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III. Now read the text carefully and check your answers.

METAL BRIDGES

Metal bridges may be constructed of cast iron, iron, steel alluminium alloys. The first cast iron bridge spanned the Severn in Great Britain in 1779. The length of the arched span was 32 meters.

In the 19-th century bridges were erected using wrought iron. At present metal bridges are built only of steel. That is why they can be called by another term – the steel bridges.

Steel is next to nothing as building material because of its rigidity and durability. Steel is easy to treat and recondition as compared to other building materials. Low alloyed steel possesses the most perfect qualities because it contains rare elements – nickel, chromium, manganese, etc. The incorrodible steel brands are widely used at present. Recently these sorts of steel were only used in space industry. Such steel brands as «CorTen» in the USA and 10ХДDП in Russia form an oxide film on their surface making painting unnecessary.

Metal superstructures are the best for medium and long spans between 50 and 1500 meters. Metal structures are rather various including continuous and discontinuous beams, frames, arches, beam trusses, cantilever-beam structures, combined systems, etc. The length of these structures ranges within 150 m for discontinuous beams and within 500 m for cantilever-beam spans.

Frame spans have 100 m length limits. Beam trusses are used for the spans of 200 m long and arches are built for 300 m span length. Metal bridges can offer the following advantages:

1.High material strength.

2.Great possible span length.

3.Durability.

4.Commercially produced elements.

5.Convenient in erection, maintenance, overhaul and, reconstruction.

Due attention should be paid to the disadvantages of metal bridges:

1.Substantial consumption of hard-to-get steel.

2.Susceptibility to corrosion. (Metal bridges are lighter than those of any other

material for a given task, but of course they have to be protected from corrosion and the weather, by painting or some other treatment. The painting problem can be quite substantial, as in the case of the Forth Bridge where, by the time the painters have reached the farther end it is time to start painting all over again!)

3.High sensibility to the dynamic load.

4.Great maintenance cost (painting).

Metal elements may be jointed by the following technique: a) welding; b) by rivets; c) by bolts.

Welding is the most thrifting method for saving materials but not so reliable

as rivets and bolts. At present rivets are not widely used because their driving involves a very complicated technique. As for the high strength bolts, they are widely employed nowadays.

IV. Match the English and the Russian equivalents.

V. Find 9 pairs of antonyms:

rigid; erect; thrift; safe; demolish; soft; common; waste; reduce; plain; increase; dangerous; rare; perfect; weak; poor; strong; complicated

VI. Fill in the adjectives from the text. Think of synonyms for each adjective. Make up a short story using these synonyms.

VII. Fill in the correct word from the list below. What part of speech do they refer to?

fastening, heating, pressing, welding, according

1.A rivet is a metal pin or bolt for … two pieces of metal together, one end being hammered or pressed flat to prevent slipping.

2.Rivet mounting is rather labor consuming and dangerous because it involves rivet … up to the red metal temperature.

3.To weld means to join pieces of metal together by hammering or … them when the metal is soften by heat.

4.Element welding of steel spans can be carried out at works by the special automatic … or in-situ by the manual welding.

5.Steel trusses built … to the standard design are widely used for spans from 33 to 132 m long.

VIII. Find in the text the ideas to explain:

- why metal bridges can be also called steel bridges.

-why metal bridges are built only of steel although steel is next to nothing as building material.

-why rivets are not widely used nowadays.

IX. Answer the questions.

1.What is the best span length for metal bridges?

2.What are the advantages of metal spans?

3.What is the most reliable method for jointing the metal elements?

4.What is the length of trusses built according to the standard design?

5.What is oxide film is formed on?

X. Copy the table and complete it comparing timber, stone and metal bridges.

XI. You are given a task to design a bridge over the Irtysh River. What bridge it will be (timber, masonry or metal)? Explain your choice.

Home Exercises

I.Memorize the words from Ex. I page 45.

II. What is the Russian for:

at present, is next to nothing, as compared to, such as, to pay due attention, as for

Use these word combinations in the sentences of your own.

III. Correct the statements. The first example is made for you.

1. The first cast iron bridge is being built now in Great Britain.

–No, it is not. The first cast iron bridge was built in Great Britain in 1779.

