Suspension bridge

A suspension bridge is a bridge be performed consisting of pylons on the supporting cables on which the track support is suspended.

A design once common, today only rarely used the suspension bridge is the Chain Bridge, the place of the ropes or chains eyes rods and other items.

3.1 pylons
3.2 Extension cable
3.3 trailer
3.4 track support
3.5 anchor blocks

5.1 The beginnings
5.2 Western chain bridges
5.3 First - wire cable suspension bridges
5.4 Development in the U.S. John A. Roebling suspension bridges 5.4.1
5.4.2 Development to larger bridges
5.4.3 New calculation methods, new construction
5.4.4 After the collapse of the Tacoma Narrows Bridge

5.5.1 truss
5.5.2 box girder

Use

Suspension bridges are often built as a large road bridges for bridging wider navigable waters, such as the Storebæltsbroen across the Great Belt. They are usually only from spans of about 900 m economical than cable-stayed bridges. For spans well over 1000 m they are the only possible construction. As a rule, railway bridges will not run because of the tendency to oscillate and larger deformations than suspension bridge.

Especially in China Suspension bridges are often used to cross deep, steep -sided valleys at high altitude, such as the Siduhe Bridge whose roadway carrier is 472 m above a mountain river.

For pedestrians, there are numerous, light and shorter suspension bridges, such as the Holbeinsteg over the river Main in Frankfurt, or as an attraction for tourists breathtaking possible constructions, such as the suspension bridge Holzgau. In developing countries, particularly simple, tailored to local conditions suspension bridges are being built, such as the suspension bridge in the Annapurna Circuit or also in Nepal over a 1.4 km wide river leading Dodhara Chandani Bridge, probably the longest pedestrian suspension bridge.

Function of the structure

The floor beams are hung with hangers to the main support cables. In order for these cables are under tension. The deflection of the ropes on the pylons causes a compressive force in the pylons, which forward them to the foundation.

Genuine Suspension Bridge

True or erdverankerte suspension bridges are those in which the tensile force at the end of the rope is taken up by an anchor in the ground. For this purpose, the supporting cables are attached in large anchor blocks in the ground. In this version of the track support is only lightly loaded by train or compressive forces and can be very easily carried out. Most of the suspension bridges are those real suspension bridges.

Loggerhead suspension bridge

Spurious or self-anchored suspension bridges are those in which the supporting cables are attached to the track support themselves. The horizontal component of tension in the support cables is thus transmitted as a compressive force on the track support, the vertical component of the tension force is balanced by its weight.

This variant requires strong and from one to the other end passing through a track, but avoids the major anchor blocks. On the other hand, more sustainable and therefore heavier cables and pylons are necessary for the comparatively heavy road vehicle. A fake suspension bridge was used where the soil did not appear sufficiently strong to absorb the force acting on the anchor blocks horizontal tension. Examples are the Mühlentorbrücke opened in 1900 in Lübeck and the bridges over the Rhine in Cologne - Mülheim Bridge from 1927 with 315 meter span and Friedrich Ebert bridge in Duisburg with 285.5 meters and the 1964 finished bridge of July 14 in Baghdad. The Krefeld- Uerdinger bridge over the Rhine with 250 meter span can be mentioned here, although it has steel beams instead of the suspension cable and hanger cables.

It is of great disadvantage that for mounting the self- anchored suspension bridge complex auxiliary structures such as Schrägabspannungen, are required because the support cables can be installed only after complete completion of the road carrier. Overall, the self-anchored suspension bridge has not enforced as a form of construction because of the larger assembly time, it was mostly replaced by the developed after the Second World War construction of the cable-stayed bridge. A modern example is the Kuznechevsky Bridge in Arkhangelsk in northern Russia. The Konohana Bridge was opened in 1990 in Osaka, Japan is selbstverankert and has only one suspension cable, which is supported by A-shaped pylons.

During the construction of the East Bay Bridge as part of the San Francisco-Oakland Bay Bridge, the principle is also applied again. The main bridge consists of a self- anchored suspension bridge einhüftigen, ie that she only has one pylon over which the supporting cables are tensioned to the two ends of the road carrier.

