2383

VII. Read the text again. Copy and complete the table.

VIII. Complete the following sentences by writing no more than three words for each answer:

1.Possible advantages of timber bridges are minimal construction cost, minimal weight of its elements for transportation and erection, ... , etc.

2.One of the disadvantages of timber bridges is …

3.The best timber species are …

4.Durability of a building depends on …

5.Most favorable rock for masonry bridges is …

6.While bridge building the Romans were good at …

IX. Give answers to the following questions.

1.What were the earliest building materials for bridges?

2.What is the most durable material for bridge building?

3.What building materials are used for stone bridges?

4.Why were the bridges the Romans built very solid and durable?

5.What bridges are difficult to mechanize?

6.What material is used for timber bridge foundation?

7.How can the service life of stone and timber bridges be prolonged?

Home Exercises

I. Memorize the words from Ex. I page 34.

II. Translate the first sentence and complete the second one in each pair. Use the Past Participle.

1.In masonry bridges only the arch structure may be used.

In timber bridges ___________ ___________.

2. Stone used for bridge construction must be durable.

Concrete ____________ must be __________.

3.The timber such as pine, fur-tree, larch, arid cedar is easily treated.

The timber species such as oak, hornbeam, and beech _________ _________.

4.Plywood structures are widely used abroad.

Log structures ___________ ____________.

III. Describe the following structures.

1.Timber bridge foundations.

2.Timber bridge supports.

3.The basic types of timber bridge spans.

Text 8 

I. Look at the following words for about 2 minutes and get ready to write them without looking back at the words. He who has no mistakes is the

A a substantial saving of steel; elimination of maintenance cost; greater rigidity.

B the variety of structural forms; difficulties of concrete laying in winter; hidden bugholes.

C hidden bugholes; a substantial saving of steel; elimination of maintenance cost.

D great dead weight; difficulties of concrete laying in winter; hidden bugholes.

REINFORCED CONCRETE BRIDGES

Concrete being an artificial stone possesses the same good qualities as natural stones. It works well in compression and bad in tension. That is why concrete has substituted natural stone in arch bridges because an arch works in compression.

At the beginning of the 19-th century concrete was reinforced by metal bars. The idea was to transfer the tension stress from the concrete to the reinforcement. This resulted in a new building material, which is known as reinforced concrete.

At present reinforced concrete bridges are widely spread because this building material is in line with short and medium spans (up to 40 – 60-m). It is also rather competitive with metal for long span structures.

The reinforced concrete spans are of a great variety because of their ability to work in compression and tension as well as flexure. It is used for producing simple beams, continuous beams, cantilever-beam systems, arches, frames and combined systems (arch + beam or arch + truss), etc.

The builders use monolithic reinforced concrete laid in situ, prefabricated reinforced concrete, which is made at the works beforehand and the bridge is assembled in-situ from the reinforced concrete segments. Prefabricated monolithic concrete is the combination of both mentioned types. To make the reinforced concrete highly strong and stiff it is prestressed by jacks and reinforcement of high strength wire.

Sometimes to reduce the structure weight they substitute the most usual coarse aggregate such as crushed rock, pebbles, and gravel by slag and bloating clay. This results in light concrete.

In comparison with other building materials the bridges made of reinforced concrete offer the following advantages: a substantial saving of steel, which is scarce to supply; elimination of maintenance cost as compared with metal bridges; greater rigidity as against metal bridges; long useful life (80 – 100 years); the variety of structural forms improving bridge appearance and architecture.

The disadvantages of the reinforced concrete bridges may be the following: great dead weight; great labor-consuming character of the bridge segments

producing; hidden bugholes may cause dangerous complications and they are difficult to be reconditioned; difficulties of concrete laying in winter.

IV. Make up word combinations as they are used in the text from the words given below. Find and translate sentences with the completed phrases.

metal laying

high-strength wire

bug bar

concrete concrete

structure holes

prestressed weight

V. Fill in the correct words from the list.

erected, reinforced, design, spans, longest, are

1.The longest spans among lattice trusses … 63m in Russia.

2.The first concrete arch bridge was … in France in 1875.

3.The first … concrete bridges were constructed in 1877.

4.The earliest Russian reinforced concrete beam bridge was built to professor Belelyubsky’s … in 1893.

5.The … spans among continuous beam systems are 105 m in Japan.

