Suspension bridges are often built as large road bridges to bridge wider navigable waters, such as B. the Storebæltsbroen over the Great Belt . They are usually only more economical than cable-stayed bridges from spans of around 900 m . For spans well over 1000 m, they are the only possible design. As a rule, railway bridges are not designed as suspension bridges due to the tendency towards vibrations and larger deformations.
There are numerous, light and shorter suspension bridges for pedestrians, such as B. the Holbeinsteg over the Main in Frankfurt , or as a point of attraction for tourists as breathtaking constructions as possible, such. B. the suspension bridge Holzgau . In developing countries, particularly simple suspension bridges tailored to local conditions are built, such as B. the suspension bridge in the Annapurna Circuit or the Dodhara Chandani Bridge , which is also in Nepal over a 1.4 km wide river , which is probably the longest pedestrian suspension bridge.
Different static principles
Real suspension bridge
Real or earth-anchored suspension bridges are those in which the tensile force at the end of the ropes is absorbed by an anchor in the subsoil . For this purpose, the suspension ropes are fixed in large anchor blocks in the subsoil. In this variant, the roadway girder is only slightly stressed by tensile or compressive forces and can be made very light. Most of the suspension bridges are real suspension bridges.
False suspension bridge
The linguistic usage usually does not differentiate between suspension bridges in which the suspension ropes run over the tops of the pylons
False or self- anchored suspension bridges are those in which the suspension ropes are attached to the track girder itself. The horizontal component of the tensile force in the suspension ropes is thereby transferred to the roadway girder as a compressive force, the vertical component of the tensile force is balanced by its weight. They are also called bridle bridges .
This variant requires strong deck girders running from one end to the other, but avoids the large anchor blocks. On the other hand, more stable and therefore heavier ropes and pylons are necessary for the comparatively heavy road girder. A fake suspension bridge was used where the subsoil did not appear to be sufficiently firm to absorb the horizontal tensile force acting on the anchor blocks. Examples are the Mühlentorbrücke in Lübeck , which opened in 1900, and the Rheinbrücken Köln-Mülheimer Brücke from 1927 with a span of 315 meters and the Friedrich-Ebert Bridge in Duisburg with 285.5 meters, as well as the July 14th Bridge in Baghdad, completed in 1964 . The Krefeld-Uerdinger bridge over the Rhine with a span of 250 meters can also be mentioned here, although it has steel girders instead of the suspension cables and suspension ropes.
A major disadvantage is that complex auxiliary structures, such as inclined anchors, are required to assemble the self-anchored suspension bridge, since the suspension cables can only be assembled after the road girder has been completely completed. Overall, the self-anchored suspension bridge has not established itself as a form of construction due to the greater installation effort; it was mostly replaced by the cable-stayed bridge that was developed after the Second World War . A modern example is the Kuznechevsky Bridge in Arkhangelsk in northern Russia. The Konohana Bridge in Osaka , Japan , opened in 1990, is self-anchored and has only one suspension cable supported by A-shaped pylons.
The principle is also used again in the construction of the East Bay Bridge as part of the San Francisco-Oakland Bay Bridge . The main bridge consists of a single - hip self-anchored suspension bridge, i. This means that it has only one pylon, over which the suspension cables are stretched to the two ends of the deck girder.
Combined suspension and stay cable bridges
When designing the Yavuz Sultan Selim Bridge , the third bridge over the Bosphorus , which on its very wide box girder girder, unites both railway tracks (not yet installed when it opened in 2016) and four lanes on each side of a motorway, Michel Virlogeux took action goes back to the concept applied by John Augustus Roebling to the Brooklyn Bridge (1883) of stiffening a suspension bridge with stay cables . In fact, Roebling had already implemented the concept for the Niagara Falls Suspension Bridge in 1854 .
The linguistic usage usually does not differentiate between suspension bridges, in which the suspension ropes are led over the tops of the pylons, or one of the following, similar designs, which are not counted among the suspension bridges in the narrower sense:
- In the tension band bridge, the bridge deck, which is usually only intended for pedestrians, lies directly on the ropes or chains and thus describes the same sagging curve as this one.
