Wind Load is due to the action of wind on the exterior of building. Therefore, wind can cause lateral movements of the structure. In addition, when wind passes over relatively flat roofs, it applies an upward load or suction. If the wind suction is greater than the roof weight, it may blow away the roof. Wind pressure increases with the height. The following figure shows the action of wind on a structure with gable roof.
Wind Action on a Building (Profile)
Wind Action on a Building (Plan)
Similar to snow, wind load depends largely on the building location and its importance in terms of possible loss of life due to a global structural failure (importance factor). As shown above, the wind pressure varies for different components of the building.
Local exposure of building greatly affects the design wind loads. If a building is located in an urban or suburban area the sheltering effect of the nearby buildings can reduce the wind loads; if the structure is located in a wide open area it may be subjected to much larger wind pressure. Buildings close to the shorelines or in hurricane-prone regions can be subjected to very large wind loads.
When the structure has a complex geometry, wind action cannot be easily predicted and wind tunnel testing is usually required to estimate the effects of wind load on the structure. A small scale replica of the structure along with other buildings in its vicinity, are placed in the wind tunnel and air is blown over from different directions. The wind pressure is then measured by the sensors placed on the structure .
