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RE: History of conventional wood framing- update -Reply

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Well put David. We sometimes forget about that little Rw factor and
overall system ductility. Although it appears that the code is slowly
reducing the required system ductility for the design of a structure by
lowering the Rw values. But remember, we do not design structures for
elastic response to ground motion! We require our structures to possess
the required ductility based on the type of lateral resisting system.
What does this mean? It means that the system gets damaged! but holds
together. It's kinda like a plane crash, any landing you can walk away
from is a good one! Isn't non structural and structural damage a good
indicator that the design and construction pretty much performed as
intended?
                    Monte Griffiths, S.E.

> ----------
> From: 	David Puskas[SMTP:david_puskas(--nospam--at)bswintl.com]
> Reply To: 	seaint(--nospam--at)seaint.org
> Sent: 	Tuesday, February 23, 1999 8:41 AM
> To: 	seaint(--nospam--at)seaint.org
> Subject: 	RE: History of conventional wood framing- update -Reply
> 
> ** High Priority **
> 
> The purpose of the building code provisions is to provide life safety
> during catastrophic events such as fire, earthquakes, etc.  It is not
> intended to prevent damage to the structure, but to provide a
> reasonably
> safe structure which when in a condition of near failure provides
> advanced warning in the form of cracks, extreme deflections, and sound
> (creaks, and groans), to warn the occupants.
> 
> In my experience at observing many residences which sustained damage
> during the Northridge earthquake I found only one two story residence
> which suffered severe damage and was in jeopardy of collapse.  The
> reason for the problem appeared to be that the structure was sitting
> on
> 20' to 25' of compacted fill which compacted  another 1 to 2%
> effectively
> settling the property a few inches.
> 
> The residences which I observed were anywhere from Thousand Oaks
> down to Hollywood and ranged in age from 1 to 75  years.  The damage
> sustained appeared to be in direct relationship to ground motion which
> the
> structure was subjected.  I viewed construction which appeared to be
> per code and also non complying conditions.  Quite frankly there did
> not
> appear to be any major inadequacies as far a protecting the occupants
> from loss of life.  There are many factors to consider in the final
> analysis
> of damage to these structures with the most prevalent factor being
> that
> of the soils. There did appear to be more damage associated with the
> non
> complying structures, however not the same degree as the effect the
> soils had on the structure.
> 
> My opinion is that the municipalities implementing the building codes
> that
> the residences were built under, the architects and/or engineers who
> designed them, and the contractors who built them, should all feel
> proud
> of a job well done in protecting the residences of these structures.
> 
> Dave Puskas
> BSW International
> 
> 
>