Read the text about the most astonishing British bridges and tell about them.

Abraham Darby, to span the Severn at Coalbrookdale, built the first cast-iron bridge, designed by Thomas Pritchard, in Great Britain in 1779. A new page was written in the world’s bridge building history. The bridge, constructed of cast-iron pieces, is a ribbed arch with nearly semicircular 30-metre span (fig. 9.1a) imitating stone construction by exploiting the strength of cast iron in compression. Each of its five thin cast-iron arch ribs is covered with cast-iron plates, and the bridge road has a slag blanket on a clay bed. The bridge is still used today but only for pedestrian traffic, despite a slight humping of the arch. It is now a British national monument.

The rise of the locomotive as a mode of transportation during the 19^th century resulted in new bridge forms strong enough to handle both the increased weight and the dynamic loads of trains. The most significant of these early railway bridges was the Britannia Bridge created by Robert Stephenson. It spans the Menai Strait in northern Wales. Stephenson used a pair of completely enclosed iron tubes, rectangular in section, supported in the centre by a pier built on Britannia Rock. The iron tubes were floated into position and lifted by capstan and hydraulic power. Completed in 1850, Stephenson’s design was the first to employ the hollow box girder, which gave the deck the extra stiffness of a truss, but it was easier to build.

The wrought-iron boxes through which the trains ran were originally to be carried by chains, but, during the building, extensive theoretical work and testing indicated that the cables were not needed; thus the towers stand strangely useless. The lengths of spans are 140 m and each abutment span is 71 m long (fig. 9.1b). The bridge, which carried the London-Holyhead railway across the strait, was severely damaged by fire in 1970. During the repairs, concrete decks – one for the railway, a second for motor traffic – supported by steel arches, replaced the tubes.

Exercises:

Complete and translate the following text:

There are two unique bridges (перекрывающие) the Firth of Forth in Scotland – the Forth Rail Bridge (fig. 9.2a) and the Forth Road Bridge (fig. 9.2b). The Forth Rail Bridge was designed and (построен) by the engineer Benjamin Baker in 1891. He joined three giant (411-m) (консоли) (projecting members supported at only one end) together with two suspended spans of 107 m each, making a total of 518 m of clear spans over either arm of the firth. The bridge cost was about $ 15,000,000. The steel structure rises 103 m above the masonry (опоры). The length of the middle span is claimed to be the second world record among non-suspension structures. The Forth Rail Bridge has no decorative elements. Nothing has been added for aesthetic purposes that do not have a structural function, and still it is a work of art that towers above the sea into the sky. The great bridge has a simple profile but the diagonal lattice braces provide a visually dense interior. It provokes wonder and admiration to people from around the world, because viewed from different angles; it takes on quite a different appearance. Perhaps it should be seen from one of the shores or from the parallel (автомобильный висячий мост).

The neighbouring (трехпролетный висячий мост под автомобильную дорогу) over the Firth of Forth was built in 1964. It carries two traffic lanes (полоса движения), a bikeway and a banquette in each direction. The main span is 1,006 m long, and ranks the bridge among the top ten structures with super long spans. Its’ (боковые пролеты) are 408 m long, and its’ (пилоны) are 154 m high. The cable diameter is 0.6 m and contains 37 strands consisting of 314 wires in each (прядь). The total number of (параллельные высокопрочные проволоки) in the cable is 11,618. The diameter of each wire is 4.8 mm. So light and delicate is its design that the bridge seems to be suspended in air.

Complete the following sentences using your own ideas:

1. London’s bridges are among the cities most popular....

2. Some bridges were named to commemorate … .

3. Tower Bridge is unique from an engineering point of view because … .

4. Scotland is proud of its famous bridges … .

5. All the bridges must provide a clear span for … .

Answer the following questions:

1. Which parts of the Old London Bridge were found during its replacement?

2. What is the design model of the Britannia Bridge?

3. When and where was the first cast-iron bridge built?

4. Name the famous suspension bridges in Great Britain.

5. What type of a movable span is used in Tower Bridge?

Translate the text into English:

Мост Тауэр – знаменитость и символ Британской столицы. Он уникален с инженерной точки зрения и представляет собой странное смешение современного стального моста с каменными величественными сооружениями прошлого: средневековый принцип разводного моста используется в башне, чтобы дать возможность кораблям с большими габаритами пройти под ним. Это единственный мост в мире, объединяющий висячие конструкции и одно разводное пролетное строение, которое является вертикально-подъёмным, перемещающимся вверх по башням-пилонам, поддерживающим несущие цепи. Длина висячих пролётных строений по 83 м, разводного 61 м.