- The rope bridge is a name for simple bridges consisting almost entirely of ropes, often in the form of a tension band bridge, which are mostly used on via ferratas in the mountains or in outdoor training.
- In the case of the cable-stayed bridge , the bridge deck is supported by cables stretched diagonally from the pylons to the bridge deck.
- The extradosed bridge is a further development of the prestressed concrete bridge , in which the prestressing cables are not arranged inside but outside the concrete profile and the supporting principles of the cable-stayed bridges are also used.
- In the case of a bridge with a trussed girder , the roadway does not hang on the supporting cable, but “stands” on it. The hangers, which are otherwise subject to tension, are replaced by compression rods.
|Components of a suspension bridge
The deck girder is attached to the main suspension cables with hangers. This means that these ropes are under tension . The redirection of the ropes on the pylons causes a compressive force in the pylons, which forward them into the foundation .
The pylons bear the weight of the superstructure, i.e. the weight of the suspension cables, the hangers and the roadway girders, as well as the traffic loads, i.e. the weight of the vehicles and people on the bridge. In addition, they absorb the forces in the transverse direction that are caused, for example, by the wind.
They are usually designed as rectangular portals with two pillars, either as a framework construction or in the form of a frame with two or more crossbars. Wide bridges often have three- pillar portals, such as the early Brooklyn Bridge or the modern Pingsheng Bridge in Foshan , Guangdong , China. In contrast to cable-stayed bridges, central central pylons are rare in suspension bridges. Fritz Leonhardt had proposed a design for the Ponte 25 de Abril in Lisbon with central pylons and a central suspension cable. Built examples are the above-mentioned Konohana Bridge , the Viaduc du Chavanon , a French motorway bridge opened in 2000, and various pedestrian bridges, such as the pedestrian bridge over Schenkendorfstrasse in Munich. Occasionally, pylons are architecturally elaborate, such as the Liede Bridge in Guangzhou , Guangdong, China.
Either steel with box cross-sections or reinforced concrete is used as the building material . The Pont de Tancarville (1958) was the first large suspension bridge with reinforced concrete pylons. Before the development of these building materials, cast iron pillars on stone plinths were used or portal towers were built from stone, e.g. B. at the Brooklyn Bridge. In very high steel pylons such as those of Akashi Kaikyō Bridge are mass dampers installed to by earthquakes or typhoons to dampen vibrations caused.
As a rule, two suspension cables are used, which are routed over the pylons and anchored in anchor blocks. On the heads of the pylons, the cables are routed over exposed or housed saddle bearings, sometimes over roller bearings. Occasionally, split cables were used between the pylons on the one hand and from the pylons to the anchor blocks on the other. In the case of wide bridges such as the Brooklyn Bridge with its portals made up of three pillars, four, sometimes three suspension cables are used.
The cables usually have a sag of 1/8 to 1/12 of the support width of the central field. Because of this essentially always similar sag, larger spans also require higher pylons. The slack does not quite follow the mathematical chain line , since with this a chain is only assumed under its own weight.
In modern large bridges, the suspension cables consist of a parallel wire rope, i.e. a bundle of parallel, high-strength steel wires that are pressed together by huge rope clamps. The suspension cables are produced on site by installing thin walkways for the workers over the pylons with the same slack as the future suspension cables.
These suspension ropes are manufactured using the air-jet spinning process . To do this, the individual wires of the suspension cables are pulled from one side to the other, bundled into strands, compressed into cables by cable press machines and then sheathed. The wires are usually hot-dip galvanized . The suspension cables must be protected from corrosion. This is done either by regularly repeating coatings with anti-corrosion paint or at significantly longer intervals by wrapping with butyl rubber tapes . On the suspension cable of large suspension bridges, there is usually a footbridge or a staircase with a simple wire rope railing for the inspection and maintenance personnel.
In Japan, parallel wire ropes made from prefabricated strand bundles are preferred, which are then bundled, compacted to form a cable and sheathed, as is the case with the Akashi-Kaikyō Bridge.
The suspension cables of medium and small bridges consist of laid wire ropes . In medium-sized bridges, 37 ropes are usually pressed together to form a hexagon for each suspension cable (with 7 ropes in the middle layer and 6, 5 and 4 each in the layers above and below). In the case of smaller bridges, the ropes are routed individually, as a pair or as a quadruple, which are provided with spacers that also serve to fasten the hangers.
