世界上最美的桥梁英文介绍共48页文档
介绍一些世界著名的桥梁英语作文100词
介绍一些世界著名的桥梁英语作文100词全文共6篇示例，供读者参考篇1Amazing Bridges Around the WorldHave you ever crossed a big bridge and looked down at the cars or water below feeling amazed? Bridges are incredible structures that help us get from one place to another over water, valleys, or roads. Some bridges are so special and famous that people travel from all over just to see them! Let me tell you about a few of the most amazing bridges in the world.The Golden Gate Bridge in San Francisco, California is probably one of the most famous bridges ever. It's a bright reddish-orange color and stretches for 1.7 miles across the San Francisco Bay. This suspension bridge is held up by huge cables and towers reaching 746 feet high! When it opened in 1937, it was the longest and tallest suspension bridge in the world. On a clear day, you can see for miles from the bridge. It's an iconic symbol of San Francisco.Another incredibly long bridge is the Danyang-Kunshan Grand Bridge in China. At over 102 miles long, it's the longestbridge in the world! This giant bridge is part of a high-speed railway line connecting cities in China. Imagine taking a train ride across a bridge longer than the entire subway system of some cities! It stretches across rivers, marshes, and even goes over a huge lake. Building this monster of a bridge was an enormous challenge.The Millau Viaduct in southern France is one of the tallest bridges on Earth. Its tallest pillar is an unbelievable 1,125 feet high – taller than the Eiffel Tower! This cable-stayed bridge spans the River Tarn valley, giving beautiful views of the French countryside from very high up. Its incredible height and grace have made it an attraction in itself.While most famous bridges carry vehicles, trains or pedestrians, the Puente Nuevo bridge in Ronda, Spain has homes built right on top of it! This stone bridge arching over a deep gorge was built way back in 1793. The views from the houses on the bridge are breathtaking, looking out over the cliff sides and countryside. I'm not sure I'd want to live on a bridge though – it might feel a bit shaky!The Sydney Harbour Bridge is one of the most photographed bridges due to its stunning setting. This giant steel arched bridge spans Sydney's famous harbor, with theiconic Sydney Opera House sitting right beside it. The bridge lovingly nicknamed the "Coathanger" by locals had its highest part topped by the Australian flag during the 2000 Sydney Olympics. How cool would it be to climb up and put a flag on a bridge?No matter where they are in the world, bridges always seem to inspire a sense of wonder and amazement. From soaring heights to grand lengths, these engineering marvels make the impossible possible – letting people, cars, and trains safely travel over what was once an uncrossable obstacle. They connect us to new places while becoming symbols and sights themselves. The next time you go over a bridge, I hope you'll pause and think about the amazing architecture and hard work that went into creating it!篇2Title: Amazing Bridges Around the WorldIntroduction:Hi everyone! Today, I want to tell you about some amazing bridges from around the world. Bridges are structures that help us cross rivers, valleys, and even oceans. Let's explore a few famous ones!Golden Gate Bridge (San Francisco, USA):The Golden Gate Bridge is an iconic orange-red suspension bridge in San Francisco. It's a symbol of the city and one of the most photographed bridges in the world. It's very long and connects San Francisco to Marin County. Isn't that amazing?Tower Bridge (London, UK):Tower Bridge is a famous bridge in London. It has two tall towers and a drawbridge in the middle, which can lift up to let large ships pass through. It's a beautiful sight, especially when it's lit up at night!Sydney Harbour Bridge (Sydney, Australia):The Sydney Harbour Bridge is a gigantic steel arch bridge that spans across Sydney Harbour. It's nicknamed the "Coathanger" because of its shape. People can walk or drive across the bridge, and some even climb to the top for a stunning view of the city.Ponte Vecchio (Florence, Italy):Ponte Vecchio is a historic bridge in Florence, Italy. What's special about this bridge is that it has shops built on it! You can find all sorts of lively shops selling jewelry, souvenirs, and even gelato. It's like a bridge and a shopping street combined!Great Belt Bridge (Denmark):The Great Belt Bridge is one of the longest bridges in the world. It connects two Danish islands, Zealand and Funen. It's an engineering marvel, and trains and cars can travel on it. Imagine going on a long drive across the sea!Conclusion:Wow! These bridges are truly amazing, aren't they? They connect people, cities, and even countries. Next time you see a bridge, remember the incredible structures they are and how they make our lives easier. Bridges are not just for crossing, they are also symbols of human creativity and ingenuity.