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Re: Residential Flexible/Rigid Diaphragm Analysis

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The superposition of seismic waves will account for parts destroyed and
parts left intact.  Kobe is such an example where swathes of about 300
meters or so showed damage and little, or no, damage alternating.  Who's to
say that superpositioning cannot be microscopic in any location.  I
personally have experienced earthquakes in Japan where I have been talking
to a friend not 10 km away and they have experienced nothing.  And that is
at least a 3.6 on ground vibration scales as measured in Japan (Modified?)

Thor Tandy  P.Eng  MCSCE
Victoria BC

-----Original Message-----
From: SDGSE(--nospam--at) <SDGSE(--nospam--at)>
To: seaint(--nospam--at) <seaint(--nospam--at)>
Date: Thursday, March 25, 1999 10:41 PM
Subject: Re: Residential Flexible/Rigid Diaphragm Analysis

>If the new flexible/rigid diaphragm or all other code changes triggered by
>Northridge Earthquake were meant to improve the performance of buildings
>limit the amount of damage to less than "safety-level" damage, then how
>one explain the fact that many structures on the same block with similar
>design and construction, and sometimes older structures, suffered no or
>less damage than others. Two houses with similar design and construction,
>in many cases with identical floor plans, built on the same block or
>lots, suffered dissimilar damage, one damaged beyond repair, the other had
>minor damage.
>I do not think that both were doomed because they were designed as flexible
>diaphragms, and somehow God intervened and saved the one that housed a
>believer. The truth is that there were factors other than the code required
>design level that caused the damage in one house but not the other. How
>pour design, construction, inspection, or soil condition?
>It's been customary to revise the code requirements after a disaster to
>correct the "deficiencies" that were not "fully understood" "then." How
>now? Do we fully understand what caused the damage in one house and not the
>other? Although, both were designed by the same designer based on the then
>same code, and built by the same builder on two adjacent lots?
>If "political" demand for higher code design level continues after each
>damaging earthquake with no rational justification, then the future looks
>             V base= MW
>Where M (multiples of W) => 1 and W=Total weight of building, including
>writers' weights, if more than 250 LBS, and the weight of any influencing
>politician, if they represent an insurance company that is not willing to
>up if a disaster occurs.
>Oshin Tosounian, S.E.