Steel Buildings

The development of structural steel systems for tall buildings can be traced back to William LeBaron Jenny, who in 1885 used metal framework for the construction of the Home Insurance Building, an eight-story structure in Chicago. This, combined with the invention of a safe passenger elevator by Otis in 1854 led to an explosion of high-rise buildings. In the ensuing 28-year period from 1885 to 1913, the design of steel frame evolved from an eight-story building to the 800-ft tall Woolworth Building in New York City. The first generation of skyscrapers culminated with the erection of the Chrysler Building in New York in 1930, immediately followed by the Empire State Building in 1931, which held the record as the world's tallest building for 41 years.

The second wave of tall buildings began in 1956 based on new building technology and new concepts in structural design, climaxing in 1974 with the completion of the Sears Tower, a 110-story, 1450-ft tall building in Chicago. Following the Sears Tower, the postsecond generation of supertall buildings has included only "mixed" construction, consisting of both steel and reinforced concrete. The 1476-ft Petronas Towers, built in Kuala Lampur, Malaysia, in 1997, and the 1667-ft tall Taipei 101 building, which attained its full height on Oct. 17, 2003, unseating Malaysia's Towers as the world's tallest building, are two examples.

Although today's building systems have evolved from an entirely different structural concept than those of the first generation of skyscrapers, it is of interest to group the systems into specific categories, each with an applicable height range, as shown in Fig. 3.1.

At the top of the list is the rigid frame with an economical height range of about 20 stories. In its simplest form it is composed of orthogonally arranged bents consisting of columns and beams with the beams rigidly connected to columns. At the other end of the list is the bundled tube system used for the Sears Tower, consisting of an exterior framed tube stiffened by interior frames to reduce the effect of shear lag in the exterior columns.

The height range for structural arrangements shown in Fig. 3.1 is particularly suitable for prismatically shaped buildings without serious plan or vertical irregularities. They can be structured by a single identifiable system. For example, a 50-story regular prismatic building can be executed with a single system such as a tubular frame consisting of closely spaced exterior columns rigidly connected to a deep spandrels. However, buildings that are emphatically irregular in shape, with an intricate configuration such as large cutouts, vertical step-backs, etc., are less amenable to a single structural system. Therefore, the engineer has to improvise in developing an architecturally acceptable and structurally economical solution. In such situations combinations of two or even more of the basic structural arrangements need to be used in the same building, either by direct combination or by adapting different systems in different parts of the building. Therefore, the structural system for a building evolves as a response to a unique set of demands, giving engineers an opportunity to combine known systems or create their own.

System

Number of stories 10 20 30 40 50 60 70 80 90 100 110 120 130

• RIGID FRAME

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