Similar designs

The use of language usually does not distinguish between suspension bridges, in which the supporting cables are passed over the tops of the pylons, or one of the following, similar designs, which are not counted as suspension bridges in the narrow sense:

When Spannbandbrücke the regular pedestrian-only bridge deck is provided directly to the ropes or chains, and thus describes the same sagging curve like this.
The cable-stayed bridge is a term for simple, consisting almost entirely of rope bridges, often in the form of a Spannbandbrücke, which are mostly used on climbing routes in the mountains or in the outdoor training.
The cable-stayed bridge, the bridge deck is supported by an angle of the pylons for the bridge deck stretched cables.
The Extradosed bridge is a further development of the prestressed concrete bridge in which the tension cables are not located within but outside the concrete profile and additionally supporting principles of the cable-stayed bridges are used.

Supporting elements

Pylons

The pylons supporting the weight of the superstructure, ie the weight of the suspension cable, the trailer and the road carrier, and traffic loads, so the weight of vehicles and people on the bridge. They also take on the forces in the transverse direction, caused for example by the wind.

They are trained mostly as a rectangular portals with two pillars either as a truss structure or frame-like with two or more cross- bars. Width bridges often have portals with three pillars, so even the early Brooklyn Bridge or the modern Pingsheng Bridge in Foshan, Guangdong, China. Unlike cable-stayed bridges centralized pylons in suspension bridges are rare. Fritz Leonhardt had proposed a draft with center cones and a central support rope for the Ponte 25 de Abril in Lisbon. Built examples are the above-mentioned Konohana Bridge, the Viaduc du Chavanon, one opened in 2000 French motorway bridge, and various pedestrian bridges, like the pedestrian bridge over the Schenkendorfstraße in Munich. Occasionally pylons are architecturally designed complex, as the songs bridge in Guangzhou, Guangdong, China.

As a building material, either steel comes with box sections or reinforced concrete used. The Pont de Tancarville (1958 ) was the first major suspension bridge with pylons of reinforced concrete. Prior to the development of these building materials cast-iron pillars were used on stone pedestals or portal towers built of stone, such as at the Brooklyn Bridge. In very high steel pylons like those of the Akashi - Kaikyo Bridge vibration absorber be installed to dampen vibrations caused by earthquakes or typhoons.

Suspension cable

Usually two suspension cables are used, which are guided on the pylon and anchored in anchor blocks. In the minds of the pylons, the cables are routed over exposed or housed in enclosures saddle bearing, sometimes on roller bearings. Occasionally divided cable between pylons are on the one hand and on the other hand, used of the pylons to the anchor blocks. For wide bridges like the Brooklyn Bridge with their portals of three pillars four, sometimes three supporting cables are used.

The cables generally have a sag of 1 /8 to 1/12 of the span of the central panel. Because this is essentially always similar sag longer spans require higher pylons. The sag does not follow all of the mathematical catenary, since in this chain will only be accepted under its own weight.

The support cables are made with modern large bridges from a parallel cable, so a bunch of lying parallel, high-strength steel wires are pressed together by giant rope clamps. The support cables are manufactured locally by leading thin walkways are set up with the same sag as the future extension cable for the workers on the pylons.

This suspension ropes are manufactured in the air spinning process. The individual wires of the supporting cable can be pulled from one side to the other bundled into strands compacted by wire presses the cable, and then coated. The wires are usually galvanized. The extension cable must be regularly painted with anticorrosive paint. On the suspension cable of large suspension bridges are mostly there is a dock or a staircase with a simple cable railing for the inspection and maintenance personnel.

In Japan, parallel wire ropes are preferably made of prefabricated strand bundles, which are then combined, compressed to the cable and are encased, so even with the Akashi - Kaikyo Bridge.

The suspension cable medium and small bridges made of beaten steel ropes. At intermediate bridges 37 mostly ropes for each suspension cable pressed into a hexagon ( 7 ropes in the middle layer and the 6, 5 and 4 in the sheets above and below it ). For smaller bridges the ropes are individually performed as a pair or quads, which are equipped with distance - holders which serve as attachment of the hanger.