The hangers connect the suspension cables to the track girder. They also mostly consist of hot-dip galvanized wire ropes. First and foremost, they have to withstand the tensile forces and influence the natural frequency of the bridge. To reduce vibrations, vertical hangers were occasionally combined with stay cables, as in the case of the Brooklyn Bridge. Sometimes the hangers are not stretched vertically, but alternately diagonally forward and diagonally backwards, so that two hangers always end at a common fastening point on the suspension cables and on the roadway girder, creating a zigzag pattern. This increases the rigidity of the road surface and reduces its deflection in the event of one-sided loading. Examples are the Severn Bridge (1966) designed by Freeman Fox & Partners and their first Bosphorus Bridge (1973) and the Humber Bridge (1981) as well as Edgar Cardoso's Ponte Samora Machel (1973) over the Zambezi . Sometimes hydraulic damping is also required at the ends of the hangers.
The roadway girder , also called stiffening girder , distributes the loads to the trailers. It is designed either as a lattice girder , as in the Akashi-Kaikyō Bridge , or with open solid wall girders , such as the Rhine Bridge Cologne-Rodenkirchen , or with a closed box cross-section , as in the Storebælt Bridge. They can be carried out rigidly from abutment to abutment through the pylons or interrupted at the pylons and supported there in an articulated manner. In order to achieve stability even at high wind speeds, the roadway girders must be made sufficiently torsionally rigid. With modern bridges, you get a cross-sectional design optimized in the wind tunnel , which avoids failure due to aerodynamic instability, as with the Tacoma-Narrows-Bridge . In the case of very wide bridges, the pavement girders are sometimes divided lengthwise into two strips with an open space to improve the aerodynamic stability. Some older bridges have also been aerodynamically optimized and retrofitted.
The ends of the suspension cables of real suspension bridges are fastened in anchor blocks. The anchor blocks must be so big and heavy and sunk so deep into the ground that they definitely withstand the maximum tensile force with which the carrying ropes of a fully loaded bridge loaded by storm and snow could pull on them. In the past, anchor blocks were made of stone blocks, today they are usually made of reinforced concrete. The anchor blocks of a larger bridge such as B. the Ambassador Bridge are as tall as a 16 story building; half of them are underground. The anchor blocks of the Storebæltsbroen , which were only placed on the seabed, work through their weight alone. They have a footprint of 122 m × 55 m and a height of 73 m. Only the tip protruding from the water can be seen.
The most common design of the suspension bridge today is the double-hipped bridge with a main opening between the two pylons, the suspension cables of which are attached to anchor blocks outside this opening. Most of the time the pylons are in the water to be crossed and the anchor blocks near the banks, so that the parts of the girder between the pylons and the banks are suspended from the suspension cables. Occasionally one or both pairs of pylons stand on the bank, so that the cables between the pylon tips and the anchor blocks are only used for anchoring and have no hangers.
The three-hipped and multi-hipped bridge, in which several spans followed one another, was originally widespread mainly in France . Already on the first cable suspension bridge , the Passerelle de Saint-Antoine in Geneva , two bridge fields were spanned by the suspension cables. The Cubzac road bridge, completed in 1833, became famous. It had five successive fields with spans of 109 m each and was probably the largest and longest suspension bridge in its time. Other examples are the bridge of Ingrandes over the Loire with eight fields and the bridges of Châteauneuf-sur-Loire , Châtillon-sur-Loire or Bonny-sur-Loire . Typical of this design are the suspension cables that only reach from pylon tip to pylon tip, the compensating cables connecting the pylon tips ( câble d'équilibre ) and separate, often multiple anchor cables. Modern examples are the Ponte Samora Machel over the Zambezi in Mozambique and the smaller suspension bridge in Naruto (Tokushima) , Japan.
In the course of the San Francisco-Oakland Bay Bridge there are also four pylons in a row. However, it is not a multi-hip bridge, but two independent suspension bridges that were built next to each other and have a common anchor pillar in the middle. Similarly, two suspension bridges were lined up at the Seto-Ōhashi in Japan and even three suspension bridges at the Kurushima-Kaikyō Bridge . A combination of a suspension and a cable-stayed bridge is the Huangpu Bridge in Guangzhou , Guangdong , China.
Suspension bridges usually only have one carriageway level, but there are also double-decker bridges , which sometimes also contain railroad tracks. Examples are the Brooklyn Bridge with a raised deck for pedestrians and cyclists, the Manhattan Bridge opened in 1909 with four subway tracks, the George Washington Bridge opened in 1931 , which was given a second level in 1962 and with a total of 14 lanes the most powerful bridge in the world World is, 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 .
In the mountains of East Asia and South America with their deeply cut valleys, rope bridges made of natural materials were the only way to cross the often raging rivers and were in use long before they were noticed in Europe. The Q'iswachaka suspension bridge over the Río Apurímac in Peru has existed for over 500 years and is considered the only remaining functional suspension bridge of the Inca . The first suspension bridge with iron chains was probably the Chagsam Bridge , built in Tibet in 1430 , over the Yarlung Tsangpo (Brahmaputra) with a span of about 137 m Range that exceeded everything that was thought possible in Europe at the time. In Europe, the first ideas of a suspension bridge (and other inventions) were published by Fausto Veranzio (Faust Vrančić, Latin Faustus Verantius) in 1616 in his book or his list of inventions Machinae Novea . Various later publications reported suspension bridges in China. All early suspension bridges, provided they were not made of natural materials, were chain bridges , as wires only reached a certain strength at the beginning of the 19th century and wire ropes were only invented in 1834 by Oberbergrat Julius Albert in Clausthal .
Western chain bridges
Built for miners in northern England around 1741 , the Winch Bridge was the first chain bridge in Europe. In the town of Weilburg , iron rod chains were stretched across the Lahn in 1784 , from which the pipes of the baroque water supply were suspended after a flood had destroyed the bridge that had previously been used. James Finley built various chain bridges in the United States from 1801 , which are considered to be the forerunners of the following suspension bridges by having suspension chains, hangers and a navigable bridge deck for the first time outside of Asia. The first large chain bridges in Europe were the Union Bridge by Samuel Brown, opened in 1820, and the Menai Bridge by Thomas Telford with a span of 176 meters, which was opened to traffic in 1826. The oldest surviving chain bridge in Germany is that of Conrad Georg coupler planned 1820/21 and in 1824 built Kettensteg in Nuremberg, which spanned the Pegnitz over 68 meters.
First wire rope suspension bridges
While the manufacture and production of iron made rapid progress in Great Britain at the beginning of the 19th century and was soon producing chains with reasonably reliable properties, France was long cut off from this development due to the continental barrier. Since wire ropes can compensate for the different qualities of the individual wires, the development in the French-speaking area concentrated from the beginning on wire rope suspension bridges.
The 82-meter-long Passerelle de Saint-Antoine , built by Guillaume-Henri Dufour in Geneva in 1823 based on ideas from Marc Seguin , is considered to be the world's first permanent wire rope suspension bridge. Marc Seguin had previously built a first test dock in Annonay . In 1824 he opened the bridge, known today as Passerelle Marc Seguin , over the Rhone in Tournon-sur-Rhône , the first passable wire rope suspension bridge.
The theoretical foundations of suspension bridges have been laid in a number of publications. In 1823, for example, Claude Navier published a first fundamental treatise on suspension bridges, which was soon translated into German and reissued in 1830, and Marc Seguin published his work Des Ponts en fil de fer in 1824 , in which he already at that time dealt with the problem of wind or lock step caused vibrations.
Over the next forty years, Marc Seguin and his company Marc Seguin et freres built over sixty suspension bridges across France. Competitive companies such as Société Bayard de la Vingtrie were similarly productive. Examples are the Cubzac road bridge, completed in 1833, which was probably the largest and longest suspension bridge in its time, and the bridges of Châteauneuf-sur-Loire , Châtillon-sur-Loire or Bonny-sur-Loire . Demand was high, as suspension bridges could cross wide rivers at a fraction of the cost that a conventional bridge with multiple stone arches had previously required. In places where it was previously not possible to build piers in the river bed due to the subsoil conditions or the current, the river could now be crossed on a bridge for the first time, such as the Pont de La Roche-Bernard in the Morbihan department over the Vilaine . The 194 m long Pont de la Caille on the road from Geneva to Grenoble, stretched over a gorge at a height of 147 m, would not have been conceivable shortly before.
