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RE: Question on "Seismic Zone Factor" (Z) in UBC

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Z is still used in the 1997 UBC. See table 16-I and Equation 30-7.

But I believe it is too elementary to consider Z as merely the ground
acceleration although it appears that way. Possibly a closer evaluation
would be Z modified by near source factors.


Bill Allen, S.E. (CA #2607)
Laguna Niguel, CA

||-----Original Message-----
||From: Jake Watson [mailto:jwatson(--nospam--at)]
||Sent: Thursday, May 25, 2000 6:36 AM
||To: seaint(--nospam--at)
||Subject: Re: Question on "Seismic Zone Factor" (Z) in UBC
||	What version of the UBC are you using?  The "Z" is
||antiquated and
||merely in the new codes for reference.  Correct me if I am wrong (I am
||way out on a limb in my knowledge) but in the 94 UBC things
||changed and
||"Z" was no longer used in the base shear calc.  The current ('97) base
||shear calc is V=(Cv*I)/(R*T).  If you divide V by "g" then
||you will have
||the design acceleration.
||Hope this helps
||Jake Watson, E.I.T.
||Salt Lake City, UT
||> Wayne Stewart wrote:
||> This is a questions regarding seismic design under the Uniform
||> Building Code.
||> It is my understanding that the magnitude of the seismic zone factor
||> (Z) in the UBC is equal to a fraction of the acceleration due to
||> gravity (9.81m/s^2).  As a practicing Canadian engineer in Edmonton,
||> Alberta, I am not really familiar with UBC and would appreciate
||> feedback from someone who is familiar with this code.
||> Please confirm that the relationship between design ground
||> acceleration (in m/s^2) and "Z" is simply the design ground
||> acceleration divided by 9.81m/s^2.
||> Thank-you.
||> Wayne Stewart, E.I.T.
||> Walters Chambers and Associates Ltd.
||> Structural Engineering Consultants
||> Suite 1330, 10130 - 103 Street
||> Edmonton, AB  T5J 3N9
||> phone:  (780) 428 - 1740 Ext. 5111
||> direct:   (780) 917 - 5111
||> fax:       (780) 423 - 3735
||> email:    wayne.stewart(--nospam--at)