Архитектура Аудит Военная наука Иностранные языки Медицина Металлургия Метрология
Образование Политология Производство Психология Стандартизация Технологии
X. Make a short summary of the text.
Text 3: The ancient world
1. What civilizations can you recollect as the ancient world?
2. What materials were the first to be used in bridge construction?
3. What were the first types or kinds of bridges?
Read the text bellow to grasp the main information.
The first bridges were simply supported by beams, such as flat stones or tree trunks laid across a stream.
For valleys and other wider channels—especially in East Asia and South America, where examples can still be found—ropes made of various grasses and vines tied together were hung in suspension for single-file crossing.
Materials were free and abundant, and there were few labour costs, since the work was done by slaves, soldiers, or natives who used the bridges in daily life.
Some of the earliest known bridges are called clapper bridges (from Latin claperius, "pile of stones"). These bridges were built with long, thin slabs of stone to make a beam-type deck and with large rocks or blocklike piles of stones for piers. Postbridge in Devon, Eng., an early medieval clapper bridge, is an oft-visited example of this old type, which was common in much of the world, especially China.
Roman arch bridges.
The Romans began organized bridge building to help their military campaigns. Engineers and skilled workmen formed guilds that were dispatched throughout the empire, and these guilds spread and exchanged building ideas and principles. The Romans also discovered a natural cement, called pozzolana, which they used for piers in rivers. Roman bridges are famous for using the circular arch form, which allowed for spans much longer than stone beams and for bridges of more permanence than wood. Where several arches were necessary for longer bridges, the building of strong piers was critical. This was a problem when the piers could not be built on rock, as in a wide river with a soft bed. To solve this dilemma, the Romans developed the cofferdam, a temporary enclosure made from wooden piles driven into the riverbed to make a sheath, which was often sealed with clay. Concrete was then poured into the water within the ring of piles. Although most surviving Roman bridges were built on rock, the Sant'Angelo Bridge in Rome stands on cofferdam foundations built in the Tiber River more than 1,800 years ago.
Asian cantilever and arch bridges.
In Asia, wooden cantilever bridges were popular. The basic design used piles driven into the riverbed and old boats filled with stones sunk between them to make cofferdam-like foundations. When the highest of the stone-filled boats reached above the low-water level, layers of logs were crisscrossed in such a way that, as they rose in height, they jutted farther out toward the adjacent piers. At the top, the Y-shaped, cantilevering piers were joined by long tree trunks. By crisscrossing the logs, the builders allowed water to pass through the piers, offering less resistance to floods than with a solid design. In this respect, these designs presaged some of the advantages of the early iron bridges.
In parts of China many bridges had to stand in the spongy silt of river valleys. As these bridges were subject to an unpredictable assortment of tension and compression, the Chinese created a flexible masonry-arch bridge. Using thin, curved slabs of stone, the bridges yielded to considerable deformation before failure.
I. Decide whether the following statements are true or false according to the text:
1. The first bridges were upheld by arches, such as flat stones or tree trunks laid across a stream.
2. Materials to construct first bridges were available and ample.
3. Clapper bridges were built with long slabs of stone and with rocks or blocklike piles of stones.
4. Bridge construction work in the Roman Empire was done by slaves, soldiers, or natives, so labour costs were few.
5. Circular arch form used by the Romans served to make spans much longer than stone beams.
6. The Romans developed the cofferdam allowing piers to be built on rocks.
7. Crisscrossing of the logs helped to reach adjacent piers.
8. Old boats filled with stones were used as cofferdam-like foundations.
II. Answer the following questions:
1. What are the main types of bridges in the ancient world?
2. What was the principle of a simple beam bridge?
3. What is a clapper bridge?
4. The Romans developed bridge construction. In what way?
5. What was the purpose of the cofferdam? The construction of what type of bridges requires the cofferdam?
6. What is the basic design of a cantilever bridge in the Ancient Asia?
III. Define the type of the bridge:
a) beam a) beam a) beam
b) cantilever b) cantilever b) cantilever
c) arch c) arch c) arch
IV. Match the meanings of these terms with their definition:
V.Fill in the correct prepositions:
for, than, with, of, into, across, of, in, by, on, through, in, into
To be supported … beams, to be poured … the water, to be laid … a stream, to be constructed … long slabs … stone, to rise … height, to be hung … suspension … single-file crossing, to be … more permanence … wood, to pass … the piers, to be built … rock, to be driven … the riverbed
VI. Read the text and say what following words are key ones in each part consequently:
1. Beam, trunk, stones, channels, ropes, suspension, clapper bridges, few labour costs, single-file crossing
2. Military campaigns, pozzolana, circular arch form, strong piers, bridges of more permanence, the cofferdam, engineers and skilled workmen, guilds
3. Wooden cantilever bridges, old boats filled with stones, iron bridges, layers of logs, less resistance to floods, masonry-arch bridge, failure
Последнее изменение этой страницы: 2016-03-16; Просмотров: 1122; Нарушение авторского права страницы