Describe the design models of The Old London Bridge, the Britannia Bridge, the Tower Bridge, and the Iron Bridge over the Severn. Work in pairs. If your partner is less confident in English than you are, help him/her by asking his/her opinion and reacting to what he/she says.

Unit 10

SUSPENSION AND CABLE-STAYED BRIDGES

After reading the text, prove the idea that suspension structures are the safest among bridgeworks.

Primitive people using vines for cables and mounting the roadway directly on cables constructed suspension bridges, one of the oldest of engineering forms. It is light, aesthetic, graceful and easily constructed, using materials that are easily transported. Besides, there is no danger of failure during erection because the principal carrying member - the cable - has a vast reserve of strength. It provides an economical solution to the problem of long spans over navigable streams or rivers because of its relatively small dead weight, which results from the use of cables. Since the cables are in tension, they are the most highly efficient load-carrying component. Besides the economic considerations, the suspension bridge has many other points of superiority.

Suspension and cable-stayed bridges are often confused. The reason is that they have very much in common: stiffening girders or trusses, anchor supports and cable hangers. The usual form of suspension structure consists of a flexible cable passing over two towers and anchored by backstays to a firm foundation. The roadway is suspended from the cable by means of hangers. The principal carrying element of a cable-stayed system is a flexible cable (fig. 10.1). The difference between these two bridge types is determined by the two following criteria:

1. A suspension structure has curved steel cables or chains (fig.10.1a).

2. A cable-stayed structure has cables that are straight. They are called stay cables (fig.10.1b).

Modern bridge building uses the suspension span model on a large scale. The Akashi Kaikyo Bridge, now the world’s longest suspension bridge crosses the strait with a main span of 1,991 m and side spans of 960 m. Its two 297 m towers, made of two hollow steel shafts connected by X-bracing, are the tallest bridge towers in the world. The two suspension cables are made of high-strength steel developed by Japanese engineers for the project. In 1995, an earthquake had its epicenter centred almost directly beneath the nearly completed Akashi Kaikyo structure; the bridge survived undamaged, though one tower shifted thus lengthening the main span by almost one metre.

The basic advantages of suspension and cable-stayed structures are:

1. The possibility to span very long distances from 500 m up to 1,990 m.

2. High efficiency of these structures is due to the weight of the span m², which is considerably less in comparison with other bridge systems.

3. Suspension and cable-stayed bridges often have merits that are more aesthetic.

The disadvantages of suspension and cable-stayed structures are:

1. Low vertical stiffness, i.e. the structure strongly exhibits a high deflection degree under live load.

2. Low horizontal stiffness, i.e. the structure exhibits considerable displacement under the wind force in a horizontal plane.

3. High sensitivity to dynamic and aerodynamic forces.

Care must be taken to ensure that the deck does not move excessively under loading. High performance in service of suspension and cable-stayed bridges is due to the following factors:

1. Only high-strength steel wires with a rated resistance of 10,000 MPa are used.

2. Stay cables work only in tension because working in compression may result in suspension bridge collapse.

3. No slacking in suspension bridge cable is allowed.

4. Cable hangers and stay cables support the stiffening girder at many sites.

5. The stiffening girder transmits its dead weight to the cable and the towers. Such girder’s behaviour is due to the special construction technique.

The stiffening girders distribute the load in the span and prevent distortion of the deck. To make the stiffening girder lighter the designers use the force regulation in stay cables. This results in the most acceptable distribution of force.

Exercises:

Make up examples with the terms describing a suspension structure.

Stiffening girder, anchor support, cable hanger, flexible cable, steel rope, vertical stiffness, horizontal stiffness, high-strength wires, square metre, and resistance.

Choose which statements are true:

1. The basic advantages of suspension structures are:

a) low horizontal stiffness b) super long spans c) force regulation.

2. A suspension cable is strong in a) compression b) tension c) flexure.

3. Cable-stayed and suspension bridges differ in a) the cable shape b) the span construction method c) architectural merits.

4. The tower for a 1,200 m suspension span may be made of:

a) steel b) reinforced concrete c) cast-iron.

5. A cable-stayed structure without thrust has:

a) no piers b) anchor supports at the span end.

