Read the text to check your answers.

What types of bridges are described in the text?

What things should be taken into account while building a bridge for it to withstand stresses and strains.? Use a dictionary and find Russian equivalents for each type of a bridge.

Bridges

Bridges are some of the most famous structures in the world. There are many different types of bridge There are fixed bridges such as arch bridges and movable bridges which can pivot, fold, tilt, or swing. The   texts describe four important types of bridge: truss, arch, suspension, and cable-stayed. A truss bridge rests on a support, such as a pier, at each end and is held up by a truss superstructure, a network of members linked to each other to resist the forces acting on the bridge. A suspension bridge is supported by cables draped over towers. The cables are fixed to secure anchorages at each end of the bridge. The deck of the bridge is linked to the cables by vertical hangers. In a cable-stayed bridge, the deck is supported directly to cables which are fixed at an angle to towers. Arch bridges transfer their weight to either end.

There are two important forces that every bridge must deal with: compression and tension. The illustrations in the text show those forces acting in different types of bridges. Compression is a force that acts to compress or shorten the thing it is acting on. Tension is a force that acts to expand or lengthen the thing it is acting on.

The site of a bridge must be carefully selected, not just to interface with the existing road or rail system but to ensure that solid foundations can be provided to support the structure. Bridges must withstand stresses and strains from the traffic they carry and from the extremes of the weather they will be subjected to. They must remain safe, despite the corrosive effects of rainwater, sea spray, and road salt and possible collision damage inflicted by passing ships or trucks.

Tunnels, like bridges, are important links in the transport network. Sometimes a tunnel is the only option. Sometimes the choice between a bridge and a tunnel must be made. Tunneling can be simpler and cheaper than bridge building but this decision can only be made when a geological survey has revealed whether the tunnel will pass through clay, rock, or gravel and how simple or complex the tunneling will be.

Engineers will use a tunnel boring machine (TBM) rather than drilling and blasting, whenever possible. There are difficulties in tunneling in urban surroundings when the ground surface must not be disturbed. TBMs do not disturb the surrounding soil or rock making them ideal for use under built-up areas. They produce a smooth tunnel which is easy to line with concrete if this is required.

Quiz yourself. Do you know the meaning of the following word combinations.

to rest a support

to resist forces activity of the bridge

cables draped over towers

cables are fixed to secure anchorage

the desk is supported directly to cables

to interface with a road

to withstand stresses and strains

to be subjected to the extremes of the weather

to disturb ground surface

to line with concrete

to provide a solid foundation

Combine the words on the left with the words on the right

1. bridge	a. network
2. transfer	b. survey
3. solid	c. damage
4. transport	d. foundation
5. geological	e. deck
6. collision	f.  weight

Memorize all the prepositions and don’t make mistakes

to act on

to rest on

at each end

to be linked to something

to be fixed at an angle to something

to be subjected to

 

Brainstorming. Work in a group of 4. Imagine that you are a team of designers. You have designed a new type of a bridge across the river for design competition you want to enter. Discuss and plan your proposal. Explain how your product will compare with other products on the market. Present your proposal to the class.

6. Work in pairs to answer this question:

1) Which of these reasons account for the importance of bridges?

1. They bring beauty into our lives

2. They are crucial for transporting goods and trade

3. They symbolize a place people live in

4. They have military significance

5. They help to communicate