Q&A for How to Calculate Wind Load

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  • Question
    I want to create a 12' diameter cylinder grain tower that's 55' high, and has a smooth surface and dome roof. How many yards of concrete does it take to anchor it for an estimated maximum wind force of 110 MPH?
    Community Answer
    The force will be around 0.0012 x ((88/60) x (110))^2. The 88/60 converts from mph to fps, and the answer is around 31 pounds per square feet. If we add the height of the dome, it is 55 + 6 = 61' tall, and 12' wide, so the area is 12 x 61 = 732 square feet. Total force acting on the tower is about 732 x 31 = 22,692 pounds, over ten tons. The force will be greatest near the top, because wind is strongest higher up, and the top will be more turbulent. Without knowing the wind gradient one can't be sure where the net force acts. You'll have to pour enough concrete to withstand over ten tons sideways near the top of your tower. We're out of space here - good luck!
  • Question
    How can I convert wind speed to wind pressure?
    Community Answer
    .0012 x the speed in feet per second squared is close enough at sea level, so that 88 FPS would give you .0012 x 88 x 88 = 9.3 pounds per square foot. 88 FPS is 60 MPH, almost 100 KPH.
  • Question
    Which instrument is used to measure wind speed?
    Community Answer
    An anemometer is used to measure wind speed. It must be recorded for 12 months to determine accurate information before the site can be detemined as usable for constructing a wind farm. Average Wind Speed is at least 5.95 meters per second to be considered viable for wind turbine energy production. It is suggested that you check out with global maps data, i.e. Valhalla, for wind speed complete information.
  • Question
    How do I find the wind load of a structure? Does the shape of a structure change the wind load?
    Community Answer
    The structure should not have a wind load. The wind will load pressure on a structure. The shape of the structure does not change the wind load, but it changes the form of the wind, and the pressures around the structure conform to the structure because of the shape. Thus pressures vary around the structure.Typically, a structure is assigned a shape factor for wind pressures, and the winds are projected from site studies into maps in the Building Codes, or into digital databases. The digital databases are just a bit more accurate, while the Building Code maps are respondent to insurance agencies risk analyses that are handled by engineers.
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