EFFECT OF OPENINGS ON WIND LOADS ON LOW-RISE BUILDINGS

Abstract

Low-rise buildings, like other structures, are designed for wind loads. External wind pressure coefficients for the design of roofs and walls are obtained from the relevant code of practices. These values depend upon shape of roof, size of building and wind incidence angle. Openings on wall surfaces lead to internal wind pressures which are also considered for the design of roof and wall claddings. However, very limited information is available in codes of practice on wind loads regarding internal wind pressure coefficients. An experimental study has, therefore, been carried out in boundary layer wind tunnel on the models of a low-rise building with flat roof. Values of wind pressures are measured on the external and internal surfaces of the walls by varying the size and locations of openings on side walls. Results obtained are presented in the form of contours and cross – sectional variation of mean wind pressure coefficients on these surfaces. The present report describes the wind tunnel study carried out to investigate the effects of wall openings on wind loads on low rise buildings. Wind tunnel studies are carried out on a 300 mm x300 mm x150 mm size Perspex sheet model with flat roof configuration. The area of openings is varied on side wall surface. The various cases of openings namely, opening on one side wall, equal openings on both side walls, opening fixed on one side wall while on the other side varying percentages opening is provided. For Case 1, openings namely 0%, 25%, 50%, 75%, 100% are considered on one side wall and pressure coefficients are obtained at wind incidence angles from 0° to 180° at an interval of 30°. For Case 2, openings namely 0%, 25%, 50%, 75%, 100% are considered on both side walls and pressure coefficients are obtained at wind incidence angle from 0° to 180° at an interval of 90°.For Case 3, openings namely 25%, 50%, 75%, 100% are kept constant on one side wall while on the other side varying percentages of opening from 0% to 100% at an interval of 25% are provided. The pressure coefficients are obtained at 0° wind incidence angle in this case. The results are presented in the form of contours and cross – sectional variation mean wind pressure coefficients. Force measurements is also done for the same cases of opening but in addition to that three more cases of openings namely, varying percentages of opening placed diagonally on side walls, opening fixed on windward wall and diagonally varying percentages of opening on iv leeward wall, opening fixed on leeward wall and parallelly varying percentages of opening on windward wall. Force measurement is done on a wooden model of same dimension as of the model used for pressure measurement. Finally, results of force and pressure studies are compared.