Generally speaking, a bridge consists of five main parts and five secondary parts. The five components refer to the superstructure and substructure of the bridge span which bear the transportation load of automobiles or other vehicles, and are the guarantee for the safety of the bridge structure, including (1) the bridge span structure (or the bridge hole structure. Superstructure), (2) supporting system, (3) pier, (4) abutment and (5) pier foundation.

A, the classification of the bridge:

According to the purpose, it can be divided into highway bridge, highway-railway dual-purpose bridge, pedestrian bridge, tractor bridge and water bridge.

According to the span size and total length of multiple spans, it can be divided into small bridges, medium bridges, large bridges and extra large bridges.

According to the structure, it can be divided into four basic systems: beam bridge, arch bridge, steel frame bridge and cable-supported bridge (cable-stayed bridge and suspension bridge), and there are also combined system bridges.

According to the location of the carriageway, it can be divided into underpass bridge, semi-underpass bridge and underpass bridge.

According to the service life, it can be divided into permanent bridge, semi-permanent bridge and temporary bridge.

According to the material type, it is divided into wooden bridge, masonry bridge, reinforced concrete bridge, prestressed bridge and steel bridge.

Bridge classification: total length of multi-hole span L (m) single-hole span L0 (m)

L≥500 L0≥ 100 of extra large bridge

Bridge L≥ 100 L0≥40

Bridge 30

Small bridge 8 ≤ L ≤ 30 5

Culvert l < 8l0 < 5

Second, the basic characteristics of all kinds of bridges:

Beam bridges include simply supported plate beams, cantilever beams and continuous beams. The span capacity of simply supported plate girder bridge is the smallest, generally 8-20m. The maximum span of continuous beam bridge in China is below 200 meters, and that of foreign countries is 240 meters.

Under the vertical load, the supports at both ends of the arch bridge produce vertical reaction and horizontal thrust. It is the horizontal thrust that greatly reduces the mid-span bending moment and increases the span capacity. Theoretically, the ultimate span of concrete arch is about 500m, and steel arch can reach1200 m. It is this thrust that requires good geological conditions when building arch bridges.

Rigid frame bridges include T-shaped rigid frame bridges and continuous rigid frame bridges. The main disadvantage of T-shaped rigid frame bridge is that there are many expansion joints on the deck, which is not conducive to high-speed driving. The continuous rigid frame beam is continuous and seamless, and the driving is stable. There is no system conversion during construction. The largest span in China is 270m (Humen Bridge Auxiliary Channel Bridge).

Cable-loaded bridges (cable-stayed bridges and suspension bridges) are the best design for building bridges with long spans. The bridge deck of a highway or railway is suspended in the air by cables, and cables are suspended between bridge towers. The main span of cable-stayed bridge can reach 890m, and that of suspension bridge can reach1991m.

Composite bridges include beam-arch composite systems, such as tied arch, truss arch and multi-span arch beam structures, and beam-frame composite systems, such as T-shaped rigid frame bridges.

Truss beam bridge: It has a strong beam with brackets at both ends. The earliest bridges were built according to this idea. They are just tree trunks or stones across the river. Modern truss girder bridges usually use long hollow trusses made of steel or concrete as beams. This makes the bridge light and strong. Bridges built in this way are called box girder bridges.

Cantilever bridge: The bridge body is divided into several long and solid parts, similar to truss bridge, but each part is supported by the middle instead of the two ends.

Arch bridge: The arch bridge pushes the ground at both ends of the bridge and bears the stress of the main span. Modern arch bridges usually adopt light open structure.

Suspension Bridge: Building a bridge with a very long span is the best design. The bridge deck of highway or railway is suspended in the air by steel cables, which are firmly suspended between bridge towers. Some older suspension bridges use chains, and some even use ropes instead of steel cables.

Cable-stayed bridge: Cable is tied to the bridge column. The steel cable supports the weight of the bridge deck and transfers the weight to the bridge column, which puts great pressure on the bridge column.

