chapter  5
The effect of wind on tall buildings
Pages 6

The history of skyscrapers, which epitomizes the twentieth century, begins in 1885 with the Home Insurance Building. Reaching a new and important point in 1931 with the Empire State Building and gathering speed in 1972 with the World Trade Center Twin Towers, this process is unfolding at an even greater rate today. Since the weight of the structural system in the first skyscrapers made vertical forces more critical than lateral forces, wind loads were not considered important. In time, with developments and innovations in structural systems and the increase in the strength-to-weight ratio of the structural elements, the weight of buildings decreased and wind loads began to be important. Consequently, because the tall buildings being constructed today are lighter, more slender and more flexible than their predecessors, they are more prone to lateral drift with low damping, and wind-induced building sway has been transformed into one of the most important problems encountered by tall building designers, becoming a basic input to the design. The wind loads affecting the building and the response of the building depend on the following factors:

• the characteristics of the wind • the building size and geometry • the stiffness of the building and the distribution of the building mass • the inherent damping characteristics of the structural system and of the construction

material, which dissipates wind-induced building sway • the surrounding topography (issues with neighbouring buildings, etc.) • the orientation (position) of the building with respect to the prevailing wind

direction.