Snow Drift loads in the Sierras
Snow Drift loads in the Sierras
(OP)
I am trying to determine the drift loading for an attached deck, but my numbers using the UBC 97 Appendix 16 equations seem very high.
Site info:
Pg = 230 psf
Pf = 161 psf
Wb = 30 ft
Width of deck = 10 ft
hr = 8.5 ft (the deck is up against a gable wall with eave height = 8.5 ft & ridge height = 15 ft, how does this affect the drifting? (there is clearly no sliding snow load)).
Our local snow is known as "Sierra Concrete", so drifting is not that common. Is it possible to make a judgement call based on local conditions?
Any comments/sugestions much appreciated,
cmhski
Site info:
Pg = 230 psf
Pf = 161 psf
Wb = 30 ft
Width of deck = 10 ft
hr = 8.5 ft (the deck is up against a gable wall with eave height = 8.5 ft & ridge height = 15 ft, how does this affect the drifting? (there is clearly no sliding snow load)).
Our local snow is known as "Sierra Concrete", so drifting is not that common. Is it possible to make a judgement call based on local conditions?
Any comments/sugestions much appreciated,
cmhski






RE: Snow Drift loads in the Sierras
In lieu of making a judgment call, you should contact the local building official and determine whether they require drift loads.
RE: Snow Drift loads in the Sierras
Good luck,
Ryan Erick Broomé, P.E.
Jacobs Consulting Inc.
RE: Snow Drift loads in the Sierras
cmhski
RE: Snow Drift loads in the Sierras
This is related to 2001 CBC Section 1612A.3.2 Exception number 2.
What is your building department's requirement in how to determine the percentage reduction? It appears to be a total judgment call. For example, flat parapetted roof presumably can't take ANY reduction where as a high-pitched roof where snow can slide may take the full 75% reduction.
RE: Snow Drift loads in the Sierras
Their website (where snow drift is not mentioned even once) states that: "One-third of the design snow load shall be added to the deadload for seismic design. (Ord. 93-05 §1(part), 1993: Ord. 88-01 §1(part), 1988: prior code §15.06.020)"
Yesterday, I also learned that they do not allow the 1.15 load duration factor for snow loads as they reasonably argue that the local snow load duration is longer than 2 months.
cmhski