Glass bridge: a bridge made of pure glass. (Pingqiao)

Covered Bridge: A bridge with pavilions, called Pavilion Bridge or Covered Bridge, can provide shade for tourists and increase the shape change of the bridge.

Third, the history of Chinese bridges

Historically and now, most bridges are built on water, and only Doug Bridge and pedestrian overpasses and vehicular overpasses in modern cities are built between tall buildings or on highways.

It is a historic leap from the utilization of natural bridge to artificial bridge construction. From simple wooden bridge to today's steel bridge; From single beam bridge to pontoon bridge, cable bridge, arch bridge, garden bridge, slab bridge and optical fiber bridge. The materials used to build this bridge are mainly wood, stone, steel and reinforced concrete, which is a very long development process. However, the bridge construction in China has made amazing achievements.

The famous historian of science and technology, Dr. Joseph Needham of Cambridge University in England, said in the History of Science and Technology in China that the bridges in China "had amazing development in the Song Dynasty, and a series of huge plate girder bridges were built". The Yangtze River Bridge built in contemporary China, Wuhan and Nanjing is even more praised by the world. It can be seen that the bridge has experienced a development process from childhood, adolescence, youth to maturity in China, and it is becoming more and more mature. 14th century ago, China was in a leading position in bridge development, and today, it is still an important bridge country in the world.

Four, the classification of the bridge:

1. Classification by span

Bridge classification by span is a means of industry management, and it can't reflect the complexity of bridge engineering design and construction. The following is the method of dividing bridges by span specified in China's highway engineering technical standard (JTJ00 1-97).

bridge

The total length of the bridge is L≥500m, and the calculated span is L0≥ 100m.

bridge

Total length of bridge 100m ≤ l < 500m, and calculated span 40m ≤ l0 < 100m.

intermediate shaft

The total length of the bridge is 30m < l < 100m, and the calculated span is 20m ≤ l0 < 40m.

pons

The total length of the bridge is 8m≤L≤30m, and the calculated span is 5m ≤ L0 < 20m.

Bridge classification: total length of multi-hole span L(m) single-hole span (L0)

Extra large bridge: l ≥ 500m l0 ≥100m.

Bridge:100m ≤ l < 500m ≤ 40m l0 <100m.

Medium bridge: 30m < l <1200m 20m ≤ l0 < 40m.

Small bridge: 8m ≤ L ≤ 30m, 5m ≤ l0 < 20m.

Due to the progress of the times, "bridge" has been given a new meaning, generally referring to people who communicate with each other, establish cooperative relations and promote friendly exchanges. The jobs and occupations that such people engage in are also collectively referred to as "bridge work".

V. Development history of bridges:

Bridges are an integral part of roads. From the perspective of engineering technology, the development of bridges can be divided into three periods: ancient, modern and modern.

(1) ancient bridge

In primitive times, humans used naturally fallen trees, naturally formed Liang Shi or stone arches, rocks protruding from streams and vines growing on the banks of valleys to cross waterways and canyons. It is difficult to verify when humans purposefully cut down trees to build bridges or piled stones to build bridges. According to historical records, China had beam bridges and pontoons in the Zhou Dynasty (1 1 century to 256 BC). For example, around 1 134 BC, Wei River had pontoons in the Western Zhou Dynasty. In BC 1800, the kingdom of Babylon built a multi-span wooden bridge with a length of 183 meters. Rome built a wooden bridge across the Tiber River in 62 1 BC and a pontoon bridge across the Heller Strait in 48 1 BC. In ancient Mesopotamia, a stone arch bridge (with stepped arches) was built in the 4th century BC.

/kloc-before the 0/7th century, ancient bridges were generally built with wood and stone, and bridges were divided into stone bridges and wooden bridges according to building materials.

