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Файл:Английский язык в сфере строительства. Учебное пособие для студентов направления подготовки бакалавров 08.03.01-Строительство
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The ancient Greeks built with pieces of stone that were skillfully fitted
together and sometimes bonded with clay. They subsequently developed mortar,
and by the 2nd century BC this was being mixed with stone to make concrete. Made
from clays, and easier to use than stone because of their size and standardization,
bricks made possible the construction of the arches, vaults, and domes that were
popular in Europe from the Roman era on.With the Industrial Revolution of the 18th
century, iron brought on a new era in building in which rigid frames could be riveted
together to support a building's weight. Iron was quickly replaced by steel in the
early 20th century, and this development, along with the invention of modern
concrete in the 1870s, made possible the multistoried buildings that epitomize
modern building construction. At the end of World War II, shortage of labour,
extensive demand for housing because of bombings, and government participation
led to the widespread development of prefabricated building systems.
The design, manufacture, transportation, and erection of components could
be accomplished for many structures from a single source company, utilizing
interchangeable parts.
Before most buildings are constructed, the function of the proposed
building must be determined, a geographic location chosen, a cost estimate drawn
up, and a design plan accompanied by sketches prepared by an architect.
Architectural design proceeds in a series of stages of increasing detail and
specificity. Schematic design sketches that give a rough idea of the building's look
and form are followed by detailed development design, comprising drawings of
plans, elevations, building cross sections, and perspectives. These are followed by
working drawings and specifications, which are contract documents that describe
the design, location, and dimensions of the elements of the building and that also
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describe the quality of materials and workmanship to be used in the construction of
the building.
Surveying and laying out, or locating, the foundation are the first steps in
the actual construction of most buildings. The foundation itself (those portions of a
building resting upon earth or rock) is dependent on the weight of the building and
on the resistance of the earth on which it rests. These two factors must balance each
other.
Wood frames are light, cheap, and simple, consisting of interlocking
arrays of vertical and horizontal beams and studs. Steel structural frames consist of
vertical members (columns) and horizontal members (girders and beams) that are
riveted, bolted, or welded together. Concrete structural frames have the advantage
of costing less than steel ones, but they must usually be reinforced by steel to carry
heavy loads. Steel rods are positioned in an interconnected framework surrounded
by a wooden or steel form, and then concrete is poured into the form. The form is
withdrawn once the concrete has set. In a method known as prestressing, highstrength wires are stretched and held tight while concrete is set around them. In this
way a concrete span as long as 100 feet (30 m) can be attained.
Flooring must support whatever loads are to be placed within the structure,
and it must transmit its load to the structural frame. Roofing may be flat or pitched,
depending upon the type of framing, the load to be carried, fire resistance required,
and the overall character of the building. Structural elements called trusses, which
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are composed of interfaced triangles, can be utilized to make vast roof spans
possible.
There are a number of auxiliaries necessary in a building, including
insulation, usually accomplished by filling in spaces within flooring or walls with
fire-resistant material; ventilation, provided by complex systems of ducts or by
windows; electricity, which is wired beneath or within the finished walls; plumbing
(both for provision of clean water and for the disposal of wastes), using cast-iron
pipe inside and clay pipe underground outside; and heating and air-conditioning,
which may be accomplished by a steam boiler system, electricity, gas, or other
energy source, such as solar radiation.
1. Read and translate the text.
2. Write down 15 unfamiliar words and make sentences with them.
3. Give a short summary of the text.
SUPPLEMENTARY READING
PRIMITIVE BUILDING: THE STONE AGE
The hunter-gatherers of the late Stone Age, who moved about a wide area
in search of food, built the earliest temporary shelters that appear in the
archaeological record. Excavations at a number of sites in Europe dated to before
12,000 BC show circular rings of stones that are believed to have formed part of
such shelters. They may have braced crude huts made of wooden poles or have
weighted down the walls of tents made of animal skins, presumably supported by
central poles. A tent illustrates the basic elements of environmental control that are
the concern of building construction. The tent creates a membrane to shed rain and
snow; cold water on the human skin absorbs body heat. The membrane reduces
wind speed as well; air over the human skin also promotes heat loss. It controls heat
transfer by keeping out the hot rays of the sun and confining heated air in cold
weather. It also blocks out light and provides visual privacy. The membrane must
be supported against the forces of gravity and wind; a structure is necessary.
