Effects of Vertical Rib Arrangements on the Wind Pressure and Aerodynamic Force of a High-Rise Building

Façade appurtenances such as vertical ribs are increasingly used on high-rise buildings to enhance the architectural appearance. These attached ribs may modify the wind pressure acting on a building by changing the local flow pattern around the building. This study investigated the effect of the extensional depth of the vertical rib on the wind pressures of a high-rise building with a square cross-section. The wind pressure distribution on different surfaces, layer force coefficient, base shear coefficient, and base bending moment coefficient were analyzed under various rib extensional depths. Moreover, the measured layer force coefficients along the heights were compared with those provided by the current codes. This study’s results show that when the building is under normal approaching flow, the negative pressure area on the front surface increases with the rib extensional depth (b). This may be induced by the local recirculation at the outermost vertical ribs, which enhances the flow separation around the building. The negative wind pressures on the leeward surface show a slight increase with the increase in the rib extensional depth. Compared to the test results, the resultant layer force coefficients provided by EN 1991-1-4:2015 and GB 50009-2012 are conservative while those from the wind effect code of Hong Kong 2019 result in an underestimated evaluation. Increasing the extensional depth of the attached vertical rib may significantly reduce the positive layer wind pressure on the windward surface by 28% but increase the negative layer wind pressure on the leeward surface by 17%. The installation of vertical ribs with a small external depth (e.g., b is less than 2% of the building width) may exert limited effects on the overall base shear and bending moment, but the maximum base shear and bending moment will be reduced by 8.8% and 7.4%, respectively, when b increases to 4% of the building width.