-on-Trent, Staffordshire (1889), where the chains are not attached to the abutement as usual, but are attached to the main girder, which is thus in compression. Here, the chains are made of flat wrought iron plate, eight inches (203 mm) wide by one inch and a half (38 mm) thick, stranded together.
Wire-cable
The first cable suspension bridge is the Spider Bridge at Falls of Schuylkill (1816), a simple and temporary buffer bridge built after the collapse of the James Finley Chain Bridge at Falls of Schuylkill (1808). The span of the bridge is 124 m, although the deck is only 0.45 m wide.
The development of cable-hanging cable-wire bridge is dated to a simple suspension bridge while in Annonay was built by Marc Seguin and his brothers in 1822. It stretches just 18 m. The first permanent cable hanging bridge was Guillaume Henri Dufour's Saint Antoine Bridge in Geneva in 1823, with two spans of 40 m. The first with cables assembled in the air in modern methods was Joseph Chaley's Grand Pont Suspendu in Friborg, in 1834.
In the United States, the first large cable hanging bridge is the Wire Bridge at Fairmount in Philadelphia, Pennsylvania. Designed by Charles Ellet, Jr. and finished in 1842, it has a range of 109 m. The Ellet Water Suspension Bridge (1847-48) was abandoned before it was completed. It was used as a scaffold for the high-rise railroad and the John A. Roebling (1855) cable car.
The Otto Beit Bridge (1938-39) is the first modern hanging bridge outside the United States built with parallel wire cables.
Maps Suspension bridge
Structural behavior
Structure analysis
The main strength in any type of suspension bridge is the voltage across the cable and compression on the pillar. Since almost all the forces on the pillars are vertically downward and they are also stabilized by the main cable, the pillars can be made quite lean, like at Severn Bridge, on the Wales-England border.
On suspended deck bridges, the wires that are suspended through the tower hold the street deck. Weight is transferred by cable to the tower, which in turn transfers the weight to the ground.
Assuming a negligible weight compared to the weight of the deck and the supported vehicle, the main cable of the suspension bridge will form a parabola (very similar to catenary, cable form unloaded before the deck is added). One can see the shape of the constant increase of the cable gradient with linear (deck) distance, the gradient increase on each connection with the deck provides the net up support power. Combined with the relatively simple constraints placed on the actual deck, this makes hanging bridges simpler to design and analyze than fixed-bridge cables, where the deck is in compression.
Benefits
- Longer main ranges can be achieved compared to other bridge types
- Less materials may be needed than other types of bridges, even in the range they can achieve, leading to lower construction costs
- Except for initial temporary wiring, little or no access from the bottom is required during construction, for example allowing waterways to remain open when the bridge is built above
- May be more able to withstand seismic movements than heavier and more rigid bridges
- The bridge deck can have the deck section replaced to widen the traffic lane for larger vehicles or add additional widths for separate biking/pedestrian paths.
Losses
- Adequate recognition or aerodynamic profile may be necessary to prevent the bridge deck vibrating under high winds
- The relatively low stiffness of the deck compared to other types of bridges (without suspension) makes it more difficult to carry heavy rail traffic where high concentrated live loads occur
- Some access below may be required during construction, to lift the initial cable or to lift the deck unit. This access can often be avoided in the construction of fixed-bridge cables
Variations
Underspanned
In an untreated hanging bridge, the main cable hangs entirely beneath the deck of the bridge, but still docks to the ground in a manner similar to conventional type. Very few of these natural bridges have been built, since the decks are essentially less stable than when hung under cables. Examples include Pont des Bergues in 1834 designed by Guillaume Henri Dufour; Micklewood Bridge James Smith Bridge; and a proposal by Robert Stevenson for a bridge over the Almond River near Edinburgh.
Roebling's Delaware Aqueduct (starting 1847) consists of three parts supported by cable. The wooden structure basically hides the cable; and from a quick view, it was not immediately apparent that it was even a suspension bridge.
Type of suspension cable
The main suspension cables on the older bridges are often made of chains or related rods, but modern bridge cables are made of multiple strands of wire. This not only adds strength but improves reliability (often called redundancy in engineering terms) because the failure of some defective threads in the hundreds used only poses little threat of failure, whereas one bad link or hole can cause a whole bridge failure. (The failure of a single hole was found to be the cause of the collapse of the Silver Bridge over the Ohio River.) Another reason is that as the range increases, the engineers are unable to lift the larger chains into position, whereas the wire cable cords can be formulated one by one in the air from the road while.
Deck type structure
Most suspension bridges have an open frame structure to prop up the road, mainly due to the unfavorable effects of using girder beams, which are found from the bridge of the Tacoma Narrows Bridge bridge (1940). In the 1960s, the development of aerodynamic bridges enabled the reintroduction of plate structures as a shallow main beam, first seen in Severn bridges built from 1961-6. In the Yichang Bridge picture, note the very sharp inlet edges and the sloped pedestal on the indicated suspension bridge. This allows this type of construction to be used without the danger of shedding vortex and aeroelastic effects, such as the one destroying the original Tacoma Narrows bridge.
