求职信_高层建筑论文中英文资料外文翻译文献48

发布时间：2016-11-08 18:35

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英文原文

Components of A Building and Tall Buildings

1. Abstract

Materials and structural forms are combined to make up the various parts of a building, including the load-carrying frame, skin, floors, and partitions. The building also has mechanical and electrical systems, such as elevators, heating and cooling systems, and lighting systems. The superstructure is that part of a building above ground, and the substructure and foundation is that part of a building below ground.

The skyscraper owes its existence to two developments of the 19th century: steel skeleton construction and the passenger elevator. Steel as a construction material dates from the introduction of the Bessemer converter in 1885.Gustave Eiffel (1832-1932) introduced steel construction in France. His designs for the Galerie des Machines and the Tower for the Paris Exposition of 1889 expressed the lightness of the steel framework. The Eiffel Tower, 984 feet (300 meters) high, was the tallest structure built by man and was not surpassed until 40 years later by a series of American skyscrapers.

Elisha Otis installed the first elevator in a department store in New York in 1857.In 1889, Eiffel installed the first elevators on a grand scale in the Eiffel Tower, whose hydraulic elevators could transport 2,350 passengers to the summit every hour.

2. Load-Carrying Frame

Until the late 19th century, the exterior walls of a building were used as bearing walls to support the floors. This construction is essentially a post and lintel type, and it is still used in frame construction for houses. Bearing-wall construction limited the height of building because of the enormous wall thickness required；for instance, the 16-story Monadnock Building built in the 1880’s in Chicago had walls 5 feet (1.5 meters) thick at the lower floors. In 1883, William Le Baron Jenney (1832-1907) supported floors on cast-iron columns to form a cage-like construction. Skeleton construction, consisting of steel beams and columns, was first used in 1889. As a consequence of skeleton construction, the enclosing walls become a “curtain wall” rather than serving a supporting function. Masonry was the curtain wall material until the 1930’s, when light metal and glass curtain walls were used. After the introduction of buildings continued to increase rapidly.

All tall buildings were built with a skeleton of steel until World War Ⅱ. After the war,

the shortage of steel and the improved quality of concrete led to tall building being built of reinforced concrete. Marina Tower (1962) in Chicago is the tallest concrete building in the United States； its height—588 feet (179 meters)—is exceeded by the 650-foot (198-meter) Post Office Tower in London and by other towers.

A change in attitude about skyscraper construction has brought a return to the use of the bearing wall. In New York City, the Columbia Broadcasting System Building, designed by Eero Saarinen in 1962,has a perimeter wall consisting of 5-foot (1.5meter) wide concrete columns spaced 10 feet (3 meters) from column center to center. This perimeter wall, in effect, constitutes a bearing wall. One reason for this trend is that stiffness against the action of wind can be economically obtained by using the walls of the building as a tube； the World Trade Center building is another example of this tube approach. In contrast, rigid frames or vertical trusses are usually provided to give lateral stability.

3. Skin

The skin of a building consists of both transparent elements (windows) and opaque elements (walls). Windows are traditionally glass, although plastics are being used, especially in schools where breakage creates a maintenance problem. The wall elements, which are used to cover the structure and are supported by it, are built of a variety of materials: brick, precast concrete, stone, opaque glass, plastics, steel, and aluminum. Wood is used mainly in house construction； it is not generally used for commercial, industrial, or public building because of the fire hazard.

4. Floors

The construction of the floors in a building depends on the basic structural frame that is used. In steel skeleton construction, floors are either slabs of concrete resting on steel beams or a deck consisting of corrugated steel with a concrete topping. In concrete construction, the floors are either slabs of concrete on concrete beams or a series of closely spaced concrete beams (ribs) in two directions topped with a thin concrete slab, giving the appearance of a waffle on its underside. The kind of floor that is used depends on the span between supporting columns or walls and the function of the space. In an apartment building, for instance, where walls and columns are spaced at 12 to 18 feet (3.7 to 5.5 meters), the most popular construction is a solid concrete slab with no beams. The underside of the slab serves as the ceiling for the space below it. Corrugated steel decks are often used in office buildings because the corrugations, when enclosed by another sheet of metal, form ducts for telephone and electrical lines.

