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RE: Simplified base shear formula in 97 UBC

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Regardless of whether you use the simplified method or the static
method, the code still requires you to check the diaphragm rigidity.
However, several cities in the Bay area allow the use of flexible
diaphragm concept if the simplified method is used.  

Regarding vertical distribution, the simplified method may be less
conservative that the static method for overturning forces for buildings
over two stories.

Gautam

-----Original Message-----
From: Alexander (Sasha) Itsekson [mailto:sasha(--nospam--at)enginious-structures.com]

Sent: Tuesday, March 13, 2007 10:10 AM
To: seaint(--nospam--at)seaint.org
Subject: Simplified base shear formula in 97 UBC

As we are still using UBC97 based code in California for fairly simple
wood building one can use the simplified base shear eqaution
V=3.0*Ca*I*W/R.  It gives you base shears of 20% higher than the general
base shear eqautions(or may be slightly less if Na=1.3 is used near a
seismic fault).  By using this approach, one can assume a uniform
vertical shear distribution within a building and can use a flexible
diaphragm assumption.

Thanks,

 
Alexander (Sasha) Itsekson, SE
Enginious Structures, Inc.
Oakland, CA
510.601.1646
www.Enginious-Structures.com

Subject: RE: shear wall program
From: "Jason Christensen" <jason.christensen(--nospam--at)wcaeng.com>
To: <seaint(--nospam--at)seaint.org>

"The 20% increase in base shear is a good investment as far as I am
concerned anyway for buildings in high seismic areas."

What increase is this?

Jason

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