Архитектура Аудит Военная наука Иностранные языки Медицина Металлургия Метрология
Образование Политология Производство Психология Стандартизация Технологии
Text 2: The History of Bridge Building (General Information)
1. How long have people use such a structure as bridge?
2. What materials served as first bridges?
Logs or vines that extended across streams probably served as the first bridges. From this at a later stage, a bridge on a very simple bracket or cantilever principle was evolved. Timber beams were embedded into the banks on each side of the river with their ends extending over the water. These made simple supports for a central beam reaching across from one bracket to the other. Bridges of this type are still used in Japan, and in India. A simple bridge on the suspension principle was made by early man by means of ropes, and is still used in countries such as Tibet. Two parallel ropes suspended from rocks or trees on each bank of the river, with a platform of woven mats laid across them made a secure crossing. Further ropes as handrails were added. When the Spaniards reached South America, they found that the Incas of Peru used suspension bridges made of six strong cables, four of which supported a platform and two served as rails.
The first bridge known to historians was an arch bridge built in Babylon about 2200 B.C. The ancient Chinese, Egyptians, Greeks, and Romans also built arch bridges, using bricks and stone as building materials.
During the Middle Ages, moveable bridges called drawbridges were built across the moats of many castles in Europe. Truss bridges were developed in the 1500’s. Most bridges were made of stone or wood until the late 1700's, when cast iron and wrought iron were first used for bridges. Many suspension bridges that hung from wrought iron chains were built in the early 1800's. Between 1830 and 1880, as railroad building expanded throughout the world, bridge design and construction were aimed to carry these heavy vehicles over new obstacles.
Designers experimented with a wide variety of bridge types and had to meet the demand for greater heights, spans, and strength. Locomotives were heavier and moved faster than anything requiring stronger bridges. The basic beam bridge was strengthened by adding support piers underneath and by reinforcing the structure with elaborate scaffolding called a truss. During the period of railroad expansion iron trusses replaced stone arches as the preferred design large bridges.
The first plate girder bridge was completed in 1847, and the modern cantilever bridge was introduced about 1870. In the late 1800s, steel became the chief material used in bridge construction.
In 1855 British inventor Sir Henry Bessemer developed a practical process for converting cast iron into steel. This process increased the availability of steel and lowered production costs considerably. The strength and lightness of steel revolutionized bridge building. In the late 19th century and the first half of the 20th century, many large-scale steel suspension bridges were constructed over major waterways in the late 19th century, engineers began to experiment with concrete reinforced with steel bars for added strength. More recently, reinforced concrete has been combined with steel girders, which are solid beams that extend across a span. When the Interstate Highway System in the United States and similar road systems in other countries were constructed in the mid- to late 20th century, the steel-and-concrete girder bridge was one of the most commonly used bridge designs. The last three decades of the 20th century saw a period of large-scale bridge building in Europe and Asia. Current research focuses on using computers, instrumentation, automation, and new materials to improve bridge design, construction, and maintenance.
I. What can it be?
Cnosurtcniot, ceniveratl, beidgr, grried, tsrsu, peri, snespsionu
II. Decide whether the following statements are true or false according to the text:
1. Logs or vines across streams served as the first bridges.
2. A bridge on the suspension principle was made by people in the Middle Ages by means of handrails.
3. The Incas of Peru used beam bridges made of six strong cables.
3. An arch bridge is known to be the first bridge.
4. Another name for a drawbridge is a cantilever bridge.
5. Designers of the 19th century had to meet the demand for greater heights, spans, and strength.
6. Railroads expansion made iron trusses be replaced by stone arches.
7. Since late 1800s reinforced concrete has been chiefly used in bridge construction.
8. A steel-and-concrete girder bridge was one of the most commonly used bridge designs in the 20th century.
III. Answer the following questions:
1. What are the earliest types of bridges?
2. What periods in bridge construction can you distinguish?
3. What is the principle of a suspension bridge?
4. How can you explain the fact that drawbridges were mainly built in the Middle Ages?
5. What was the reason of adding additional support to a basic beam bridge in the 19th century?
6. What was Sir Henry Bessemer famous for? In what way did his invention develop bridge construction?
7. When did large-scale bridge building start? What are the reasons?
8. What does current research focus on?
IV. Match the meanings of these terms with their definition:
1. unhewn piece of a felled tree; any large rough piece of wood
2. a structure providing a way across a river, road, railway, etc.
3. iron or steel beam or compound structure for bridge-building etc.
4. hinged retractable bridge, esp. over a moat.
5. bridge with a roadway suspended from cables supported by towers
6. strong malleable alloy of iron and carbon
7. a support of an arch or of the span of a bridge; pillar
8. thing that obstructs progress, stands in the way
V. Match the period with the description:
VI. Can you decipher the message?
L..s that extended across streams probably served as the first b…..s. That was a c……..r bridge. A simple bridge on the s……..n principle was made by early man by m…s of ropes. A platform of w…n mats was laid across ropes to make a secure c……g. The first bridge k…n to historians was an a..h b….e built in Babylon about … . Romans used b….s and s…e as building materials.
During the M….e Ages, m……e bridges called d………s were built. In the 1500’s t…s bridges were d…….d.
During the period of railroad e…….n iron trusses r……d stone a….s. In the late 1800s, s…l became the chief m……l used in bridge c……….n. This s….g and l…t material revolutionized bridge b……g.
In the 20th c…..y the steel-and-c……e g….r bridge was one of the most commonly u..d bridge d…..s. New materials are being looked for to i…..e bridge design, construction, and m………e.
VII. Make the word combinations using the derivatives from the words in brackets:
(strong) of the material, bridge (construct), (suspend) bridges, (available) of steel, to be (embed) into the banks, (addition) support, ropes (suspend) from rocks, elaborate (scaffold), period of railroad (expand), to cost (consider), one of the most (common) used, concrete (reinforce) with steel bars.
VIII. Find the synonyms to the words in italics:
Wood beams were set into the banks on each side of the river. Moveable bridges called drawbridges were constructed across the ditches of many castles in Europe. Truss bridges were made in the 1500’s. The basic girder bridge was made stronger by adding support piers underneath and by intensifying the structure with elaborate falsework called a truss. As railway building expanded all over the world, bridge design and building were aimed to carry these heavy vehicles over new obstructions.
IX. Find key-words in the text to give general information about the history of bridge construction. How many of them do you need?
Последнее изменение этой страницы: 2016-03-16; Просмотров: 1649; Нарушение авторского права страницы