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

• To: seaint(--nospam--at)seaint.org
• Subject: Re: Question on "Seismic Zone Factor" (Z) in UBC
• From: Jake Watson <jwatson(--nospam--at)inconnect.com>
• Date: Thu, 25 May 2000 07:36:25 -0600
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)walterschambers.com
>