Tat Chiu Ho

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Wind loading codes have been mostly based on wind data on isolated buildings without consideration to the significant effect of the surroundings. Even though the surroundings tend to decrease the wind loads on average, enormous variability among wind loads on low buildings is introduced. Development of probability-based codes requires estimates of wind load statistics on a wide variety of buildings under various surroundings conditions.;This thesis determines the variability of low building wind loads through a series of wind tunnel experiments on 20 low buildings with a range of geometry and with various surroundings in a number of upstream exposures. The large amount of aerodynamic data is compressed to expected peak load coefficients by predicting the loads that would occur if the buildings were exposed to a wind climate with equal directional probability using an upcrossing method. These predicted loads are further reduced using the orthogonal decomposition technique to a series of common shapes (orthonormal functions) among the buildings and corresponding amplitudes. Specified code values are determined from the amplitudes using second moment reliability theory with consideration to variability due to other parameters in the wind load equation. Internal pressures have been analytically estimated and included in the reliability analysis. A new datum for external pressures is suggested to eliminate the bias introduced when low buildings are submerged in surroundings with structures of similar or larger heights.;Two code models are developed; a simple and a detailed model. The detailed model offers more accurate wind load distributions for designers who would forego simplicity for economic designs. The variability of wind loads is found to be significantly higher than previously estimated from isolated building results. The impact of this increased variability to wind code values is discussed through comparisons between the suggested code models and the 1990 National Building Code of Canada provisions.



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