External Wind Load refers to the forces exerted by the wind on the external surfaces of a building or structure. These loads are crucial considerations in structural design to ensure the stability, safety, and performance of the building under wind loading conditions. External Wind Load calculations take into account various factors such as wind speed, exposure, building shape, orientation, and the aerodynamic properties of the structure.
Different types of External Wind Load can be categorized based on the surfaces they act upon:
- Windward Wall Load: Windward Wall Load refers to the force exerted by the wind on the windward side of a building or structure. The windward side is the side directly facing the oncoming wind. The pressure on the windward wall is typically higher than atmospheric pressure, and it varies with wind speed, building height, shape, and orientation. Windward Wall Load calculations utilize pressure coefficients to determine the distribution of pressure on the windward wall, which is then multiplied by the reference wind pressure to calculate the total wind load.
Example: Consider a tall office building with a large glass facade facing the prevailing wind direction. The windward wall load would be calculated by assessing the wind speed, building dimensions, shape, and orientation. Pressure coefficients obtained from wind tunnel testing or computational fluid dynamics (CFD) simulations would be used to determine the distribution of pressure on the windward wall. This load is then considered in the design of the wall and its supporting structure to ensure it can withstand the wind forces.
- Leeward Wall Load: Leeward Wall Load refers to the force exerted by the wind on the leeward side of a building or structure. The leeward side is the side opposite to the direction from which the wind is coming. On the leeward side, the pressure is typically lower than atmospheric pressure, resulting in a suction or negative pressure force. Leeward Wall Load calculations also utilize pressure coefficients to determine the distribution of pressure on the leeward wall, which is then multiplied by the reference wind pressure to calculate the total wind load.
Example: Continuing with the previous example of the tall office building, the leeward wall load would be calculated by considering the wind speed, building dimensions, shape, and orientation. The pressure coefficients for the leeward wall would be determined to account for the suction forces. The design of the leeward wall and its supporting structure would be based on the calculated leeward wall load to ensure their stability and integrity under wind loading conditions.
- Roof Load: Roof Load refers to the force exerted by the wind on the roof of a building or structure. The wind flows over the roof surface, creating pressure differences that result in uplift forces or downward pressures. The distribution of pressure on the roof depends on factors such as wind speed, roof slope, shape, and the presence of nearby obstructions. Roof Load calculations consider pressure coefficients specific to the roof surfaces to determine the pressure distribution, which is then multiplied by the reference wind pressure to calculate the total wind load.
Example: Consider a warehouse with a flat roof. The roof load would be calculated by assessing the wind speed, roof dimensions, slope, and nearby obstructions. Pressure coefficients specific to the roof surface would be determined to account for the pressure distribution. The design of the roof structure, including the selection of materials and fastening systems, would be based on the calculated roof load to ensure its resistance to wind forces.
External Wind Load calculations are vital in the design of buildings and structures to withstand the forces exerted by the wind. They help engineers determine the appropriate structural elements, materials, and connections required to ensure the safety and stability of the structure under wind loading conditions. Compliance with local building codes and standards is crucial to accurately calculate and consider external wind loads during the design process.
