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RE: Seismic loads using ASCE 7

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Hi Dave, Joe, Doug, and company;
	Up here in Jackson we are in a seismic ?hole? ? inside of the Ss =
0.4 line on the seismic map -- where single-family and two-family residences
are NOT required to have a seismic analysis!  We have used that to keep our
fees competitive but still calc wind lateral so I am quite comfortable with
the "level" of lateral resistance.  It's always been my theory that the best
engineered lateral calculations coupled with good detailing followed by good
construction practices are priceless when addressing these issues.  The
builder has to match the cartoons -- construction drawings -- as one
building official tells me.  :)
	Under the old 1997 UBC, the "level" of lateral resistance for
Seismic Zone 3 was not that different than 70 mph Wind, Exposure C, with one
or the other governing in the long (seismic) or short (wind) direction of a
typical structure.  The new 2007 CBC level (ASCE7-05) basically has a
similar lateral resistance level so I don't really see the difference
whether I run the actual numbers for seismic or not.  Since the seismic
numbers are currently half to one-third the wind numbers, the whole exercise
seems like a waste of time -- at least in our area.  As long as the
structure is properly tied together and the shear transfer system is
calculated and detailed based on a rational analysis, the structure should
perform.
	Take care,


Terry Weatherby
Weatherby-Reynolds-Fritson
Engineering and Design
206 Peek Street
Jackson, CA 95642
p (209) 223-0381
f (209) 223-0716
e terry(--nospam--at)wrfed.com
i http://www.wrfed.com  

________________________________________
From: Dave Adams [mailto:davea(--nospam--at)laneengineers.com] 
Sent: Friday, June 06, 2008 9:44 AM
To: seaint(--nospam--at)seaint.org
Subject: Seismic loads using ASCE 7

Happy Friday, everyone!

One of the things that we are sort of struggling with here (old ?zone 3?
country) is that we are finding seismic loads via ASCE 7 wind up being less
(sometimes uncomfortably) than what we used to calculate using the 1997
UBC.  As a result, we?ve sort of adopted our own internal ?company minimum
seismic coefficient? that we are comfortable with.  Are most people
discovering the same thing and what are your thoughts?

Thanks!

Dave K. Adams, S.E., P.Eng.
LANE ENGINEERS, INC.
979 N. Blackstone Street
P.O. Box 1059
Tulare, CA  93275
Direct Line:  (559) 688-5263
Direct FAX:  (559) 688-8388
E-Mail: davea(--nospam--at)laneengineers.com
Web: www.training4engineers.com



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