ABSTRACT
The earth’s terrain roughness slows the wind near the ground, thus giving rise to the planetary boundary layer, within which the wind velocity increases with height. Wind turbulence in the planetary boundary layer is typically expressed by the longitudinal turbulence intensity, which is the ratio of the standard deviation of velocity fluctuations in the mean wind direction to the mean velocity. The wind pressures on a tall building fluctuate, not only because the oncoming wind is turbulent, but also because the building creates its own signature turbulence. The fluctuations in wind load due to the direct action of the instantaneous wind pressures applied over all exterior surfaces of the building are called the background loading. Cladding is affected primarily by the exterior local wind pressure acting on a small area of the building envelope, such as the area of a single glazing unit or curtain wall panel.