The main form of stone bridge is stone arch bridge. According to research, as early as the Eastern Han Dynasty (AD 25-220), stone arch bridges appeared in China, such as the unearthed portrait bricks of the Eastern Han Dynasty, engraved with arch bridge graphics. The existing Zhao Zhouqiao (also known as Anji Bridge), built in 605 ~ 6 17 with a clear distance of 37 meters, is the first hollow (open-shouldered) arch with a lower abdomen arch on the main arch ring. The arch rings and piers of ancient stone arch bridges in China are generally thin and light, such as baodai bridge, which was built in 8 16 ~ 8 19 years, with a total length of 3 17 meters, thin and flat piers and exquisite structure.

In Roman times, there were many arch bridges in Europe. For example, from 200 BC to 200 AD, eight stone arch bridges were built on the Tiber River in Rome, among which the Fabbrizio stone arch bridge built in 62 BC has two holes, each with a span of 24.4 meters. In 98 AD, Spain built the 52-meter-high Al Bridge. In addition, there are many stone arch bridges and waterway bridges, such as the existing Garde diversion bridge in France, which was built in BC 1 century. The bridge is divided into three layers, with 7 holes at the bottom and a span of 16 ~ 24 meters. Arch bridges in Roman times were mostly semi-circular arches, with a span of less than 25m and a pier width, accounting for about one third of the arch span. Figure 1 [Schematic Diagram of Lemini Bridge] is a schematic diagram of Lemini Bridge built in Roman times.

Hundreds of years after the fall of the Roman Empire, little progress has been made in bridge construction in Europe. 1 1 century later, pointed arch technology spread from the Middle East and Egypt to Europe, and pointed arch bridges began to appear in Europe, such as avignon Bridge built by11188, which is a 20-span pointed arch bridge. The Thames Bridge built in Britain 1 176 ~ 1209 is a pointed arch bridge with a span of about 7 meters. Many arch bridges were built in Spain in the13rd century, such as San Ding Qiao in Toledo. Besides circular arch and secant arch, arch bridge also includes elliptical arch and flat arch. Pierre Bridge in France, which was built from 1542 to 1632, is an elliptical arch with seven holes and unequal spans, with a maximum span of about 32 meters. Oval arches were popular at that time. 1567 ~ 1569 A three-span flat arch bridge was built in Santa Trinita, Florence, with a height-span ratio of 1∶7. Bridges built in11~17th century, some of which have shops on both sides, such as Rialto Bridge in Venice.

Liang Shi Bridge is another form of stone bridge. Baqiao Bridge near Xi, Shaanxi, China, formerly known as Liang Shi Bridge, was built in the Han Dynasty, with a history of more than 2,000 years. From 1 1 to12nd century, dozens of large-scale Liang Shi bridges, including Luoyang Bridge and Anping Bridge, were built in Quanzhou in the Southern Song Dynasty. Anping Bridge (Wuli Bridge) was originally 2500 meters long with 362 holes, but now it is 2070 meters long with 332 holes. Some existing stone bridges in Dartmoor, England have a history of more than 2000 years.

In the early wooden bridges, most of them were beam bridges. For example, the Wei Qiao built on the Weihe River in the Qin Dynasty was a multi-span beam bridge. The span of wooden beam bridge is not large, and the span of wooden bridge with legs can be increased. Fig. 2 Schematic diagram of wooden cantilever bridge. In the 3rd century AD, China built a "long 150 step" outboard wooden bridge at the junction of Anxi, Gansu and Turpan, Xinjiang. From 405 to 4 18, a cantilever wooden bridge was built near Linxia, Gansu, with a river width of 40 feet and a bridge height of 50 feet. The splayed wooden bridge (Figure 3 [schematic diagram of splayed wooden bridge]) and arched wooden bridge can also increase the span. /kloc-Bassano Bridge in the 6th century was a splayed wooden bridge.

