Tall or high-rise buildings are frequently encountered in society, especially in developed nations. According to Mark Fintel (1974), the socio-economic problems that came with industrialization in the 19th century and the insatiable need for space in the big cities gave the big impetus to high-rise construction. Thus, by the latter part of the 19th century land in the rapidly developing cities was very scarce and the only option was to go up.
The development of high-rise buildings faced enormous obstacles associated with their vertical load-bearing capability in the earlier part of the 19th century. With the discovery of reinforced concrete and steel as construction materials, most of these problems were eliminated. When broken down, the effective use of these materials was facilitated by the development of high-strength materials, the development of new design concepts, the development of new structural systems, and improved construction methods. Thus, a number of high-rise buildings in existence are erected with reinforced concrete, steel, or both.
Outside the effect of its vertical loads which is usually the primary concern of structural engineers designing any kind of building, high-rise buildings face the challenge of two forces of nature that come as lateral loads in buildings. These are wind forces and earthquake forces. The effect of these forces which increases with the height of storey become more significant following the increasing use of light curtain wall, dry-wall partitions, and high-strength concrete and steel reinforcement in tall buildings. Designs try to incorporate the effect of these forces in building designs. Wind forces for instance, that are coming from a building are usually transformed into pressure. The intensity of pressure at any point on the building depends on the shape of the building, the angle of incidence of the wind, the velocity and density of the air, and the lateral stiffness of the engaged structure. Though in design, an effective lateral stiffness is designed for the structure such that it can enable the structure to withstand wind forces. However, assigning certain shapes to the buildings, which have previously been identified as one of the factors on which the intensity of wind pressure depends, can help to ameliorate the effect of these lateral forces.
In summary, the shape of structures (other than rectangular blocks) has a substantial effect on their lateral resistance. Previously, analysis of such structures was difficult but with the advent of powerful computer programs, it is easy to conceptualize, analyse and design any kind of shape for structures. The following shapes for tall structures have been identified as suitable shapes to aid in the reduction of the intensity of lateral pressures on tall buildings.
