2383

one fewer it should be remembered that this was a war bridge, and the pointed cutways were carried right up to the roadway to act as vantage points in defending the bridge against boats gathered by the enemy underneath; a narrow arch was easier to defend than a broad one. Furthermore, if as a last resort an arch had to be demolished, the thrust of a wide arch on the unbalanced pier might lead to total collapse of the bridge. In those days bridges had to be built very slowly, and the total ruin of a bridge would have been a major disaster.

Normal civilized life having been resumed; bridges were built everywhere, some great, and some small. Before the arrival of iron and steel there was no alternative to masonry but wood, and although wooden beams were sometimes laid on stone piers, for permanence stone was used throughout. Even in modern times it is sometimes desirable, for reasons of good artistic taste, not to use steel where stone will serve, for a stone bridge blends better into the landscape. Switzerland is a good example. The Swiss are very clever at building stone bridges, especially in extremely awkward places. Coming down the St. Gotthard Pass, which has been an international highway for hundreds of years, there is a small stone bridge, the Devil’s Bridge, springing from one nearly vertical wall of the gorge to the other. With the passing of time, this bridge became too small and too awkward for the greatly increased traffic using the road, so just above the old one, and still it springs from one wall to the other. When the river is in spate with melting snow, the passage of this gorge is a fearsome business.

Switzerland, being very mountainous, has always presented difficulties for transport. By the accident that the railway was invented long before the motor car, the Swiss, as with other nations, built railways, and had to build them in the face of great natural obstacles. A railway locomotive cannot climb the steep gradients that a motor car can manage with comparative ease, because of the weight of the train and the lack of adhesion between the steel wheels and the steel rails. For very steep climbs the railway engineer has resort to the rack system, where a pinion on the engine engages with a rack laid between the running rails. This is not a good system for regular traffic, so the ordinary railways have to be laid out with fairly gentle gradients. In mountainous country this is not easy, and spiral curves and unusual bridges are required.

The Albula Railway is one of the most tortuous in Switzerland, because of the difficult country it passes through, and has some intricate tunnels and remarkable bridges. One of the most impressive is the bridge across the Landwasser gorge which is unusual in several ways. It is built of stone, and its great height of 223 feet above the bottom of the gorge is exceptional. It is built on a curve, whereas bridges are nearly always straight; this was necessary because the take-off and landing points did not face each other. The arches are straight, but are set at an angle to each other on the piers, and the rails are continuously curved, the curvature being quite sharp for a railway, with a radius of only 328 feet. Finally, the bridge ends abruptly against a vertical cliff through

which the railway passes into a tunnel.

The Albula Railway is part of the system called the Rhaetian Railway. The numerous bridges on this, as on the other Swiss railways are always masonry bridges, for the stone was at hand and the method of building stone bridges well understood. But when a new branch of the Rhaetian was constructed in 1914, another technique was adopted for the fine Langwies viaduct, which is of reinforced concrete.

The great advantage of concrete, or synthetic stone, is that it does not need masons to trim or join it, for the whole bridge is usually one vast solid mass or monolith. Concrete itself has high resistance to compression, but not to shear (sideways thrust) or tension; its strength to these forces is very greatly increased by moulding the liquid concrete round iron or steel reinforcing bars. The strength of this combination is much greater than the strengths of the two materials separately.

II. Do the puzzle.

1.a curved structure

2.a layer of matter, often deep under the earth, that has formed naturally

3.to protest from harm

4.pushing something violently

5.a strong material

6.involving the skillful and imaginative use of something

7.a line or surface that bends round

8.all the features of an area that can be seen when looking across it

9.a thing that blocks one’s way

10.to make something smooth by cutting away untidy parts

11.a narrow valley with steep sides usually with a river

12.a drawing

III. Cross out the unsuitable word. Give your arguments.

The Pont du Card: three-tiered; ancient; fortified; famous; arched; Roman

The bridge across the Landwasser gorge: stone; remarkable; Swiss; straight; high; having a cliff as a support

IV. Say if the sentences are true, false or not given according to the text.

1.The total height of the Pont du Card is less than 48.8 meters.

2.A good example of reinforced concrete construction is in the new Waterloo Bridge in London.

3.The “white coal” of Switzerland is waterpower.

4.The second tier of the Pont du Card is the geometrical centre.

5.The Pont Valentre in France was a war bridge.

6.Reinforced concrete bridges are found all over the world, but France seems to have a particular genius for this type of construction.

7.First reinforced concrete bridges appeared in Switzerland in 1914.

V. Make up questions from the words below and answer them.

1.what / is / of a / the structure / famous / aqueduct / French / Pont du Card of the?

2.who / the designer / the Pont du Card / was / of?

3.what / in Europe / is / the Dark Ages?

