The point and area-averaged wind pressure influenced by conical vortices on saddle roofs

This paper investigates the point pressure and area-averaged wind pressure distributions on saddle roofs occurring below conical vortices. A wind tunnel study was firstly conducted to obtain the actual wind pressure distribution under different wind attack angles. The mean pressure distribution is used to identify the flow conditions that favor the formation of conical vortices. The vortex strength is compared under different wind directions. Suction and correlation coefficients beneath vortex cores were analyzed to identify the most unfavorable wind direction for saddle roofs, i.e. along the connection of the roof points with the highest elevations. The non-Gaussian distributions of pressure fluctuation on saddle roofs exposed to conical vortices are presented. Exponential decay function representing the suction decay throughout the influence area of conical vortices on saddle roofs is proposed. Second, the area-averaged pressures are calculated by averaging all pressure taps within the area at each instant of time. A relationship between peak loads over various tributary zones and increasing tributary areas is presented, fitted, and verified by comparing with the probability density curve of single point pressures. The Non-Gaussian feature of the area-averaged pressure time series is compared with that of point pressures using higher order moments (i.e. skewness and kurtosis). Results indicate that area-averaged pressures, whose uniform fluctuations concentrate on low-frequency ranges, are more normally distributed than individual pressures.

► The worst wind angle for saddle roof is along the connection of highest points.
► The suctions induced by conical vortices attenuate in an exponential manner.
► The decay of peak loads on tributary areas can be represented by one fitted formula.