Gust effect factors for regions of separated flow around rigid low-, mid-, and high-rise buildings

Abstract

This paper examines the gust effect factor model for regions of separated flow on rigid buildings. Boundary layer wind tunnel data for a total of 58 buildings, with heights ranging from low-rise to high-rise were analyzed. The results show that the characteristics of separated flow determine the statistical distribution of surface pressures. It was found that the reattachment of separated flows onto building surfaces reduces the skewness and kurtosis of area-averaged surface pressures, causing them to follow the Gaussian distribution more closely. However, the pressures tend to have non-Gaussian distributions for surfaces without flow reattachment. Strong Karman-like vortex shedding increases aerodynamic admittance functions around the Strouhal number, along with the peak factors and gust effect factors of area-averaged side wall pressures. For surfaces with flow reattachment, Solari's (1993a) model predicts the gust effect factors with reasonable accuracy, particularly for uplift on low-rise buildings, mid-rise buildings with height-to-width ratios, H/W = 1 and high-rise buildings with height-to-width ratios, H/W > 4, and length-to-breadth ratios, L/B > 2. For separated flows without reattachment on the building, particularly for H/W > 4 and L/B < 2, periodic Karman-like vortex shedding tends to cause inaccuracies in the gust effect factor model, as might be expected.