篇3Title: Amazing Bridges Around the WorldHello, everyone! Today, I want to tell you about some incredible bridges from around the world. These bridges are famous for their unique designs and historical importance.Golden Gate Bridge, San Francisco, USA:This red-colored suspension bridge connects San Francisco to Marin County. It's one of the most photographed bridges in the world!Tower Bridge, London, UK:This iconic bridge is located on the River Thames. It has two towers and opens up to let big ships pass. It's a symbol of London!Sydney Harbour Bridge, Sydney, Australia:Also known as the "Coathanger," this bridge is a steel arch bridge. It offers breathtaking views of Sydney's beautiful harbor.Great Wall of China, China:Yes, the Great Wall is not just a wall; it also has many bridges! These ancient stone bridges were built to help defend against enemies.Ponte Vecchio, Florence, Italy:This old bridge is unique because it has shops built on it! You can find jewelry, art, and souvenirs while walking across it.Akashi Kaikyo Bridge, Kobe, Japan:This suspension bridge is the longest in the world! It connects the city of Kobe to Awaji Island and can withstand earthquakes and strong winds.Rialto Bridge, Venice, Italy:Venice is famous for its canals and beautiful bridges. The Rialto Bridge is the oldest and most famous bridge in Venice. It's a must-visit!These bridges are not only important for transportation but also symbols of their cities. They attract tourists from all over the world. Next time you see a bridge, remember how it connects people and places!I hope you enjoyed learning about these amazing bridges. Remember, bridges are not just structures; they bring people together!篇4Famous Bridges Around the WorldThere are many amazing bridges in the world that connect cities, countries, and even continents. Let's discover some of the most famous bridges!Golden Gate Bridge: Located in San Francisco, California, the Golden Gate Bridge is an iconic symbol of the city. It's a suspension bridge that spans the Golden Gate Strait, connecting San Francisco to Marin County. The bridge is famous for its bright orange color and stunning views of the ocean.Tower Bridge: Found in London, England, Tower Bridge is a famous symbol of the city. It crosses the River Thames and has two towers connected by a walkway. What makes it special is that it can open up in the middle to let tall boats pass through.Sydney Harbour Bridge: Situated in Sydney, Australia, the Sydney Harbour Bridge is one of the largest steel arch bridges in the world. It connects the central business district to the North Shore and offers breathtaking views of the Sydney Opera House and the harbor.Great Wall of China: Although not a traditional bridge, the Great Wall of China is an incredible structure that stretches over mountains and valleys. It was built to protect China from invaders and is considered one of the most impressive architectural wonders in the world.Brooklyn Bridge: Located in New York City, the Brooklyn Bridge is an iconic landmark. It connects the boroughs of Manhattan and Brooklyn, spanning the East River. The bridge is famous for its Gothic-style arches and is a popular spot for walking and cycling.These are just a few examples of the many famous bridges around the world. Each bridge has its own unique beauty and significance, attracting millions of visitors every year. Bridges notonly connect places but also bring people together. They are engineering marvels that remind us of human ingenuity and the power of unity.I hope you enjoyed learning about these famous bridges!