1、 1 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
2、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 ele
3、vator. 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 frame
4、work. 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
5、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 an
6、d 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 1880s in Chicago had walls 5 feet (1.5 meters) thick at the lower
7、 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” r
8、ather than serving a supporting function. Masonry was the curtain wall material until the 1930s, 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 . After the w
9、ar, 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 height588 feet (179 meters)is exceeded by the 650-foot (198-meter) Post Office Tower in Lo
10、ndon and by other towers. 2 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 column
11、s 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 a
12、nother 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
13、 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
14、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
15、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
16、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 s
17、lab 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
18、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 t
19、he 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 mechanic
20、al 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 3 suspended below the upper floor construction, conceals the ductwork and contains the lighting units. Electrical wiring for powe
21、r 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 Am
22、erican 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
23、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 str
24、atification, 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
25、 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 so
26、ils 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
27、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 so
28、il. 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, exempl
29、ified by the leaning towers in Pisa and Bologna, can have damaging effectsthe 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
30、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, carefu l 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
