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SKYSCRAPERS

Skyscrapers are the world's tallest buildings. They provide space for offices, hotels, apartments, stores, restaurants, sports clubs, and other facilities. Some skyscrapers resemble small cities. The World Trade Center in New York City occupied a 16-acre site in Manhattan. The Center included two towers of 411 m high, several smaller office buildings, a hotel, numerous restaurants, a large mall, a plaza, a railway station, and parking garages. The whole complex covered 1.1 million sq. m of space. About 50,000 people worked in the World Trade Center; it received about 70,000 visitors daily.

A skyscraper consists of 2 main parts: the foundation (the part below ground) and the superstructure (the part above ground). Both parts help support the load of the building. The superstructure transmits the load to the foundation. The foundation consists of steel or concrete supports that rest on a layer of hard soil, to which the load is finally transmitted. In skyscrapers, a steel or concrete frame made up of beams, girders, and columns, supports the building and carries the load of roofs, walls, and floors. The walls have no load-bearing function: they hang on the frame like curtains. The curtain walls made of glass, stone, or metal are fixed to the frame by means of vertical and horizontal members. In skyscrapers over 40 stories high, the wind load is even more important than the weight of the structure.

Building a skyscraper requires careful planning. First, a construction crew digs a very deep hole for the foundation. Then, factory-made steel beams and columns of the framework are delivered to the site. After the foundation has been completed, the crew uses cranes to install the prefabricated frame units. Other workers bolt the units together, lay the floors, and put on the outside walls. Nowadays, a construction firm can put up a skyscraper frame in a few weeks, but it may take several years to finish the building.

A skyscraper's interior contains rentable space and service areas. Service areas include corridors, stairs, lobbies, elevators, machine rooms, etc. These areas provide such internal systems as plumbing, heating, air conditioning, ventilation, electrical supply, etc. Plumbing systems consist of a water supply system and a drainage system. In a skyscraper, pumps increase the pressure within the pipes so that water reaches the upper storeys.

Air conditioning and ventilation systems control the temperature by circulating warmed or cooled air inside the skyscraper. Electrical systems supply power for lighting and office equipment, as well as for communication services, including telephones and computers. In skyscrapers, elevators travel at speeds as high as 600 m (1,970 ft) per minute. A group of elevators typically serves a zone of 15–20 storeys.

Many parts and systems of a modern skyscraper did not all appear at once. The skyscraper has been developing since the 1890's. At that time, builders began to use new technologies that made skyscrapers possible. Skyscrapers first appeared in Chicago and New York City, due to the rising land costs, and because business people wanted concentrated centers that would provide quick access to offices and banks.

FROM THE HISTORY OF BUILDING

Many thousands of years ago there were no houses such as people live in today. In hot countries people sometimes made their homes in the trees and used leaves to protect themselves from rain or sun. In colder countries they dwelt in caves.

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Later people left their caves and trees and began to build houses out of different materials such as mud, wood or stones.

Later people found out that bricks made of mud and dried in the hot sunshine became almost as hard as stones. In Ancient Egypt especially, people learned to use these sun-dried mud bricks. Some of their buildings are still standing after several thousands of years.

The Ancient Egyptians discovered how to cut stone for building purposes. They erected temples, palaces and huge tombs. The greatest tomb is the stone pyramid of Khufu, king of Egypt. The ancient Egyptians often erected their huge constructions to commemorate their kings or pharaohs.

The ancient Greeks also understood the art of building with cut stone, and their buildings were beautiful as well as useful. They often used pillars partly for supporting the roofs and partly for decoration. Parts of these ancient buildings can still be seen today in Greece.

The Romans were great bridge, harbour and road builders. In road work the Romans widely used timber piles. They also erected aqueducts, reservoirs, water tanks, etc. Some of their constructions are still used till now. It is known that the manufacture of lime is one of the oldest industries used by man. Lime is a basic building material used all over the world as today so in the ancient world. One of the Romans, Marcus Porcius Cato, gave an idea of a kiln for lime production: its shape and dimensions. Such kilns were fired with wood or coal and were extremely inefficient.

