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    Posted 10-16-2018 10:14 AM
    Edited by Tirza Austin 10-16-2018 10:13 AM
    A set of pictures of a 3D printed gridshell inverted umbrella (CANDBRELLA) in the Candela style construction of groined vaulted shells is presented together with the completed hybrid GRIDSHELL-MEMBRANE INVERTED UMBRELLA video to illustrate the concepts of lightweight tensegrity hypar structures. The nanoscale model will be left outdoors to be tested for rain, wind, and snow loading conditions. Let's see how it behaves under environmental typical rain, wind, and snow. One key question I have when working with nanoscale models is: If I were to compare a small scale model to a real size structure say for a 100 mph wind, what would be the corresponding wind velocity to be applied to the nanoscale model to have representative wind pressure on the surface of the hypars in relation to the 100 mph on the real size structure. Would it be higher or lower than the 100 mph and how could I do the correlation? If anyone has any guidelines for this question, it would be great to hear about it.

    Pedro Munoz Ph.D., P.E., M.ASCE
    PRM Engineering, LLC
    Methuen MA


    Posted 10-18-2018 03:02 PM
    Edited by Tirza Austin 10-18-2018 03:02 PM
    Dr. Munoz,

    I think what you are trying to do is very interesting. We have designed a few structures for wind loads based on wind tunnel testing. I have visited the RWDI's facility in Guelph, Ontario, Canada. They built scale model of the structure and surrounding terrain in the wind tunnel and measure the wind pressures. They only measure the wind pressures for wind speed of 35 mph in the tunnel. I was a bit surprised when I learned this. How can they estimate wind pressures for 140 mph design wind speed based on a 35 mph test speed? The answer was that fluid dynamics formulas can be applied to estimate the pressures for the design wind speeds. Many of the top scientists at RWDI are involved in writing the ACSE 7 code's wind section. Dr. Peter Irwin was one of the partners at RWDI and now is a professor at Florida International University. I believe he runs the "Wall of Wind" - a large, high speed wind testing facility. It is capable of generating hurricane level wind speeds. You may be able to get more information from him. Good luck.

    Sivananthan Sritharan P.E., M.ASCE
    S & F Engineers Inc



    Posted 10-19-2018 07:17 AM
    Edited by Tirza Austin 10-19-2018 07:16 AM

    Follow up ASCE code 7-05 to use the pressure equation and select CD factor. Pressure equals to 0.00256 x V^2. V is in mph. Once you calculated pressure, plug it in in general equation to solve for wind load. F = P x A x CD. To answer your question, the wind load depends on surface area (A). For huge structure, it increases and for nano -models, it would decrease.

    Sayed Maqsood S.M.ASCE

    Oakland CA