As an extreme example, the Pont du Rouergue may apply in La Réole, Gironde department, which crosses the Garonne with a span of 170 m and to employing two sets of cables superimposed on three ropes.

Trailer

The hangers connect the extension cable to the road carrier. They too are usually made of galvanized wire ropes. You must first withstand the tensile forces and influence the natural frequency of the bridge. To reduce vibrations, vertical hangers were sometimes combined with cable-stays, like the Brooklyn Bridge. Sometimes the hangers are not vertical, but alternately obliquely forwardly and obliquely backward stretched, so that always end up on the supporting cables and the track support two hangers on a common mounting point, so that a zig -zag- shaped pattern. Thus, the stiffness of the roadway deck raises and lowers its deflection with unidirectional load. Examples are designed by Freeman Fox & Partners Severn Bridge (1966 ), the First Bosphorus Bridge (1973) and the Humber Bridge ( 1981) and Edgar Cardoso's Samora Machel Ponte (1973 ) on the Zambezi River. Sometimes hydraulic losses at the ends of the hangers are needed.

Track support

The track support, also known as stiffening girder, distributes the loads on the trailer. He is either a truss, as in the Akashi - Kaikyo Bridge, or open full wall supports, such as the Rhine bridge CologneRodenkirchen, or with a closed box section, as in the Great Belt Bridge, is formed. They can be rigidly carried out by abutment to abutment through the pylons or interrupted at the pylons and be stored there articulated. In order to achieve stability even at high wind speeds, the track support must be sufficiently trained Rigidity. Can be obtained from modern bridges optimized in the wind tunnel cross-sectional design, the aerodynamic instability, as in the Tacoma Narrows Bridge, avoids a failure. With very wide bridges the track support according to the length is sometimes divided into two strips with an open space for improving the aerodynamic stability. Older bridges such as the Golden Gate Bridge have been aerodynamically optimized and upgraded.

Anchor blocks

The ends of the suspension cable suspension bridges are fixed in real anchor blocks. The anchor blocks must be large and heavy, and so deeply sunk in the ground, that they resist in any case, the maximum tensile force with which the supporting cables of a fully laden, burdened by storm and snow bridge could attract them. Previously anchor blocks were built of stone blocks, today they generally consist of reinforced concrete. The anchor blocks of a larger bridge such as the Ambassador Bridge are as high as a 16-storey building, but are half underground. The anchor blocks of Storebæltsbroen that were set only on the seabed, act alone by their weight. You have a floor area of 122 × 55 m and a height of 73 m. However, to see is just the tip protruding from the water.

Designs

The most common design of the suspension bridge is now the zweihüftige bridge with a main span between the two pylons, whose suspension cable are attached outside the opening in the anchor blocks. Usually the pylons stand in the waters to be crossed and the anchor blocks near the shore, so that the parts of the roadway carrier between the pylons and the banks are suspended on the support cables. Occasionally there are one or two pairs pylon on the shore, so that the cables between the pylon tips and the anchor blocks purposes only and have no anchor hanger.

Originally widespread in France was the three - and mehrhüftige bridge in which a plurality of tension fields immediately followed each other. At the very first wire suspension bridge, the Passerelle de Saint -Antoine in Geneva two spans were covered by the support cables. Became famous in 1833, completed road bridge of Cubzac, which had five consecutive fields with spans of 109 m and in its time was probably the biggest and längeste suspension bridge. Other examples are the bridges of Châteauneuf -sur -Loire, Châtillon -sur -Loire or Bonny- sur -Loire. Typical for this design are the pylon to top reaching only pylon top suspension cable, the compensating ropes connecting the pylon tips ( câble d' équilibre ) and separate, often multiple -scale anchoring ropes. Modern examples are the Ponte Samora Machel on the Zambezi River in Mozambique and the smaller suspension bridge in Naruto ( Tokushima ), Japan.

