الفهرس 
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Abstract
SUMMARY AND CONCLUSIONS
This thesis is an attempt to present a comprehensive investigation or the actual wind pressure distribution on buildings in Egypt, taking into consideration the data of wind velocities collected from over 50 meteorological stations scattered all over Egypt during the period from 1960 to 1991. From these data, the maximum annual mean wind speeds are extracted. The parameters of extreme wind speed are computed for each site using the techniques of extreme value statistics. Thus the design wind speed and design wind pressure for any chosen return period at any
site in Egypt can be computed.
For strong winds there are three values of height corresponding to the three types of roughness conditions, these values are 270 m, 400 m and 510 m. The lowest height at which the wind is unaffected by the roughness the surface terrain is in the range of 2500 m. Many empirical and theoretical formulae have been derived to represent the variation of wind velocity with height, such as the power law and the logarithmic law. The wind velocity reaches its maximum value over a longer height in urban terrain where the power law coefficient reaches its maximum value of about 0.50. Thus, the wind velocity varies and increases corresponding to the height over ground surface which is called the depth of boundary layer and the value of power law coefficient CL varies according to terrain
roughness.
At any instant, the velocity consists of a mean velocity component plus a random fluctuating component and the longest averaging time used in structural engineering practice is one hour. The averaging time decreases when the wind speed in structural design is usually in the ran of 100-150 km/hour, for an average period of 30-60 sec.
Extensive studies of wind records have shown that the wind speed’ stationary over a period of time ranging from 15 minutes to 2 hours. Moreover, the wind speed variation has a wide range of time seal ranging from several hours to fraction of a second. The choice of the average time for the mean wind speed depends upon readily available data. Davenport [37] gave the ideal averaging period between 10 and 15 minutes. The natural periods of structures are usually less than 10 seconds. On the other hand, 10-15 minutes are usually enough time for steady state conditions to be developed. The wind velocity fluctuations are unsteady and random in nature. The main characteristic feature of these fluctuations are described. Expressions for the standard deviation, probability density functions, auto-correlation function and power spectral density functions of the wind velocity fluctuations are presented. Davenport [34] showed that the standard deviation CJ’v is dependent on the gradient mean wind speed, and obtained many values for CJ’v for various terrains open country, wood land and city centers.