Wooden arch bridge (Figure 4 [Schematic Diagram of Wooden Arch Bridge]) appeared earlier. 104 * * The Trajan wooden arch bridge built on the Hungarian Danube River has 2 1 holes, each with a span of 36 meters. Hongqiao (Figure 5 [Schematic Diagram of Hongqiao]) built by China in Kaifeng, Henan Province, with a clear distance of about 20 meters, is also a wooden arch bridge, built in A.D. 1032. The Ribbon Bridge built by the Japanese in Jinchuan River in Iwakuni is a five-hole wooden arch bridge, which was built around 300 AD with the help of Dai Mangong, an independent Buddhist monk from China.

There is a bamboo cable bridge made of bamboo strips in the southwest of China. The famous bamboo cable bridge is Zhupu Bridge in guanxian, Sichuan. The bridge has 8 holes, with a maximum span of about 60 meters and a total length of more than 330 meters. It was built before the Song Dynasty.

The ancient bridge foundation adopted the cofferdam method of Roman times, that is, piled the wooden boards into cofferdams, and built the bridge foundation and piers in them after pumping water. The foundation of the arch bridge on Thames River in England, which was built in 1209, was constructed by cofferdam method. But at that time, only manual piling was used to pump water, and the foundation was shallow. China 1 1 At the beginning of the century, the famous Luoyang Bridge threw stones all over the river at the bridge site. After keeping oysters on it for two or three years, the raft foundation was cemented, which was a pioneering work.

(2) Modern bridges

The production and casting of iron in the 0/8th century provided new building materials for bridges. However, cast iron is not a good bridge-building material because of its poor impact resistance, low tensile strength and easy fracture. Since 1950s, with the development of acid converter steelmaking and open hearth steelmaking technology, steel has become an important bridge-building material. Steel has high tensile strength and good impact resistance, especially the appearance of steel plate and rectangular rolled section steel in 19 years, which created conditions for the factory to assemble bridge components and made steel widely used.

/kloc-At the beginning of the 8th century, cement was invented by mixing and calcining lime, clay and hematite. In 1950s 19, steel bars were placed in concrete to make up for the poor tensile performance of cement. Since then, this reinforced concrete bridge was built in the 1970s of 19.

Modern bridge construction promotes the rise and development of bridge scientific theory. 1857, Saint-Werner put forward a relatively complete beam theory and deflection theory on the basis of previous research on arch theory, statics and material mechanics. During this period, the theory of continuous beam and cantilever beam was established one after another. The analysis of bridge trusses such as Warren truss and Howe truss has also been solved. After 65438+70s, with the efforts of German K. cullmann, British W. j. m. m. Rankin and J. C. Maxwell, structural mechanics has made great progress, and the stress of bridge members under load can be analyzed. The development of these theories promotes the development of trusses, continuous beams and cantilever beams. By the end of 19, the elastic arch theory has been improved, which has promoted the development of arch bridges. The rise of soil mechanics in the 1920s promoted the theoretical research of bridge foundation.

Modern bridges are divided into wooden bridges, stone bridges, iron bridges, steel bridges and reinforced concrete bridges.

Wooden Bridge wood truss existed before16th century. 1750, Switzerland built many wooden bridges with arch-truss combination, such as Lechinau Bridge, with a span of 73 meters. /kloc-from the mid-8th century to the mid-9th century, the United States built many wooden bridges, such as 1785, the first wood truss Bridge on the Connecticut River in Belozfalls, Vermont, with two spans of 55 meters each; 18 12 arch-truss composite wooden bridge built on the Kiel River in Skur, Philadelphia, span 104m. Truss bridge is widely used because it omits the arch and diagonal bracing structure and simplifies the structure. Due to the development of truss theory, various types of truss wooden bridges have appeared one after another, such as Pratt, Howe and Tang. (Figure 6 [Truss Bridge]). Because the wooden bridge uses a lot of iron, it is better to use all iron economically. Therefore, wooden bridges were gradually replaced by steel bridges in the late19th century.