As part of the San Francisco-Oakland Bay Bridge also stand behind the other four pylons. However, this is not a mehrhüftige bridge, but two independent suspension bridges that were built together and have a common anchor pillar in the middle. Similarly, were in the Seto Ōhashi in Japan and two in the Kurushima Bridge Kaikyō even strung together three suspension bridges. A combination of a suspension - with a cable-stayed bridge is the Huangpu Bridge in Guangzhou, Guangdong, China.

Suspension bridges usually have only one road plane, but there are also double-deck bridges, which sometimes also include railway tracks. Examples are again the Brooklyn Bridge with a raised deck for pedestrians and cyclists, which opened in 1909 Manhattan Bridge with four subway tracks, which opened in 1931, George Washington Bridge, which in 1962 received a second level and a total of 14 lanes, the most powerful bridge the world, the San Francisco-Oakland Bay Bridge (1936 ), the Ponte 25 de Abril (1966 ) in Lisbon, the Rainbow Bridge (1993 ) in Tokyo and the Tsing Ma Bridge (1997) in Hong Kong.

History

The beginnings

In the mountains of East Asia and South America with their deep valleys rope bridges were the only way, often to cross raging rivers, and has long been in use before it was taken from them in Europe note from natural materials. The suspension bridge over the Rio Apurimac Qu'eswachaka in Peru has existed for over 500 years and is considered the only remaining functioning suspension bridge of the Incas. The first suspension bridge with iron chains was probably the built in Tibet 1430 Chagsam bridge over the Yarlung Tsangpo ( Brahmaputra ), with a wingspan of about 137 m. She was certainly the first bridge with the division in carrying chains, hangers and Bridges and had a wingspan that surpassed everything that has been held at that time in Europe possible. In Europe, first ideas of a suspension bridge ( and other inventions ) by Fausto Veranzio ( Faust Vrančić, Latin Faustus Verantius ) published in 1616 in his book and his invention Listing Machinae Novea. Several subsequent publications reported on suspension bridges in China. All early suspension bridges were, unless they were made of natural materials, but chain bridges, as wires only at the beginning of the 19th century reached a certain strength and wire ropes were first invented in 1834 by Julius Albert Oberbergrat in Clausthal.

Western chain bridges

The approximately 1741 in the north of England built for miners Winch Bridge was the first chain bridge in Europe. In the town of Weilburg in 1784 were stretched rod of iron chains on the Lahn, where the tubes of the baroque water supply were suspended after a flood had destroyed the bridge previously used. James Finley built from 1801 different chain bridges in the United States, which are regarded as precursor of the suspension bridges by they had outside of Asia for the first time carrying chains, hangers and a trafficable bridge deck. The first large suspension bridges in Europe were opened in 1820, Union Bridge by Samuel Brown and the Menai Bridge by Thomas Telford with 176 meters span, which was opened to traffic in 1826. The oldest surviving bridge in Germany is the chain of Conrad Georg coupler 1820/21 planned and built in 1824 chain bridge in Nuremberg, which spanned the Pegnitz about 68 meters.

First cable - suspension bridges

While the production and manufacture of iron at the beginning of the 19th century in Britain made rapid progress and soon produced chains with reasonably reliable material properties, France remained cut off long due to the continental blockade of this development. Since cables can compensate for different qualities of the individual wires, the development has been concentrated in the French -speaking world from the beginning to wire rope suspension bridges.

The in Geneva to ideas of Marc Seguin built by Guillaume -Henri Dufour 1823, 82 meters long Passerelle de Saint -Antoine is considered the first permanent wire cable suspension bridge in the world. Marc Seguin had previously built a first attempt to dock in Annonay. In 1824 he opened the now Passerelle Marc Seguin called bridge over the Rhone in Tournon -sur -Rhone, the first drive- wire suspension bridge.

In a series of publications, the theoretical foundations of suspension bridges were laid. So published Claude Navier in 1823 a first basic treatise on suspension bridges, which was soon translated into German and 1830 reprint, and Marc Seguin in 1824 his writing Des Ponts en fil de fer, in which he even then the problem of wind or lockstep vibrations caused dealt.

