Roof Snow Drift

Flat roof snow load p f this is the snow load calculated in the previous section.

Roof snow drift.

A walk through and example of calculating snow drift loads and how to apply them roof designs usually present multitudes of roof elevations and rarely offer one single roof height. Rather there are upward wind flows on the overall building that keep high roof snow from settling onto the high roof. Density snow density γ. Version 0 0 2 september 14 2020.

The amount of additional snow load or surcharge. Because of this there are roof areas higher and lower than each other and are subject to snow drifts. Density snow density γ. Snow drift on sloped roof vmirat structural op 18 aug 09 11 36.

For leeward snow the snow doesn t blow sideways across the high roof and drop vertically down to the low roof. Rain load s r. The snow turbulence eventually results in the upper. The addition is a lower roof which is sloped shed roof.

Background and applications definition of exceptional snow drift exceptional snow drift load arrangement which describes the load of the snow layer on the roof resulting from a snow deposition pattern which has an exceptionally infrequent likelihood of occurring these load arrangements treated in annex b of en 1991 1 3 may result from. We re designing an addition to an existing building. Windward drift results from snow blown against a projection or wall below a high roof. Roof slope factor for multiple folded plate sawtooth and barrel vault roofs.

Ground snow load s s. Ground snow load s s. If your structure has a sloped or flat roof you still need to calculate the flat roof snow load. Snow drift loading lower adjacent roofs.

Typically the windward drift height hdw is less than the leeward drift height hdl unless the length of the lower roof is considerably longer than the length of the upper roof. Even with a 20 ft parapet snow will drift onto the lower roof. After you obtain the roof slope factor from those sections in asce 7 10 the. Factors lower roof c b.

Rain load s r. The lower roof slope is 4 in 12. Combination of over the ridge drift loads with roof step drift distribution of drift loads when the space available for drift formation varies in the direction perpendicular to the upwind fetch slope of the top surface of snow drift on a gable roof as a function of roof slope use this new drift load guidance as the basis for a. Snow drift loading lower adjacent roofs.

Importance factor i s. Snow capture wall roof step drift ratios variable dr generally decreasing functions of pg lu 67 snow capture wall want wall big enough to capture all expected snow transport factor of 2since dr based on capture of half expected snow transport trapping efficiency 50 aw γ 2 dr pg lu aw αho2 ho 2 dr pg lu αγ 68.