Ask Experts Questions for FREE Help !
Ask
    BRT505's Avatar
    BRT505 Posts: 1, Reputation: 1
    New Member
     
    #1

    May 2, 2008, 07:58 AM
    Wind load formula
    Have an object that is 477 square feet and the wind speed is 50 mph. what would be the wind load/force on this object? Also what would be the formula that could be used for other wind speed on this object ?

    Thanks
    ebaines's Avatar
    ebaines Posts: 12,131, Reputation: 1307
    Expert
     
    #2

    May 7, 2008, 07:34 AM
    The general formula for drag from wind resistance is:



    where is the object's drag coefficient, which depends on the shape of the object (typically 0.25 - 0.50 for a car, and usually assumed to be about 1.17 for a flat plate), is the density of the medium (air in this case , which is 1.293 kg/m^3), A is the frontal surface area, and v is the velocity of the wind.

    See: Drag (physics - Wikipedia, the free encyclopedia) for details.

    Putting everything into SI units:
    A is 477 ft^2 = 44.3 m^2
    v is 50 MPH = 22.35 m/s

    So:
    Gordon4900's Avatar
    Gordon4900 Posts: 2, Reputation: 1
    New Member
     
    #3

    Feb 18, 2011, 08:35 AM
    The force of a water jet (a fluid) with area A and velocity v onto a stationery flat plate is given by the formula:

    F = density of water x A x v2

    When I compare this with the formula above for a wind (also a fluid) why do we half the force for wind loading? I can be contacted on [email protected] if anyone wants to give me an answer.

    Thanks
    ebaines's Avatar
    ebaines Posts: 12,131, Reputation: 1307
    Expert
     
    #4

    Feb 18, 2011, 09:34 AM

    Gordon - Your formula assumes that the full momentum of the stream of water is absorbed by the plate, and the velocity of the water once it hits the plate is zero. It is derived from:



    For a stream of water of area A and velocity v:



    So if you get your formula.

    For this to be true the plate must be larger in area than the area of the stream of water. However, The aerodynamic drag formula I gave is for a body immersed in the air, so the area of the stream of air is larger than the area of the body, and the wind is deflected around the body. Also note that for the formula I gave A is the area of the body, whereas for your formula A is the area of the stream.
    Gordon4900's Avatar
    Gordon4900 Posts: 2, Reputation: 1
    New Member
     
    #5

    Feb 18, 2011, 10:24 PM
    Comment on ebaines's post
    Ebaines - OK, thanks for this. I understand the requirements for 50% to be used and it makes sense. Regards.
    mayan02's Avatar
    mayan02 Posts: 1, Reputation: 1
    New Member
     
    #6

    Apr 9, 2011, 05:42 AM
    given velocity(V) in meter per second
    pressure is equal to 0.0000473V*V
    then Force(F) = pressure(area)
    F = wind load

    for trusses:
    normal pressure = P(2sin(angle))/ 1 + square of sin(angle)
    horizontal pressure = 0.0000473V*V
    same goes in computing for F
    Archon01's Avatar
    Archon01 Posts: 1, Reputation: 1
    New Member
     
    #7

    Jul 25, 2011, 09:14 AM
    An airplane can average 130mph. If a trip takes 2 hours on way and the return takes 1hour and 15 minutes. What is the wind speed assuming it is constant? *** help
    ebaines's Avatar
    ebaines Posts: 12,131, Reputation: 1307
    Expert
     
    #8

    Jul 25, 2011, 09:28 AM

    Please do not tag a new question onto an old thread - it's better to start a new question, especially since the subject matter is so different.

    But to get you started - recall that distance = rate times time. Here the plane flies the same distance in both directions, and so you have



    and



    So



    Given a wind speed of W, the rate of travel of the plane is 130 MPH + W in one direction and 130 MPH - W in the other. You've been given values for T_1 and T_2, so can you take it from here?

Not your question? Ask your question View similar questions

 

Question Tools Search this Question
Search this Question:

Advanced Search


Check out some similar questions!

Wind load for signs calculation [ 1 Answers ]

We have a specification for a sign to withstand 30 psf minimum lateral load. How can we calculate what wind speed this can resist (what mph and at what height)?

Wind Load [ 1 Answers ]

Can someone please tell me how to calculate the wind load for a sign that is going in at my Dad' office. I don't have a copy of the International Building Code, or ASCE 7.02. The sign is 7' x 2', with 4 4"x6"'s that will hold up the sign in 2' concrete. The sign itself is 14 ft^2, and I came up...

Fiquring Wind Load [ 2 Answers ]

Have set up a small Fire Training Facility in Florida and have been asked to give the side wind load in MPH. Unit is 4 steel ocean containers stacked two high side by side and welded together and welded to concrete piers that are 36" deep and 19" in diameter. Whole unit set up is 17' tall x 16'...

Wind load [ 1 Answers ]

How can I calculate wind load on anchor bolts for chain link fence posts? Then, how to calculate same load if posts are anchored and buried in 30" of concrete?


View more questions Search