Iron bridges include cast iron bridges and forged iron bridges. Cast iron is brittle, suitable for compression, not for tension, and suitable for arch bridge construction. The first cast iron bridge in the world is the Severn River Bridge built by Dell Factory in Colebrook, England. Built in 1779, it is a semi-circular arch consisting of five arch ribs with a span of 30.7 meters. The tensile property of wrought iron is better than that of cast iron. /kloc-in the middle of the 0/9th century, the forged iron chain suspension bridge was used for highway bridges with a span of more than 60 ~ 70 meters. Due to the lack of stiffness of suspension bridge, the railway adopts truss bridge. For example, the Brittany double-track railway bridge built in Britain 1845 ~ 1850 is a box forged railway bridge. /kloc-since the middle of the 0/9th century, beam theory and structural analysis theory have been established one after another, which has promoted the development of truss bridges and various forms of truss beams have appeared. However, at that time, the understanding of bridge wind resistance was insufficient, and bridges generally did not take wind protection measures. 1879 18 months ago, Yang's forged iron bridge of Taiwan Railway was built after the strong wind blew down, because there was no horizontal continuous wind-resistant structure on the bridge.

On 1705, China built the Luding Chain Suspension Bridge on the Dadu River in Sichuan. This bridge is 100 meters long and 2.8 meters wide, and it is still in use today. The first chain suspension bridge in Europe is the Tis River Bridge in Britain, which was built in 174 1, with a span of 20 meters and a width of 0.63 meters. From 1820 to 1826, Britain built a suspension bridge with a middle hole177m in the Menet Strait in northern Wales. The bridge was rebuilt on 1940 due to the lack of stiffening beam or wind-resistant structure. The world's first suspension bridge built with iron cables instead of chains is the Fribourg Bridge in Switzerland, which was built in 1830 ~ 1834 with a span of 233 meters. This bridge uses 2000 iron wires to pay off in situ, suspended from the tower and anchored in the anchorage pit with a depth of18m.

1855, the Niagara Falls Highway Railway Bridge in the United States was completed. This bridge is a suspension bridge with forged iron cable stiffening beam, with a span of 250 meters. From 1869 to 1883, the United States built a suspension bridge in Brooklyn, new york, with a span of 283+486+283 meters. The construction of these bridges provides the experience of using stiffening trusses to reduce vibration. Since then, all long-span suspension bridges built in the United States have used stiffening beams to increase their rigidity, such as the Golden Gate Bridge in San Francisco built in 1937 (main hole length1280m, side hole length 344m and tower height 228m), and the Oakland Bay Bridge in San Francisco built in the same year (main hole length 704m, side hole length 354m and tower height 628m).

1940 Taco Ma Haixia Bridge in Washington, USA was completed. The main span of the bridge is 853 meters, the side holes are 335 meters, the stiffening beam is 2.74 meters high, and the bridge width is 1 1.9 meters. In the same year1October 7th, 165438, when the wind speed was only 67.5km/h, the middle hole and side hole of the bridge were blown down by the wind. This incident has prompted people to study the relationship between aerodynamics and bridge stability.

Steel Bridge Izz Bridge on the Mississippi River in St. Louis, Missouri, USA, built at 1867 ~ 1874. It is an early articulated steel truss arch bridge for highway and railway, with a span of153+153m. The new technology of cantilever installation was adopted in the erection of this bridge. Arch ribs are hung on both sides of the pier, pulled by slings of temporary wooden rafts on the pier, spliced one by one, and finally connected to the two arches in the middle of the span. The foundation is sunk to 33 meters by pneumatic caisson. Due to the lack of safety measures, serious caisson disease occurred in 1 19, and 14 people died. At the end of 19, the elastic arch theory was gradually improved, which promoted the construction of long-span steel arch bridges in the 1920s and 1930s. The famous ones are: Yuemen Bridge in new york, built in 19 17, with a span of 305m, new york Beiyong Bridge, built in 193 1 year, with a span of 504 m; Sydney Harbour Bridge, Australia (see color map [Sydney Harbour Bridge, Australia]), built in 1932, with a span of 503 meters. All three bridges are double-hinged steel truss arches.

