Influence of Upstream Mature Trees on Wind Loading on the Gable Roof of a Low-Rise Building—A Wind Tunnel Study

Abstract

AbstractTrees planted in rows have been used as shelterbelts to protect crops from strong winds. Similarly, trees can be used as windbreaks to reduce wind loading on buildings to protect them from wind damages. This hypothesis was tested in this study by conducting a series of wind tunnel tests using scaled-down models of a gable-roofed, low-rise building, and a mature tree, which is taller than the building. The tree was fabricated using steel wires and wool at a length scale of 1:50, similar to the building model, and resulted in a drag coefficient (Cd) of 0.75. Several model trees were installed at various distances upstream with side-by-side, staggered, and V-shaped configurations. Wind loads acting on the building roof were estimated by measuring external wind pressure using a synchronized pressure measurement system (SPMS). The results revealed significant variations in wind pressure with the number of trees, their configurations, and distance to the building. With upstream trees, some areas of the windward roof slope, such as the windward eave, lateral edges, and the area just upstream of the ridge, were subjected to increased negative wind pressure, but its magnitude decreased on the leeward roof slope. Negative wind pressure of the roof became smaller with the increase of separation distance between the building and trees except for densely arranged trees in a row. The results also suggested mature trees increased the roof uplift force by 10–30% compared to the treeless case. Among the tested tree configurations, staggered and linearly arranged sparse trees within a 2D distance should be avoided to alleviate the adverse negative pressure of the roof. Furthermore, this study recommended planting trees in rows at a 3D upstream distance (D = building width) or in a V-shaped configuration if the separation distance is less than 3D to reduce wind loading on the gable roof of a low-rise building.KeywordsLow-rise buildingGable roofWind tunnel testingSurrounding treesExternal wind pressure