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Wind and Structures
  Volume 3, Number 3, September 2000 , pages 143-158

Near-ground wind and its characterization for engineering application
Jay H. Crandell, William Farkas, James M. Lyons and William Freeborne(U.S.A.)rn

    This report presents the findings of a one-year monitoring effort to empirically characterizernand evaluate the nature of near-ground winds for structural engineering purposes. The current windrnengineering practice in the United States does not explicitly consider certain important near-ground windrncharacteristics in typical rough terrain conditions and the possible effect on efficient design of low-risernstructures, such as homes and other light-frame buildings that comprise most of the building population.rnTherefore, near ground wind data was collected for the purpose of comparing actual near-ground windrncharacteristics to the current U.S. wind engineering practice. The study provides data depicting variabilityrnof wind speeds, wind velocity profiles for a major thunderstorm event and a northeaster, and the influencernof thunderstorms on annual extreme wind speeds at various heights above ground in a typical roughrnenvironment. Data showing the decrease in the power law exponent with increasing wind speed is alsornpresented. It is demonstrated that near-ground wind speeds (i.e., less than 10 m above ground) are likelyrnto be over-estimated in the current design practice by as much as 20 percent which may result in windrnload over-estimate of about 50% for low-rise buildings in typical rough terrain. The importance ofrnthunderstorm wind profiles on determination of design wind speeds and building loads (particularly forrnbuildings substantially taller than 10 m) is also discussed. Recommendations are given for possiblernimprovements to the current design practice in the United States with respect to low-rise buildings inrnrough terrain and for the need to study the impact of thunderstorm gust profile shapes on extreme valuernwind speed estimates and building loads.
Key Words
    wind velocity profile; power law; near-ground wind characteristics; wind engineering; extreme value; thunderstorms; shielding; exposure; topographic effects; variability.
Jay H. Crandell , William Farkas

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