Experimental Evaluation of ABL and Downburst Wind Loads on an Elevated Building
Abstract
Elevated low-rise buildings are vulnerable to cladding damage underneath the structure due to extreme winds and the absence of proper wind loading codes and standards such as the National Building Code of Canada (NBCC). The space between the ground and the horizontal base surface of an elevated structure affects its aerodynamics differently compared to a ground-mounted structure. Despite the widespread use of elevated low-rise buildings, there is still limited understanding of the wind interaction across building surfaces for different stilt heights and wind types. This research aims to evaluate the impact of atmospheric boundary layer (ABL) and downburst wind loads on an elevated low-rise building with typical northern Canadian architecture, using experimental testing facilities at Western University. The Boundary Layer Wind Tunnel Laboratory was used to simulate ABL winds in open terrain and to measure the external pressure coefficients on the building model. Additionally, the WindEEE Dome was used to generate downburst-like winds and measure their resultant wind loads. The analysis of both datasets indicates that stilt height has a significant impact on surface pressures on the base surface of the building, resulting in increased peak suction near the corners and edges when the stilt height is increased. The wind loads from both test series were compared to the newly introduced ABL wind loading provisions for elevated structures in ASCE 7-22 to assess the adequacy of these design pressures on the study building. The enveloped negative external pressure coefficients due to both ABL and downburst winds were effectively covered by the ASCE 7-22 design loads for stilt heights below 2.5 m. However, 2.5 m and 3 m stilt heights produced external pressure coefficients which exceeded the design pressures of ASCE for tributary areas below 5 m2. Therefore, further refinement of external design pressures and components and cladding zones may be necessary to ensure a more conservative design of elevated structures. The results of this study can be used to improve the NBCC by incorporating aerodynamic information for elevated buildings.