How Do Nature-inspired Porous Fractal Parapets Change Rooftop Pressures over a Low-rise Building?*

The increasing occurrence of severe wind events poses a growing threat, resulting in substantial fatalities and economic losses annually in the United States. Among affected civil structures, low-rise buildings are particularly vulnerable, as revealed by post-disaster surveys. The damage originates at windward corners and roof edges due to peak suctions induced by flow separation and conical vortices along rooftops. This study evaluates the efficacy of porous and nature-inspired cross-grid pattern fractal parapets with 40% porosity in mitigating rooftop suction on a 1:6 scale TTU building model for a near full-scale Reynolds number (Re = 0.92 x 106). Wind tunnel experiments at Florida International University's Wall of Wind facility involve four test cases: bare roof (no parapet), fractal parapet, and two porous parapet configurations with different strut thicknesses. The rooftop pressure statistics, the mean, rms, and peak pressure coefficients, are analyzed for several cornering wind directions. Overall, parapets exhibit effectiveness across all tested wind directions. In particular, the bio-inspired fractal parapet outperforms its counterparts, achieving peak suction reductions of about 90% depending on the wind direction. Using bio-inspired fractal cross-grid parapets is a promising passive flow control strategy to mitigate peak rooftop sections. This study contributes to ongoing efforts to find solutions to reduce damage and losses of low-rise buildings resulting from severe strong wind events.