Ответьте на вопросы к тексту.

1. What is prestressed concrete?

2. How is concrete prestressed?

3. What is tendon?

4. Why is prestressed concrete particularly useful for beams?

5. How does the use of prestressed concrete influence cracking?

6. What would be the result if steel tendons were tensioned and placed along the centroidal axis of the beam?

7. Why are tendons rarely placed along the centroidal axis?

8. What is the influence of loads on a beam with the eccentric prestress?

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Урок 1.9 Фонетическое задание

Прочитайте транскрипцию в списке A, соотнесите её с соответствующим словом из списка B и переведите слово на русский язык. Учтите, что не все слова списка В даны в списке А.

A

["xlq'mInIqm]; [Ik'stent]; [kWv]; [streIt]; ["Instq'bIlItI]; ['IndqstrI]; [TWd]; ['kwPntItI]; [kqm'baIn]; ['Genqrql]; ["kxrIktq'rIstIk]; [dI'zaIn]; ['aI¶n]; ['brItl]

B

Текст A

METAL

Construction materials are used in large quantities and it is therefore important that the materials which are used are cheap. Although bulk costs of metal are higher than those of most other building materials, the costs of iron and steel, and aluminium to a much lesser extent, are still reasonable when they are compared to those of other metals and these metals have found wide application in building.

Structural carbon steel is the most important class of steel for the construction industry. These steels are cheap and convenient to use; the class includes steels which have not more than 0.25 % carbon. There are several grades of structural carbon steel available. Those grades which have higher carbon contents are stronger. However steels which have higher carbon contents are, in general, more brittle at low temperatures and more difficult to weld.

The important general characteristics of structural carbon steels and steel structures are as follows:

• Steel has a high ratio of strength to weight that is combined with a low ratio of cost to strength, which accounts for the wide use of steel as roof beams.

• Steel for construction purposes is produced in the form of straight or curved rolled sections of various cross-sectional shapes, or flat plate.

• Although the use of high strength steel will often produce a lighter structure for the same design strength than one in a weaker material, the structure may suffer from excessive deflection or instability.

• Steel loses strength and stiffness at high temperatures. At 480°C (900°F) steel keeps about two-thirds of its original stiffness and strength. However the loss of stiffness is rapid above this temperature.

Notes:

bulk costs общие издержки

carbon steel углеродистая сталь

class n. класс, разряд, категория