When considering wind loads on structures, two important terms often come up: upward wind load and leeward wind load. Let’s understand what each of these terms means:
- Upward Wind Load: Upward wind load refers to the force exerted by wind on the underside of a horizontal surface, such as the roof of a building. When wind blows over the roof, it creates a pressure difference between the upper and lower surfaces. The higher pressure on the lower surface results in an upward force, commonly known as uplift or suction.
Upward wind load is particularly significant for buildings with large roof areas, such as warehouses or open structures. It can impose considerable stress on the roof structure, leading to issues like roof membrane damage, loss of insulation, or even structural failure if not properly accounted for in the design.
To counteract the uplift force, various design techniques are employed, such as using ballast, mechanically fastening the roof, or incorporating specific shapes to disrupt the flow of air and reduce the pressure difference.
- Leeward Wind Load: Leeward wind load refers to the force exerted by wind on the side of a structure that faces away from the oncoming wind. The leeward side typically experiences a higher pressure due to the wind being obstructed by the structure, causing it to “pile up” against the surface.
The leeward wind load can be significant, especially for tall buildings or structures with large surface areas. It can result in a lateral force that tries to push the structure in the direction opposite to the wind. This force is commonly addressed by structural design measures, such as reinforcing walls, using appropriate bracing systems, or considering the dynamic response of the structure to wind-induced vibrations.