The increase in strength of the wires due to the pulling during manufacture enabled more powerful suspension cables than when using suspension chains. The Zähringer Bridge in Freiburg im Üechtland ( Le Grand Pont Suspendu ) was the world record holder from 1835 with a span of 273 meters. Their suspension ropes consisted of 1056 individual wires with a diameter of 3 millimeters each. The individual wires were arranged parallel to each other, as the twisted (twisted) wire rope was first invented by Oberbergrat Julius Albert in 1834 .
This construction method was retained for larger suspension bridges, the suspension ropes of which were so large and heavy that they could only be produced on the construction site using the air-jet spinning process, which was originally invented by the French Louis-Joseph Vicat and introduced in 1830. John Augustus Roebling later developed this process further in the USA, so that suspension ropes could be manufactured over large spans directly at the place of use in a comparatively short time and at affordable costs.
The French suspension bridges mostly had carriageway girders that were similar to one another, but pylons in all shapes common in the architecture of the time, e.g. B. as Doric or Egyptian columns, in the form of obelisks or often as small triumphal arches. However, the bridges were often only designed for loads of 200 kg / m² and without large reserves, were built lightly and provided with a bridge deck that was not very rigid. The anchorages of the suspension cables in the masonry of the pylons were not accessible and therefore susceptible to corrosion.
Initially, a number of collapses as a result of storms were accepted. However, when the suspension ropes of the Angers suspension bridge (Pont de la Basse-Chaîne) were torn from their anchorages on April 16, 1850 and a total of 226 people died in this accident, 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 to reject further suspension bridges. As a result, hardly any suspension bridges were built in France over the next forty years, while John Augustus Roebling was showing the solution to the problem in the United States around the same time.
In the French-speaking area, suspension bridges were only built again at the end of the 19th century, mainly by Ferdinand Arnodin , and even more older bridges were modernized according to his ideas. Outwardly visible was the stiffening combination of fan-shaped stay cables on the sections of the track girders near the pylons with conventional suspension 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 developed a special type of ordinary lay rope with several layers, in which the individual wires were loaded more evenly than before. He built anchor blocks with accessible anchorages for the suspension cables, stiffened the bridge decks with a steel frame and the inclusion of stable railings. He also took the view that the load-bearing parts of a bridge should be replaceable without disrupting traffic. The Pont Sidi M'Cid in Constantine , Algeria , completed in 1912 , was the highest bridge in the world at the time.
In the rest of Europe, various chain bridges, but hardly a wire rope suspension bridge, were built in the 19th century. The Lion Bridge was built in Berlin's Tiergarten in 1838 . The wire bridge (1870) in Kassel , the Rosental bridge (1880) in Braunschweig and the suspension bridge over the Argen (1897) near Langenargen on Lake Constance are further examples of rather modest dimensions.
Development in the USA
The Wheeling Suspension Bridge over the Ohio River , completed in 1849, was the first large suspension bridge with a span of over 300 m. However, its deck was already vibrated, twisted and destroyed by a storm in 1854, so that it too serves as an example of the basic problems this type of bridge could apply.
John A. Roebling's suspension bridges
The development of suspension bridges in the USA was therefore mainly influenced by John Augustus Roebling , who had built a wire rope factory in Trenton (New Jersey) . John A. Roebling built the Niagara Falls Suspension Bridge in 1851-54 , a double-decker bridge for the railroad and wagons with a span of 251 m, in which he took special measures to avoid vibrations, such as additional stay cables and the formation of the track girder as a truss construction similar to a box girder. Similar measures were taken in his next bridges, such as the Cincinnati – Covington Bridge opened in 1866 with a span of 322 m (later called John A. Roebling Suspension Bridge ) and the one-span Brooklyn Bridge, completed by his son in 1883 after his death The Brooklyn Bridge was much longer and larger than its predecessor and quickly became a New York landmark, but at the same time marks the end of the Roebling era with brick pylons, heavy girders and additional stay cables.
