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RE: Snow load in combination with seismic.

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I would think it would depend on the roof and building configuration.  With a flat roof with parapets, where the snow has no where to go, I would use 100%.  But if you have sloped roof, and the seismic event might cause the roof to "shed" some of the snow, you may be able to use a lower percentage.  However, with this reasoning, and low roof might then get a lot of snow dumped on it.
 
Just my two cents.
 

Charles F. Espenlaub, III, P.E.
Martin-Espenlaub Engineering
Tel  215-665-8570
Fax 215-561-5064

-----Original Message-----
From: Bill Marczewski [mailto:bmarczewski(--nospam--at)martind.com]
Sent: Wednesday, June 06, 2001 5:30 PM
To: 'seaint(--nospam--at)seaint.org'
Subject: Snow load in combination with seismic.

I have a multi-story building with high snow loads located in a very low seismic region (zone 1).  The building official is unable to provide information regarding the percentage of snow load in excess of 30psf that should be used in combination with the seismic load.  My preliminary calculations consisted of using 100% of the snow in the seismic dead load, and I feel this is a significant penalty.  I have previously been able to use only 25% of the snow load in seismic zone 3 in Jackson, Wyoming.  On the other hand, Steamboat Springs, Colorado (zone 1) has required 100% of the snow load to be used in combination with the seismic load.  The 1997 UBC states that snow loads beyond 30psf must be considered in seismic design, but may be reduced up to 75% when approved by the local building official.  What should I do, or does anyone have any recommendation on what percentage of snow to use when the building official cannot provide guidance on this issue?  I think the use of 100% snow load in combination with seismic is really to harsh.  Comments would be great.  Thank you.
 

Bill S. Marczewski
Martin Design, Inc.
1360 S. Clarkson St.
Denver, CO 80210
bmarczewski(--nospam--at)martind.com