There are still many remains of kilns in some places of Great Britain as well as roads and the famous Hadrian Wall, which was erected to protect Romans from the celtic tribes in the first century A.D. Britain was a province of the Roman Empire for about four centuries. There are many things today in Britain to remind the people of the Roman: towns, roads, wells and the words. In a period of 800 to 900 years the Romans developed concrete to the position of the main structural material in the empire. It is surprising, therefore, that after the fall of the Empire, much of the great knowledge should have disappeared so completely. The knowledge of how to make durable concrete has been lost for centuries, but mention was made of it in the writings of architects from time to time.

Fusion of Roman and North European traditions in construction was reflected in many ways. Buildings combined the Roman arch and the steep peaked roof of Northern Europe. Roman traditions were continued in the architectural form known as Romanesque. London Bridge, finished in 1209, took thirty-three years to build. It consisted of nineteen irregular pointed arches with its piers resting on broad foundation, which was designed to with stand the Thames current.

The Roman period was followed by other periods each of which produced its own type of architecture and building materials. During the last hundred years many new methods of building have been discovered. One of the recent discoveries is the usefulness of steel as a building material.

Nowadays when it is necessary to have a very tall building, the frame of it is first built in steel and then the building is completed in concrete. Concrete is an

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artificial kind of stone, much cheaper than brick or natural stone and much stronger than they are. The Egyptians employed it in the construction of bridges, roads and town walls. There are evidences than ancient Greeks also used concrete for the building purposes.

The use of concrete by the ancient Romans can be traced back as far as 500 B.C. They were the first to use it throughout the ancient Roman Empire on a pretty large scale and many structures made of concrete remain till nowadays thus proving the long life of buildings made of concrete. Of course, it was not the concrete people use today. It consisted of mud, clay and pure lime, which were used to hold together the roughly broken stone in foundations and walls. It was so-called «pseudoconcrete». The idea of such building material might have been borrowed from the ancient Greeks as some samples of it were found in the ruins of Pompeii.

DESIGN OF RESIDENTIAL AREAS

The term «design» in connection with residential areas means the arrangement of the various parts (the houses, roads, and so on) in such a way that they function properly, can be built economically and give pleasure to look at. The appearance of the area develops from its function and the way it is built, and is not something which is applied after the scientific, constructional and economic problems have been solved. These latter problems which are at the root of design, have received a fair share of attention in technical publications, and judging by results, are better understood than those concerned with appearance.

The term «residential area» is commonly taken to mean an area of urban development in which the majority of buildings are dwellings and from which conflicting buildings are excluded. It has now become generally accepted that an area of dwellings, however well designed, is not by itself sufficient to meet the needs of the inhabitants. Schools, shops, playing fields, a meeting hall and other communal facilities are necessary to meet these needs, and an area which contains them is generally called «a neighborhood». There may be very wide variations in size and shape between one neighborhood and another, depending on the structure of the town as a whole and on the topography.

There is a strong aesthetic argument for subdividing the neighbourhood into housing units. An area of some two or three thousand dwellings is likely to be exceedingly dull in appearance, simply because there is little visual relief from bricks and mortar. Even a variety of dwellings will not help matters, because a general impression of the same kind will remain. If, on the other hand, the area is subdivided into a series of areas, each having its own characteristics (so that it is distinguished from the others), and if all of them are held together by the structure of the neighborhood plan, there will be variety through the contrasts of each area and unity within the neighborhoods as a whole.

BUILDING MATERIALS

Materials that are used for structural purposes should meet several requirements. In most cases it is important that they should be hard, durable, fireresistant an easily fastened together.

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The most commonly used materials are steel, concrete, stone, wood and brick. They differ in hardness, durability and fire-resistance. Wood is the most ancient structural material. It is light, cheap and easy to work. But wood has certain disadvantages: it burns and decays.