Complete and translate the following sentences:

1. Sometimes it is difficult to tell difference between (висячие и вантовые мосты). Suspension bridges may have (наклонные подвески) which resemble stay cables (fig. 10.1c). On the other hand, there are so called cable truss bridges, which look like suspension structures (fig. 10.1c).

2. Most cable-stayed bridges have powerful steel or reinforced concrete (балка жесткости). It resists a cable-stay (распор) (fig. 10.1b). Suspension bridges are constructed either with (анкерные опоры) or without them. In case of anchor supports, they transmit the thrust to the foundations. The bridges of this type are called (распорные) (fig. 10.1a). When suspension bridges are built without anchor supports, the thrust is transmitted to the stiffening girder. They are defined as (безраспорные) (fig. 10.1c).

3. One running metre weight of the stiffening girder in suspension and cable-stayed bridges is considerably less in comparison with other bridge systems. That is why (динамические нагрузки) make a suspension structure highly vulnerable to aerodynamic forces and sensitive to vibration when the bridge spans are rather long. To reduce these effects bridge designers use (висячие системы повышенной жесткости). The cable is rigidly attached to the stiffening girder or an additional cable is secured.

4. (Возведение пилонов) is the most complicated building process in case of suspension and cable-stayed structures. The building material for towers is reinforced concrete for 300-500 m spans or steel for longer spans. The tower works simultaneously in (сжатие с изгибом). That is why its calculation requires fine precision.

Answer the following questions:

1. What bridge model provides an economical solution for long spans?

2. What is the main carrying component in suspension bridges?

3. Why are suspension and cable-stayed bridges often confused?

4. What bridge elements are alike in suspension and cable-stayed structures?

5. What country holds a world record for suspension span length?

6. What makes a suspension structure highly vulnerable to aerodynamic forces?

7. Do you know the disadvantages of suspension and cable-stayed bridges?

8. Where were the most famous suspension and cable-stayed bridges built?

Describe the Golden Gate Bridge using the following information.

Location: San-Francisco, California, the USA; Completion Date: 1937;

Length: more than a mile long; Purpose: motorway; Materials: steel, concrete;

Setting: over Golden Gate Straight connecting San Francisco Bay with the Pacific Ocean; Oceanic Conditions: rapidly running tides, frequent storms and fogs;

Engineer(s): Joseph Strauss, Consulting Architect: Irving Morrow

Consult this list of bridge terminology while doing the exercises.

1. Backstay, stay cable	a) ванта
2. Bridge structure without thrust	b) безраспорный мост
3. Curved cable	c) криволинейный кабель
4. Deflection	d) прогиб, провисание
4. Distortion of the deck	e) деформация мостового полотна
5. Failure	F) потеря устойчивости
6. Hollow shaft	g) полый ствол
7. Overhead cable	h) подвесной кабель
8. Performance in service	g) эксплуатационная характеристика
9. Rated resistance	h) номинальное сопротивление
10. Slackening in cable	i) ослабление натяжения кабеля
11. X-bracing	j) крестообразный раскос

Unit 11

NOVOSIBIRSK’S BRIDGES

You should have pictures of Novosibirsk's bridges. Look at them while reading the text. Having read the text, supplement the information with details you may notice in the pictures.

Novosibirsk is the third largest city in Russia. Its development in the 21st century is supported by its ideal geographical location, at the crossing of basic transportation routes – railways, airlines, waterways and motorways. It was founded as an important transport centre for both the internal and external transportation of goods from Siberia, the Far East, the Kuzbass region, the Altai Region, Central Asia, Kazakhstan, Mongolia, China, Japan and the World. The role of the railway network is of paramount importance for it gave rise to the business activities of these regions. The Trans-Siberian Railway is the longest in Russia, stretching from Moscow 9,198 km east to Vladivostok. It has and had great importance in the economic and military history of our country, and carries 9.5 million tons of cargo each year crossing many unique bridges.

At the end of the 19^th century, the builders of the Trans-Siberian Railway had to bridge the mighty rivers of Siberia. In 1893, the surveying party headed up by N. Garin-Michailovsky chose the most suitable place for crossing the Ob River.

Professor N. Belelyubsky designed the huge railway bridge, which was completed in 1897 (fig. 11.1). During the years of construction, a settlement sprang up there, and the largest city in Siberia developed where there was only the village of Krivoshchekovo, on the left bank.

