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RE: Wind and Seismic for Redding CA

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I would urge a caveat to the exclusion of snow loads under 30 psf from the
seismic mass. I think this footnote in the UBC is based on the assumption
that low snow loads correspond to warmer climates where the snow does not
hang around very long, so the risk of simultaneous earthquake and high snow
load is pretty low. This is especially true for steeper pitched roofs, where
a quake would help shake the snow off in a hurry anyway.

On structures with large, flat roofs, particularly if they are unheated or
well insulated, the snow can hang around for quite a while. In those
situations, I would be inclined to throw some snow load into the mass, even
if the code doesn't require it. Also, if you are working in a climate where
you get a lot of alternating rain and snow, I think you can get saturated
snow which is pretty heavy. Local knowledge is vital if when are dealing
with snow loads.

-----Original Message-----
From: Mark Pemberton [mailto:Markp(--nospam--at)]
Sent: Wednesday, January 03, 2001 9:11 AM
To: 'seaint(--nospam--at)'
Subject: RE: Wind and Seismic for Redding CA

The 1997 UBC does not require snow loads of 30 psf
or less to be combined with seismic loads.
(1612.3.2 exception #2)

Mark Pemberton, P.E.

-----Original Message-----
From: Structuralist [mailto:dennis.wish(--nospam--at)]
Sent: Tuesday, January 02, 2001 11:00 PM
To: seaint(--nospam--at)
Subject: RE: Wind and Seismic for Redding CA

It's my understanding that Redding also has a snow load of 30-psf. Are you
required in zone 3 to use a percentage of the SN in your lateral analysis?

Dennis S. Wish, PE

-----Original Message-----
From: kendeb [mailto:kendeb(--nospam--at)]
Sent: Tuesday, January 02, 2001 6:59 PM
To: seaint(--nospam--at)
Subject: Re: Wind and Seismic for Redding CA

Well, since I live in (near) Redding, CA, I think I can help a little. I use
80mph with Exposure B most of the time. I only use Exposure C if the
specific site
location requires it. Most all of the terrain around Redding can qualify as
Exposure B. I believe that I began using 80 mph rather than 75 mph at the
request of
the City B.O. The county (Shasta) probably would accept 75 mph. Seismic zone
is 3. And both the City of Redding and Shasta County accept the '97 UBC.

Ken Reed, PE

Ken Peoples wrote:

> I have a client who needs to specify a tank that will
> be installed near Redding CA.  He has asked me what to
> tell the manufacturer about wind and seismic loads.
> Being from the east coast, I would just like to check
> with some of you CA Engineers to be sure that what I
> am going to tell him is OK.  I guess my first question
> is whether I can use 1997 UBC.  If I can, I think I
> can tell him Seismic Zone 3 with a Minimum Basic Wind
> Speed of 80 mph. Any comments are appreciated.
> Ken
> =====
> Kenneth S. Peoples, P. E.Lehigh Valley Technical Associates2102 Main St.
Suite 200Northampton, PA 18067ph: 610-262-6345fax: 610-262-8188email:
> __________________________________________________
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