Development towards larger bridges
For the third suspension bridge over the East River , the Manhattan Bridge planned by Leon S. Moisseiff and completed in 1909, the deformation theory (deflection theory) was applied for the first time , which enabled a significantly lighter construction method compared to the previous bridges . The advancement of this theory as well as improvements in steels, ropes and construction methods led to ever larger bridges, such as the Bear Mountain Bridge , the Benjamin Franklin Bridge and the Ambassador Bridge . In 1929, the Royal Gorge Bridge was probably the first suspension bridge built for tourist purposes, which became famous because it crossed a canyon in Colorado at a height of 291 m and held the title of tallest bridge in the world until 2001.
Othmar Ammanns opened the George Washington Bridge in 1931 with a span of 1067 m and the Golden Gate Bridge , built by Joseph B. Strauss and opened in 1937, with a span of 1280 m set new standards. The Lions Gate Bridge in Vancouver became the longest suspension bridge outside the United States with a span of 472 m in 1938 and retained this title until the Pont de Tancarville in France opened in 1959 .
New calculation methods, new construction methods
When funds for bridges also became scarce in the Great Depression , it was gladly accepted that the deformation theory, instead of high lattice girders, now enabled flat solid wall girders that were significantly lighter, required less steel and were easier to assemble. This made it possible for the first time to finance long two-lane suspension bridges in which the ratio of both the height of the deck to its length and its width to length became smaller and smaller. Since deformation theory dealt with static wind loads, the lower wind resistance of a flat pavement girder seemed more important than the stiffness caused by high trusses. However, vibrations occurred during the construction of the Thousand Islands Bridge, which was completed in 1938, and the Deer Isle Bridge , which was built almost at the same time , which its planner, David B. Steinman , could only control with the help of additional tensioning ropes and struts.
These events were not taken into account in the case of the Tacoma Narrows Bridge , an extremely slim and lightweight bridge planned by Leon S. Moisseiff, which at the time had the third largest span of all suspension bridges at 853 m. Far more than gale-force storms had been used as a basis for their planning. But here, too, vibrations were observed during construction. On November 7, 1940, only four months after its opening, the only gale winds (wind force 8) gave rise to increasing vibrations and twisting, which led to the bridge girder breaking and thus the destruction of the bridge. At first one puzzled about the causes, since the aerodynamic effects on bridges were not understood at all at that time. It took many years, many wind tunnel tests and calculations, until the dynamic effects of wind on bridge structures and the effects of aeroelastic flutter were reasonably understood.
After the Tacoma Narrows Bridge collapsed
The immediate effects were initially that Ammann's also very slender Bronx-Whitestone Bridge was subsequently stiffened to reassure the ( toll-paying ) motorists, although it had significantly better key figures than the Tacoma-Narrows Bridge. As a counter-reaction to the deformation theory, which favored slender carriageway girders, the new construction of the Tacoma Narrows Bridge, completed in 1950, and above all by David B. Steinmans in 1957, the Mackinac Bridge was provided with high and already visually solid-looking trusses. Othmar Ammann also used high and stiff trusses for the Throgs Neck Bridge (1961); with the Verrazzano-Narrows Bridge (1964) the problem did not arise because of the two-story construction.
American and European construction methods
In the long term, the knowledge gained from the collapse of the Tacoma Narrows Bridge led to two different methods, which are also known as American and European construction methods.
With the American construction method, large trusses were and continue to be used to stiffen the road girder. Care is taken to ensure that they have the lowest possible wind resistance despite their size. Large American- style suspension bridges are, for example, the Pont de Tancarville (1959) near Le Havre , the Forth Road Bridge (1964) near Edinburgh , the Emmerich Rhine Bridge (1965), the Pont Pierre-Laporte (1970) in Québec, the Kammon- Bridge (1973) in Japan and the Akashi Kaikyō Bridge (1998), the longest of all suspension bridges to date, which has a 14 m high stiffening beam. The highest bridge above the valley floor, the Siduhe Bridge (2009) in the Chinese province of Hubei, also has a truss.
With increasing knowledge of the aerodynamic processes in a bridge, the trusses were also analyzed, tested in wind tunnel tests and aerodynamically optimized.
