I. Decide whether the following statements are true or false according to the text:

1. An incomplete structure may be subjected to tension and compression

2. Serious research is done before any actual construction is done.

3. The construction of bridges is always greeted by the public.

4. The collapse of several girder bridges in the 1960’s helped to understand the stresses better.

5. The variation in stresses during construction demands jacking.

6. Excavation for foundation is always taken through unsuitable ground before solid rock is reached.

7. The pillars of the towers of suspension bridges are stabilized by cables which are removed after the completion.

8. Arches are usually supported by towers.

9. ‘Keystone’ is an important part of a finished arch.

II. Answer the questions

1. What are the most ingenious parts of bridge building?

2. Why is the construction work a grave hindrance to normal life in the area?

3. What is done before any construction work?

4. How can computer simulations supplement the tests?

5. How can the stresses of the structure differ?

6. When must jacking be provided?

7. What are the difficulties in excavation for foundations?

8. How can the pillars of the towers of big suspension bridges be stabilized?

9. What is a keystone?

LANGUAGE FOCUS

III. Match the words with their synonyms.

1. complicated a) accessible

2. ingenious b )suggestion

3. available c) destruction

4. investigation d) complex

5. proposal e) inventive

6. collapse f) research

7. feat g) connect

8. join h) exploit

IV. Match the words with their opposites

1. top a) mild

2. solid b)above

3. severe c) proper

4. below d) to forget

5. unsuitable e) to disappear

6. temporary f) bottom

7. to remind g) constant

8. to arise h) soft

V. Insert the prepositions.

To subject … sth, … the form of sth, in conjunction … sth, in case … sth, a great variety … sth, an opposition … sth, to differ … sth, a set … sth, to prevent … sth, the origin … sth, the value … sth, to deal … sth.

VI. Insert the words from the list

spans, cantilevers, jack, rams, completion

1. The four legs of the Tour Eiffel were provided with … which were adjusted from time to time as the structure grew. Even after … a concrete structure may be subject to creep and the ground may settle.

2. Above ground, until … are joined wind, can be a great hazard.

3. Before the Pont de Normandie was completed? There was serious discussion about the use of active stabilizers to keep the long thin … in place.

4. Large weight would have been moved by … .

VII. Make the precis of the text

Text 3: CAISSON

Caisson in building, is a watertight chamber used in the construction of building foundations, bridges, tunnels, and other structures. Caissons provide an area in which construction crews can safely work underground or underwater. Caissons also may be filled with concrete and become part of the finished structure.

Most caissons have the shape of a cylinder or a box. The walls may be made of steel, concrete, or timber. All caissons are open at the bottom, where digging takes place. But they may be open or closed on top. The two main types of caissons are open and pneumatic. An open caisson has an open top and bottom. The bottom edges, called cutting edges, are constructed so they can cut into the ground. The caisson sinks deeper into the ground as earth is removed beneath it.

A pneumatic caisson is closed at the top. It uses compressed air to keep water out of the working chamber and to provide oxygen for the workers. This type of caisson consists of two sections. The lower section, where the workers are, has cutting edges like those of open caissons. Concrete is poured into the upper section. Its weight helps drive the caisson deeper into the ground. Workers and materials move in and out of the lower section through a shaft. Pneumatic caissons are usually used to support bridge piers that are located in deep water.

Before workers enter a pneumatic caisson, they must step into a large airtight chamber called an air lock. The outer door is closed, and the air pressure in the air lock is gradually increased until it is the same as the pressure in the working chamber. When workers prepare to leave the caisson, they again pass through the air lock and the pressure is gradually reduced. If workers go through a change of pressure too quickly, they may develop bends, a painful condition also known as caisson disease. Bends can be fatal in some cases.

COMPREHENSION CHECK