Wind pressures on buildings with stepped roofs

Abstract

The paper describes an experimental study for the evaluation of wind pressures on buildings with roofs of two different heights, such as one building with roofs at two levels or, more commonly, two flat-roofed buildings in a row. The study is experimental and consists of an extensive series of tests in a boundary layer wind tunnel simulating the flow over an open country terrain exposure. The basic model of the study has been designed and constructed in sections so that it can represent flat roofs in steps of different relative heights and widths. The maximum height of the model is variable and can represent a building up to 60 m high. The results of the study for buildings with a two-level flat roof are discussed in the paper. Data are presented in pressure coefficient form (both mean and peak values) measured locally on a number of pressure taps placed at strategic locations on the roof and wall sections of the model. The results of the study are compared with the flat-roof specifications described in the American National Standards Institute wind standard and the National Building Code of Canada. It has been found that some modifications of these standards are required to accommodate the wind loading of these building configurations. In particular, the inclusion of positive pressure coefficients must be considered for stepped roofs. Key words: building, code, design, loads, pressure, roof, wall, wind.