Membranes of hides are strong in tension (stresses imposed by stretching forces),
but poles must be added to take compression (stresses imposed by compacting
forces). Indeed, much of the history of building construction is the search for more
sophisticated solutions to the same basic problems that the tent was set out to solve.
The tent has continued in use to the present.
The Saudi Arabian goats' hair tent, the Mongolian yurt with its collapsible
wooden frame and felt coverings, and the American Indian tepee with its multiple
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pole supports and double membrane are more refined and elegant descendants of
the crude shelters of the early hunter-gatherers. The agricultural revolution, dated
to about 10,000 BC, gave a major impetus to building construction. People no longer
traveled in search of game or followed their herds but stayed in one place to tend
their fields. Dwellings began to be more permanent. Archaeological records are
scanty, but in the Middle East are found the remains of whole villages of round
dwellings called tholoi, whose walls are made of packed clay; all traces of roofs
have disappeared. In Europe, tholoi were built of dry-laid stone with domed roofs;
there are still surviving examples (of more recent construction) of these beehive
structures in the Alps.
In later Middle Eastern tholoi a rectangular antechamber or entrance hall
appeared, attached to the main circular chamber-the first examples of the
rectangular plan form in building. Still later the circular form was dropped in favour
of the rectangle as dwellings were divided into more rooms and more dwellings
were placed together in settlements. The tholoi marked an important step in the
search for durability; they were the beginning of masonry construction. Evidence of
composite building construction of clay and wood, the so-called wattle-and-daub
method, is also found in Europe and the Middle East. The walls were made of small
saplings or reeds, which were easy to cut with stone tools. They were driven into
the ground, tied together laterally with vegetable fibres, and then plastered over with
wet clay to give added rigidity and weatherproofing. The roofs have not survived,
but the structures were probably covered with crude thatch or bundled reeds. Both
round and rectangular forms are found, usually with central hearths. Heavier timber
buildings also appeared in Neolithic cultures, although the difficulties of cutting
large trees with stone tools limited the use of sizable timbers to frames. These
frames were usually rectangular in plan, with a central row of columns to support a
ridgepole and matching rows of columns along the long walls; rafters were run from
the ridgepole to the wall beams.
The lateral stability of the frame was achieved by burying the columns deep
in the ground; the ridgepole and rafters were then tied to the columns with vegetable
fibres. The usual roofing material was thatch: dried grasses or reeds tied together in
small bundles, which in turn were tied in an overlapping pattern to the light wooden
poles that spanned between the rafters. Horizontal thatched roofs leak rain badly,
but, if they are placed at the proper angle, the rainwater runs off before it has time
to soak through. Primitive builders soon determined the roof pitch that would shed
the water but not the thatch. Many types of infill were used in the walls of these
frame houses, including clay, wattle and daub, tree bark (favoured by American
Woodland Indians), and thatch. In Polynesia and Indonesia, where such houses are
still built, they are raised above the ground on stilts for security and dryness; the
roofing is often made of leaves and the walls are largely open to allow air movement
for natural cooling.
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Another variation of the frame was found in Egypt and the Middle East,
where timbers were substituted for bundles of reeds. Bronze Age and early urban
cultures It was the cultures of the great river valleys-including the Nile, the Tigris
and Euphrates, the Indus, and the Huang Ho-with their intensive agriculture based
on irrigation, that developed the first communities large enough to be called cities.
These cities were built with a new building technology, based on the clay available
on the riverbanks. The packed clay walls of earlier times were replaced by those
constructed of prefabricated units: mud bricks. This represented a major conceptual
change from the free forms of packed clay to the geometric modulation imposed by
the rectangular brick, and the building plans too became strictly rectangular. Bricks
were made from mud and straw formed in a four-sided wooden frame, which was
removed after evaporation had sufficiently hardened the contents. The bricks were
then thoroughly dried in the sun. The straw acted as reinforcing to hold the brick
together when the inevitable shrinkage cracks appeared during the drying process.