The cantilever beam designed according to mechanics appeared in the middle of19th century. According to the Tibetan wooden cantilever bridge in China, the British put forward the idea of combining anchor span, cantilever span and suspended span, and built a railway cantilever beam bridge at the mouth of the Foss River in Edinburgh, England 1882 to 1890. This bridge has six cantilevers, the cantilever length is 206m, the cantilever span length is107m, and the main span length is 519m (Figure 7 [Schematic Diagram of Flowserve Cantilever Beam Bridge]). At the beginning of the 20th century, cantilever beam bridges were all the rage, such as the Queensburg Bridge in new york, which was built in the United States from 190 1909. It is a cantilever bridge, with middle anchor span190m, cantilever span150m and cantilever span180m. Quebec Bridge in Canada, built in 1900 ~ 19 17, is also a cantilever steel bridge. The Danish Small Waterway Bridge completed by 1933 is a five-hole cantilever beam highway-railway bridge with a span of137.50+165+200+165+137.5 meters.

1896 Belgian engineer Frendale invented the vierendeel truss bridge. Belgium has built several riveted welded hollow truss bridges.

Reinforced concrete bridge 1875 ~ 1877, French gardener Moniere built a pedestrian reinforced concrete bridge with a span of 16m and a width of 4m. 1890 A pedestrian reinforced concrete arch bridge with a span of 40 meters was exhibited at Bremen Industrial Exhibition in Germany. 1898, Chaste Luo reinforced concrete arch bridge was completed. This bridge is a three-hinged arch with a span of 52 meters. Fig. 8[] is a schematic diagram of a three-hinged arch and bridge. 1905, the Tavana-Sa Bridge was completed, with a span of 5 1 m, a box-shaped three-hinged arch bridge with a height of 5.5 meters. 1928, Britain built a 4-span reinforced concrete arch bridge in Luo Jaarte Wade, Beric, with a maximum span of 1 10 meter. 1934, the Traberry Arch Bridge with a span of 18 1m and a height of 26.2m was built in Sweden: 1943, and the Sander Arch Bridge with a span of 264m and a height of nearly 40m was built (Figure 9 [Schematic Diagram of Sander Arch Bridge in Sweden]).

In the construction of bridge foundation, vertical shaft began to be used in18th century. When repairing Westminster Arch Bridge in Britain, wooden caissons are floated to the bridge site, then they are sunk with stones, and then the foundation and pier are repaired. 185 1 year, when the Medway Bridge was built in Rochester, Kent, England, compressed air caissons were used for the first time. From 1855 to 1859, a forged iron cylinder with a diameter of 1 1 m was used in the construction of the Royal Albert Bridge in Soltash, Cornwall, and a compressed air caisson was set under the cylinder. 1867, the United States built the Izz River Bridge, also using compressed air caissons to build the foundation. In the construction of compressed air caisson method, if workers work under the condition of compressed air for a long time, or suddenly come out of the compressed air box without decompression chamber, or decompress too fast, caisson disease will easily occur.

After 1845, steam pile drivers began to be used in bridge foundation construction.

(3) Modern bridges

In 1930s, prestressed concrete and high-strength steel appeared one after another, and great progress was made in the research of material plasticity theory and limit theory, bridge vibration, aerodynamics and soil mechanics. Thus, it provides scientific basis for saving bridge building materials, reducing bridge weight, predicting foundation subsidence depth and determining its bearing capacity. Modern bridges can be divided into prestressed reinforced concrete bridges, reinforced concrete bridges and steel bridges according to building materials.