Stone belongs to one of the oldest building materials used by men. It is characteristic of many properties. They are mechanical strength, compactness, porosity, sound and heat insulation and fireresistance. Bricks were known many thousands of years ago. They are examples of artificial building materials.

Concrete is referred to as one of the most important building materials. Concrete is a mixture of cement, sand, crushed stone and water. Steel has come

into general use with the development of industry. Its anufacture requires special equipment and skilled labour.

Plastics combine all the fine characteristics of a building material with good insulating properties. It is no wonder that the architects and engineers have turned to them to add beauty to modern homes and offices.

All building materials are divided into three main groups:

1.Main building materials such as rocks and artificial stones, timber and

metals.

2.Binding materials such as lime, gypsum and cement.

3.Secondary or auxiliary materials which are used for the interior parts of the buildings.

We use many building materials for bearing structures. Binding materials are

used for making artificial stone and for joining different planes. For the interior finish of the building we use secondary materials. Natural building materials are: stone, sand, lime and timber. Cement clay products and concrete are examples of artificial building materials.

TIMBER

Timber is the most ancient structural material. In comparison with steel timber is lighter, cheaper, easier to work and its mechanical properties are good. On the other hand, timber has certain disadvantages. First, it burns and is therefore unsuitable for fireproof buildings. Second, it decays.

At present an enormous amount of timber is employed for a vast number of purposes. In building timber is used too.

Timber is a name applied to the cut material derived from trees. Timber used for building purposes is divided into two groups: softwoods and hardwoods. Hardwoods are chiefly used for decorative purposes, as for panelling, veneering in furniture, and some of them are selected for structural use because of their high strength and durability, in modern construction timber is often used for window and door frames, flooring, fences and gates, wall plates, for temporary building and unpainted internal woodwork.

Timber cannot be used for either carpenters' or joiners' work immediately it has been felled because of the large amount of sap which it contains. Elimination of this moisture increases the strength, durability and resilience of timber.

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STONE

Stone has been used as a structural material since the earliest days. Almost of all famous buildings of classic times, of the medieval and Renaissance periods and of the eighteenth and early nineteenth centuries were erected of stone masonry. In some places stone was used because of the scarcity of timber, bin in other places stone was preferred because of its durability.

The stones which are usually used for masonry work are as follows:

1.Granite is very hard, strong and durable. It is used particularly for basements base courses, columns and steps and for the entire facades. Its colour may be gray yellow pink or deep red.

2.Sandstone. Sandstone is composed of grains of sand or quarts cemented together. Sandstones form one of the most valuable materials. The durability of sandstones depends very largely upon the cementing material.

Thus, there are different kinds of sandstones. Many sandstones are exceptionally hard and are selected for steps, sills etc. The excellent state of preservation of many ancient buildings built of this stone is evidence of this. But city buildings constructed of sandstone often assume a drab appearance owing to the dark colour. It is an excellent material for concrete aggregate.

3.Marble is a crystalline stone chiefly used for decorative purposes

White and black marbles are used for ornamental decoration where the beauty of the marble is shown to its best advantage.

CONCRETE

It is difficult to imagine modern structure without concrete. Concrete is the very building material which led to great structural innovations. The most important quality is its property to be formed into large and strong monolithic units. The basic materials for making concrete are cement, aggregate and water. Cement is the most essential material and the most important one for making concrete of high quality. Cement is made of limestone and clay. It is burnt at high temperature and ground up into powder. During the grinding a small percentage of raw gypsum is added otherwise it would set too quickly. Depending on the kind and composition of the raw materials different types of cement are obtained: Portland cement, blast furnace cement, rapid-hardening cement and many others.

