Vocabulary notes

prestressing предварительное напряжение (бетона)

span пролет

long-span (beam) длинная балка

load нагрузка

dead load постоянная нагрузка

live load переменная нагрузка

stress напряжение

tensile stress растягивающее напряжение

shrinkage усадка

plastic flow пластическое течение

to compress сжимать

compression strength сила сжатия

to superpose совмещать; накладывать (одну вещь на другую)

to crack образовывать трещину

cracking растрескивание

elastic capacity мощность на растяжение

excess load перегрузка

EXERCISES

I. Read the texts “Reasons of Prestressing” and “Principles of Prestressing”. Translate them into Russian.

II. Answer the following questions:

1. When did the application of reinforced-concrete structures begin?

2. What are the main reasons for using steel structures?

3. Why was it necessary to develop new ideas and systems?

4. What are the principles of prestressing?

5. What is the main advantage of prestressing?

III. Make the following sentences simple.

1. Up to present, steel constructions, rather than reinforced concrete, have succeeded in holding the field of long-span bridges and other long-span engineering structures.

2. The use of high strength reinforcing steel in unprestressed reinforced concrete is limited because of the considerable elongation of the steel under high tensile stresses.

3. One of the fundamental principles of conventional reinforced-concrete theory is the proper transmission of stresses from concrete to steel so that the steel may be considered as an incorporated part of the concrete section.

Systems and methods of prestressing

The classifications often used in existing literature on prestressed structures are sometimes based on the methods used to transfer the stretching forces from steel to concrete, and are even based on the techniques used in tensioning and anchoring the prestressed reinforcement. Such methods of classification are not completely suitable. A more desirable method of classification would be based on the static carrying action of the prestressed structure. According to this method of classification two different groups of prestressed structures may be distinguished:

a) prestressed beams, arch beams, slabs, shells;

b) prestressed trussed beams, trussed arch beams, trussed girders and open-spandrel arches.

In the first group, the prestressed steel reinforcing is a properly incorporated part of the concrete section and is not an independent structural member. The entire member, with its concrete and steel components, act statically as a homogeneous structural unit.

In the second group, the pretensioned main steel reinforcing is not an incorporated part of the concrete section but acts separately as an independent structural member in a structural system. Such a combined framework, having members of different materials with different stiffness, may be considered as a structural system with non-homogeneous static action.

Vocabulary notes

to transfer переносить, передавать, перемещать

stretching force сила натяжения

tensioning напряжение

beam балка

arch beam арочная балка

trussed beam шпренгельная балка

shell раковина; кожух

slab панель

trussed girder шпренгельная ферма

open-spandrel arch сквозное надарочное строение

framework каркас

stiff жесткий

stiffness жесткость

EXERCISES

I. Translate the following text.

II. Annotate the text in Russian.