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Unbalanced snow distribution is one of the main reasons for the collapse of multi-span arch roofs due to excessive snow loads in the valley and leeward areas. The formation of uneven snowdrifts is closely related to the shape of the building as it seriously affects the turbulent structure and snow drifting process. This study aims to investigate the snowdrift characteristics of multi-span arch roofs based on a multiphase snowdrift approach. Firstly, the prediction accuracy of the flow field is tested to select a reasonable turbulence model. Then, the reliability of this multiphase approach is validated by comparing the results with a wind tunnel experiment of snowdrifts on a multi-span arch roof. The result preliminarily proves that this approach could well reproduce the unbalanced snowdrift on each span roof and at the trough. The snowdrift characteristics of multi-span arch roofs are investigated under different rise/span ratio and span number conditions based on the validated approach. The formation mechanism and characteristics of snowdrifts on different roofs are clarified by analysis. Finally, several typical distribution patterns are derived based on the statistical analysis of results. It is found that the middle-span roof bears a larger snow load than the roofs at both ends. • The paper proposes a multiphase approach that could accurately predict the snowdrifts on arch roofs. • The multiphase approach could well reproduce the snow drifting process and the sliding effect at roof edge. • Two kinds of unbalanced triangular snow loads are formed on the single-span arch roof according to the rise/span ratio. • The stacking snow load at the trough of the multi-span roof is about twice the peak snow load of the single-span roof. • The middle-span arch roof bears a larger snow load than the roofs at both ends of the multi-span building. [ABSTRACT FROM AUTHOR]

This study aims to provide a multiphase approach that could better consider the snow drifting development on a building roof and then apply it to the investigation of the snowdrift development on a long-span spherical roof. Firstly, the CFD prediction accuracy for the flow field and the snowdrift on a two-level step building is examined by comparing simulated results with that of a field measurement. The windward snowdrift caused by building's blocking effect and trajectories of snow particles under the action of aerodynamic force and gravity are both well reproduced by incorporating an additional source term and a slip term into the transport equations. Secondly, the prediction accuracy of the snowdrift formed on a spherical roof is confirmed through the comparison with a wind tunnel test. The snow slipping effect at the edge of the roof is also well reproduced by considering the angle of repose of the snow. Based the validated approach, the snowdrift characteristics on a long-span spherical roof are investigated under different inflow velocity conditions. Three kinds of distribution patterns, i.e., the full-span balanced distribution, half-span unbalanced distribution and transitional distribution between them, are observed. Furthermore, the predicted results correspond well with the resultant design codes developed by ISO 4355. Finally, the size effect of the building roof on snowdrifts is explored by simulating the snowdrift on the spherical roofs with different spans. It is found that the spherical roof would have to bear a larger snow load with the increasing roof span, namely, the long-span spherical roof has more risks due to the adverse snow load. • The paper proposes a multiphase approach that could accurately predict the snowdrifts on long-span roofs. • The multiphase approach could well reproduce the motion of snow and the non-equilibrium drifting process. • Three typical snow distribution patterns on the spherical roof and their corresponding inflow velocities are specified. • The long-span spherical roof is more likely to experience the most adverse snow loads. [ABSTRACT FROM AUTHOR]