Concrete is made by binding together particles of sand and gravel, stone or broken brick. The binding agent used is a paste of Portland cement and water, in suitable proportions. When water is added to the cement, hydration takes place. This causes the whole mixture to set and harden, forming a solid mass. Cement starts hardening one hour after the water has been added and the process of hardening lasts for about twenty-eight days. The process is called concrete curing. The strength of concrete under favourable conditions increases with age. The strength of concrete is very rapid in the early stages, but continues more slowly for an indefinite period amounting to years. The sand, gravel (or broken stone) are termed «aggregate»; sand is known as «fine aggregate», and gravel as «coarse aggregate». Concrete can be made on a building site and poured into position as a wet mix, or it may be used as the materials for making prefabricated units in a plant.

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The characteristics of concrete depend upon the quality of the materials used, grading of the aggregates, proportioning and amount of water. The most important requirements for concrete are: it should be hard, strong, durable, fire-resistant and economical. To get the best of concrete the following considerations should be kept in mind:

1.The most suitable proportions of cement and aggregate are: 1 part cement, 2 parts sand and 4 parts of gravel.

2.The water used for mixing cements, limes and plasters must be reasonably clean. Pond, river and canal water often contain different impurities and should not be used without examination. Water fit for drinking can be assumed to be free from harmful ingredients. Excess of water is detrimental to the ultimate strength of the concrete.

3.The sand should be clean. Therefore, if impurities are present, the binding is

affected.

Concrete can be divided into two classes: mass or plain concrete and reinforced concrete (ferro-concrete) where it is necessary to introduce steel. Plain or mass concrete can be used for almost all building purposes. Ferro-concrete is used in building bridges and arches, dams and dock-walls, for structures underwater, for foundations, columns and beams. The use of concrete and ferro-concrete is almost universal.

Urban growth increases average travel time and mobility of people, there is a sharp increase In the intensity of road haulage and the number of transportation facilities. On roads and streets, as is known, the number of vehicles increases several times faster -than the road network causing super saturation by transportation of the street network and traffic congestion which is already to be observed in many large cities of the United States and other capitalist countries.

The main problem facing large modern cities is to make the most effective use of urban land without further encroachment on adjacent land.

Towns now in the planning stage or under construction should not only meet man's present day needs but also his diversified activities in the years to come. A part of the buildings including residential and service buildings will either be replaced by new ones or eliminated altogether by future generations, but the main skeleton of the city will remain much longer. It is difficult to accurately predict development in such areas as atomic energy, new building materials and components, self-powered transportation, and other areas of scientific-technological progress affecting the development of city planning but it is precisely this that makes it necessary to predict the further development of cities, their plan' structure and architectural and spacial composition.

In this connection, it is advisable to take a look, if only briefly, at some of the most widespread concepts in modern city planning and prospects for its development, in particular:

New population distribution systems.

Plan structure of new and rehabilitated old cities. New building materials and components.

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New types of transportation.

WATER AND AIR POLLUTION PROBLEMS

Water and air pollution are the two main factors that destroy the environment in big cities. Paris has no industry, so the Seine is not polluted by industrial effluents but by sewer waters. However, this problem is being solved by building pollution control stations in a Paris suburb. The sewage is channeled into them and cleansed before it goes into the Seine. When visiting these installations, one can often see how pure water the processed water is – the engineers who work there drink it quite cheerfully.

Water is purified by mechanical and biological methods. The purified water is treated with chlorine and released into the rivers, whence it enters the water supply systems where it undergoes further and finer treatment.

Air is mainly polluted by heating systems and cars. When you look at a modern city from a hill top you get the impression of vapour (smog) lingering over the city especially when there are no winds which can air the city. However, when there is no wind they have smog. As regards heating, mazut and gas are used rather than coal for last years. The poisoned air is the most modern quarters of the city.

District heating is an effective method. Several heat-and-power plants generate steam, which is piped underground all round the city.

As for cars you know, of course, how heavy traffic is in big cities. The slower the traffic, the more exhaust fumes are. This problem will be solved in the near future.

The acuteness of the problem depends on how well the country is developed and on the number of the cars. Many of these problems are international in nature.

HEATING, VENTILLATION AND AIR CONDITIONING

When designing a small home that is to be air-conditioned, many factor must be considered to achieve economical installation and low operating costs. A system controlling the temperature, humidity and filtering of the air is adequate for home conditioning.