The design represented a multi-span superstructure with a cantilever-beam metal truss. The suspended span was 87 m long and rested on the cantilevers of the adjacent trusses. The main advantage of a cantilever-beam truss is that each pier has one carriage. It reduces pier proportions at the bridge front (fig. 11.2a). The headroom provided 118 m of navigable waterway (fig. 11.2a). The carrying capacity of the bridge elements and the state of the riveted joints could not resist modern live loads. The carriage deterioration after 90 years of continuous operation called for reconstruction, which began in 1981. The starlings were encased in concrete, and new metal trusses were put on the encasement. The old spans were redesigned and turned into welded trusses with a triangular truss of standard construction. In that way, Belelyubsky’s piers entered their next cycle of service life (fig. 11.2a).

The next railway bridge over the Ob River was constructed in 1935. It has a metal riveted truss with a top flange of polygonal shape (fig. 11.2b). The bridge was constructed within a short period due to the enthusiasm of young people. That is why it is called the Komsomolsky Bridge.

Insecurity in transport communication held back the growth of the economy in the rapidly developing city. Until 1956 the communication links between the right and left riverbanks of Novosibirsk were facilitated by the floating bridge in summer and the ice passage in winter. Further industrial growth was encouraged due to Oktyabrsky Bridge, which solved the traffic problem. The first city bridge in Novosibirsk is one of the finest bridgeworks in our country (fig. 11.2c). The combined structure including a mighty metal girder and a flexible 126 m arch span complements the magnificent city view, and the spandrel arch looks especially attractive. The bridge deck is made of reinforced concrete slabs allowing the asphalt to be applied much easier. The piers resisting the thrust from the arches might look rather ponderous but due to the nice granite encasement, they decorate the bridge.

Novosibirsk is a rapidly developing city because it is situated at the most important overland transport cross routes. The Main Federal Motorway carries heavy traffic through our city that causes great inconvenience in the streets. The problem of traffic congestion, noise and air pollution made the authorities build a bypass road for freight transportation, at the northern border of the city. Again, the Ob River became a natural obstacle to the new road, and a reinforced concrete bridge had to be built. It was opened to traffic on October 22^nd in 2008. The Prime Minister of The Russian Federation visited that major event. Senior government and RZD COMPANY officials, as well as the Transport Minister, other high-ranking persons, and the General Manager of the West-Siberian Railway Branch accompanied Mr. Putin. Having examined the new bridge, they arrived at Siberian State University of Railway Engineering and discussed the plans for future transport development. The Prime Minister signed a document called The Strategy of Transport Development up to 2030, which provides many solutions for solving our transport problems.

Exercises:

What bridge across the Ob River do you prefer and why? Express your opinion using the following word combinations:

Transport connection, Multi-span Superstructure, Heavy traffic, Traffic jams, Traffic accident, Municipal Transportation, and Individual transport

Answer the following questions:

1. What bridgework laid the foundation for the city of Novosibirsk?

2. Who designed the first bridge crossing over the Ob River?

3. What role do the bridges over the Ob River play in the development of the city’s economy?

4. When was the last bridge crossing in Novosibirsk constructed?

5. What are the plans of the Novosibirsk municipal administration and transport authority in terms of developing transport links over the Ob River?

Match the English and Russian terms.

1. Adjacent trusses	a) ажурное надсводное строение
2. Riveted joints	b) однопутная железная дорога
3. Single rail system	c) типовая конструкция
4. Spandrel arch	d) верхний пояс
5. Standard construction	e) изыскательская партия
6. Surveying party	f) заклепочное соединение
7. Top flange	g) смежные фермы

Describe your “dream bridge”. Do you have any ideas that will surprise your classmates? Think of a place where your bridge could be constructed?

Unit 12

A BRIDGE OR A TUNNEL?

Read the text and give your reasons for making a choice between a bridge and a tunnel.

Vast bodies of water, all over the world, represent natural obstacles to communication. People have been striving to overcome water obstacles by bridging the gap between continents, islands, etc. The English Channel separating Great Britain and Europe, the Straits of Gibraltar between Spain and Africa, the Bosporus between Europe and Asia, the Bering Straits connecting the Eurasian and American continents are of great economic importance as it is used as a shipping route. The shores of these straits and Japanese islands are dotted with villages, towns and cities, and might provide the missing link for the rapid increase in overland railway networks and motorway systems. Some water crossings are a mixture of bridges and tunnels, such as the Denmark to Sweden link and the Chesapeake Bay Bridge-Tunnel in the eastern United States. Examples of water-crossing tunnels built instead of bridges include the Holland Tunnel and Lincoln Tunnel between New Jersey and Manhattan in New York City, and the Elizabeth River tunnels between Norfolk and Portsmouth.

