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I. Decide whether the following statements are true or false according to the text.
1. Truss bridges are supported by frameworks called girders.
2. The parts of the trusses are arranged in the form of rectangles.
3. A main span may attend more than 300 metres.
4. Most truss bridges have two sets of trusses.
5. The roadway of a through truss bridge runs on the top of the trusses.
6. Each truss extends between two abutments in a simple span truss bridge.
7. Truss bridges require less construction material than the girder type.
8. Early arch bridges consisted of stone blocks in the form of an arch.
9. The road of arch bridges can lie both on the top of the arch and below the curve on the arch.
10. The roadway is supported by the abutments.
II. Answer the following questions:
1. What is a truss?
2. Where are truss bridges built?
3. How are the parts of the trusses arranged?
4. What may the length of a main span be?
5. What does each truss consist of?
6. What is the difference between a deck truss bridge and a through truss bridge?
7. Why do engineers prefer to build truss bridges?
8. Why are arch bridges called so?
9. What were early arch bridges made of?
10. How must arch bridges be designed?
11. Where can the roadway of arch bridges lie?
12. How is the roadway supported?
13. What is done to prevent the ends from spreading out?
14. What weight do the abutments support?
III Match the meanings of these terms with their definition:
truss bridge, arch bridge framework, girder bridge
1. A support or skeleton; stiff part that gives shape to a thing
2. A bridge supported wholly or chiefly by trusses.
3. A bridge made of large iron or steel beams for bearing load.
4. A bridge made of curved structures as a support.
IV. Match the word with its translation. Find the corresponding pairs of words:
1. trussa) надсводная стойка
2. deck truss bridge b) мост со сплошными или сквозными фермами
3. through truss bridge c) мост с разрезными пролетами
4. simple span truss bridge d) закругление
5. continuous truss bridge e) арка
6. girder bridge f) проезжая часть
7. arch g) мост с решетчатыми фермами с ездой поверху
8. span h) мост со сквозными фермами
9. roadway i) береговой устой
10. spandrel columns j) скрепленный арочный мост
11. tied arch bridge k) пролет
12. curve l) балочный мост
13. abutment m) ферма
V. Read the passage and answer the question:
What functions have had bridges?
In addition to providing a passage for traffic, bridges have often had other functions, including service as fortifications and as business districts. The Old London Bridge, for example, which stood from the 13th to the 19th century, was a crowded thoroughfare, full of shops and houses. The original functions of bridges have also been modified for new uses.
VI. Fill in the missing words from the list:
beams, light, weight, stability, trusses, steel, frameworks, triangular, inexpensive, outward, concrete, gap, abutments
1. Truss bridges utilize strong, rigid … that support these bridges over a span. …are created by fastening … together in a … configuration. The truss framework distributes the … of the bridge so that each beam shares a portion of load. Truss bridges can carry heavy loads and are relatively …. They are also … to build.
2. Arch bridges are characterized by their … In an arch, the force of the load is carried … from the top to the ends of the arch, where … keep the arch ends from spreading apart … and … arches are particularly well suited for bridging ravines or chasms with steep, solid walls.
VII. Make the precis of the text
Text 4. CANTILEVER BRIDGES
Cantilever bridgesconsist of two independent beams called cantilevers thatextend from opposite banks of a waterway. The two cantilevers are joined together above the middle of the waterway by a beam, girder, or truss. Cantilever bridges may have spans as long as about 1,800 feet (549 meters).
Each cantilever has two sections, an anchor arm and a cantilever arm. The anchor arm extends between an abutment and a pier. One end of the cantilever arm is supported by the pier, and the other end extends freely over the waterway. The free ends of the two cantilevers are joined together by a suspended span.
Most cantilever bridges have two anchor spans and one center span. Each anchor span consists of an anchor arm. The suspended span and the two cantilever arms make up the center span.
Many cantilever bridges have truss frameworks. Most bridges of the cantilever type are made of steel or prestressed concrete.