The bricks were laid in walls with wet mud mortar or sometimes bitumen to join
them together; openings were apparently supported by wooden lintels. In the warm,
dry climates of the river valleys, weathering action was not a major problem, and
the mud bricks were left exposed or covered with a layer of mud plaster. The roofs
of these early urban buildings have disappeared, but it seems likely that they were
supported by timber beams and were mostly flat, since there is little rainfall in these
areas. Such mud brick or adobe construction is still widely used in the Middle East,
Africa, Asia, and Latin America.Brick walls and corbel vault at the entrance to the
tomb chamber of Ur-nammu in the royal mausoleum.
Later, about 3000 BC in Mesopotamia, the first fired bricks appeared.
Ceramic pottery had been developing in these cultures for some time, and the
techniques of kiln-firing were applied to bricks, which were made of the same clay.
Because of their cost in labour and fuel, fired bricks were used at first only in areas
of greater wear, such as pavements or the tops of walls subject to weathering. They
were used not only in buildings but also to build sewers to drain wastewater from
cities.
The well-developed masonry technology of Mesopotamia was used to
build large structures of great masses of brick, such as the temple at Tepe Gawra
and the ziggurats at Ur and Borsippa (Birs Nimrud), which were up to 26 metres
(87 feet) high. These symbolic buildings marked the beginnings of architecture in
this culture.The development of bronze, and later iron, technology in this period led
to the making of metal tools for working wood, such as axes and saws. Less effort
was thus required to fell and work large trees. This led in turn to new developments
in building technics; timbers were cut and shaped extensively, hewed into square
posts, sawed into planks, and split into shingles. Log cabin construction appeared
in the forested areas of Europe, and timber framing became more sophisticated.
Although the excavated remains are fragmentary, undoubtedly major advances were
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made in timber technology in this period; some of the products, such as the sawed
plank and the shingle, are still used today.
Copyright (c) 1994-2002 Encyclopedia Britannica, Inc.
(6800)
MODERN BUILDING PRACTICES
THE ECONOMIC CONTEXT OF BUILDING CONSTRUCTION
Buildings, like all economic products, command a range of unit prices
based on their cost of production and their value to the consumer. In aggregate, the
total annual value of building construction in the various national economies is
substantial. In 1987 in the United States, for example, it was about 10 percent of the
gross domestic product, a proportion that is roughly applicable for the world
economy as a whole. In spite of these large aggregate values, the unit cost of
buildings is quite low when compared to other products. In the United States in
1987, new building cost ranged from about $0.50 to $2.50 per pound. The lowest
costs are for simple pre-engineered metal buildings, and the highest represent
functionally complex buildings with many mechanical and electrical services, such
as hospitals and laboratories. These unit costs are at the low end of the scale of
manufactures, ranking with inexpensive foodstuffs, and are lower than those of most
other familiar consumer products. This scale of cost is a rough index of the value or
utility of the commodity to society.
Food, although essential, is relatively easy to produce; aircraft, at the high
end of the scale, perform a desirable function but do so with complex and expensive
mechanisms that command much higher unit prices which reflect not only the
materials and labour required to produce them but also substantial capital and
research investments. Buildings fall nearer to food in value; they are ubiquitous and
essential, yet the services consumers expect them to provide can be supplied with
relatively unsophisticated technology and inexpensive materials. Thus there has
been a tendency for building construction to remain in the realm of low technology,
for there has been relatively little incentive to invest in research given consumer
expectations.
Within this general economic context, there are a number of specific
parameters that affect the cost of buildings. First are government building codes,
which are enacted to protect public health and safety; these take the form of both
prescriptive and performance requirements. Structural requirements include
description of the loads buildings must support, beginning with the constant
everyday loads of building contents imposed by gravity and extending to the less
frequent but more extreme loadings of wind and earthquake forces. These are
specified on a statistical basis, usually the maximum expected to occur with a 100year frequency.
