I. Decide whether the following statements are true or false according to the text:

1. The construction of an overpass beam bridge with one support begins with excavation.

2. Wooden beams are usually made on-site.

3. Metal pieces provide a connection between beam and slab.

4. A plate girder consists of separate top and bottom flanges.

5. Beams for short and long spans are usually of a constant depth.

6. Arches are made in a factory, shipped to the site and set in place by cranes.

7. When the ends at an arch meet, the cables or falsework are removed.

8. Foundations of suspension bridges are made by sinking caissons.

9. Suspension bridge towers have always been made of steel.

10. An anchorage is a length of metal with a hole at the ends.

11. Spinning is done by cables that carry each wire across the top of the towers to the opposite anchorage and back.

12. For steel cantilever bridges the steel frame is built out from the abutments toward the towers.

13. Falsework is not used in the construction of cantilever bridges.

14. Cable-stayed and cantilever bridges are built in the same way.

II. Answer the questions:

1. What does the construction of beam bridges begin with?

2. Where are steel beams made ?

3. What are metal pieces used for?

4. What is the difference between beams for short and long spans?

5. When are the cables or falsework removed?

6. How are foundations for bridges requiring piers made?

7. What is an eyebar?

8. What is done to prevent corrosion of the wires?

9. How is the steel frame built for cantilever bridges?

10. What does the cantilever method consists of?

11. What is done to avoid the need for falsework?

LANGUAGE FOCUS

III. Insert the words from the list

substantial, continuous, material, away, complete,

multi-arch, falsework, size, rigidly,

to maintain, beam bridges, hindrance

1. The construction of an arch requires…. The type of falsework depends on the… of which the bridge is made and the… of the bridge. Massonry arches need… support and this type of falsework is called centring. For large bridges, the centring will be a … structure in its own right and will be expensive. For a … bridge it is desirable to re-use the centring for each span. In the case of a bridge across a river the centring will be in the form of a tied arch … it integrity.

2. … are generally in the form of plate girders, box girders or trusses. In all cases, a common construction method is to build the beam … from the final position and slide or lift it into place as a … unit.

3. A great advantage of cantilever is that it can be built out from a support without a … to traffic or navigation below. The technique depends on whether the cantilever is attached … to a free standing tower.

IV. Translate the words in brackets.

A major improvement over the single (балка) was the circular (арка), the basic design which was perfected by the ancient Romans. Because the (силы) on an arch bridge extend outward as well as (вниз) a condition called (сжатие) they could be build with longer (пролёты) and with (каменные блоки) rather than with single (брёвна) or slabs of stone. A variant type of a (подвесной мост) is the cable stayed span in which the supporting (тросы) run directly from tall vertical (башни) to the horizontal deck. Besides design, the other great challenge in building (прочные) bridges has been in the methods and materials used in their construction.

Text 5: MATERIALS

The four primary materials used for bridges have been wood, stone, iron, and concrete. Of these, iron has had the greatest influence on modern bridges. From iron, steel is made, and steel is used to make reinforced and prestressed concrete. Modern bridges are almost exclusively built with steel, reinforced concrete, and prestressed concrete.

Wood and stone. Wood is relatively weak in both compression and tension, but it has almost always been widely available and inexpensive. Wood has been used effectively for small bridges that carry light loads, such as footbridges. Engineers now incorporate laminated wooden beams and arches into some modern bridges.

Stone is strong in compression but weak in tension. Its primary application has been in arches, piers, and abutments.

Iron and steel. The first iron used during the Industrial Revolution was cast iron, which is strong in compression but weak in tension. Wrought iron, on the other hand, is as strong in compression as cast iron, but it also has much greater tensile strength. Steel is an even further refinement of iron and is yet stronger, superior to any iron in both tension and compression. Steel can be made to varying strengths, some alloys being five times stronger than others. The engineer refers to these as high-strength steels.

Concrete. Concrete is an artificial stone made from a mixture of water, sand, gravel, and a binder such as cement. Like stone, it is strong in compression and weak in tension. Concrete with steel bars embedded in it is called reinforced concrete. Reinforcement allows for less concrete to be used because the steel carries all the tension; also, the concrete protects the steel from corrosion and fire. Prestressed concrete is an important variation of reinforced concrete. A typical process, called post-tensioned prestressing, involves casting concrete beams with longitudinal holes for steel tendons—cables or bars—like reinforced concrete, but the holes for the tendons are curved upward from end to end, and the tendons, once fitted inside, are stretched and then anchored at the ends. The tendons, now under high tension, pull the two anchored ends together, putting the beam into compression. In addition, the curved tendons exert an upward force, and the designer can make this upward force counteract much of the downward load expected to be carried by the beam. Prestressed concrete reduces the amount of steel and concrete needed in a structure, leading to lighter designs that are often less expensive than designs of reinforced concrete.

COMPREHENSION CHECK