Roof Projections And Parapets Snow

20 s 20 where s is the spacing in feet.

Roof projections and parapets snow.

Check for ice dams and icicle loads. Drifting snow generally causes large loads at relatively concentrated locations on buildings and other structures when compared to flat snow loads that blanket an entire roof area. Fig i 7 fig i 8 fig i 23. G 5 snow drift load obstruction fig.

Superpose the drift load on the base snow load. Done calculate drift surcharge load. Check for loads due to snow sliding from an upper roof. The drift on the upwind side of rooftop units rtus is a windward drift as it is for parapet walls.

See section 7 9 asce 7. Parapets can be both a safety feature designed to stop falls from the edge of the roof and also a constructional and stylistic feature a large percentage of flat roofs also feature a parapet of some height. Walls and parapets drifts on lower roof sections snow accumulation deposits in roof valleys and drifts on the leeward downwind side of objects obstructions and ridges known as aerodynamic shading figure 8. Parapets on modern roofs.

The drift on the downwind side is a somewhat reduced leeward drift composed of snow originally on the roof upwind of the rtu plus a small contribution from snow originally on top of the rtu itself. Roof snow load snow drift load step fig. Section column axial compression web crippling stiffener steel column baseplate. Generally the wind will create snow buildup against higher surfaces e g.

For simplicity asce 7 16 requires a windward drift on each side of the unit based on the larger of the two fetch distances. For roof projections l u shall be taken equal to the greater of the length of the roof upwind or downwind of the projection 33 outline minimum roof snow load thermal factor unbalanced load drift load on adjacent roof parapet wall rtu drift sliding load on adjacent roof ponding faq s 34 sliding load on adjacent roof sliding load on lower roof in 7 05. Section strength bolted connection lag screw withdrawal. See section 7 4 5 asce 7.

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