篇5Title: Amazing Bridges Around the WorldHello! Today, I want to tell you about some amazing bridges around the world. Bridges are structures that help us cross over rivers, valleys, and even oceans. Let's explore a few famous ones!The Golden Gate Bridge: Located in San Francisco, USA, this red-orange suspension bridge is one of the most iconic landmarks. It's so big and beautiful!Tower Bridge: Found in London, England, this bridge has two towers with a drawbridge in the middle. It's like a castle gate over the River Thames!Sydney Harbour Bridge: In Sydney, Australia, this amazing steel arch bridge connects the city's central business district to the North Shore. Wow, it's huge!Great Belt Bridge: This bridge in Denmark connects two islands, Funen and Zealand. It's one of the longest suspension bridges in the world. Impressive!Pont du Gard: This ancient Roman aqueduct bridge in France is more than 2,000 years old! It carried water across the river and is now a UNESCO World Heritage site. How cool is that?Remember, bridges are not just for crossing, they also show the incredible engineering skills of humans. Next time you see a bridge, look closely and appreciate its beauty and importance. Bridges bring people together!That's all for now. I hope you enjoyed learning about these famous bridges. Keep exploring and have fun!篇6Title: Famous Bridges around the WorldIntroduction:Hi everyone! Today, I want to tell you about some famous bridges around the world. Bridges are amazing structures that help people cross rivers, valleys, and even oceans. Let's explore these incredible bridges together!Golden Gate Bridge, San Francisco, USA:The Golden Gate Bridge is located in San Francisco, USA. It is a huge red-colored suspension bridge that connects the city to Marin County. It's called the Golden Gate Bridge because it crosses the Golden Gate Strait. It is one of the most iconic and beautiful bridges in the world.Tower Bridge, London, UK:Tower Bridge is in London, UK. It is a magnificent bridge that crosses the River Thames. What makes it special is that it can open in the middle to allow big ships to pass through. The bridge has two tall towers that people can visit and learn about its history.Sydney Harbour Bridge, Sydney, Australia:Sydney Harbour Bridge is in Sydney, Australia. It is a huge steel arch bridge that connects the city to the North Shore. People can walk or drive on the bridge, and some even climb to the top for an amazing view of the city. It's a famous landmark in Australia!Great Wall Station Bridge, Antarctica:The Great Wall Station Bridge is in Antarctica. It's a small, simple bridge that connects two parts of the research station. It's called the Great Wall because it looks like a mini version of theGreat Wall of China. It's really cool that there's a bridge in such a snowy and cold place!Conclusion:Bridges are not just a way to cross rivers, but also symbols of human creativity and engineering skills. These famous bridges I told you about are just a few examples of the incredible bridges around the world. I hope you enjoyed learning about them as much as I did sharing with you!。
介绍金门大桥的英语作文
介绍金门大桥的英语作文The Kinmen Bridge, also known as the Kinmen Grand Bridge, is a long bridge that connects the Kinmen Islands to mainland China. It is an important infrastructure project that facilitates the transportation and communication between the two regions.The Kinmen Bridge is a cable-stayed bridge with a total length of 2,237 meters. It was constructed to replace theold ferry service that used to transport people and goods between Kinmen and Xiamen. The bridge has not only improved the efficiency of transportation but also promoted economic development in the region.The construction of the Kinmen Bridge started in 2011and was completed in 2015. The bridge has become a symbolof cooperation and friendship between Kinmen and Xiamen. It has also become a popular tourist attraction, offering panoramic views of the surrounding seascape.The Kinmen Bridge has helped to strengthen the ties between Kinmen and Xiamen, promoting cultural exchanges and economic cooperation. It has also facilitated the movementof people and goods, boosting trade and tourism between the two regions.金门大桥，又称金门大桥，是一座连接金门群岛和中国大陆的长桥。
介绍桥的英语作文
介绍桥的英语作文Title: Bridges: Connecting Worlds。
Bridges, the magnificent structures that traverse rivers, valleys, and even seas, serve as vital links between communities, cultures, and economies. Throughout history, they have symbolized human ingenuity, perseverance, and the desire to overcome obstacles. In this essay, wewill delve into the significance of bridges, exploringtheir architectural marvels, historical importance, and contemporary relevance.First and foremost, bridges are remarkable feats of engineering and architecture. From the ancient Roman aqueducts to the modern marvels like the Golden Gate Bridge, these structures showcase human innovation and creativity. Engineers and architects meticulously design bridges to withstand immense pressures, from the forces of nature to heavy vehicular traffic. The intricate balance of form and function in bridge design reflects the marriage of art andscience, capturing