Suspension bridgesare perhaps the most impressive type of bridge because of their long main span and especially attractive appearance. These bridges have a roadway that hangs from steel cables that are supported by two high towers. Suspension bridges are used to span great distances. Most suspension bridges have a main span more than 1,000 feet (300 meters) long. Some have a main span longer than 4,000 feet (1,200 meters). Suspension bridges also are used to cross deep water or steep canyons, and in other places where the construction of piers is especially difficult and expensive. These bridges require only two piers, each of which supports a tower.
The main span of a suspension bridge stretches between the two towers. Each of two side spans extends between a tower and an anchorage. Most anchorages are huge blocks of concrete set at the ends of the bridge.
The cables that are supported by the towers are called the main cables. A suspension bridge has at least two main cables. Each of these cables extends from one end of the bridge to the other and is secured at each end by an anchorage. The main cables are connected to the top end of vertical suspender cables. The bottom end of each suspender cable attaches to the roadway of the bridge.
A suspension bridge may sway in a strong wind. To minimize such movement, most suspension bridges have a thick structure that supports the roadway. This type of structure helps stiffen the bridge and is called a stiffening girder or stiffening truss.
I. Decide whether the following statements are true or false according to the text:
1. The two cantilevers are joined together in the form of an arch.
2 The span length of cantilever bridges is 1000 feet.
3. Each cantilever has an anchor arm, a cantilever arm and a suspended span.
4. Most cantilever bridges have one center span and two anchor spans.
5. Two anchor arms and suspended span make up the centre span.
6. Suspension bridges are the most impressive type of bridges because of their huge arches.
7. These bridges have a roadway below the curve of the arch.
8. Suspension bridges require only two piers each of which supports as tower.
9. A suspension bridge has at least four main cables.
II. Answer the questions:
1. What do cantilever bridges consist of?
2. How are the two cantilevers joined together?
3. What are the two sections of each cantilever?
4. How are the free ends joined together?
5. What does a center span consist of?
6. What are cantilever bridges made of?
7. Why are suspension bridges considered to be the most impressive type of bridges?
8. What is the length of the main span?
9. Where are suspension bridges built?
10. How many cables does a suspension bridge have?
III. Match the meanings of these terms with their definition:
suspension bridge, anchor arm, cable, cantilever bridge, suspender, anchorage
1. A bridge made of two cantilevers whose projecting ends meet but do not support each other.
2. A bridge that has its roadway hung on cables and chains between towers.
3. A part of a cantilever bridge between the shore and the pier.
4. A place to anchore.
5. A strong thick rope, now usually made of wires twisted together.
6. A thing that suspends
A refinement of the beam, called a cantilever, is used to construct bridges with even longer spans. In simple cantilever bridges, such as those that are found in many parts of Asia, the structure rests on crisscrossed log foundations with narrow bases that flare outward as they rise to support the roadway. A modern cantilever bridge may use only two intermediate piers set a short distance from either bank. The main support members of a suspension bridge are parallel cables composed of thousands of individual strands of wire. These run, supported by each tower and curving at the middle, the entire length of the bridge and are anchored on either end.
V Insert the words from the list:
cables, roadway, diagonal, railroad, tower,
cantilevered, load, beam-bridge, outward,
self-supporting, suspended span, scaffolding, rigidity, trains
1. Cantilever bridges are a more complex version of a design. In a cantilever design, a … is built on each side of the obstacle to be crossed and the bridge is built … or … from each tower. The towers support the entire … of the cantilevered arms. The arms are spaced so that a small: can be inserted between them. Cantilever bridges are … during construction. They are used in situations in which the use of … or other temporary supports would be difficult.
2. Suspension bridges consist of two large or main … that are hung from towers. The … is suspended from smaller vertical cables that hang down from the main cables. In some cases … cables run from the towers to the roadway and add … to the structure. Suspension design is rarely used for … bridges, because … are heavier and can travel faster than highway traffic.
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