Prestressed reinforced concrete bridge 1928, after 20 years' research, French Fraissinet engineers made prestressed reinforced concrete with high-strength steel wire and concrete. This material overcomes the shortcoming that reinforced concrete is easy to crack, so that the bridge can be constructed by cantilever installation of incremental launching method. With the continuous development of high-strength steel wire and high-strength concrete, the structure and span of prestressed reinforced concrete bridges are constantly improved.

Prestressed reinforced concrete bridges are simply supported, continuous, cantilever, arch, truss, rigid frame and cable-stayed bridge. The span of simply supported beam bridges is mostly below 50 meters. Continuous beam bridges, such as the French Oleron Bridge built in 1966, are prestressed concrete continuous beam bridges with 26 spans of 79 meters. The Wharf Bridge in Houston, USA, built at 1982, is a prestressed concrete continuous beam viaduct with a mid-span of 229 meters, which is constructed by balanced cantilever method. Cantilever beam bridge, such as Bendorf Bridge built by the Federal Republic of Germany in Brenc in 1964, with a main span of 209 meters; Japan Binming Bridge, 1976 completed, with a main span of 240 meters; Chongqing Yangtze river bridge, completed in China 1980, with a main span of 174m (see color map [Chongqing Yangtze river bridge, prestressed concrete T-shaped rigid frame bridge of expressway]). Truss bridge, such as the Montfarr Valley Bridge in the Federal Republic of Germany built in 1960, is the first prestressed concrete truss bridge in the world with a span of 90+ 108+90 meters. 1966, the Soviet Union built a prestressed concrete truss continuous bridge with a span of106+3×166+106m. Rigid bridges such as Saint Michel Bridge in Toulouse, France, which was built in 1957, were built by floating method. The French Bonhome Bridge, completed at 1974, with a main span of 186.25m, is the largest prestressed concrete rigid frame bridge at present (Figure10 [Bonhome Bridge Schematic Diagram]). Prestressed reinforced concrete suspension bridge is a self-anchored system composed of prestressed beam and prestressed steel wire rope in stiffening beam. Melebeck Bridge and Maria Keck Bridge in Ghent, Belgium were built in 1963, with main spans of 56 meters and 100 meters respectively, which are prestressed reinforced concrete suspension bridges. Cable-stayed bridges such as Lake Maracaibo Bridge in Venezuela were built in 1962. The bridge is a 5-hole 235-meter continuous beam, and the cantilever beam is hoisted by prestressed stay cables suspended on the A-tower. The beam of cable-stayed bridge is suspended on a multi-elastic support composed of cables, which can reduce the beam height and improve the wind resistance and torsional vibration resistance of the bridge. The main girder can be installed with cables, which is beneficial to crossing the river, so it is widely used. Prestressed concrete cable-stayed bridges, such as Wa Diekoff Bridge built by Libyan 197 1, with a main span of 282m; 1978 The Pasco-Kennewick Bridge on the Columbia River in Washington State, built by the United States, with a main span of 299 meters; 1977 Brotons Bridge on the Seine River built by France, with a main span of 320 meters. More than ten prestressed concrete cable-stayed bridges have been built in China, among which the main span of the Yellow River Bridge in Jinan, Shandong Province, which was built in 1982 is 220 meters (see color map [Jinan Yellow River Highway Bridge, prestressed concrete continuous cable-stayed bridge, built in 1982] [vehicles]).

Reinforced Concrete Bridges After World War II, many long-span reinforced concrete arch bridges have been built in the world, such as Yalada Arch Bridge in Portugal, which was opened to traffic on 1963, with a span of 270 meters and a rise of 50 meters. Glades weir bridge in Sydney Harbour, Australia, 1964 completed, with a span of 305 meters.