the imagination of all who behold them.Beyond their technical brilliance, bridges hold profound historical significance. Throughout the ages, bridges have played pivotal roles in shaping the course of civilizations. They facilitated trade and commerce, allowing goods and ideas to flow freely between regions. The Silk Road, for instance, relied heavily on bridges to connect the vast expanse of Asia with Europe, facilitating cultural exchange and economic prosperity. Moreover, bridges often served as strategic military assets, enabling armies to cross rivers and conquer new territories.In addition to their historical importance, bridges continue to play a crucial role in modern society. In an increasingly interconnected world, bridges serve as vital conduits for transportation and communication. They reduce travel time, improve accessibility, and foster economic development by linking previously isolated regions. Moreover, bridges are often architectural icons that define the skylines of cities and serve as symbols of civic pride. Tourists flock to marvel at landmarks like the Tower Bridgein London or the Brooklyn Bridge in New York City, admiring their beauty and significance.Furthermore, bridges transcend mere physical connections; they also serve as metaphors for human relationships and the bonds that unite us. Just as bridges span rivers and valleys, they bridge gaps between individuals, communities, and cultures. In times of crisis, bridges serve as lifelines, enabling aid and support to reach those in need. They embody the spirit of cooperation and collaboration, reminding us of our shared humanity and the power of solidarity.However, it is essential to acknowledge the challenges that bridges face in the modern world. Climate change poses a significant threat to infrastructure, leading toincreased risks of flooding, erosion, and structural damage. As sea levels rise and extreme weather events become more frequent, engineers must innovate and adapt bridge designsto withstand these new challenges. Additionally, the rapid pace of urbanization and population growth puts pressure on existing infrastructure, necessitating investments inmaintenance, rehabilitation, and expansion.In conclusion, bridges are more than mere structures; they are symbols of human ingenuity, connectivity, and resilience. From ancient stone arches to futuristic cable-stayed spans, bridges have played pivotal roles in shaping the course of history and continue to connect people and places in the modern world. As we navigate the challenges of the 21st century, let us remember the significance of bridges, both as physical marvels and as metaphors for the bonds that unite us as a global community.。
伦敦大桥的英文介绍作文
伦敦大桥的英文介绍作文英文：London Bridge is one of the most iconic landmarks in London. It spans across the River Thames, connecting theCity of London and Southwark. The bridge has a rich history, dating back to Roman times, when the first wooden bridgewas built in AD 50. Since then, the bridge has been rebuilt several times, with the current bridge being opened in 1973.One interesting fact about London Bridge is that itused to be the only bridge over the Thames in London for over 600 years. This made it a vital transportation linkfor the city and an important symbol of its growth and development. Today, the bridge is still an important partof London's transportation infrastructure, with thousandsof people crossing it every day.Another interesting fact about London Bridge is that it has been the subject of many myths and legends over theyears. One of the most famous of these is the story of how the nursery rhyme "London Bridge is Falling Down" was inspired by the bridge's supposed instability. While thereis no evidence to support this claim, it is still a popular story that is often told to children.Overall, London Bridge is a fascinating landmark thatis steeped in history and culture. Whether you are atourist or a local, it is definitely worth a visit.中文：伦敦大桥是伦敦最具标志性的地标之一。
世界上最美的桥梁英文介绍
1. Salginatobel Brücke(瑞士萨尔基那山谷桥) 2. Golden Gate Bridge (美国旧金山金门大桥) 3. The Brotonne Bridge (法国东纳大桥) 4. Kirchheim Overpass (德国克西汉姆跨线桥) 5. Orly Airport Overpass (法国奥利机场跨线桥) 6. First Bosphoros Bridge (土耳其博斯布鲁斯大桥) 7. Sunniberg Bridge (瑞士桑尼伯格大桥) 8. Normandy Bridge (法国诺曼底大桥)
2. Golden Gate Bridge (美国旧金山金门大桥)
The bridge was built in 1937. Bridge color is orange, the main span of 1280m, located in the San Francisco Bay entrance. "She sleek, proportion, is the jewel in bridge engineering, so that the designers of this century has been unable to go beyond."
