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Re: Effective Peak Acceleration to Velocity Related Acceleration

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>I am looking for any formulas or rule of thumb to convert "Peak Ground " 
>accelerations to "Effective Peak Velocity Related Accelerations ". I 
>have ASCE 7-93 which provides definition of these accelerations, i.e Aa 
>and Av, the difference being the periods....I have a "Seismic Response 
Assessment  
>Report" from a consultant... 
 
Does the "Seismic Response Assessment Report" include any response spectra?  
If you have response spectra, you can account for period dependent response 
directly. 
 
>The report states  "For 1000 Average Return Period (criteria for this 
>project), the computed Mean Peak Ground Acceleration is 0.183g"....  
>How does one determine the Equivalent UBC Zone with the above 
>information ? Is it UBC Zone 2B or Zone 3 ?  (UBC Return Period is 475 
>years versus 1000 years on my project).  
 
The SEAOC Commentary from 1988 states "the seismic zone factor Z represents 
the maximum effective peak ground acceleration (EPA) for each zone".  
According to NEHRP and ATC, the effective peak acceleration (EPA) and 
effective peak velocity (EPV) are determined by drawing straight lines between 
defined period ranges on a response spectrum based on actual ground motion.  
Thus the peaks and valleys in an irregular response spectrum are approximately 
averaged for a smooth effective response spectrum.  This spectral response is 
then divided by a "normalization" factor of 2.5 - I cannot find a clear 
description of this factor, but presumably it is intended to scale the peak 
response back down to the ground motion (ie, similar to Cmax = 2.75 in UBC).  
 
My own interpretation of this is that your ground accelerations are reasonably 
within the equivalent ground accelerations of UBC Zone 2B.  However, I cannot 
directly define the applicability of these provisions to your particular 
region and site.  


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I am looking for any formulas or rule of thumb to convert "Peak Ground "
accelerations to "Effective Peak Velocity Related Accelerations ". I
have ASCE 7-93 which provides definition of these accelerations, i.e Aa
and Av, the difference being the periods.

Actually I have a "Seismic Response Assessment Report" from a consultant
done long time ago for my project, located in Middle East. This
consultant is no longer providing any services to the project.

The report states  "For 1000 Average Return Period (criteria for this
project), the computed Mean Peak Ground Acceleration is 0.183g". The
report also provides Mean Ground Accelerations for other return periods
- 500 years is 0.127g, 5000 years is 0.354g and 10,000 years is 0.452g.
It does not provide any information on Velocity Related Acceleration. 

How does one determine the Equivalent UBC Zone with the above
information ? Is it UBC Zone 2B or Zone 3 ?  (UBC Return Period is 475
years versus 1000 years on my project). The AISC Seismic provisions and
ASCE categories is based on "Effective Peak Velocity Related
Accelerations". UBC Zoning is also based on this. 

Is it safe for me to assume that this site (not located in US) is
equivalent to UBC Zone 2B ? According to "Project Guidelines" prepared
prior to my arrival on the project, the site was classified as UBC Zone
3. From my drawing reviews, detailing of concrete structures, ductility
requirements, for Zone 3 has not occurred. It is a Lump Sum Turn Key 
Contract and the Contracor is trying to convince the owner that
detailing for UBC Zone 2B is adequate and that there was an error in the
"Project Guidelines". The majority of the structures that get effected
are concrete and some steel connections are doubtful.    

Any comments or words of wisdom

Eqbal M Kassam, P.E




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