Builders always have the choice between bridge and tunnel crossings (fig. 12.1). Each sort of structure offers its own advantages and has some imperfections. One should bear in mind the influence of strong sea currents, great water depth, large-capacity vessels with great overall dimensions (the headroom must be about 65 m high for free shipping), and the difficult geological structure of the seabed. Seabed silt is rather soft for pier foundations, and besides, the risk of seismic activity may jeopardize the foundations. Other reasons for choosing a tunnel instead of a bridge include avoiding difficulties with tides, weather and shipping during construction, aesthetic reasons, and for weight capacity reasons (it may be more feasible to build a tunnel than a sufficiently strong bridge).

The advantages of a bridge crossing may be the following: low construction costs in comparison with tunneling, though sometimes the reverse may be true; low maintenance costs in comparison with tunnels which require costly water discharging, ventilation, illumination, etc.; the longer the sub aqueous tunnel is then heavier outlays are required.

The advantages of the tunnel are:

1. Unobstructed shipping is very important for intensive navigation. Tunnels are much safer as compared to bridges because the piers must withstand berthing impact. Being deep beneath the water’s surface, tunnels do not interfere with navigation. Besides, the weather does not influence the traffic.

2. The design aspect of the tunnel is more attractive because there is no need to erect high approach embankments.

The final decision for choosing between the two structures depends on the fact that in some cases bridges are more convenient solutions which were realized in such outstanding structures as the bridge across the Bosporus constructed in 1974, the bridge crossing connecting some Japanese islands in 1985, and the bridge spanning the strait separating Denmark and Europe. Nevertheless, the choice fell on a tunnel underneath the English Channel. In 1994, the railway tunnel from Great Britain to France was put into operation. It provides a high-speed rail-link with shuttle trains reducing the travel time between the two countries to three-and-a-half hours. Needless to say, that the cost of this tunnel is enormous. Currently tunnels are widely used in states surrounded by water for instance; in 1987, some Japanese islands chose tunnels for safe and rapid communication. Making their well-reasoned choice, the engineers have to be up to different challenges. The problem “a bridge or a tunnel” is being discussed for planning future structures in Italy, across the Straits of Gibraltar, and across the Bering Straits. The choice falls on a bridge crossing in Europe, and on a tunnel for Alaska due to harsh northern conditions.

Exercises:

Complete and translate the following information.

1. The Bosporus is 30 km long, with a maximum width of 3.7 km and a minimum width of 750 m. Its depth varies from 36.5 to 124 m in midstream. Two bridges have been built across the strait. The first, the Bosporus Bridge, was completed in 1973 and has a main span of 1,074 m and its side spans are 231 and 255 m long. To avoid (столкновение судов и опор) the builders constructed a three span suspension bridge. The width of the (проезжая часть) is 33.4 m and it allows six (полоса движения автомобильного транспорта) and two (пешеходные дорожки). The stiffness girder of the tubular cross section is 3.0 m high. It has good (обтекаемость) for increasing the aerodynamic stability of the bridge. The experimental scaled down version, representing 1/50^th the bridge’s actual size, was placed into a wind tunnel for (испытания). The bridge (был рассчитан) to resist wind forces and withstood gusts up to 162 km/h. One (пилон) is built on the European side and another one on the Asian side in order not to interfere with the transit of commercial and naval vessels through the strait.

The second bridge, the Fatih Sultan Mehmed, was completed in 1988 and has a main span of 1,090 m.

2. Currently, the preliminary study of the (подводный) tunnel construction through the Bering Straits is being considered as technologically feasible. A bridge crossing could not (выдерживать) strong sea currents and stay in serviceable condition over a long period due to low temperatures and difficult ice conditions. The miners will have to dig through unpredictable (вечная мерзлота). Nevertheless tunnelling under constant temperatures is much more advantageous in comparison with concrete (укладка), metal (сварка), bolt (установка) at -40˚C below zero. The prolonged building experience within the Polar circle shows that mankind can develop and master new suitable technologies.

3. For water crossings, a tunnel construction is generally more costly than a bridge. Navigational considerations may limit the use of high bridges or (подъемный мост) spans intersecting with shipping channels. In areas with expensive real estate, such as Manhattan and urban Hong Kong, this is a strong factor in a tunnels favour. Boston’s Big Dig project replaced elevated motorways with a tunnel system to increase traffic capacity and hide (поток транспорта).