4.why / Devil’s Bridge / was / built / a new?

5.why / Landwasser gorge / the / most impressive / is / the bridge / across / the / one?

VII. Work in pairs. Draw schemes of two bridges from the text and let your partner describe them.

Home Exercises

I.Memorize the words from Ex. I page 93.

II. Paraphrase the following sentences using there is/there are.

1.You can see a three-tiered bridge in front of you.

2.The third tier has 35 arches.

3.The water channel is blocked up with thick deposits of lime.

4.France has many fortified bridges.

5.Before the arrival of iron and steel the only alternative to masonry was wood.

6.The Devil’s Bridge is situated in the St. Gotthard Pass.

7.Switzerland is very mountainous.

8.The Albula Railway has intricate tunnels and remarkable bridges.

III. You are a participant of an International Bridge Congress. Prepare your speech concerning some problems with bridges in your country (France or Switzerland). Then make a list of the problems, discuss them in your group and suggest possible solutions.

Text 25 

II. Read the text and answer the question “What modern and ancient bridges are there in China?”

Ancient and Modern Chinese Bridges

The art and science of bridge building has been long practiced in China. Ancient and modern bridges in this country have much in common. The Anji Bridge in Hebei Province was completed around the year 599, during the Sui Dynasty. It is the oldest surviving open spandrel stone arch bridge in the world. The width of the bridge deck is 10 m. The arch stones are about 1 m thick and 0.25 – 0.4 m wide so that the arched rings vary in width from 9.0 to 9.6 m. Thus, the external rings of the parallel longitudinal arches incline slightly inward, helping to resist collapse.

Between adjacent stones of each arch, two X-shaped iron anchors were placed, about a third of which survived until the mid-1950s, when major repair work was undertaken. It is worth noting that prior to this repair work the Anji Bridge was still open to truck traffic. However, some of the arched rings had collapsed several times during the long history of the bridge.

To consolidate the transverse junction between arched rings, 5 iron bars with capped heads were installed, as was an anchorage bar. A protective layer of facing stones was applied to the upper surface of the main arch. Additionally, 6 L-shaped stones, each 1.8 m long were fitted on each side of the bridge.

The abutments were built up using 5 layers of stone with total thickness of about 1.55 m and a width slightly greater than that of the arch. These stones rest directly on layers of natural coarse sand and are much lighter than normally found in ancient stone bridges.

Some original stones protecting the arches remain in use on side faces. Others in the middle field of the arch have been replaced by cover slabs made of reinforced concrete – with toothed connections. Cement mortar was also used, and additional layers of waterproof materials were applied.

After 1949, many open spandrel stone arch bridges were constructed in China, some with main span lengths of over 100 m, such as the Rainbow Bridge (1961) in Yunnan Province and the Jiuxigou Bridge (1971) in Sichuan Province, These were the longest open spandrel stone arch bridges in the world when they were built. Currently, the longest such span is found on the bridge completed in 1991 across Wuchao River in Hunan Province. This is an arch bridge with two ribs and a clear span of 120 m. Thus, the stone arch open spandrel bridge has continually developed in China throughout the course of history.

Timber cantilever bridges are found throughout China. Because timber beams cannot span long distances, and because of the difficulties in constructing piers in deep valleys and riverbeds in ancient times, the cantilever technique of bridge construction was developed.

According to literary sources, timber cantilever bridges were constructed in China as early as the 2nd century. A 5th century geographical survey “Annotations to River Couige Systems” records a timber cantilever beam bridge with span of more than 13 m in Gansu Province.

The Lu River Bridge in Hunan Province was an 8-span continuous cantilever bridge with stone piers and timber beams. The distance centre-to- centre between the piers was about 21 m. The span between cantilever ends was about 10 m. This bridge was first constructed in the Southern Song Dynasty (1127-1279), and repaired and reconstructed many times subsequently.

One later repair used 3 long timber beams bound together and connected with iron nails. More than 10 such longitudinal beams were placed at every pier, each with a cantilever of about 1.3 m. On this base, a layer of longitudinal beams followed by another of transverse members were repeatedly piled up to a total of more than 20 layers. Finally, the beams over the cantilevers were erected and inclined timber struts were added later at the 4th layers of timber cantilevers.

Today, the longest continuous box beam bridge in China is the pre-stressed concrete LiUku Bridge over the Nir River in Yuiman Province, completed in 1990 with a maximum span of 154 m. The Second Qiantang River Bridge is a box beam highway bridge constructed parallel to a railway bridge and completed in 1992. Both bridges are continuous, with 18 spans of 45 + 65 +14 x 80 + 65 + 45 = 1340 m without internal expansion joints.