5. Orly Airport Overpass (法国奥利机场跨线桥)
Built in 1958. "It was delicate and graceful curves gives a strong feeling."
6. First Bosphoros Bridge (土耳其博斯布鲁斯大桥)
世界上最美的桥梁英文介绍
4. Kirchheim Overpass (德国克西汉姆跨线桥)
The bridge built in 1993, in the span 54m, beam height 0.5m-1.7m, bridge width of 6 meters. The bridge is the essence of this relatively rare antihanging design, the lower sling force, supported by the upper deck overhang belt, really wonderful idea. "Sleek shape and bending moment diagram is similar to the beam, gives a sense of strength."
bridge is 1560 m long .33 meters wide, 165 meters high, six lanes. October 30, 1973 the official opening, like a bond connecting the two parts of Europe and Asia together, there are 25 million people that day across the bridge from Europe to reach Asia. "The Eurasian designed by the British Bridge is a memorable structure."
2. Golde was built in 1937. Bridge color is orange, the main span of 1280m, located in the San Francisco Bay entrance. "She sleek, proportion, is the jewel in bridge engineering, so that the designers of this century has been unable to go beyond."
世界绝美桥梁
世界绝美桥梁1. Henderson Wave Bridge (Singapore)亨德森波浪桥（新加坡）亨德森波浪桥是新加坡最高的人行天桥，衔接了花柏山公园和直落布兰雅山公园，约274米长，晚上由一排LED照明灯来加强效果。
创新点：波浪状桥身给人以视觉上的冲击力，动感十足；内部的长凳设计可以让游客坐在上面休憩并欣赏新加坡美丽的夜空。
2. The Mur River Wooden Bridge (Graz City, Austria)穆尔岛桥（奥地利，格拉茨市）穆尔岛人行桥位于奥地利格拉茨市，为了庆祝“格拉茨2003文化之都”而建立。
创新点：巨大的银色贝壳状的人工岛屿两边各有桥梁连接河岸，人工岛屿内设有日光浴区，时尚酒吧，咖啡馆和露天表演场，被认为是艺术与建筑，梦幻与现实融合的经典之作，绚丽灿烂。
3. Langkawi Sky Bridge (Langkawi Island, Malaysia)兰卡威天空之桥（马来西亚，兰卡威群岛）这座壮美的大桥位于马来西亚的兰卡威群岛，建成于2004年10月，主体由钢材料构成，总长125米。
创新点：整个桥梁只用一根87米高的支柱来支撑，然后再由8根钢缆牵引，整个桥就这样吊在海拔687米的高空，连接着两个山头。
桥面不足1.8米宽，半月形的设计让兰卡威群岛尽收眼底。
4. Magdeburg Water Bridge (Germany)马格德堡水桥（德国）这座长度达918米的跨河水道桥于1997年动工，2003年开始投入使用。
它将东部的米特兰德运河与西部的易北河-哈维尔运河连接了起来。
既有行人行走其上，又有船只航行，构成了这座桥的奇妙景观。
5. Eye of Tianjin-Yongle Bridge (Tianjin, China)天津之眼-永乐桥（中国）永乐桥全长330米，跨度100米，横跨子牙河。
大桥分为两层，上层为机动车专用道路，双向六车道，下层为人行道桥。
关于桥梁的英语简介
BridgesBridges are among the most important, and often the most spectacular,of all civil engineering works. The imposing bridges that have survived from ancient times are arched structures of heavy masonry, usually stone dr brick..Herodotus,the greek historian of the fifth cenury B.C., however mentions a wooden bridges across the Euphrates River at Babylon. In rome, the bridge of Fabricis, built in 62B.C.and named for its engineer,still carries traffic across the ataiber River,asdoes the Sant′Angelo Bridge, built in about 136A.D.Both of these bridges, and many other Roman bridges,have a series of arches supported by heavy piers that extend down to bedrock. Ancient sources also mention pontoon bridegs, usually in connection with military operation.A pontoon is a hollow drum that can float; a series of pontoons anchored to a riverbed can support a oadway. The Incas of per-Columbian Peru built remarkable suspension bridges, supported by cables of natural fibers, that crossed many of the deep gorges in their monutainous country.The sudden expansion in transportation systems that began in tha eighteenth century,and still continues in our own day, has enormously increaed the need for bridges as a part of highways and railroad, Better understanding of the forces that are exerted on structures and the improved materials that became available in the nineteenth century have made it possible to build increasingly longer ang stronger bridges.With the ability to span greater distances,the damlike effect of masonry arch bridges with several heavy piers that ; block he flow of a stream can be largely eliminaed.The simplest type of span is a beam bridge,consisting of a rigid beam between two supports. Today most simple beam bridges are strengthened by a truss, which is based on the triangle. Diagonal bams that extend between the horizontal and vertical beams give support against both comperssion and tension. Many early truss bridges were built of wood; one that was eected across the Susquehanna River in Pennslvania in 1815 had a span of 110 meters. Iron and then steel were later used in the consruction of truss bridges, still further increasing their stength. Trusses are not only strong but also light, because all unnecessary