2376

4 – a small narrow river

5 – a tall upright piece of stone, wood or metal used as a support for a bridge

Down:

1 – a thing made of several parts put together in a particular way 2 – anything that is being carried or waiting to be carried

3 – a long piece of wood, metal, concrete, usually supported at both ends, that bears the weight of part of a structure

V. Answer the questions.

1.What is the origin of the first bridge?

2.What bridges were used for the passage of armies in Homer’s times?

3.Where was a short span structure built about 780 B.C.?

Home Exercises

I.Use Passive constructions instead of Active ones.

Model: The profession of an engineer is considered to be the most universal one.

1.We consider bridge building to be a science.

2.We believe many bridges to have been constructed 2000 years ago.

3.Nature has given to man the idea of bridge.

4.We know the Romans to have brought arch bridge construction to its high degree of perfection.

II. Try to translate the text considering it to be:

-a fairy-tail

-a report

-a terrifying story.

Text 6 

33

Find the words you have read in the text below and translate the word combinations having these words. Use the words in the sentences of your own.

II. Work in pairs. Think of 2 or 3 questions using the words from Ex. I. Answer the questions of your partner.

III. Read the text and try to understand its main idea.

FORM AND STRUCTURE IN BRIDGE DESIGN

The work of designing should be considered as a rational, cognitive process in that it has to propose concrete solutions based on real needs. For a structure to be not only functional but also socially acceptable, there are a number of variables involved, which can be divided into subjective and objective considerations. Subjective variables are qualitative in nature, having to do with aesthetics, with judgements of taste, which are not necessarily universal. The judging of a structure as handsome or ugly remains an individual opinion and thus highly problematic.

A proper method for the analysis of subjective variables, however, can lead to a choice of form, which is justifiable regardless of whether an individual perceives the work as handsome or ugly. This method should enable a project to be developed along lines that can command the validity of a logical process.

Statics define the structure, with direct consequences on the effects of light and colour, the way shadows fall, and the materials used. Statics, thus, define architecture. Following a design-method that considers the demands not only of statics, but of shape, context and the effects of light and colour will lead to a proposal which encompasses all relevant variables. These objective variables must be evaluated individually and as they relate to each other in order to identify the most appropriate of the infinite number of possible design solutions for a given structure.

34

Considering statics in relation to shape, the basic conditions of the structure can essentially be reduced to the following three elements: the behaviour of the arch, which is chiefly subjected to axial load; the behaviour of the beam, which mainly undergoes bending moment; the combined behaviour of arch and beam, featuring a majority of axial load or bending moment, according to whether the arch or the beam component is prevalent.

Similar considerations hold true, for cable-stayed and suspended structures in which tensile stress prevails. In any event, various static schemes give rise to a project design, which can be formally valid, within its self-defined context.

Relationships between statics and shape are not restricted to the overall design of the structure; but can also be used to define structural details. Thus, by “playing” with statics, various formal solutions can be reached, even for cablestayed structures.

Statics is a science, which carried to a variety of equally valid formal solutions. But how to choose between them?

The structure, as a shape, may be said to produce an image of itself which is to be inserted in a spatial context. The term “context”, from the Latin cum + texqre, means to weave together and thus implies the combination of a number of variables. Every location has individual and unique features, stemming from the interplay of dimensional or distributional restrictions, and this is exactly where the difficulty lies in attributing a value, which may qualify a given context as “better” or “worse” than another.

The space itself is something, which already exists in nature. As soon as a man-made construction is placed within it, space is converted into place, and therefore becomes a context. The context produces a relationship between the structure and the effects of light upon it. The fundamental challenge is to avoid creating the wrong sense of scale.

Considering a structure from various observation points provides the means for verifying and simulating the impact of the structure on a given context while still in the design phase.

Geometrical aspects could also be taken into account, such as symmetry as a possible means for making the two banks on either side of the bridge alike, as opposed to asymmetry, which emphasises contrast. Perspective (from the Latin per-spicgre, to see through), or, better still, the optical science, which the ancient Greeks called optikhe, is the important theme for analysis by engineers.

