Advancing wind load assessment of low-rise buildings: CFD and wind tunnel approaches

Abstract

Understanding wind hazards is essential for designing low-rise buildings that are resilient over time. These structures located within the turbulent Atmospheric Boundary Layer (ABL) are particularly vulnerable to wind-induced damage. In more realistic scenarios where, low-rise buildings are surrounded by similar structures, the flow and, consequently, the pressure distribution can be significantly altered. The characteristics of incident wind flow significantly influence pressure patterns and magnitudes on building façades. During windstorms, the cladding of low-rise buildings often suffers damage due to uplift forces, compromising their structural integrity. Roof damage is typically triggered by high suction regions caused by flow separation at edges and corners, forming conical and separation bubble vortices. Most previous studies focused on tall buildings for accurately evaluating and aerodynamically mitigating the wind load experimentally and numerically. Therefore, the main objective of this research is to develop a framework to accurately evaluate and effectively mitigate the wind load on low-rise buildings to enhance safety and structural integrity. The first objective of this research is to investigate the impact of discontinuous corner and ridgeline parapets on stand-alone low-rise buildings with complex roof geometry located in suburban terrain in reducing wind load by displacing the flow separation zones from the corners and edges using parapets. As for the second objective, it aims to estimate and correlate the effective parameters controlling the accuracy of the numerical wind pressure evaluation using Large Eddy Simulations (LES) on a low-rise building based on comparing wind pressures (i.e., mean and RMS) to wind tunnel results. In the third objective, the thesis aims to systematically define the required computational fluid dynamics (CFD) details to produce accurate ABL flows with LES models, particularly including a discussion aimed to efficiently select turbulence maximum frequency (𝑓𝑚𝑎𝑥) employed as an input in the turbulence flow generator concerning grid size in the refinement zones that can accurately capture the pressure fluctuation induced on the building façade. The fourth objective is to experimentally evaluate the effectiveness of parapets in reducing wind pressures on low-rise buildings under two different terrain roughness conditions and with two parapet configurations added to the benchmark model. To address the challenges faced during the experimental testing, the fifth objective is to optimally reduce the number of pressure sensors needed while maintaining accurate wind load evaluations, ultimately enhancing the resilience of buildings against wind-induced damage. This research uses multi-resolution Dynamic Mode Decomposition (mrDMD) to decompose multiscale wind pressure data into modes representing different timescales. QR-Pivoting then identifies key dynamic modes that best capture the pressure field’s dynamics. Together, these techniques can help identify sensor locations that minimize the required sensors while ensuring accurate pressure field reconstruction. This research provides a comprehensive framework for enhancing the resilience of low-rise buildings against wind-induced damage by addressing numerical and experimental challenges in wind load evaluation and mitigation.