Gust factors: from theoretical considerations to filed measurements

Gust factors (GFs), typically defined as the ratio between the mean value of the maxima of a quantity related to the buffeting action of wind to its mean value, have historically played a pivotal role in the design of structures under winds. While the GFs may be related to velocity, pressure, or structural response, this paper is limited to a discussion on those related to wind fluctuations only as the pressure and response related factors have been extensively addressed in the literature. The wind fluctuations are random; therefore, ideally the GFs could be derived from theoretical considerations concerning the statistics of the attendant random processes. The theoretical treatment of GFs relies on the assumptions of stationarity and Gaussianity. Any departure from these assumptions, as often is the case in the field, results in inconsistencies between the measured and theoretical estimates. Another important variable is the averaging period, as the ratio of the peak in different averaging periods to the mean hourly average would obviously differ. Nonstationary features rooted not only in the variations in the mean values, but also in the fluctuations, both related to amplitude (variance) and frequency (spectral description) play an important role in defining the GF. These characteristics come into play more decisively near the eye wall of hurricanes and in thunderstorms and downbursts. This is further complicated by the very nature of turbulence whose genesis may diffe