If the area is degraded, it may be desirable to requalify it by proposing a design which tends to emphasise the structure in relation to its context and thus to attract attention. On the other hand, in a project for an area of natural beauty, it would be more suitable to create a structure in harmony with its environment. It is worth remembering Menn’s words: “Engineering structures lean fundamentally change urban and natural landscapes. The visual form of structures must therefore be selected with care. Bridges are among the most technically

35

challenging and culturally significant of engineering works [and] bridges can be regarded as a link between engineering and architecture…”

The statics and context of structures can be considered as follows:

-statics is a science which proposes shapes which comply with its laws, but a single static idea can yield a variety of shapes, all equally valid and acceptable;

-context is a term of reference for choosing one of the various static shapes by analyzing a whole range of other parameters.

The choice between the various statically and contextually valid shapes is made on the executive level. The final formal choice must comply in a general sense with the parameters of “construction theory” and, as specifically concerns the problems of the materials involved, but other variables, such as executive methods, costs, timing, inconvenience to users, must not be overlooked.

The choice of fabrication method may call for a construction yard on site, or for prefabricating elements elsewhere and then transporting them to the site. Prefabricated elements call for less equipment than traditional construction methods and thus take up less space in the area where the structure is to be built. On the other hand, a good road communications network is essential for the transport of particularly heavy and bulky elements, while a construction yard on site only requires a supply of concrete and reinforcement steel.

The use of prefabricated elements reduces construction time, thus reducing inconvenience to road users. Even the choice of one type of equipment as opposed to another depends on evaluation of the problems specific to the area concerned, which may suggest the use of fixed scaffolding (e.g., provisional piers, usually made of metal) in some cases, or movable elements (e.g., a launching truck) in others. It is therefore the local conditions that dictate a certain type of solution!

So the focus shifts to the actual erection of the structure, meaning by this that the project cannot avoid taking into account the practical solutions involved.

IV. Match a verb from the left with a noun from the right. Make up your own sentences with the formed word combinations.

V. Complete the definitions with the words in the box.

outline parts form circumstances

36

I. Memorize the words from Ex. I page 29.

II. Complete the word-building table.

III. Complete the sentences, use can + one of these verbs: to use, to divide, to reduce, to lead, to avoid

1.There are a number of variables involved, which can … into subjective and objective considerations.

2.A proper method for the analysis of subjective variables can … to a choice of a justifiable form.

3.The basic conditions of the structure can … to three elements.

4.Relationships between statics and shape can … to define structural details.

5.The project cannot … taking into account the practical solutions involved.

IV. Retell the text using the word combinations below.

1. The title of the story I want to tell you is… 2. First of all … 3. Second I would like to say that… 4. For your information… 5. As far as I understand… 6. In fact… 7. As far as I remember… 8. In conclusion I’d like…

Text 7 

38

Find the words you have read in the text below and translate the word combinations having these words. Use the words in the sentences of your own.

II. Work in pairs. Think of 2 or 3 questions using the words from Ex. I. Answer the questions of your partner.

III. What building materials do you know? What advantages and disadvantages of different building materials can you find? Then scan the article and check your answer.

IV. You are going to read a text about timber and masonry bridges. Five sentences have been removed from the text. Choose from the sentences A – E the one that fits each gap (1 – 5) to complete the text.

TIMBER AND MASONRY BRIDGES

The early bridges were made of stone and timber because these building materials could be easily found everywhere. The earliest type of stone bridge is one that requires no designing. When large flat stones could be found it was a simple enough matter to build piers of square stones in the stream and lay the large flat slabs on the tops of the piers. Obviously, such a construction was very limited in application, for to find a flat stone large enough to span a reasonable distance was hard enough to start with, and when found would be difficult to handle with primitive tools owing to its weight. 1 The local name for these is clap-

per bridges, and the Postbridge clapper bridge has three spans of 15 feet each. Such bridges are examples of beam or girder bridges in stone.

Stone used for bridge construction must be durable, weather proof and resistant to freezing and thawing. 2 Sometimes the builders use the arti-

ficial stone i.e. concrete made of cement, crushed rock or pebbles, sand and water.