material has been eliminated in their design.Another type of beam bridge is the cantilever, in which a horizontal beam extends beyond its support.Cantilever bridges, like tusses, had also been built before iron and steel became available. Most cantilever bridges have wo arms of truss structure that meet or support a section between them. Cantilevers enabled bridges.During the ninteenth century, cantilevers were frequently used to build railroad bridges.The Quebec Bridge, which crosses the St. lawrence River in Canada, is the longest cantilever bridge in the world, with a span of 540 meters. It was completed in 1917, and until 1919 it was the longest bridge of any type in the world.A third type of moder bridge is he steel arch bridge, which can carry a roadway either above or below its arch of steel beams. An arch exerts strong downward and diagonal thrusts, so the piers that support it must be especially strong. Probably the most famous steel arch bridge is the Sydeny H arbor Bridge in Australia, wih a span of 495 meters. The Bayonne Bidge between New Jersey and Staten Island in New York has a span one meter longer.Suspension bridges span even longer distance than other types of bridge. The longest bridge of any type is the Verrazano-Narrows Bridge in New York, with a span of 1,280 meters. The deck or roadway of a suspension bridge is suspended from steel cables are supported by massive towers. The first modern suspension bridges usedlinked chains made of wroughe iron. Some of them survived for many years, like one across the Danube River in Budapest, Hungary. It was completes in 1849 and destroyed during World War, nearly a hunded years later.When steel became available, cables of steel wires replaced chains of wrought iron. Several suspension bridges built in this manner collapsed, however, as a result of storms or the movement created by the rhythm of the loads moving across them. It was later discoversd that these failures were caused by the lack of truss supports for the deck. The first major cable-type suspension bridge to overcomg these faults was designed by John A.Roebling at Niagara Falls. Its span of 250 meters was strengthened by trusses between the two decks. Roebling also used stays, inclined cables that ran from the main supporting cables to the deck, to stabilize the bridge. Roebling went on to design the Brooklyn Bridge in New York, which was completed in 1883 by his son, George Washington Roebling. The Booklyn bridge, with a span of 486 meters, is one of he most important-and one of the most esthetically satisfying-bridges ever built. The mothod devised by the Roeblings for laying the Brooklyn Bridge is essentially the same technique used today.He evelopment of reinforces and prestressed concrete has given engineers other important materials for bridge building. Concrete has been used particularly for relatively short-span bridges that are a part of freeway system. These bridges often use precast concrete beams. Many arch bridges have also been constructed of concrete. Currently, the longest concrete arch bridge is the Gladesville Bridge in Sydney, Australia. It has a span of 305meters, and its deck is above the arch.This is another example of an esthetically pleasing bridge.Many bridge that pass over rivers or canals must be movable so that shipping can pass under them. One type is the lift bridge, with towers that can raise the entire span between them by means of counterbablances and electric motors. Another type is the swing or pivot bridge, which pivots the span on a pier so that the bridge can swing openn parallel to the river or canal.A third type is the bascule bridge, which has one or two arms that can open upward at an angle by means of counterweights. A bascule with one arm is a single-leaf bridge, and with two arms it is a double-leaf bridge.Bridge constuction can present extraordinry difficulties. Usually the foundations for the piers must rest on bedrock, and often under water. One technique for working in these conditions is by means of a cofferdam. Piles usully made of interlocking steel plates are driven into the water bed. The water is then pumped out from within the use area that been