2. In the 20-th century bridges were erected using wrought iron.

–No, ……………………………………………………………………………

designs for bridges in consultation with Ministry. The study examined single and multi-span bridges, with spans ranging from 15 to 29 m, and the steel designs were based on the use of high tensile weathering steel (which does not require painting) to cut costs and eliminate maintenance. An alternative study was based on the use of nonweathering high tensile steel with a high-grade protection treatment system.

The Cement and Concrete Association has questioned the validity of the report and has said that the study attempts to draw comparisons between designs that are not comparable and that the steel designs prepared by the consultants do not comply with the Department’s own design criteria for bridges of this type. The Association also argues that the precast concrete beams examined in the study are less expensive than the compliers of the report assumed, whereas, since the time of the report, steel costs have risen some 10%. Another objection, says the Association, is that the steel designs are based on the use of weathering steel, which are not generally available.

V. Give Russian equivalents to the following word combinations: independent firm of consultants, single and multi-span bridges, high-grade protection treatment system, precast concrete beams.

VI. Find the definition of the following prepositions. Use the prepositions in the sentences of your own.

VII. Answer the questions to the text.

1.What is the way of cutting the cost of bridges on major roads?

2.What bridges were studied?

3.For what purpose was non-weathering high tensile steel with a high-grade protective treatment system used?

4.What has the Cement and Concrete Association questioned?

5.What are arguments of this Association?

VIII. Fill in the gaps without looking back at the text.

1.It is possible to save ... of many bridge decks by using steel for the main members.

2.The British Steel Corporation and the British Constructional Steelwork Association studied bridges with spans ranging....

3.The Cement and Concrete Association reported that weathering steel is not...

Find the words you have read in the text below and translate the word combinations having these words. Use the words in the sentences of your own.

II. Work in pairs. Think of 2 or 3 questions using the words from Ex. I. Answer the questions of your partner.

III. Do you know the difference between the suspension and cable-stayed structures? Read the text and find the answer to this question.

SUSPENSION AND CABLE-STAYED BRIDGES

Suspension and cable-stayed bridges are often confused. The matter is that they have very much in common: stiffening girders or trusses, anchor supports and hangers. And besides their main carrying element is a flexible stayed cable.

The difference between these two bridge types is determined by the two following indications:

1.A suspension bridge has a curvilinear steel rope called a cable or a chain.

2.A cable-stayed bridge steel ropes are rectilinear. They are called cable stays. The next indication is that suspension bridges usually have a continuous

steel rope from the first tower top to the second one.

The Hamber Bridge in Great Britain is claimed as world record for a suspension structure because of its 1410 m span length. The cable-stayed bridge across the Freiser River in Canada has a 465 m span, which is the longest one for this sort of structures all over the world.

The basic advantages of the suspension and cable-stayed bridges are as follows:

1. They provide the possibility to construct very long spans from 500 to 1500

2.When suspension bridges are built without anchor supports the thrust is transferred to the stiffening girder. In case the suspension bridge has the anchor supports they transfer the thrust to the … .

3.One per meter run weight of a stiffening girder for suspension and cable-stayed bridges is considerably … in comparison with other bridge systems.

4.Erecting of towers is the most … working process for suspension and cablestayed bridge construction.

VII. Answer the following questions:

1.What are the basic advantages of suspension bridges?

2.What is the principle disadvantage of suspension and cable-stayed bridges?

3.What is the difference between cable-stayed and suspension bridges?

4.Does the stiffening girder work in tension?

5.Why is it necessary to apply force regulation for the cable-stayed bridges?

6.Why is a suspension span sensitive to the dynamic load?

VIII. Read the following information and look at fig. 5, 6. Guess which story describes the construction of a suspension bridge and which story describes the construction of a cable-stayed bridge. Match the stories with the pictures.

1.In the case of … bridges, foundations are made by sinking caissons into the riverbed and filling them with concrete. Towers are built atop the caissons. Next, the anchorages are built on both ends, usually of reinforced concrete with embedded steel eyebars to which the cables will be fastened. When the cables are complete, suspenders are hung, and finally the deck is erected – usually by floating deck sections out on ships, hoisting them with cranes, and securing them to the suspenders.

2.In the case of … bridges, foundations are made by sinking caissons into the riverbed and filling them with concrete. Then towers and anchorages are erected. After the tower is built, one cable and a section of the deck are constructed in each direction. Each section of the deck is prestressed before continuing. The process is repeated until the deck sections meet in the middle, where they are connected. The ends are anchored at the abutments.