A bridge over the Whitewater River in Gansu Province was first mentioned in literature as early as the Western Jin Dynasty (266-316). At the, end of the 19th century, the Yinping Bridge was reconstructed as a timber cantilever beam bridge and remains in service today. The supports of this bridge are constructed of 10 gradually cantilevered layers of timber, the ends of which are raised to achieve a large angle, of elevation. These cantilevers not only reduce the span of the bridge, but also assume the function of inclined struts.

Cantilevering techniques, with ever larger angles of elevation formed by the overhangs of the piled layers, evolved into timber strut arch bridges using individual inclined struts. A typical example is the Gannan Bridge in Gansu Province, a type that serves as a precedent for modern strut-frame bridges.

Two methods for constructing chain suspension bridges are drawn from the Ming Dynasty book, written around 1600. Later in the 17th Century, the German C. C. Schraman painted the iron chain Yuringn Bridge and attributed it to the 1st century. The suspending chains were joined with the horizontal base chains, so it can be only considered a flexible suspension chain bridge without stiffening girders.

As for chain bridges with stiffening girders no ancient examples survive. Since wood was the only material likely to have been used for stiffening girders, it is difficult to imagine timber girders with very large spans, although middle piers were apparently sometimes employed.

The largest modern suspension bridge in China is the Dazi Bridge in Tibet, with a main span of 500 m. The largest composite cable-stayed bridge of double tower form in China is the Nanpu Bridge in Shanghai, completed in 1991, with a main span of 423 m. At present, several cable-stayed bridges with a main span

length of 400 m and more are being constructed in China. These projects include the composite cable-stayed Yangpu Bridge in Shanghai with a main span 602 m and other prestressed concrete cable-stayed bridges with main spans exceeding 400 m. All these bridges are for highway use.

III. Find 9 pairs of antonyms:

add; modern; repair; consolidate; develop; ancient; resist; demolish; assist; divide; suddenly; upper; heavy; bottom; light; confine; reduce; gradually

IV. Match the beginnings and the endings of the sentences and arrange them in the correct order according to the text.

1.Ancient and modern bridges in a) … a precedent for modern strut-

V. Read the text once again and complete the tables (but first copy the tables into your notebook).

The Anji Bridge

The LiUku Bridge

location

year of construction

type

maximum span length

number of spans

total length

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

1.Bridge building in China has a ________ history.

2.In middle of the 20th century ________________ bridges were constructed in China.

3.It was decided to develop the cantilever technique of bridge construction because of some problems connected with ___________________________.

4.Timber strut arch bridges appeared due to _____________________.

5.There were no ancient chain bridges with ______________________ in China.

6.Nowadays in China there are several _______________ and _____________ bridges.

Home Exercises

I.Memorize the words from Ex. I page 98.

II. Translate from English into Russian. Discuss the translation in your group.

1.Stones protect the arches.

2.He stones cherries.

3.This plant can’t be layered.

4.The abutments consist of 5 layers.

5.Don’t forget to wood.

6.Wood stiffened girders.

7.The road parallels the river.

8.This house is timbered.

9.Timber beams cannot span long distances.

10.He longed to be a chief engineer.

III. Get ready to tell a collective story about bridges in China using Ex. VI as a plan.

Text 26 

I. Read the text and define the words in bold.

OUNASJOKI BRIDGE

One Finnish periodical gives some details on the Ounasjoki Bridge located on the highway № 4, at the border of the city of Rovaniemi, which is on the Arctic Circle. It crosses the river Ounas.

The structure is 4 span concrete box girder, prestressed both in longitudinal and transverse directions. Its overall length amounts to 254 m; the two central spans are each 70 m long. Abutments and piers are founded on bored piles.

The bridge was erected according to a cantilever method. The concrete deck was poured in 3.50 m with the aid of a trolley suspended from the cantilever. The choice of the method was influenced by the tight schedule due to climatic factors, giving very little time for the erection of the centering and pouring of concrete. The first end span, followed by a cantilever, 22.75 m long, was poured on forms supported by the scaffolding inside a protective cover. The outside temperatures at that time varied from –20˚ to – 30˚C.

After this stage concreting was continued by the cantilever method. As the length of the cantilever grew, it was suspended by means of cables on mast and by a temporary support until the next pier was reached. The same stages were repeated for each span; and when the opposite shore was reached the trolley was dismantled.

The cantilever method proved quite satisfactory for these arctic conditions. Special precautions were taken to protect concrete against frost such as heating concrete during laying, etc.

The bridge was constructed for the National Road of Public Roads and Waterways by A-Betoni Oy Company.

II. Translate into Russian.

Climatic factors; concrete deck; longitudinal directions; special precautions; central span; outside temperature; transverse direction; temporary support.

III. Read the figures and say how they are used in the text.

4 3.5

2 22.75

IV. Work in pairs. Ask and answer the questions.

1. What is overall length of the Ounasjoki Bridge?