China created the reinforced concrete hyperbolic arch bridge in 1964. The bridge is composed of arch ribs and arch waves, with curvature in both longitudinal and transverse directions, and also in the form of arch waves in the transverse direction (Figure 1 1 [Schematic Diagram of Hyperbolic Arch Structure]). Arch rib and arch wave are prefabricated in sections, so they can be installed with light lifting facilities. In this way, a long-span arch bridge can be built without heavy transportation and heavy lifting equipment. The first experimental hyperbolic arch bridge was built in Wuxi, Jiangsu, China, with a span of 9 meters. Since then, Xiangjiang Bridge in Changsha, Hunan Province has been built 1972. It is a hyperbolic arch bridge with a span of 16, a large span of 60m, a small span of 50m and a total length of1250m.

Reinforced concrete truss arch bridge (Figure 12 [Schematic Diagram of Truss Arch Bridge]) is a structure composed of arch and truss, with less materials, light weight and simple construction.

After World War II, with the appearance of steel with high strength, good toughness, good fatigue resistance and corrosion resistance, the appearance of light high-strength orthotropic slab bridge welded by flat steel plates and reinforced by angle steel and plate steel, and the application of high-strength bolts, steel bridges have made great development.

Bridges of steel plate beams, box-shaped steel beams and concrete, orthotropic slab bridges and box-shaped steel beams are widely used in long-span bridges. The Dü sseldorf-Neuss Bridge built by the Federal Republic of Germany 195 1 is an orthotropic slab-box girder with a span of 206 meters. The Dü sseldorf North Bridge built in the Federal Republic of Germany from 65438 to 0957 is a 6-hole 72-meter steel plate girder bridge. Belgrade sava river Bridge, built in Yugoslavia 1957, is a steel plate girder bridge with a span of 75+261+75m and an inverted U-beam. 1973 Martigue Inclined Leg Rigid Frame Bridge built in France with a main span of 300 meters. Sfara Sand Bridge, which was built in Italy from 65438 to 0972, spans 376 meters and is the largest steel inclined leg rigid frame bridge in the world. 1966 The astoria Bridge in Oregon, completed in the United States, is a continuous steel truss bridge with a span of 376 meters. 1966 The portal bridge built in Japan is a continuous steel truss bridge with a span of 300 meters. Nanjing Yangtze River Bridge, built in China 1968, is a continuous steel truss bridge with highway and railway functions. The main bridge128+9×160+128 meters, with a total length of 6 kilometers (see color map [Nanjing Yangtze River Bridge, the largest bridge in China at present]). The port bridge of Osaka Port, built in Japan in 1972, is a cantilever steel bridge with a length of 980m m.. It consists of 235m anchor hole, 162m cantilever hole and 186m suspension hole. New york Victoria razzano Suspension Bridge, completed in USA 1964, has a main span of 1298m and a tower height of 26548. 1966 Severn suspension bridge built in Britain, with a main hole of 985 meters. According to the wind tunnel test, the bridge adopts the box-shaped stiffening beam with shuttle-shaped orthotropic plate for the first time, and the height of the beam is only 3.05 meters. 1980 Humbil Suspension Bridge, built in England, has a main span of 14 10 meter, and also uses shuttle-shaped orthotropic box-type stiffening beams, with a beam height of only 3 meters.

After 1960s, steel cable-stayed bridges developed. The first steel cable-stayed bridge is the Strender Songstrait Bridge built in Sweden, which was built in 1956 with a span of 74.7+ 182.6+74.7 meters. There are two stay cables on the left and right sides of the tower, and reinforced concrete slabs and welded steel plate beams are combined into longitudinal beams. The Cologne steel cable-stayed bridge built by the Federal Republic of Germany 1959 has a main span of 334 meters. 197 1 erskine steel cable-stayed bridge built in Britain, with a main span of 305 meters; 1975 French-built St. Nazaire Bridge with a main span of 404 meters. The cables of this bridge are arranged in dense bundles, which reduces the length between envoys and the height of the beam, which is only 3.38 meters. At present, by improving the wind resistance and seismic performance of steel cable-stayed bridge, the span of cable-stayed bridge has gradually increased.

The foundations of steel bridges are mostly built with large-diameter piles or thin-walled shafts.

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