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

In established residential areas it is not uncommon for existing schools an d shopping plazas to be well shielded by trees and dwellings for most direc tions 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 circumst ances; but to ignore the shielding would result in a significant overestima te of the wind loads for the design of extensions or modifications to bring existing;Structures up to present day standards. This study predicts the u plift 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 o f small open fields, can refine the prediction of uplift forces on flat roo f 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 a n array of elements was used to develop a method to apply the local exposur e factors to a structural system. (C) 1998 Elsevier Science Ltd. All rights reserved.