Wind effects of parapets on low buildings: Part 1. Basic aerodynamics and local loads

This is the first paper in a series on the effects of parapets on the wind-induced loads on low buildings. Part 1 focuses on the basic aerodynamic effects of parapets and the local (components and cladding) loads. Wind tunnel data were obtained from about 700 pressure taps in the area of a corner panel of 3.7mx7.6m (equivalent full-scale dimensions) for several parapet heights and configurations. Significant downward loads were observed which exceed code values for all parapet heights. This may be significant when combined with other loads (such as snow or water). It was also found that parapets alter the suction loads on the roof by changing the location of the corner vortex relative to the roof, for continuous perimetric parapets, and the type of vortex formed, for isolated (single wall) parapets. In the ASCE-defined interior region, the measured coefficients for component and cladding loads exceed those in the code for all parapets and areas examined. For the edge zone, the experimental coefficients for areas less than 1 m(2) exceed the code values (except for tall perimetric parapets). However, it was found that the component and cladding loads in the ASCE 7 adequately envelope the uplift caused by perimetric parapets in the corner zone for H = 4.6 m, but not for isolated parapets, in particular for areas less than 1 m. It was also discussed that the ASCE 7 will be unconservative for larger eaves heights since H-2 is the correct normalizing factor for roof areas beneath the separated flow. Furthermore, the use of edge zone coefficients in the corner zone for It >= 0.9 m should be changed to h/(H + h) >= 0.23 in the ASCE 7. (c) 2005 Elsevier Ltd. All rights reserved.