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RE: relation b/w peal ground acceleration and Seismic Zones

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Well spoken, Doug Copp.
 
I agree with you and like your _expression_; especially
the "survival void"/"triangle of life" at the end.
 
Thanx a lot indeed and best regards.
 
Syed Faiz Ahmad; MEngg, MASCE
Senior Structural Engineer
Saudi Oger Ltd
P.O. Box: 1449
Riyadh-11431
Saudi Arabia
Cell: +966-508-169304
-----Original Message-----
From: AmerRescue(--nospam--at)aol.com [mailto:AmerRescue(--nospam--at)aol.com]
Sent: Monday, October 17, 2005 2:07 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: relation b/w peal ground acceleration and Seismic Zones

In a message dated 10/16/2005 3:58:04 A.M. Atlantic Daylight Time, sfaiz(--nospam--at)saudioger.com writes:
Dear Sherman:
 
I was a little busy and forgot to send
my thanx to you for your help.
 
Thanx again and best regards.
 
Syed Faiz Ahmad; MEngg, MASCE
Senior Structural Engineer
Saudi Oger Ltd
P.O. Box: 1449
Riyadh-11431
Saudi Arabia
Cell: +966-508-169304
-----Original Message-----
From: Sherman, William [mailto:ShermanWC(--nospam--at)cdm.com]
Sent: Monday, October 10, 2005 4:24 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: relation b/w peal ground acceleration and Seismic Zones

This would be my approach to resolve this question:
 
2.4 to 4.0 m/s^2 = 7.87 to 13.1 ft/s^2 = 0.24g to 0.41g  (where g=32.2 ft/s^2)
 
If the Soil Factor is 1.0, this would roughly relate to Zones 3 to 4 (Z=0.30 to 0.40).  However, "ZS" should be considered together to determine the ground acceleration for a given site.  If "S" is higher than 1.0 then the related "Z" would be lower.
 
For ASCE 7 related parameters, Sds is 2.5*ground acceleration, so these values would relate to Sds values in the range 0.61 to 1.02.  Again, these factors would include soil effects (Fa).  (The related MCE value at short period, Ss, would be 1.5*Sds/Fa.)

William C. Sherman, PE
(Bill Sherman)
CDM, Denver, CO
Phone: 303-298-1311
Fax: 303-293-8236
email: shermanwc(--nospam--at)cdm.com

 

From: Syed Faiz [mailto:sfaiz(--nospam--at)saudioger.com]
Sent: Sunday, October 09, 2005 4:49 AM
To: SEAINT
Subject: relation b/w peal ground acceleration and Seismic Zones

Dear all:

I write to you all for a small favor and I am sure some of
you being expert on the subject should be able to provide
that help to me.

Could any of you give me a correlation between Peak Ground
Acceleration (in m/s2) and the Seismic Zoning? For example
what in your opinion should be Zone number for a region having
a predicted Peak Ground Acceleration value of between
2.4 to 4.0 m/s2?

Your help and immediate response shall be appreciated.

Thanks in advance and best regards.

Syed Faiz Ahmad; MEngg, MASCE
Senior Structural Engineer
Saudi Oger Ltd
P.O. Box: 1449
Riyadh-11431
Saudi Arabia
Cell: +966-508-169304 
 

Dear Syed:
 
To focus on the matter of real concern is: Will the building collapse and will the people survive.
 
People who survive are people who find themselves in a void, inside of the rubble, which is large enough to allow their body not to be squashed. These survivable voids (bigger than the body in it)  are found next to large, bulky objects.
 
The more  force applied to a structure the more likely that it will exceed the critical point and have structural failure:
 
To determine the amount of force which will be applied to the structure based upon a presumption or 'guesstimate' of peak ground acceleration and a nomenclature of seismic zoning is like looking at a photograph of someone's feet and guessing their weight, height and eye color.
 
There are so many relevant factors in the equation which will determine force applied to the structure ( magnitude of wave, duration of wave, type of wave, frequency of wave, depth of wave, direction of wave, soil type, surrounding soil type, subterranean rock formations, water content of soil, adjacent interacting structure types, frequency of structures etc etc etc etc) that it becomes little more than a series of probabilities based upon the interaction and combination of another series of probabilities. 
 
Better to make buildings as safe as economically appropriate, put them in areas which are less likely to induce liquefaction and/or intensify wave force, in areas less likely to have earthquakes, and then tell the people to avoid being squashed should the building collapse by getting into a survivable void/'triangle of life' .
 
It all becomes more important than an intellectual guessing game or parlor game when the net result is smashed bodies.
 
doug copp