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[SEAOC] Re: [SEAOC] Problem with AOL

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Shafat Qazi wrote:
> AOL users, please send your email to seaoc(--nospam--at) Do NOT use
> seaoc(--nospam--at) address. There seems to be a problem when sending to that
> address from AOL.
> Thank you
> Shafat


It seems that the problem is more than just with AOL.  The attached mail from 
epix was never received by seaoc.  Since the attached mail was sent last 
Saturday, many discussions have been posted on the subject of FEMA 178 vs. 
FEMA 273.  The attached mail tried to answer the original question without 
getting into the debate of which one is better.

In the response to ASCE survey on the upgrading of FEMA 178, I suggested that 
the current force based method be maintained for its simplicity instead of 
changing it to a dispacement based method.


Chang chen, apollo(--nospam--at)
Subject: Re: [SEAOC] Seismic Rehabilitation: FEMA-172 vs. FEMA 273/274
Date: Sat, 30 Nov 1996 13:25:20 -0800
From: Chang Chen <apollo(--nospam--at)>
Organization: Apollo Consulting, Inc.
To: seaoc(--nospam--at)
References: <329CBDF4.67E7(--nospam--at)>

tnhanc(--nospam--at)Alaska.NET wrote:
> What are the significant differences between the two (other than the fact
> that one is a ballot version)?   Does anyone know the history of these?
> Ref:
> FEMA 172 "NEHRP Handbook of Techniques for the Seismic Rehabilitation of
> Existing Buildings," 1992
> Ballot Version of ATC-33/FEMA 273/274 "NEHRP Guidelines for Seismice
> Rehabilitation of Buildings and Commentary," 1996
> Thanks,
> Dave Evans, P.E.


FEMA 172 describes only rehabilitation methods without evaluations.  For
evaluations, one is referred to FEMA 178 which is a companion volume of
FEMA 172.  Thus, it is more appropriate to discuss the differences
between FEMA 178 and FEMA 273 than those between FEMA 172 and FEMA 273.

As described in Chapter 10 of FEMA 273, FEMA 178 is referred to as a
simplied rehabilitation method.  In contrast, FEMA 273 is a comprehensive
method.  Other differences are as follows:

1.      FEMA 273 is a dispacement based method, while FEMA 178 is a
        checklist and force based method.

2.      FEMA 178 is limited to life safety level rehabilitation which is
        silimilar to building codes for new buildings, while FEMA 273 can
        be applied to life safety and enhanced rehabilitation level,
        e.g., immediate occupancy or operational.

3.      The ground spectrum of FEMA 178 is based on mean valus, while
        that of FEMA 273 is based on mean value plus one standard

4.      The hazard maps of FEMA 178 is based on effective peak
        acceleration coefficient, Aa, and effective velocity-related
        acceleration coefficieint, Av, while those of FEMA 273 are
        response spectrum values at short and long periods, As and Al.

FEMA 178 is in the process of being upgraded to being more compatible
with FEMA 273.  Hope that the above helps to solve part of the puzzle.


Chang chen, P.E., Ph.D.