The Ponte 25 de Abril (1966) in Lisbon , the Minami-Bisan-Seto Bridge (1988) in the Seto-Ōhashi bridge combination in Japan and the Tsing Ma Bridge (1997) in Hong Kong are double-deck railroad and road bridges and therefore inevitably have a high truss.
Fritz Leonhardt had already designed the first Rhine bridge between Cologne and Rodenkirchen , which was built between 1938 and 1941, with a solid stiffening girder that was only 3.30 m high. At 378 m it was the widest-span suspension bridge in Europe, but significantly shorter than the American bridges and not exposed to the wind at great heights. In 1953, he drew the conclusion from the Tacoma accident that it would be better to avoid the creation of wind currents, which lead to the oscillations and twisting, by a streamlined design of the bridge deck, instead of counteracting the oscillations with large lattice girders. Wind tunnel tests initiated by him at the National Physical Laboratory in Teddington near London confirmed his theory.
Freeman Fox & Partners , who had just started the construction of the Severn Bridge , then changed the bridge deck from a truss to a flat box girder with cantilevered, thin pavement slabs. The Severn Bridge in England, built from 1961 to 1966, was the first large suspension bridge that did not use a truss structure, but a flat, only 3 m high steel box girder, the profile of which was determined in wind tunnel tests .
Freeman Fox and Partners also constructed the first Bosphorus Bridge (1973) and the Humber Bridge (1981) as well as the second bridge over the Bosphorus, the Fatih Sultan Mehmet Bridge (1988) with flat, aerodynamically optimized box girder profiles and thus established them this construction.
Other suspension bridges with box girders are the Högakusten Bridge (1997) in Sweden and the Jiangyin Bridge (1997) over the Yangtze River in China . The second longest suspension bridge to date, the Xihoumen Bridge (2008), also has a flat box girder.
Pedestrian suspension bridges in developing countries
In developing countries with mountainous areas, simple suspension bridges are often the only way for residents of remote, otherwise inaccessible villages to cross ravines and rivers. The construction of many of these bridges is supported by committed private individuals such as Beat Anton Rüttimann and organizations such as Helvetas Swiss Intercooperation or the USA-based Bridges to Prosperity .
These bridges often have the same properties: Discarded ropes from cable cars , crane systems or container cranes are mostly used for their suspension ropes . The pylons are made of standard steel tubes, which are often made available at reduced prices or free of charge. The stiffening girder or the walkway is formed from gratings or battens that are attached between ropes stretched from bank to bank. The railings consist of standard wire netting attached to other ropes . Vibrations of the bridge girder are dampened by side bracing, which often transfer the system of suspension cables and hangers horizontally: a main rope stretched in a wide arc on both sides of the bridge is connected to the bridge girder by numerous damping ropes.
Plans for large-scale suspension bridge projects sometimes run into massive financial difficulties. For this reason, the bridge over the Strait of Messina , which is supposed to connect Italy and Sicily and, with a main span of 3,300 meters, would have become the largest suspension bridge in the world, or the Puente Bicentenario de Chiloé in Chile, have not yet been realized. There are also plans to bridge the Strait of Gibraltar , as well as plans for a bridge over the Sunda Strait , a bridge over the Strait of Malacca and a bridge over the Bali Strait . These constructions would then result in significantly longer center spans.
The longest suspension bridges
(detailed information on the 100 longest suspension bridges in the world)
|Akashi Kaikyō Bridge
|Osman Gazi Bridge
|Fourth Nanjing Yangtze River Bridge
|Yavuz Sultan Selim Bridge
|Tsing Ma Bridge
|Hong Kong , China
|Verrazzano Narrows Bridge
|Golden Gate Bridge
|oldest suspension bridge still in use today
|Replaced by arched bridge in 1924
|Wheeling Suspension Bridge
|Lewiston – Queenston Suspension Bridge
|destroyed, later new building
|Wheeling Suspension Bridge
|John A. Roebling Suspension Bridge
|Falls View Suspension Bridge
|Replaced in 1899
|Bear Mountain Bridge
|first suspension bridge with concrete deck
|Benjamin Franklin Bridge
|George Washington Bridge
|Golden Gate Bridge
|Akashi Kaikyō Bridge
- Suspension rope bridge or pedestrian suspension bridge or rope suspension bridge
- Bridge rope inspection device
- Literature on suspension bridges in the catalog of the German National Library
- Structurae: suspension bridges
- Bridge building database and links
- Website by Bernd Nebel with descriptions of bridges
- Karl Gotsch's website with a bridge lexicon
- Bridgemeister , database of suspension bridges worldwide
- The track hangs in the suspension cable , FAZ April 11, 2006
- Self-anchored suspension tension , Bay Bridge Public Information Office. April 2009. Retrieved April 27, 2009.
