Quantitative analysis of wind driven rain and wind loading effects on large-span roof structures

Wind-driven rain (WDR) research has predominantly targeted building facades and low-rise buildings, leaving gaps in understanding its effects on large-span roof structures. This study addresses this by analyzing WDR impacts on roofs through computational modeling, focusing on rainfall intensity, rise-to-span ratios, and aerodynamic interactions. The study focuses on the immediate mechanical loading effects of WDR events on intact roof structures. Firstly, raindrop catch ratio evaluations to quantify WDR distribution across curved roofs. Secondly, pressure coefficient comparisons between WDR and wind loading under varying geometries and wind angles. Finally, turbulence intensity assessments on low-sloped roofs using point vortex and Stokes theories. Results demonstrate that 95% of WDR impact was concentrated within 50%-60% of the windward roof surface, diminishing with higher rainfall intensities. Compared to wind-only conditions, WDR results in significantly altered pressure distributions and turbulence patterns, with more pronounced effects observed on curved roofs. On the low-sloped roofs, WDR induces stronger turbulence under equivalent wind angles. These findings demonstrate the spatial non-uniformity of WDR and its compounded interaction with wind loads, challenging conventional wind-resistant design assumptions. Roof covering type exerts only a marginal influence on wind-driven-rain characteristics. The study underscores the necessity of integrating coupled wind-rain simulations into large-span roof engineering to enhance weather resilience. By bridging gaps between architectural aerodynamics and precipitation dynamics, this work provides a foundational framework for optimizing roof geometries and improving predictive models against multi-hazard environmental conditions.