Marc Seguin built in the next forty years with his company Marc Seguin et freres throughout France over sixty suspension bridges. Competitors such as the Société Bayard de la Vingtrie were similar productive. Examples are the 1833 completed road bridge of Cubzac to their time probably the largest and längeste Suspension Bridge, and the bridges of Châteauneuf -sur -Loire, Châtillon -sur -Loire or Bonny- sur -Loire. Demand was high, as wide rivers could be crossed at a fraction of the cost with suspension bridges that had to be expended up to that for a conventional bridge with several arches. At places where the construction of piers in the river bed was not previously possible because of the ground conditions or the flow, the river could be crossed on a bridge for the first time, as the Pont de La Roche -Bernard in the Morbihan department of the Vilaine. The 194 m long Pont de la Caille on the road from Geneva to Grenoble would previously have been unthinkable in 147 m height above a ravine stretched, briefly.

The increase in strength of the wires by pulling on the production enabled more efficient than when using the suspension cable supporting chains. The Zaehringen bridge in Fribourg (Le Grand Pont Suspendu ) was in 1835 with 273 meter wingspan, the global record holder. Your support cables consisted of 1056 single wires each with 3 mm diameter. The individual wires were arranged side by side in parallel because the rotated ( beaten ) wire rope was invented in 1834 by Julius Albert Oberbergrat.

This design was maintained in larger suspension bridges, the suspension ropes were so large and heavy that they could be made only on the site in the air spinning method, which was originally invented by Frenchman Louis -Joseph Vicat and presented in 1830. Later, John Roebling developed this method in the USA, so that carrying cables over long spans of time could be produced directly at the place of deployment in a relatively short time and at reasonable cost.

The French suspension bridges were mostly similar to each other track support, but pylons in all common in the former architectural forms, eg as Doric or Egyptian pillars in the form of obelisks or frequently than small triumphal arches. However, the bridges were often calculated only for loads of 200 kg / m² and without large reserves, slightly built and with a little stiff bridge deck. The anchorages of the cables in the walls of the pylons were not accessible and therefore susceptible to corrosion.

Initially, a series of collapses due to storms were accepted. However, when the supporting cables of the suspension bridge of Angers ( Pont de la Basse- Chaîne ) were torn from their moorings on April 16, 1850 and during this tragedy total of 226 people died, the public attitude turned. The storm that destroyed the bridge deck of the Pont de La Roche -Bernard on October 26, 1852 encouraged the public in the rejection of further suspension bridges. This meant that over the next forty years in France barely a suspension bridge was built, while John Roebling about the same time showed the solution of the problem in the U.S..

In the French- speaking world of the 19th century were re- built suspension bridges mainly by Ferdinand Arnodin and still more modernized older bridges according to his ideas at the end. Externally visible was that of the stiffening serving combination of fan-shaped cable stays on the portions of road carriers in the pylons with konventionlellen supporting cables and hangers in the middle third and the use of hangers made of steel rods with forged ends instead of the usual ropes. He had a special kind of regular lay ropes with several layers developed, in which the individual wires were more evenly than in the past burden. He built anchor blocks with accessible anchorages suspension cable, the bridge deck stiffened by a steel skeleton and by the inclusion of stable railings. He also took the view that the load-bearing parts of a bridge would have to be replaced without interrupting the traffic. As an example can serve the completed in 1912 Pont Sidi M'Cid in Constantine, Algeria, at that time the highest bridge in the world.

In the rest of Europe different chain bridges, but hardly a wire rope suspension bridge were built in the 19th century. In the Berlin Tiergarten, the lion bridge was built in 1838. The wire bridge ( 1870) in Kassel, the Rose Valley Bridge (1880 ) in Braunschweig and the suspension bridge over the evil one (1897 ) to Langenargen on Lake Constance are other examples of more modest degree.

Development in the U.S.