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Safety factors for materials are specified to allow for accidental
overloading and lapses of quality control. Economic considerations are also
reflected; for example, buildings must perform well under normal gravity loads, but
no code requires a building to resist direct exposure to the wind and low-pressure
effects of a tornado, for its cost would be prohibitive. Planning and zoning
requirements provide for height and floor area limitations and building setbacks
from lot lines to ensure adequate light and air to adjoining properties. Zoning
regulations also establish requirements for permitted building usages, parking
spaces, and landscaping and even set standards for the visual appearance of
buildings. Another example is requirements for building atmosphere conditions;
these include minimum (but not maximum) temperatures and rates of air change to
dilute odours and provide an adequate oxygen supply.
Life-safety requirements include adequate stairways for emergency exits,
emergency lighting, smoke detection and control systems, and fire-resistant
building materials. Sanitation requirements include adequate numbers of plumbing
fixtures and proper pipe sizes. Electrical requirements include wire sizes,
construction requirements for safety, and location of outlets.Beyond the government
standards there are market standards, which reflect user expectations for buildings.
One example is elevator systems; elevators are not required by building codes, but
in the United States, for example, the number of elevators in office buildings is
calculated based on a maximum waiting period of 30 seconds. Cooling of building
atmospheres is also not required by code but is provided in climates and building
types where the marketplace has shown it to be cost-effective.
Building systems and components are perceived as having two dimensions
of value. One is the purely functional dimension: the structure is expected to resist
loads, the roof must keep out rain. The other is the aesthetic or psychic dimension:
stone is perceived as more durable than wood; an elevator system with a waiting
time of 30 seconds is preferable to one with a waiting time of two minutes. For these
perceived differences many users are willing to pay more.
When symbolic buildings such as temples, cathedrals, and palaces play an
important role in society, the aesthetic dimension is important in valuing buildings;
for example, the Parthenon of Athens or Chartres Cathedral commanded a level of
investment in their economies that might be roughly compared to the U.S. Apollo
space program. But in most buildings the functional dimension of value is dominant.
Because of its relatively low level of technology, wide geographic distribution,
highly variable demand, and wide variety of building products, the building industry
in industrialized countries is subdivided into many small enterprises. This lack of
centralization tends to discourage research and keeps building components sturdy
and simple, following well-tried formulas.
Within this diversity there are a number of fairly well-defined markets
based on building types; these include low-rise residential buildings, low-rise
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commercial, institutional, and industrial buildings, high-rise buildings, and longspan buildings. A somewhat similar pattern is found in eastern Europe, although the
building industry there is more centralized. There is also a much smaller low-rise
residential market, with most new housing being provided in high-rise buildings.
In developing countries the major market is for low-rise residential
buildings to house rapidly growing populations. Much of the construction is
undertaken by local craftsmen using simple building products. Local timber is
widely used, and masonry materials still include the ancient mud brick. More
sophisticated long-span and high-rise technologies are found only in major cities.
BUILDING DESIGN AND CONSTRUCTION
DESIGN PROGRAMMING
The design of a building begins with its future user or owner, who has in
mind a perceived need for the structure, as well as a specific site and a general idea
of its projected cost. The user, or client, brings these facts to a team of design
professionals composed of architects and engineers, who can develop from them a
set of construction documents that define the proposed building exactly and from
which it can be constructed. Building design professionals include those licensed
by the state-such as architects and structural, mechanical, and electrical engineerswho must formally certify that the building they design will conform to all
governmental codes and regulations. Architects are the primary design
professionals; they orchestrate and direct the work of engineers, as well as many
other consultants in such specialized areas as lighting, acoustics, and vertical
transportation.
The design professionals draw upon a number of sources in preparing their
design. The most fundamental of these is building science, which has been gradually
built up over the past 300 years. This includes the parts of physical theory that relate
to building, such as the elastic theory of structures and theories of light, electricity,
and fluid flow. There is a large compendium of information on the specific
properties of building materials that can be applied in mathematical models to
reliably project building performance. There is also a large body of data on criteria
for human comfort in such matters as thermal environment, lighting levels, and
sound levels that influence building design.In addition to general knowledge of
building science, the design team collects specific data related to the proposed
building site. These include topographic and boundary surveys, investigations of
subsoil conditions for foundation and water-exclusion design, and climate data and
other local elements.