As the stones were “dressed”, that is cut, shaped and finished by stone masons, buildings in dressed stone are called masonry. The greater the skill of the masons the longer does the building last, and this applies to bridges as well as houses and castles. Of course, wars and weather play their part too, but other

39

things being equal, a bridge built of carefully wrought masonry will last longer than one stuck together, as it were, with cement or mortar. The Romans knew this, although they were experts at making concrete. 3 But the Romans frequently depended entirely on a good fit between the stones for many of their greatest works.

Today it would require quite careful design by engineers to construct a bridge by up-to-date methods, using modern materials. But the Romans had nothing to guide them but common sense and experience.

The masonry bridges offer the following advantages:

1.Long durability. Some Roman bridges survive to our days. The only reasons for their destruction are wars and disasters.

2.Aesthetic values of these bridges adorn many cities.

3.Greater rigidity under the extra heavy super load.

4.Considerable elimination of maintenance cost.

Possible disadvantages of masonry bridges are:

1.Greater dead weight as a stone density is between 2 and 2.7 t/m3

2.Only the arch structure may be used. It produces the horizontal force – the thrust, which requires powerful foundations and solid ground to rest on.

3.Masonry bridge construction is difficult to be mechanized. It requires much handwork. So it takes the builders much more time to erect a masonry bridge in comparison with other bridge types.

Timber bridges are used as temporary structures during 10 – 15 years. Piles and cribs made of wood are often applied as bridge foundations. 4 But

metal spans save much time during bridge construction because they may be much longer than those made of wood.

The best timber for bridge building is pine, fur-tree and other soft wood as well as larch, arid cedar. 5 .

The expensive timber species such as oak, hornbeam, and beech are used only for the most important elements – the caps and dowels.

To increase its waterproof, timber is impregnated with antiseptics. It results in the service life prolongation up to 25 – 30 years. Plywood structures are widely used abroad and the spans made of this material are more durable, rigid and lighter than those made of logs and square sawn timber.

AExamples of bridges of this type are found in Cornwall and Devon, owing to the prevalence of flat granite slabs on the moors, and a good example is still to be seen at Postbridge on Dartmoor.

BSome of their bridge piers had, in fact, to be demolished by dynamite when the bed of the River Humber was deepened some 1500 years after their construction.

CThis sound wood is easily treated and does not decay.

40

DMost favorable rock for this purpose is granite, basalt, dolomite and widespread and rather cheap sandstone and limestone.

EWood is also used for bridge supports and spans.

V. Translate the following word combinations into English.

деревянный мост, высокая прочность, высушенная древесина, временная конструкция, эксплуатационные расходы, твердый грунт, клееная фанерная конструкция

VI. From the lists (1) and (2) write out the words with same meaning.

VII. Read the text again. Copy and complete the table.

VIII. Complete the following sentences by writing no more than three words for each answer:

1.Possible advantages of timber bridges are minimal construction cost, minimal weight of its elements for transportation and erection, ... , etc.

2.One of the disadvantages of timber bridges is …

3.The best timber species are …

4.Durability of a building depends on …

5.Most favorable rock for masonry bridges is …

6.While bridge building the Romans were good at …

41

IX. Give answers to the following questions.

1.What were the earliest building materials for bridges?

2.What is the most durable material for bridge building?

3.What building materials are used for stone bridges?

4.Why were the bridges the Romans built very solid and durable?

5.What bridges are difficult to mechanize?

6.What material is used for timber bridge foundation?

7.How can the service life of stone and timber bridges be prolonged?

Home Exercises

I.Memorize the words from Ex. I page 34.

II. Translate the first sentence and complete the second one in each pair. Use the Past Participle.

1.In masonry bridges only the arch structure may be used. In timber bridges ___________ ___________.

2.Stone used for bridge construction must be durable. Concrete ____________ must be __________.

3.The timber such as pine, fur-tree, larch, arid cedar is easily treated.

The timber species such as oak, hornbeam, and beech _________ _________.

4.Plywood structures are widely used abroad. Log structures ___________ ____________.

III. Describe the following structures.

1.Timber bridge foundations.

2.Timber bridge supports.

3.The basic types of timber bridge spans.

Text 8 

I. Look at the following words for about 2 minutes and get ready to write them without looking back at the words. He who has no mistakes is the

42