The cantilever bridge

A cantilever bridge is generally composed of anchored trusses, cantilevered out of the piers and connected by a shorter, suspension span.

The first modern cantilever bridge was built in 1867 by Heinrich Gerber across the river Main in Germany with a central span of 425 feet. Named after this engineer, cantilevers were at first called “Gerber” bridges.

In the United States the first bridge of this type was built by Smith in 1876 – the Kentucky River Viaduct.

In 1883, a notable railway cantilever bridge was built over the Niagara River, and this Structure was the first to receive the distinctive name of “cantilever”. The finest example of this type in the world is the Railway Forth Bridge still as good as when it was built as far as 1889.

XIV. Give some examples of cantilever bridges.

III

The Arch Bridges

Another bridge building method was even simpler. Two long trunks were jammed into the river banks, if necessary with their lower ends under the water, and their outer ends touching, so as to form an inverted V. Another pair was then set alongside the first. Then planks were laid from each bank to the cross strut. This is the simplest form of the arch bridge.

РИСУНОК 4

In a wider river a central support or pier would be built, as in the case of the beam bridge, with an arch from one bank to the pier, and another from the pier to the other bank. Any number of piers could be used as were necessary. Arches may be round, pointed, elliptical.

РИСУНОК 5

Round Arch

РИСУНОК 6

Pointed Arch

РИСУНОК 7

Elliptical Arch

It is impossible to erect a big arch bridge in stone. So in crossing a wide river, more piers are required. Piers in midstream are always difficult to build. They are a barrier to the flouring water, an extreme example being old London Bridge, which was nearly a dam across the river. The next step were metal bridges. Since the use of cast iron, wrought iron and steel, bridges began to cross gaps that were previously impossible to span. 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.

Exercises

I. Pay attention to the pronunciations of the following words:

Pier, pile, cast-iron, support, necessary, impossible, nearly, through, wrought-iron, previously, corrosion.

II. Translate the following nest of words:

1. success, succeed, successive, successively.

2. width, wide, widen, widely.

3. suspension, suspend, suspended, suspender.

4. near, nearly.

III. Match the equivalents:

1. require 1. чугун

2. pier 2. свая

3. wrought-iron 3. ряд

4. nearly 4. сварочное железо

5. impossible 5. опора, бык

6. pile 6. невозможно

7. a number of 7. требовать

8. cast iron 8. почти

IV. Match the synonyms:

1. timber 1. bank

2. require 2. build

3. use 3. wood

4. erect 4. call for

5. shore 5. apply

V. Pay attention to the translation of the words:

1. так как

as - 2. когда

3. как

as to - что касается

1. As bridges became bigger foundation jobs became bigger too. 2. As load passes across a suspension bridge the strain is taken by the ropes. 3. As an example of the bridge-builder’s art the Hell Gate arch is of great interest. 4. As to metal bridges they are lighter than those of any other material.

VI. Pay attention to the translation of the underlined words: