Collaborative Research: Hybrid Experimental-Numerical Methodology and Field Calibration for Characterization of Peak Wind Effects on Low-Rise Buildings and Their Appurtenances

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Mitigating hurricane damage to building envelopes and appurtenances, particularly for low-rise buildings, remains a principal challenge to achieving coastal resilience. Building envelopes include roof and wall cladding systems and openings such as windows, doors, and garage doors. Building appurtenances include roof-mounted renewable energy devices such as photovoltaic arrays, rooftop equipment, telecommunications equipment, and architectural ornamentation such as spires and trellises. During hurricanes, damage to cladding elements and appurtenances can puncture the building envelope and render the building unusable due to water intrusion and loss of interior contents. Such damage largely results from underestimation of peak wind loads on these components. This research will synthesize field data, experiments, and numerical analysis to more accurately characterize peak wind loads and wind-induced vibrations on low-rise buildings. Better characterization of peak wind loads can lead to better design and retrofit of cladding and appurtenances, thus reducing building vulnerabilities and community losses during major windstorm events. This research will foster sustainable, high-performance buildings with wind-resilient and renewable on-site energy generation systems, to reduce societal disruption from windstorm-induced power outages. The project will enhance the education of underrepresented student groups by leveraging STEM programs and using research outcomes to inform the next generation professionals on windstorm damage mechanisms of low-rise building roofs and how to improve on-site renewable energy systems. Finally, telepresence will be used during testing to increase awareness of wind hazard impacts and serve as a multiplier to reach additional audiences. Data from this project will be made available in the NSF-supported Natural Hazards Engineering Research Infrastructure (NHERI) Data Depot (https://www.DesignSafe-ci.org). Major gaps in fundamental knowledge exist in the estimation and mitigation of peak wind effects on low-rise buildings and their non-structural components, which are vulnerable to damage under high winds. First, for low-rise buildings, large-scale models are needed for accurate testing. However, these scales impose constraints on turbulence simulation, resulting in unconservative wind tunnel estimates of peak aerodynamic loads in areas of strong vorticity where damage is typically initiated. Second, for building appurtenances (e.g., rooftop solar panels), wind-induced resonant vibrations at high frequencies are unaccounted for in current wind load provisions. The research objective is to create a new physics-based, hybrid experimental-numerical methodology for accurately predicting peak wind effects on low-rise building cladding and appurtenances that (a) uses large-scale, high Reynolds number physical model tests that accurately simulate high frequency turbulence, (b) augments the test results with post-test numerical analysis to incorporate the effects of missing low frequency turbulence and dynamic responses, and (c) accounts for interference effects from surrounding structures. This methodology will be developed through a synthesis of in-situ data on building components with results from large-scale experiments at the NSF-supported NHERI Wall of Wind experimental facility at Florida International University and associated numerical analysis. This new methodology, supported by field calibration, will allow obtaining peak wind load estimates that: (a) are not subject to errors due to scaling effects, (b) include the effects of various scales of turbulence in the oncoming flow, including low frequency gusts and smaller eddies generated by the surrounding structures and by the building itself, and (c) incorporate the resonant amplification of vibrations of smaller appurtenances induced by high frequency turbulent eddies. This research will also contribute to formulating procedures that will enhance the ability of conventional boundary layer wind tunnels to simulate turbulence for larger model scales than are currently possible, and achieving new design guidelines for wind-induced dynamic effects on building components, needed in view of observed widespread hurricane-induced damage to such components. In addition, this research will lay the foundation for the formulation of structural and functional fragility curves with and without retrofitting strategies that can incentivize citizens to adopt cost-effective retrofits. Field data on peak wind effects, made available in the NHERI Data Depot, will inform the research and professional communities and help benchmark future computational fluid dynamics tools to enhance design and achieve more resilient communities.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.