6.The longest … among arch bridges are 228 m in the Ukraine.

VI. Read the text once again and make two columns of advantages and disadvantages of reinforced concrete (do it in your notebook).

VII. Cross out 3 words/word combinations, which cannot be used in description of reinforced concrete. Prove your answer.

Wide-spread, light, used for producing arches, rigid, durable, flexible, withstand great compression, relatively cheap, waterproof.

VIII. Read the text and say if these statements are true, false or not given.

1.Concrete works well in flexure.

2.Reinforced concrete spans are the best for the lengths of 50 m.

3.Reinforced concrete is used for producing circular beams.

4.Light concrete can be made by substitution of slag and bloating clay for

crushed rock, pebbles, and gravel.

5. Bugholes in reinforced concrete bridges always cause dangerous complications.

IX. Discuss in groups the following questions:

1.Is there any difference between concrete and reinforce concrete?

2.What is the best length for the reinforced concrete spans and why?

3.What structural model is most preferable for the reinforced concrete bridges?

Home Exercises

I. Memorize the words from Ex. I page 38.

II. Open the brackets.

The first use of iron-reinforced concrete was by the French builder François Coignet in Paris in the 1850s. Coignet’s own all-concrete house in Paris, the roofs and floors (to reinforce) with small wrought iron I beams, still stands. But reinforced concrete development began with the French gardener Joseph Monier’s 1867 patent for large concrete flowerpots (to reinforce) with a cage of iron wires. The French builder François Hennebique applied Monier’s ideas to floors, (to use) iron rods to reinforce concrete beams and slabs; Hennebique was the first (to realize) that the rods had to be bent upward to take negative moment near supports. In 1892 he closed his construction business and became a consulting engineer, building many structures with concrete frames (to compose) of columns, beams, and slabs. In the United States Ernest Ransome paralleled Hennebique’s work, constructing factory buildings in concrete. Highrise structures in concrete followed the paradigm of the steel frame. Examples include the 16-story Ingalls Building in Cincinnati, which was 54 metres tall, and the 11-story Royal Liver Building, built in Liverpool by Hennebique’s English representative, Louis Mouchel. The latter structure was Europe's first skyscraper, its clock tower reaching a height of 95 metres. Attainment of height in concrete buildings progressed slowly (to owe) to the much lower strength and stiffness of concrete as (to compare) with steel.

III. Match the names of the people you have read about with their activities.

the durability of concrete bridge decks under assimilated harsh environmental conditions is significantly affected by stresses resulting from traffic, settlement, slab warping and volume changes in the concrete.

The experiments indicated that stress does play a slight part in freeze-thaw durability as regards surface scaling. Surfaces subjected to static tensile strength deteriorated at a slightly faster rate than did unstressed surfaces. On the other hand, surfaces subjected to static compression or biaxial stress deteriorated at a slower rate. Slabs subjected to cyclic loading scaled faster than their unstressed companions; however, scaling was never observed to occur in a stressed specimen without it also occurring in the unstressed companion.

The importance of obtaining adequate cover over reinforcing bars was also determined by the laboratory studies. The report spells out the various patterns of cracking experienced for different depths of concrete cover subjected to various loads simulating those assumed to result from corroded reinforcing steel. The University of Illinois research report does not conclusively solve the problem of concrete bridge deck scaling and spalling. It does, however, shed light on the effects of stress in accelerating distress. It offers additional evidence concerning air entrainment, thermal characteristics, and the failure mode of corroded reinforcing steel, as well as suggestions for what might be tried in design and construction to produce more durable concrete bridge decks.

IV. Give Russian equivalents to the following word combinations: reinforced concrete decks, the rate of failure and deterioration, concrete durability, freeze-thaw durability, volume changes, thermal characteristics, biaxial stress.

V. Find 7 pairs of synonyms:

major, spall, to study, to suggest, failure, specimen, important, deficiency, pattern, significant, to offer, primary, crack, to investigate.

VI. What is the English for the following word combinations?

сделать вклад (в), подписать контракт, суровые условия окружающей среды, предел прочности на разрыв, циклическая нагрузка, пролить свет (на), статическое сжатие

VII. Choose one of the words from the text and draw a picture about it. Show your picture to the group and let the group guess it.

VIII. Find the best continuation to the following ideas.