Troop
Three types of troops operate on any bridge: dead loads, live loads, and dynamic loads. Dead load refers to the weight of the bridge itself. Like other structures, the bridge has a tendency to collapse only because of the gravitational force acting on the bridge made material. Direct load refers to traffic moving across bridges as well as normal environmental factors such as changes in temperature, rainfall, and wind. Dynamic loads refer to environmental factors that transcend normal weather conditions, factors such as sudden wind and earthquakes. These three factors should be considered when building bridges.
Use other than road and rails
Principles of suspension used on a large scale can also appear in less dramatic contexts than road or rail bridges. Lightweight cable suspensions may prove to be less expensive and seem more elegant for cycles or bridges than strong girder support. An example is the Nescio Bridge in the Netherlands.
Where such a bridge stretches a gap between two buildings, there is no need to build a special tower, because the building can install cables. The cable suspension can also be coupled with the stiffness attached to structures that have much in common with tubular bridges.
Order of construction (cable strand type)
Suspension bridges are usually ranked according to their main range length. These are the ten bridges with the longest spans, followed by the span length and the year the bridge is opened for traffic:
- Akashi Kaiky? Bridge (Japan), 1991Ã, m (6532Ã, ft) - 1998
- Xihoumen Bridge (China), 1650 m (5413Ã, ft) - 2009
- Large Belt Bridge (Denmark), 1624 m (5328Ã, ft) - 1998
- Osman Gazi Bridge (Turkey), 1550 m (5085Ã, ft) - 2016
- Yi Sun-sin Bridge (South Korea), 1545 m (5069Ã, ft) - 2012
- Runyang Bridge (China), 1490 m (4888 ft) - 2005
- Nanjing Yangtze Fourth Bridge (China), 1418 m (4652Ã, ft) - 2012
- Humber Bridge (UK, United Kingdom), 1410 m (4626Ã, ft) - 1981 (longest range from 1981 to 1998)
- Yavuz Sultan Selim Bridge (Turkey), 1408 m (4619 ft) - 2016
- Jiangyin Bridge (China), 1385 m (4544Ã, ft) - 1997
Another example
(Chronological)
- Union Bridge (UK/Scotland, 1820), longest range (137 m) from 1820 to 1826. The oldest in the world is still in use today.
- Roebling's Delaware Aqueduct (USA, 1847), the oldest suspension cable bridge still operating in the United States.
- Suspension Bridge of John A. Roebling (USA, 1866), then the world's longest cable hanging bridge at 1,057 feet (322 m) main range.
- The Brooklyn Bridge (USA, 1883), the first steel wire suspension bridge. Bear Mountain Bridge (AS, 1924), longest suspension range (497 m) from 1924 to 1926. The first suspension bridge has a concrete deck. The construction methods pioneered in building them will allow some larger projects to follow.
- The Ben Franklin Bridge (Philadelphia, PA, USA, 1926), replaces the Bear Mountain Bridge as the longest span at 1,750 feet between towers. Includes an active subway line and a trolley station that is never used in that range.
- San Francisco-Oakland Bay Bridge (USA, 1936). It was once the longest high-level steel bridge in the world (704 m). The eastern (cantilever bridge) has been replaced with a suspension bridge which is the longest type in the world. It is also the largest bridge in the world.
- The Golden Gate Bridge (USA, 1937), the longest suspension bridge since 1937 to 1964. It was also the highest bridge in the world from 1937 to 1993.
- Mackinac Bridge (USA, 1957), the longest suspension bridge between anchors in the western hemisphere.
Important collapse
- Silver Bridge, Point Pleasant, West Virginia - Sidewalk side chain bridge, built in 1928, which collapsed in late 1967, killing forty-six people.
- Tacoma Narrows Bridge, (USA), 853 m - 1940. The Tacoma Narrows bridge is susceptible to structural vibrations in strong and sustained winds due to its plate deck gel structure. Wind causes a phenomenon called aeroelastic fluttering that causes its collapse just a few months after its completion. The collapse was captured in the film. No human life is lost in collapse; some drivers run away from their cars on foot and reach anchorages before the span decreases.
See also
- Category: Suspension bridge - for articles on special suspension bridges.
- List of longest suspension bridges
- Timeline of the three longest ranges of bridges, air tram lines, powerline, ceiling, or dome, etc.
- Cable-stayed bridges - superficially similar to hanging bridges, but cables from towers directly support the road, rather than roads indirectly suspended by additional cables from the main cable connecting the two towers.
- Inca rope bridges - have the same features as suspension bridges and precede them for at least three hundred years. However, on the bridge the rope deck itself is suspended from the berthing dock and the fence is non-structural.
- Hanging suspension bridge - incorporating bridge suspension elements and fixed-cable bridges.
- Simple suspension bridge - the modern application of rope bridges using steel cables, although the upper guardrail or bottom cables may be the main structural cables.
References
External links
- Historical American Engineering Record (HAER) no. NJ-132, "Contextual Essay on Wire Bridge"
- New Brunswick Canada limits footbridges
- Structurae: hanging bridge
- American Society of Civil Engineers History and heritage of civil engineering - bridges
- Bridgemeister: Most suspension bridges
- Wilford, John Noble (May 8, 2007). "How to Inca Leapt Canyons". The New York Times .
Source of the article : Wikipedia
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