Wind load is one of the factors caused by climatic conditions, which has a variable effect on buildings. It results from the pressure distribution around a structure, which is subject to a wind flow.
It generally acts as an area load perpendicular to the contact surface and is primarily a combination of pressure and suction. The slowing of the air current creates an overpressure on the frontal surfaces exposed to the wind. In the areas of the roof and side surfaces, the air current dissipates at the edges of the building creating an underpressure (suction) at these locations. An underpressure is also generated by the wake vortex on the lee side of the building.
The key factors influencing the extent of the wind load are those of the location with the local wind climate and the topography. The wind climate is recorded in the Eurocode 1 or DIN 1055-4 standards using a wind zone map, which provides a time-weighted average wind speed for various geographic regions. The topography and nature of the site surrounding the building location are provided in the standards through the terrain categories.
Additional influencing factors arise from the geometry of the building or component. Wind speed at ground level is practically zero and increases with increasing distance from the ground, i.e. with the height of the building. As well as the height of the building, the geometric form influences the intensity of the forces of pressure and suction. This is taken into account using aerodynamic coefficients.
The resulting wind force on a building or component is calculated as the product of the speed pressure, aerodynamic force coefficients and building surface areas.