The 1849 finished Wheeling Suspension Bridge over the Ohio River was the first major suspension bridge with a span of about 300 m. Your roadway deck but was already transformed in 1854 by a storm in vibrations, twisted and destroyed, so that they could be regarded as an example of the basic problems of this bridge type.

John A. Roebling Suspension Bridge

The development of suspension bridges in the United States was therefore mainly influenced by John August Roebling, of Trenton (New Jersey) had built a cable factory. John A. Roebling built 1851-54, the Niagara Falls Suspension Bridge, a double-deck bridge for the railways and wagons with a span of 251 m, in which he met special measures to avoid vibrations, such as additional cable stays and the training of road carrier as a truss structure similar to a hollow box. In his next bridges similar measures were taken, in 1866, opened Cincinnati - Covington Bridge with a span of 322 m ( later called the John A. Roebling Suspension Bridge ) and after his death by his son in 1883 completed Brooklyn Bridge with a span of 486 m. The Brooklyn Bridge was much longer and larger than their predecessors and quickly became a New York City landmark, but also represents the conclusion of the embossed Roebling epoch is with brick pylons, heavy road carriers and additional cable stays.

Development to larger bridges

The first was made entirely of steel bridge which opened in 1903 Williamsburg Bridge with a span of 488 m, in which they had dispensed with the stay cables.

In the third suspension bridge over the East River, planned by Leon S. Moisseiff and 1909 finished Manhattan Bridge, the first time the deformation theory ( Deflektionstheorie ) was used, which allowed a comparison to previous bridges significantly lighter construction. The further development of this theory as well as improvements of the steels, ropes and construction methods led to ever larger bridges, such as the Bear Mountain Bridge, the Benjamin Franklin Bridge and the Ambassador Bridge. 1929 was built with the Royal Gorge Bridge probably the first suspension bridge for tourist purposes, which became known because it crosses a canyon in Colorado at 291 m height and held the title as the highest bridge in the world until 2001.

Othmar Ammann established in 1931, George Washington Bridge, with a span of 1067 m and was built by Joseph B. Strauss and the Golden Gate Bridge opened in 1937, with a span of 1280 m, setting new standards. The Lions Gate Bridge in Vancouver in 1938 with a span of 472 m, the longest suspension bridge outside the United States and kept that title until 1959, the Pont de Tancarville was opened in France.

New calculation methods, new construction

As well as funding for bridges were scarce in the Great Depression, it took on like that the deformation theory instead of the high truss now enabled flat plate girders, which were much easier, required less steel and easier to assemble were. Characterized dual suspension bridges were first long affordable, where the ratio was of both the height of the track carrier to its length as well as of its width to the length of smaller and smaller. Since the deformation theory dealt with static wind loads, the less wind resistance of a flat road carrier seemed to be more important than that caused by high truss stiffness. However, when building completed in 1938 Thousand Islands Bridge and at the same time almost built Deer Isle Bridge occurred vibrations that could control her planner, David B. Steinman, only with the help of additional tension cables and struts.

In the Tacoma Narrows Bridge, one of Leon S. Moisseiff planned, extremely slim, lightweight bridge that then with 853 m had the third largest wingspan of all suspension bridges, these events were not considered. In their planning more than hurricane-like storms were based on widely. But even with her were already observed vibrations during construction. On November 7, 1940, just four months after its opening, occurred in only stormy winds ( force 8 ) increasingly stronger vibrations and distortions, which led to the split of the road carrier and therefore to the destruction of the bridge. It puzzled at first about the causes, since the aerodynamic effects on bridges were not yet understood at the time. It took many years, many wind tunnel tests and calculations, to the dynamic effects of wind on bridge structures and the impact of aeroelastischem flutter were reasonably understood.

After the collapse of the Tacoma Narrows Bridge

The immediate effects were, first, that Ammann was also very slim Bronx - Whitestone Bridge to calm the (toll payable ) motorists stiffened afterwards, although she had much better figures than the Tacoma Narrows Bridge. As a backlash to the slim floor beams preferable deformation theory was completed in 1950 construction of the new Tacoma Narrows Bridge, and especially David B. Steinman's Mackinac Bridge Opened in 1957, with high and already visually solid acting trusses provided. Othmar Ammann also used in the Throgs Neck Bridge (1961 ) high and stiff truss; at the Verrazano -Narrows Bridge ( 1964) it became not the problem because of the two-story construction.