5. Mechanical and Electrical Systems

A modern building not only contains the space for which it is intended (office, classroom, apartment) but also contains ancillary space for mechanical and electrical systems that help to provide a comfortable environment. These ancillary spaces in a skyscraper office building may constitute 25% of the total building area. The importance of heating, ventilating, electrical, and plumbing systems in an office building is shown by the fact that 40% of the construction budget is allocated to them. Because of the increased use of sealed building with windows that cannot be opened, elaborate mechanical systems are provided for ventilation and air conditioning. Ducts and pipes carry fresh air from central fan rooms and air conditioning machinery. The ceiling, which is suspended below the upper floor construction, conceals the ductwork and contains the lighting units. Electrical wiring for power and for telephone communication may also be located in this ceiling space or may be buried in the floor construction in pipes or conduits.

There have been attempts to incorporate the mechanical and electrical systems into the architecture of building by frankly expressing them； for example, the American Republic Insurance Company Building(1965) in Des Moines, Iowa, exposes both the ducts and the floor structure in an organized and elegant pattern and dispenses with the suspended ceiling. This type of approach makes it possible to reduce the cost of the building and permits innovations, such as in the span of the structure.

6. Soils and Foundations

All building are supported on the ground, and therefore the nature of the soil becomes an extremely important consideration in the design of any building. The design of a foundation depends

on many soil factors, such as type of soil, soil stratification, thickness of soil lavers and their compaction, and groundwater conditions. Soils rarely have a single composition； they generally are mixtures in layers of varying thickness. For evaluation, soils are graded according to particle size, which increases from silt to clay to sand to gravel to rock. In general, the larger particle soils will support heavier loads than the smaller ones. The hardest rock can support loads up to 100 tons per square foot(976.5 metric tons/sq meter), but the softest silt can support a load of only 0.25 ton per square foot(2.44 metric tons/sq meter). All soils beneath the surface are in a state of compaction； that is, they are under a pressure that is equal to the weight of the soil column above it. Many soils (except for most sands and gavels) exhibit elastic

properties—they deform when compressed under load and rebound when the load is removed. The elasticity of soils is often time-dependent, that is, deformations of the soil occur over a length of time which may vary from minutes to years after a load is imposed. Over a period of time, a building may settle if it imposes a load on the soil greater than the natural compaction weight of the soil. Conversely, a building may heave if it imposes loads on the soil smaller than the natural compaction weight. The soil may also flow under the weight of a building； that is, it tends to be squeezed out.

Due to both the compaction and flow effects, buildings tend settle. Uneven settlements, exemplified by the leaning towers in Pisa and Bologna, can have damaging effects—the building may lean, walls and partitions may crack, windows and doors may become inoperative, and, in the extreme, a building may collapse. Uniform settlements are not so serious, although extreme conditions, such as those in Mexico City, can have serious consequences. Over the past 100 years, a change in the groundwater level there has caused some buildings to settle more than 10 feet (3 meters). Because such movements can occur during and after construction, careful analysis of the behavior of soils under a building is vital.

The great variability of soils has led to a variety of solutions to the foundation problem. Where

firm soil exists close to the surface, the simplest solution is to rest columns on a small slab of concrete(spread footing). Where the soil is softer, it is necessary to spread the column load over a greater area；in this case, a continuous slab of concrete(raft or mat) under the whole building is used. In cases where the soil near the surface is unable to support the weight of the building, piles of wood, steel, or concrete are driven down to firm soil.

The construction of a building proceeds naturally from the foundation up to the superstructure. The design process, however, proceeds from the roof down to the foundation (in the direction of gravity). In the past, the foundation was not subject to systematic investigation. A scientific approach to the design of foundations has been developed in the 20th century. Karl Terzaghi of the United States pioneered studies that made it possible to make accurate predictions of the behavior of foundations, using the science of soil mechanics coupled with exploration and testing procedures. Foundation failures of the past, such as the classical example of the leaning tower in Pisa, have become almost nonexistent. Foundations still are a hidden but costly part of many buildings.

The early development of high-rise buildings began with structural steel framing. Reinforced concrete and stressed-skin tube systems have since been economically and competitively used in a number of structures for both residential and commercial purposes. The high-rise buildings ranging from 50 to 110 stories that are being built all over the United States are the result of innovations and development of new structural systems.

Greater height entails increased column and beam sizes to make buildings more rigid so that under wind load they will not sway beyond an acceptable limit. Excessive lateral sway may cause

serious recurring damage to partitions, ceilings, and other architectural details. In addition, excessive sway may cause discomfort to the occupants of the building because of their perception of such motion. Structural systems of reinforced concrete, as well as steel, take full advantage of the inherent potential stiffness of the total building and therefore do not require additional stiffening to limit the sway.

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