Concurrently with the collection of the site data, the design team works
with the client to better define the often vague notions of building function into more
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precise and concrete terms. These definitions are summarized in a building space
program, which gives a detailed written description of each required space in terms
of floor area, equipment, and functional performance criteria. This document forms
an agreement between the client and the design team as to expect building size and
performance.
Copyright (c) 1994-2002 encyclopedia Britannica, Inc.
(7500)
MODERN BUILDING PRACTICES
BUILDING DESIGN AND CONSTRUCTION.
DESIGN DEVELOPMENT
The process by which building science, site data, and the building space
program are used by the design team is the art of building design. It is a complex
process involving the selection of standard building systems, and their adaptation
and integration, to produce a building that meets the client's needs within the
limitations of government regulations and market standards. These systems have
become divided into a number of clear sectors by the building type for which they
are intended. The design process involves the selection of systems for foundations,
structure, atmosphere, enclosure, space division, electrical distribution, water
supply and drainage, and other building functions. These systems are made from a
limited range of manufactured components but permit a wide range of variation in
the final product. Once the systems and components have been selected, the design
team prepares a set of contract documents, consisting of a written text and
conventionalized drawings, to describe completely the desired building
configuration in terms of the specified building systems and their expected
performance. When the contract documents have been completed, the final costs of
the building can usually be accurately estimated and the construction process can
begin.
CONSTRUCTION
Construction of a building is usually executed by a specialized construction
team; it is normally separate from the design team, although some large
organizations may combine both functions. The construction team is headed by a
coordinating organization, often called a general contractor, which takes the primary
responsibility for executing the building and signs a contract to do so with the
building user. The cost of the contract is usually an agreed lump sum, although costplus-fee contracts are sometimes used on large projects for which construction
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begins before the contract documents are complete and the building scope is not
fully defined. The general contractor may do some of the actual work on the
building in addition to its coordinating role; the remainder of the work is done by a
group of specialty subcontractors who are under contract to the general contractor.
Each subcontractor provides and installs one or more of the building systems-e.g.,
the structural or electrical system. The subcontractors in turn buy the system
components from the manufacturers. During the construction process the design
team continues to act as the owner's representative, making sure that the executed
building conforms to the contract documents and that the systems and components
meet the specified standards of quality and performance.
Copyright (c) 1994-2002 Encyclopedia Britannica, Inc. (2280)
HIGH-RISE BUILDINGS
STRUCTURAL SYSTEMS WIND LOADS
The structural systems of tall buildings must carry vertical gravity loads,
but lateral loads, such as those due to wind and earthquakes, are also a major
consideration. Maximum 100-year-interval wind forces differ considerably with
location; in the interiors of continents they are typically about 100 kilograms per
square metre (20 pounds per square foot) at ground level. In coastal areas, where
cyclonic storms such as hurricanes and typhoons occur, maximum forces are higher,
ranging upward from about 250 kilograms per square metre (50 pounds per square
foot). Wind forces also increase with building height to a constant or gradient value
as the effect of ground friction diminishes. The maximum design wind forces in tall
buildings are about 840 kilograms per square metre (170 pounds per square foot) in
typhoon areas.The effect of wind forces on tall buildings is twofold. A tall building
may be thought of as a cantilever beam with its fixed end at the ground; the pressure
of the wind on the building causes it to bend with the maximum deflection at the
top. In addition, the flow of wind past the building produces vortices near the
corners on the leeward side; these vortices are unstable and every minute or so they
break away downwind, alternating from one side to another.
The change of pressure as a vortex breaks away imparts a sway, or periodic
motion, to the building perpendicular to the direction of the wind. Thus, under wind
forces there are several performance criteria that a high-rise structure must meet.
The first is stability-the building must not topple over; second, the deflection, or
sidesway at the top, must not exceed a maximum value (usually taken as 1/500 of
the height) to avoid damage to brittle building elements such as partitions; and,
third, the swaying motion due to vortex shedding must not be readily perceptible to
the building occupants in the form of acceleration, usually stated as a fraction of
gravity, or g. The threshhold of perception of lateral motion varies considerably
with individuals; a small proportion of the population can sense 0.003 g or 0.004 g.
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