American and European designs

In the long run led the lessons learned from the collapse of the Tacoma Narrows Bridge insights into two different methods, which are also referred to as American and European designs.

Truss

When were the American construction and large truss to stiffen the platform girder continue to be used. It is ensured that they have a very low wind resistance, despite their size. Large suspension bridges in the U.S. construction include the Pont de Tancarville (1959 ) in Le Havre, the Forth Road Bridge ( 1964) in Edinburgh, the Rhine bridge Emmerich (1965 ), the Pont Pierre- Laporte (1970 ) in Quebec, the Kammon bridge ( 1973) in Japan and the Akashi Kaikyo Bridge (1998), the longest of all suspension bridges, which has a 14 m high stiffening girder. The highest above the valley floor standing bridge, the Siduhe Bridge ( 2009) in the Chinese province of Hubei has a truss.

With increasing knowledge of the aerodynamic processes in a bridge, the truss then were analyzed, tested in wind tunnel tests and aerodynamic optimized.

The Ponte 25 de Abril (1966 ) in Lisbon, Minami Bisan - Seto Bridge (1988 ) in the Seto Ohashi bridge combination in Japan and the Tsing Ma Bridge (1997) in Hong Kong are double-decker railway and road bridges and therefore necessarily have a high truss.

Box girder

Fritz Leonhardt had already constructed the first built from 1938 to 1941 Rhine Bridge CologneRodenkirchen with only 3.30 m high solid-walled stiffening girder. She was 378 m at the time the most expansive bridge in Europe, but much shorter than the American bridges and not exposed to the wind like this in high altitude. In 1953 he moved from the Tacoma accident to the conclusion that it was better to be avoided by a streamlined design of the bridge deck, the development of wind currents, which lead to the vibration and distortion, rather than counteract the vibrations caused by large truss. From it caused wind tunnel tests at the National Physical Laboratory in Teddington, near London confirmed his theory.

Freeman Fox & Partners, who had just begun the construction of the Severn Bridge, presented on the construction of the bridge deck of a truss to a flat hollow box with cantilevered thin flagstones. The built 1961-1966 Severn Bridge in England, making it the first major suspension bridge in which no truss structures, but a flat, only 3 m high steel box was used, whose profile was determined in wind tunnel tests.

Due Leonhardt Council the construction of built between 1965 and 1970 Ny Little Belt Little Belt in Denmark in 1964 switched to the box girder construction.

Freeman Fox and Partners designed the First Bosphorus Bridge (1973) and the Humber Bridge ( 1981) and the second bridge over the Bosphorus, the Fatih Sultan Mehmet Bridge (1988 ) with flat, aerodynamically optimized hollow box sections and thus established this construction.

Other suspension bridges with box girders are the Högakustenbrücke (1997 ) in Sweden, the Jiangyin Bridge ( 1997) on the Yangtze River in China. Also, the previously second longest suspension bridge Xihoumen Bridge ( 2008) has a flat box girder.

Construction projects

Plans of suspension bridges major projects initiated in part to massive financial difficulties. For this reason, about the bridge over the Straits of Messina, which will connect Italy and Sicily, and with a main span of 3,300 meters could would become the largest suspension bridge in the world, or the Puente Bicentenario de Chiloé are not yet implemented in Chile. Furthermore, there are considerations to bridge the Straits of Gibraltar, as well as plans for a bridge across the Sunda Strait, a bridge over the Straits of Malacca and a bridge over the Bali Strait. These constructions were then significantly longer means spans the consequence.

The longest suspension bridges

( detailed information on the 100 longest suspension bridges in the world )

The longest suspension bridges in Germany, the Rhine bridge Emmerich from 1965 with 500 meter main span and the bridge over the Rhine CologneRodenkirchen of 1941

378 meters.

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