Calculate wind load on any building

Mahreen Zamir Abro14ce-16

Wind load : Wind represents masses of air moving mainly horizontally (parallel to the ground) from an area of high pressure to an area with low pressureThe main effect of wind is a horizontal loading of buildings (especially high-rise). This effect of the wind on the structure (i.e. the response of the structure), depends on the size, shape and dynamic properties of the structure

When the wind enters the building from the windward side and leeward side is relative closed, internal pressure is developed that acts like negative pressure Similarly, when high speed wind passes by a building, it produces a vacuum on the leeward side, this vacuum results in internal suction producing negative pressure from the structure Keeping the movements in the upper levels of the building to acceptable human tolerances is the goal of the structural engineer

Types of Wind Load Forces on Buildings:

Shear Load Lateral Load Uplift Load

To assist in your wind loading analysis, use the following wind load calc to get the necessary wind load calculations. Accurate wind load calculations will that a safe, durable structure is assembled

Wind Load Calculation :In order for a structure to be sound and secure, the foundation, roof, and walls must be strong and wind resistant. When building a structure it is important to calculate wind load to ensure that the structure can withstand high winds, especially if the building is located in an area known for inclement weather.

Calculations :The generic formula for wind load is  Fw = A x P x Cd  . This equation is useful for estimating the wind load on a specific object, but does not meet building code requirements for planning new construction.

The simple formula for wind pressure P in imperial units (pounds per square foot) is P=0.00256V^{2} and the pressure in SI units (Newtons per square meter) P=0.613V^{2}.  

Drag is the force that air exerts on the building, affected by the building's shape, the roughness of its surface, and several other factors. Engineers typically measure drag directly using experiments, but for a rough estimate you can look up a typical drag coefficient for the shape you are measuring. For example: The standard drag coefficient for a long cylinder tube is 1.2 and for a short cylinder is 0.8. These apply to antenna tubes found on many buildings.The standard coefficient for a flat plate such as the face of a building is 2.0 for a long flat plate or 1.4 for a shorter flat plate.The drag coefficient has no units.

For example, let’s say you want to determine the wind load on an antenna that is 3 feet long with a diameter of 0.5 inches in a gust of 70mph win ds. Start by estimating the projected area.In this case,  A=dw=(3ft)(0.5in)(1ft/12in)=0.125ft^{2}Calculate the wind pressure: P=0.00256V^{2}=0.00256(70^{2})=12.5psf}.For a short cylinder the coefficient of drag is 0.8.Plugging into the equation: F=APCd=(0.125ft^{2})(12.5psf)(0.8)=1.25lbs.}1.25 lbs is the amount of wind load on the antenna

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