Units with very accurate controls, as used in industrial or large commercial installations are not required for small residence.

A house to be efficiently and economically air-conditioned should be designed so that the heat gain is as low as possible. This is achieved by proper orientation, location of glass areas, insulation and ventilation of roof. Natural elements such as trees, planting and water areas should be utilized to provide shade and cooling.

For the sake of economy and efficiency in the small home the central core plan is often advised. The central service core has the following advantages:

1. Economical structure. 2. Grouped plumbing. 3. Efficient ductwork. 4. Flexibility of plan around core to utilize orientation.

The air conditioning unit should be located in the center of the plan to minimize ductwork and insulation. Oversize units are as inefficient as undersized conditioning units. The proper unit that will operate steadily, rather than in surges of

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cooling periods, will provide better results, because between surges humidity builds up and destroys the comfort balance. Ideal interior humidity is 50%.

The cost and availability of electricity and water should be obtained to estimate operating costs of equipment. If supply of water is limited or expensive, conditioning systems with water saving devices are necessary.

WATER AND WATER SUPPLY

Centralized water supply dates back to 2500 BC. Ancient Egypt had complex engineering structures for the purpose. Yet to this day the percentage of the population enjoying centralized water supply on the African continent and in Asia, too, is very low.

In our country, at the time of the Revolution of 1917, only one third of the towns had running water laid on, and, then, as a rule, only in the central part of the town. In the pre-war period of industrial development running water reached millions of flats all over the country. Water supply of the systems are practically all in the western and central parts of European Russia, were destroyed during the war and had to be built anew.

Fresh water shortage was first mentioned soon after the end of the Second World War. The first to feel the stint was Europe. The problem came to many as a complete surprise, something in the nature of an unexpected “catastrophe”. This catastrophe, however, should have been foreseen, for it follows logically from the development of human life on our planet and of Man’s industrial activity.

In the absence of centralized water supply, a man can do with about 25 litres of water a day for his various personal needs. But in the modern city water consumption per person is much higher. An average of 300 to 500 litres of water is spent daily on household and sanitary needs per one inhabitant of a modern city. You can see this vastly exceeds the necessary minimum of 25 litres. Why the discrepancy (difference)? Not because people leave their taps open. Because water is so abundant nobody thinks twice about taking a shower, or a bath, using the washing machine, washing the car, etc. The volume of water consumption is indicative not only of the efficiency of the water supply but also of the population’s living standards.

One need in water is growing. Simultaneously, the globe’s population is growing. In the past century the consumption of water by the world’s largest cities, such as Paris, London, Berlin and Moscow, has grown 80 to 100 times. During the famous heat wave of 1972 Moscow «drank» almost 5,000,000 cubic metres of water a day. This staggering figure seems to confirm the immediacy of the water dearth problem. In actual fact, however, the problem consists not so much in where to get pure water but in how to deliver it to where people need it.

WATER POLLUTION IN THE USA

The problem of solving pollution from the technical view-point has turned out to be more difficult than expected.

First of all, it became evident that in certain reservoirs such great qualitative changes had taken place that it was practically very difficult to return them to their

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former state. Irreversible changes have taken place in the Great Lakes, because the disturbances in the organic environment of the lakes are irremediable.

New types of pollution are being discovered. Not so long ago a stable and dangerous pollutant called PChB (polychlorinated biophenyl) was identified. The danger is doubled because of the fact that PchB accumulates in the bottom sediments and is preserved in rivers for many years after it is no longer dumped into them. The concentration of this pollutant is very great in the Great Lakes, in such rivers as the Hudson, the Connecticut, the Mississippi, the Missouri, the Ohio, the Sacramento, the Rio Grande, and the Yukon.

