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Read the text about the most astonishing British bridges and tell about them.
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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 19th 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.
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