enclosed.Anpther tachnique is the use of the pneumatic caisson. The caisson is a huge cylinder with a bottom sdge that can cut into the water bed. When compressed air is pumped into it, the water is forced out. Caissons must be used with extreme care. For one thing, workers can only stay in the compression chamber for short periods of time. For another, if they come up to normal atmospheric pressure too rapidly, they are subject to the bends,or caisson disease as it is also called, which is a crippling or even fatal condition caused by excess niteogen in he blood. When the Eads Bridge across the Mississippi River at St.Louis was under construction between 1867and 1874,at a time when the danger of working in compressed air was not fully understood, fourteen deaths were caused by the bends.When extra strength is necessary in the piers, they are sometimes keyd into the bedock-that is, that are extended down into the bedrock. This method was used to build the piers for he Golden Gate Bridge in San Francisco, which is subject to strong tides and high winds,and is located in an earthquakezone. The drilling was carried out under water by deep-sea divers.Where bedrock cannot be reached, piles are driven into the water bed. T ody, the piles in construction are usually made of prestressed concrete beams. One ingenious technique,used for the T appan Zee Bridge across the Hudson River in New York, is to rest a hollow concrete box on top of a layer of piles. Whenthe box is pumped dry, it becomgs buoyant engough to support a large propotion of the weight of the bright of the bridge.Each type of bridge, indeed each individual bridge, presents special construction problem. With some truss bridge,the span is floated into possition after the piers have been erected and then raised into place by means of jacks or crames. Arch bridges can de constructed over a falsework, or temporary scaffolding. This method is usually employed with reinforced concrete arch bridges. With steel arches,however,a technique has been developed where by the finished sections are held in place by wires that supply a cantilever support. Cranes move along the tension in the cables increases.With suspension bridges, the foundations and the towers are built first. The foundation and the towers are built first. Then a cable is run form the anchorage concrete block in which the cable is fastened-up to the tower and across to the opposite tower and anchorage. A wheel that unwinds wire from a reel runs this cable. When the reel reaches the other side, anther wire is placed on it, and the wheel returns to its original position. When all the wires have been put in place ,anoth machine moves along the cable to compact and to bind them. Constryction begins on the deck when the cables are in place, with work progressing toward the middle from each end of the structure.Bridge design is probably the hardest brain work in civil engineering. Bridge designers have a long period of training, only the best of them succeed, and only a small fraction of the bridge they design are built. The time from the first proposal for a bridge to the provision of the money for its construction is usually long and many bridge have been built only after the beath of their designer. A fine bridge engineer, shirley smith, who was the contactor′agent for the Forth Road Bridge, has written very well about his love of bridge work in his book Great Bridges of the World.For those who work on the site, bridge is hard in other way. They cannot settle down in one house because they rarely work in one place for longer than a year or two, and the working site is usually unprotected and something dangerous.The builders of the Forth Road Bridge〈1965〉were particularly prould of the fact no lives were lost in spite of the heavy winds,the snow and the cold rain. Word on bridge foundations,usually in cofferdams and something in caissons under comperssed air has often caused loss of life.One of the most intersting recent birdges, which will remain for many years the world′ largest, if not its longest, is the Verrazano-Narrows Bridge, New York, compieted in 1964, a suspension bridge of 4,260ft main span, having six traffic lanes