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[SEAOC] Re: [SEAOC] Single jolts like an EQ......

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At 02:39 PM 11/6/96 -0700, SFOAN (415) 243-3726 wrote:
>Dear Antonio...
>I am a concerned that the building may have had serious damage during the 
>Northridge earthquake.  As you know welded steel moment frame buildings 
>suffered serious damage in terms of fracture of steel conncetions and column
>base plates.  I recommend that the building should be immediately inspected.
>I am sure you are aware of the SAC guidelines.  If not let me know, I'll 
>provide you with the reference.
>
>ahmed nisar
>dames & moore
>san francisco
>

I would not discount Mr. Nisar's letter, he may have a very valid point.
However, after repairing numerous wood framed structures with lightweight
concrete floor finishes I found that the greatest complaint by the tenants
was excessive vibration experienced after the earthquake. We did extensive
investigation of the building and uncovered some poor construction
techniques, but no major structural deficiencies.
I believe that the tenants were simply more conscience of the most minute
vibration - fearing the worst. Long span Joists with lightweight concrete
tend to be more flexible and transfer vibration from surrounding areas.
This includes apartments in different area's of the building as well as
trucks on the street. 
Recently, I stayed in an apartment in Chicago and thought that we were
having consistent earthquakes until I adjusted to the traffic. The building
vibrated like crazy - and this one was steel framed with wood diaphragms.
My point is that you should rule out an increased (heightened) level of
awareness by the tenants as the reason for their complaints. 
If after following Mr. Nisar's suggestion you don't find structural
problems, you may be dealing with psychological problems.

Dennis Wish PE

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