Материал: Types of Movable Bridges. задания по английскому языку для студентов-магистрантов направления подготовки 08.04.01 «Строительство». Мордовцева Т.В., Зотова М.М

V. Retell the text briefly

UNIT 2

TYPES OF MOVABLE BRIDGES

I.Read the text and then try to name the famous bridges of this type

A bascule bridge is a moveable bridge with a counterweight that continuously balances a span throughout its upward swing to provide clearance for boat traffic. It may be single or double leafed. The name comes from the French term for balance scale, which employs the same principle. Bascule bridges are the most common type of movable span because they open quickly and require relatively little energy to operate.

Bascule bridges have been in use since ancient times. However, it was not until the adoption of steam power in the 1850s that very long, heavy spans could be moved quickly enough for practical application. The Blagoveshchensky Bridge (Lieutenant Schmidt Bridge) across the Neva River in Saint Petersburg was the first large bascule bridge, opened in 1850. (fig.1)

Fig. 1. Blagoveshchensky bridge

II.Read the text and answer the questions:

1.Is Pegas bridge a type of beam bridge?

2.Why was it called Pegas bridge?

3.What is the main peculiarities of this bridge?

4.Does the project allow a greater clearance of the bridge?

Pegasus Bridge is a bascule bridge (a type of movable bridge), built in 1934, that crossed the Caen Canalin Normandy, France. The name is derived from the shoulder emblem worn by the British airborne forces, which is the flying horse Pegasus)

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Design

The structure of Pegasus Bridge is an example of a subtype of bascule bridge or "rolling bridge". Bridges of this type do not pivot about a hinge point, but roll back on curved tread plates attached to the girders of the main span. This design allows a greater clearance of the waterway for a given opening angle (fig. 2).

Fig. 2. A rolling lift bridge (such as the Pegasus Bridge)

III.Read the text below and say if the following sentences true or false.

T F

The fixed –trunnion rotates back on curved treat plates

The rolling lift trunnion raises the span by rolling on a

The "Scherzer" rolling lift is a patented refinement by Kerbedz

The rarer Rall type was patented (1901) by William Donald Scherzer

A bascule's span may be located either above or below the bridge deck.

There are three types of bascule bridge designs and counterweights required to balance a bascule's span (fig. 3) may be located either above or below the bridge deck. The fixed-trunnion rotates around a large axle that raises the span(s). The rolling lift trunnion (sometimes a "Scherzer" rolling lift), raises the span by rolling on a track resembling a rocking chair base. The "Scherzer" rolling lift is a patented refinement by the American engineer William Donald Scherzer. The Rall type combines rolling lift with longitudinal motion on trunnions when opening. It was patented (1901) by Theodor Rall. One of the few surviving examples is the Broadway Bridge (1913), in Portland, Oregon a "Scherzer" rolling lift (fig. 5).

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Fig. 3. Bascule bridge

Fig. 4. Vertical lift bridge

Fig. 5. Swing bridge

IV. Translate the texts from English into Russian using the word list below.

Design

The Rolling Bridge was conceived by British designer Thomas Heatherwick, designed by Anthony Hunt with Packman Lucas. The bridge consists of eight triangular sections hinged at the walkway level and connected above by two-part links that can be collapsed towards the deck by hydraulic cylinders, which are concealed in vertical posts in the bridge parapets. To allow the passage of boats, the hydraulic pistons are activated and the bridge curls up until its two ends join, to form

an octagonal shape measuring one half of the waterway's width at that point. (fig. 6).

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Fig. 6. Rolling bridge

Folding bridge – a drawbridge with multiple sections that collapse together horizontally (fig. 7).

Fig. 7. Folding bridge

V. Read the text and say what the benefits over other movable bridges vertical-lift bridge has and what its the biggest disadvantage is.

Vertical-lift bridge – the bri dge deck is lifted by counterweighted cables on mounted towers. (fig. 8).

A vertical-lift bridge or lift b ridge is a type of movable bridge in which a span rises vertically while remaining parallel with the deck.The vertical lift offers several benefits over other movable brid ges such as the bascule and swing-span bridge. Generally speaking they cost less to build for longer

moveable spans. The counterweights in a vertical lift are only required to be equal to the weight of the deck, whereas bascule bridge counter-weights mu st weigh several times as much as the span b eing lifted. As a result, heavier materials can be used in the deck, and so this type of bridge is especially suited for heavy ra ilroad use. Although most vertical-lift bridges use towers, each equipped with counter-weights, some use hydraulic jacks loc ated below the deck. Another design u sed balance beams to lift the deck, with pivotin g bascules located on the top of the lift towers. The biggest disadvantage to the vertical-lift bridge (in comparison with ma ny other designs) is the height restriction for vessels passing under it. This is a result of the deck remaining suspended above the passageway.

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Fig. 8. Vertical-lift bridge

VI. Match the expressions from the left column with those from the right one

Word List

bascule - крыло раскрывающегося моста; подъёмная, разводная часть моста counterweight – контргруз, противовес

swing - качать; раскачивать; размахивать; качание; колебание clearance - отверстие (моста)

leaf bridge – разводной мост

leaf of bascule bridge - кры ло раскрывающегося моста scale – чаша весов, взвешивать

adoption – принятие subtype – подтип

rolling bridge - откатный мост

pivot - точка опоры (рычага) ; точка вращения hinge – петля

roll back – откатываться назад

tread ступень (лестницы) 2) перекладина лестницы-стремянки 3) обод колеса; звено гусеничного хода

girder - балка; брус; перекл адина; балочная ферма

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