- Mark Hansford: Third Bosphorus Bridge to mirror New York design. In: nce.co.uk. July 5, 2012, accessed on May 20, 2016 (full text possibly via Google search, English).
- Leonardo Fernández Troyano: Tierra sobre el Agua. Vision Histórica Universal de los Puentes. Colegio de Ingenieros de Caminos, Canales y Puentes, Madrid 1999, ISBN 84-380-0148-3 , p. 537
- Günter Ramberger, Francesco Aigner: suspension bridges . In: Handbuch Brücken, Gerhard Mehlhorn (Ed.) , Pp. 388–394, Springer-Verlag Berlin Heidelberg 2007. ISBN 978-3-540-29659-1
- Rainer Saul, Oswald Vorteilel: "Wrapping with butyl rubber tapes - an innovative corrosion protection for fully locked bridge ropes", https://structurae.net/literature/journal-article/umwickeln-mit-butylkautschukbandern-ein-innovativen-korrosionsschutz-fur-vollverschlossen- bridging ropes
- Gerhard Mehlhorn (Ed.): Handbook bridges. 2nd edition, Springer-Verlag, Berlin Heidelberg 2010, ISBN 978-3-642-04422-9
- The lighter version has 19 ropes with 5 ropes in the middle layer.
- For the second bridge over the Bosporus, the Fatih Sultan Mehmet Bridge (1988), Freeman, Fox & Partners again used vertical hangers
- Müller, Rudolf: From the Chain Bridge to the Ernst-Dienstbach-Steg (PDF; 2.7 MB)
- Claude Navier: Report to Monsieur Becquey, conseiller d'état, directeur général des ponts et chaussées et des mines; et mémoire on the ponts suspendus . Imprimerie Royale, Paris 1823 (digitized on Google Books)
- Des Ponts en fil de fer , (1st edition 1824) 2nd edition, Bachelier, Paris, 1826 (digitized on Google Books)
- Ponts suspendus réalisés by Marc Seguin et freres , on art-et-histoire.com. Retrieved March 9, 2013
- Société Bayard de la Vingtrie on art-et-histoire.com
- Marcel Prade: Ponts & Viaducs au XIXe Siècle . Brissaud, Poitiers 1988, ISBN 2-902170-59-9
- Sven Ewert: Bridges - The development of spans and systems . Ernst & Sohn, Berlin 2003, ISBN 3-433-01612-7 , pp. 57-59
- By mistake here is often a Henry Vicat called
- Historical Development of Iron and Steel in Bridges
- Louis Vicat , on Encyclopædia Britannica Online
- Louis-Joseph Vicat: Description du pont suspendu construit sur la Dordogne à Argentat ... , Paris 1830
- American literature does not speak of a high carrier, but of a deep truss
- Richard Scott: In the wake of Tacoma, suspension bridges and the quest for aerodynamic stability . ASCE Press, Reston, Va. 2001, ISBN 0-7844-0542-5
- The lattice girders attached to the Bonx-Whitestone Bridge were only able to dampen vibrations a little during storms; it was not until the aerodynamically shaped cladding that was attached in 2004 that the bridge survived Hurricane Sandy without major vibrations.
- Leonardo Fernández Troyano: Tierra sobre el Agua. Vision Histórica Universal de los Puentes. Colegio de Ingenieros de Caminos, Canales y Puentes, Madrid 1999, ISBN 84-380-0148-3 , p. 563
- Fritz Leonhardt: Bridges, Aesthetics and Design / Bridges, Aesthetics and Design. Deutsche Verlagsanstalt, Stuttgart 1982, ISBN 3-421-02590-8 , pp. 290-293
- Bridges to Prosperity