Wind Loads on Low-slope Roofs of Low-rise and Mid-rise Buildings with Large Plan Dimensions

The present study examines wind loads on low-slope roofs of low-rise and mid-rise buildings with large plan dimensions (118 m) to investigate the suitability of wind provisions of the North American codes and standards to such buildings. Examination of such buildings is necessary since the wind provisions of the North American codes and standards were established based on wind tunnel studies involved in the determination of wind loads on buildings with common plan dimensions, i.e. less than 60 m. The size of roof pressure zones and the magnitude of pressure coefficients on low-sloped roofs of low-rise and mid-rise buildings with large spans have been examined experimentally in the wind tunnel of Concordia University. Three building models were constructed at a length scale of 1:400 with identical plan dimensions (118 m x 118 m) and different heights (5 m, 10 m, and 20 m). The models were tested in simulated open country and suburban exposures for 7 wind directions: 0°, 15°, 30°, 45°, 60°, 75° and 90°. The pressure measurements have been presented in terms of contours of enveloped pressure coefficients, local pressure coefficients, and area-averaged pressure coefficients. The results of the current study have been compared with previous studies, full-scale data and the wind provisions of the North American codes. It was found that the magnitude of external peak pressure coefficients recommended by ASCE 7-16 for low-slope roofs of low-rise buildings are much higher than the experimental findings and using those recommended by ASCE 7-10 is safe and more economical for large low-rise buildings. Also, for buildings of 8 m height or more, the corner zone should be sized according to ASCE 7-10 and NBCC 2015; and shaped based on ASCE 7-16. Moreover, for large low-rise building with low heights, say 5 m, it was found that wind loads on the roof corner are approximately equal to those on the edge zone. Exceptions for low-rise buildings with large configurations and low-slope roofs are proposed for ASCE 7 and NBBC regarding roof pressure zones and the magnitude of cladding and components external peak pressure coefficients