The influence of small open fields on wind loads on low buildings

In established residential areas it is not uncommon for existing schools and shopping plazas to be well shielded by trees and dwellings for most directions but to be open over a very limited fetch of a playground or a parking area. Few codes provide advice on the evaluation of loads in such circumstances; but to ignore the shielding would result in a significant overestimate of the wind loads for the design of extensions or modifications to bring existing;Structures up to present day standards. This study predicts the uplift loads on these types of structures through an analysis of a database of calculated reactions measured on several structures. The paper outlines the development of local exposure factors that, by accounting for effects of small open fields, can refine the prediction of uplift forces on flat roof buildings in suburban areas. A modification to the National Building Code of Canada model is used to apply these factors. A study of the flow over an array of elements was used to develop a method to apply the local exposure factors to a structural system. (C) 1998 Elsevier Science Ltd. All rights reserved.