High Reynolds number aerodynamic testing of a roof with parapet

Abstract

Aerodynamic testing was executed on a large-scale building with two distinct aspect ratios (1:6 and 1:3), at a large open-jet facility, Louisiana State University (LSU). To illustrate, a 1:15 scale test model was extensively investigated by experimental testing at a high Reynolds number (~2.3 × 107). The objective was to understand the performance of parapets in reducing the magnitude of localized and area-averaged roof pressures. Through analogy with bare-roof and several parapet configurations, the paper explores the performance of parapet walls and why they can be employed in aerodynamic mitigation. The results suggest installing a parapet wall will act as an aerodynamic mitigation device to reduce negative (uplift) loads. Large-scale testing indicates that the taller the parapet, the higher the reduction in mean and fluctuating pressures. However, depending on the roof’s aspect ratio, there is an optimal parapet height. The study concludes that 40–50% reductions in roof pressures can be achieved with parapets. Along the same lines, to yield high reductions in roof pressures, the parapet height is a key parameter. Short parapets may have low performance under conical vortices. The importance of the current study is that parapets, as well as other architectural features, are widely considered difficult to investigate by small-scale testing, at low Reynolds numbers, the leading cause of discrepancies between the laboratory and field measurements. Consequently, the current paper contributes to knowledge useful to explain the role of parapets in reducing aerodynamic pressures, for buildings to withstand wind loads at high Reynolds numbers.