on each of its two deck. It is also probably one of the world′s highest bridges since its m ain span has to be 216ft above the shipping channel whiah is 2,00ft wide. Its capacity is estimated at 13 million vehicles in the first year, rising eventually to 48 million vehicles, and it cost some 324million dollars to build.The main parts of a suspension bridge are the deck, the two cables and many suspenders transferring the deck load to the cables, the towers over which the cables passand the anchorages on the two banks. The Narrows Bridge has four cables, two on each side. In a self-anchored suspension bridge thereare no anchorages, the two ends of the cables being tied to the shore ends of the bridge structure.Most road bridges have pies rising outof the valley, on which the girders rest, with a deck carried by the girders and a wearing surface on top of the deck. Railway bridges sometimes differ in the wearing surface being unnecessary and therefore left out completely, so that wearing surface being unnecessary and therefore left out completely, so that there are then gaps between the bridge beams.The clear span of a bridge is athe gap from the near edge of one pier to the near edge of the next. The effective span is the spacing between the centres of bridge piers. The span, which is large than the clear span, is used in the design of the girders. At each shore, every bridge has foundation called abutments,an abutment being a foundation which carries horizontal load.An interesting and economical bridge which has become popular in Europe in the last twenty years and was first used in Germany is called the cable cantilever or bridle chord bridge, though other names have been used for it. It is always of steel, and like the self-anchored suspension bridge it has two towers over which its cables pass. A bridge of this type was completed in 1965 over the river Usk at Newport,Monmouthshire,England〈Fig.26〉.The 150-metre main span is supported at twelve point by ropes from the two towers, making it into a 13-span continuous beam with twelve elastic internal supports and two rigid end supports. The complete esign was analysed by a strain energy method and the analysis was checked by a plastic model. The cables pass over towers 52m high and are anchored on the shore side to the concrete approach spans. The towers are hollow concrete boxsection and the concrete in them is never under under tension, the maximum compressive stress being 100kg/〈cm*cm〉.The test cubes taken from the concrete of the towers were specified to have a minimum strength of 400/〈cm*cm〉. At high tide, the least height under the dridge is 13m, and the tidal range is 9.2m at the bridge. The main girder on this bridge are steel welded section and were mard by barge to the site and joined thre into a continuous structure. Because of the support from the cables, the main girder depth is remarkably small, only 1.3.Highway bridges and railway bridges are designed for dead load, live load, impact, temperature stresses, wind load, traction and braking forces, and on curves also for centrifugal force. Railway bridges have to be designed also for nosing, a sideways force from the flanges of the engine wheels on to the rails at curves.Americans generally use either the short ton or the kip in their stress calculations, the short ton being 2,000 pounds, considerably less than the metric ton, and the kip or kilo-pound being 1,000 pound. The kip is very widely used in the United States and many British engineers also find it convenient for calculations. The long ton of 2,240 pounds used in Britain is about 17 kg larger than the metric ton.Proplem involving moving loads are conveniently solved by influence line, which are used in all countries of the world. Shear diagrams and bending moment diagrams or envelopes show the effect of shear or bending moment at all points along the bridge span, but an infulence line shows the effect, at one point, of a load placed at any point on the structure. The base length of an influence line is the same as that of a bending moment diagram so it is important to state on the diagram what it it,otherwise misunderstandings may occur.桥梁是最重要的，往往是最壮观的所有民用工程。