Variability of low building wind loads due to surroundings

Abstract A myriad of surface obstructions form the basic roughness that generates the Earth's planetary boundary layer. Among these are the class of structures termed low buildings. Ironically, attempts to determine wind loads on low buildings have been hampered by the random nature of these surface elements and researchers have been forced to simplify to deal with the complex problem. As a result, almost all low building research to date has been carried out on simple rectangular block-like buildings in homogeneous surroundings. While the aerodynamic behaviour of wind on isolated low buildings has been well researched, the effect of realistic surroundings has not been examined in detail. Whether the results from these simplified tests lead to the most appropriate design values remains an open question. With the establishment of a set of rational design values for low buildings in mind, it is proposed that a series of experiments be carried out to determine the wind loads experienced by low buildings in realistic environments. The experiments will be designed to collectively represent the entire spectrum of full-scale situations, i.e. the statistical distribution of parameters associated with geometry and surroundings will be matched between model and full scale. The wind loads measured in the wind tunnel will then be statistically representative of the wind loads expected on all low buildings. These expected wind loads and their variability will form a good basis to further examine the determination of appropriate wind loads for design. The first phase of this proposed study has been to examine the effect of the surroundings on the wind loads on flat-roofed low buildings, as well as to determine the relative significance of some of the more basic wind load parameters, such as effects of simulated upstream terrains, in relation to the variation introduced by the local effects of different realistic sites.