Experimental and numerical analysis of wind load distribution on large-span double-curved spherical shell roofs under downburst conditions: Terrain effects and radial position sensitivity

This study systematically investigated the influence of downbursts on the wind load distribution of large-span hyperbolic spherical roofs under different terrain conditions through the design of scaled models, combined with wind tunnel experiments and Computational Fluid Dynamics (CFD) numerical simulations. The results indicate that when the downburst core acts directly above the model, the upper roof surface experiences significant vertical impact loads, with an average wind pressure coefficient (C_p) reaching 1.0 and exhibiting a radial decrease, while the lower roof surface shows a slightly lower C_p (0.8–0.9) but with a uniform distribution. Under flat terrain conditions, as the radial distance increases (≥1.25D_jet), the Cp on the upper roof surface decays to a stable value (≈0.6), while the C_p on the windward side of the lower roof surface decreases linearly with minimal change on the leeward side, and a localized high-speed zone appears at 1.25D_jet. In contrast, under sloped terrain conditions, the C_p on the upper roof surface turns negative with an increasing absolute value, while the C_p on the windward side of the lower roof surface transitions from positive to negative, with the maximum negative pressure zone located at the edge. The CFD velocity contour lines validated the surface pressure distribution, demonstrating a high degree of consistency between the numerical and experimental data, thereby providing a reliable basis for related research.