Structural systems in the early twentieth century buildings were basically designed to resist vertical loads. Today, thanks to developments in this field and to high-strength materials, with the increase in the height of buildings and the decrease in their weight, wind and earthquake induced lateral loads have become the primary loads, especially in tall buildings, and have begun to pose more of a threat than before. As a result, for structural engineers, providing the strength to resist lateral loads in tall buildings, whether wind or earthquake induced, has become an essential input in the design of new structural systems. Owing to developments in computer technology, construction materials and structural design, tall building structural systems have gone far beyond the rigid frame system of the 12-storey, 55 m high Home Insurance Building (Chicago, 1885) (Figure 1.2), recognised as the first skyscraper, and have today reached a point that could not have been dreamed of in Le Baron Jenney’s time, attaining a level that has made possible the construction of buildings using outriggered frame systems, such as the 101-storey, 508 m high Taipei 101 (Taipei, 2004) (Figure 3.36), and the 163-storey, 828 m high Burj Khalifa (Dubai, 2010) (Figure 3.30). As the height of buildings increases, the choice of structural system decreases. While the choice of structural system in low-rise buildings is considerable, the alternatives in choice of a structural system become restricted by limitations imposed by the height of buildings. Therefore, especially in tall buildings, architectural and structural design should be considered together. Buildings can be classified on the basis of the materials used in their structural systems [structural materials of the columns, beams, shear trusses (braces), shear walls and outriggers] as:
• steel • reinforced concrete • composite.