The difficulties in combating PChB also lie in the fact that so far it has not been accurately established what kind of pollutants bring about its formation in reservoirs. The variety of polluting sources is growing. The expansion of urban territories with asphalt-covered roads, the increase in the production and the complex composition of chemical substances and combinations used in everyday life had led to the increasing role in polluting water resources played by the drainage from the territory of cities, towns and villages. Besides that, the sphere of water pollution is broadening. During the recent years there appeared a new problem – the pollution of ground water. The pollution of ground water is caused by a great variety of reasons: numerous waste dumps scattered all over the area and exposed to the influence of rainwater, polluted surface reservoirs, the disposal of sewage from factories (waste matter as well), and the use of water on oil-fields.

Water supply at the expense of ground water plays an important role in the lives of many towns and cities and in the production of foodstuffs. The water supply of 12-15 million families depends upon individual underground boring wells, which have no purifying facilities. 71 per cent of the public water supply is based upon the ground water. The complexity of the issue is in the fact that the physico-chemical processes of the transformation of ground water are still not fully explored.

Internal economic and political problems are impediments to solving the pollution problem. For several years conflicts have been taking place between private companies, the federal government and the authorities of separate states. The Association of the Chemical Industry for example, has declared that it is unrealistic to expect the modernization of purifying technology, as required by law. Quite often local authorities do not plan building a system of second time purification. Discussions are in the progress, while polluted water runs into reservoirs creating a threat to the health of the people, and complicating the second utilization of sewage.

The arms race and the energy crisis have an impact on the problem of reproduction of water resources. Attempts to overcome the energy crisis have brought about the postponement of many water purification measures.

The problem of providing the country with water resources is still far from being solved.

WATER RESOURCES OF THE USA

The USA is one of the first countries whose developing economy has met with a shortage of pure fresh water. Such conflicting situations have been caused by the exceptionally rapid growth of water consumption and by the constancy of the size of

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river runoff. The water crisis began to show at the beginning of the 60s. It was then when the gigantic projects were born to transport fresh water from Canada and Alaska to the main territory of the USA. At the end of 60s it became evident that the problem could not be solved by purifying utilized water.

By spending large sums of money on developing gigantic desalination plants it became clear that by channeling the runoff from the neighbouring territories and from the ocean an increase in the volume of polluted water would be brought about, which even at present overfills the rivers and lakes of the country.

It is the run off which can be used without a full regulation of rivers by hydro technical installations. It is possible by recycling the same volume of water, which claims great requirements to the quality of their purification.

The main increase in water consumption takes place in that sphere of national economy, where water is necessary principally for cooling purposes – in industry, especially in heat-power engineering.

How can water losses be replenished? It is necessary to note the evergrowing consumption of ground water. The removal of considerably greater volumes of ground water that are taken at present will not diminish their total storage for a long time. Water supply at the expense of ground water is also convenient to satisfy the every day necessities of the population.

Other reserves that can be used are the water of the ocean. A wide substitution of fresh water for salt water for cooling purposes is assumed, mainly in heat-power engineering.

Over one quarter of the whole consumption of water will become possible due to the use of seawater. As concerning the above mentioned projects according to which fresh water is to be transported from Canada and Alaska and the entailed possibility to use the great reserves of hydropower of the western part of the continent, they have been cancelled.

PANEL HEATING

(1)Heating and ventilation are two branches of engineering which are very closely connected and concerned with providing a required atmospheric environment, former with respect to heat supply to produce a desired temperature for maintaining comfort and health, the latter with supply and removal of air often with emphasis on contamination of the air.

(2)Heating prevents the too rapid loss of heat from the body. By heating the ambient air of walls, ceiling or floor the rate of heat loss from the body is controlled. The determination of the capacity or size of the various components of the heating system is based on the fundamental concept that heat supplied to a space equals heat lost from the space. The most widely used system of heating is the central heating, where the fuel is burned in one place – the basement or a specially designed room and from which steam, hot water or warm air is distributed to adjacent and remote spaces to be heated.

(3)There two most common systems of heating – hot water and steam. Both systems are widely used nowadays. A hot-water system consists of the boilers and a system of pipes connected to radiators. They are suitably located in rooms to be

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