Characteristics of local wind pressure distribution and global aerodynamic forces on a vertical forest

Vertical forests comprise of high-rise buildings with trees planted on their balconies. When trees are planted on a building, they change its exterior, and may influence local wind pressure and global aerodynamic forces. Wind-borne debris caused by local extreme wind pressures lead to negative effects on living environments, and large acceleration responses induced by global aerodynamic forces result in occupants’ uneasiness. Therefore, it is important to investigate the local and global wind loads on vertical forests. In this study, wind tunnel tests of simultaneous multi-channel pressure measurement were conducted to investigate the effects of trees on local wind pressures (mean and fluctuating wind pressures on different positions of building facades). High-frequency-base-balance (HFBB) wind tunnel tests were performed to probe the impacts of trees on the global aerodynamic force of the building (base bending and torsional moments). Pressure measurements reveal that trees have minimal effects on mean and extreme values of wind pressure on windward and leeward facades; however, trees decrease the values of extreme wind pressure at the separation area. The results of HFBB show that vegetation slightly increases the intensity of mean global wind load at along-wind directions, decreases the peak value of power spectral density (PSD) of lift forces corresponding to vortex shedding. In general, trees on balconies reduce wind pressures at separation area as well as the across-wind fluctuating forces for the building with the side ratio of 1.67. However, there is no significant effects on the rest of wind pressures and loads. Therefore, to some extent, trees planted on balconies were found to improve wind-resistant performance of vertical forests compared with conventional high-rise buildings.