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

• To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
• Subject: RE: Question on "Seismic Zone Factor" (Z) in UBC
• From: Todd Hill <thill(--nospam--at)tkarch.com>
• Date: Thu, 25 May 2000 09:18:23 -0500
```Actually, "Z" was phased out in the 97 UBC, not 94.
And as far as antiquated codes are concerned, the municipality I work in
still uses 1991 UBC.

-----Original Message-----
From: Jake Watson [mailto:jwatson(--nospam--at)inconnect.com]
Sent: Thursday, May 25, 2000 8:36 AM
To: seaint(--nospam--at)seaint.org
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)walterschambers.com
>

```