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Re: Seismic Design Hypothetical

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I think it would be difficult to tell the difference from the sidewalk. Some of these things are evident from the plans and details, but not in the ground.  I suspect a 4x6 snapshot of a wind-resistant structure and a seismic resistant structure would look nearly identical.  Moreover, I think you would have to be accomplished in designing for the particular system (steel, concrete) in seismic to have much of a chance to see the difference in a photo with enough detail to make any determination.

How about that parking garage? If there were fewer openings in the SF PG, would that be an indication of greater lateral strength or of a different architectural intent?

Like you, I do very little seismic, and nothing on the scale of a 20 story facility, though my masters research was on changes in concrete construction for modern seismic codes applied to early 20th century architecture.  I think you may have answered your own question: "I don't do seismic design, so I don't have a good feeling for it.  Hence my question."   My redesign of parts of a 1920s concrete building for modern (1990s) codes resulted in a bunch of differences hidden behind 1.5" of concrete cover, in member sizes too small to notice from the street level.  When it comes to steel, you'd get a big shrug from me. The little shakes we get here sometimes control, but we usually just build 'em for a bigger (wind) load.


PS - I think people don't know what we do because we tend to prevent things from happening, rather than make them happen.  Doctors cure people, politicians spend money, builders, well, build things, scientists discover things.  We prevent things from falling down. When we do our job well - which happens most of the time - nothing occurs, and things function properly.

gskwy(--nospam--at) wrote:
Just to make it clear, I am not looking for specific answers for a specific situation.  It's just kind of a general question.  It has been said (often) that engineers don't get any respect because nobody knows what they do.  And maybe nobody knows what they do because they don't seem to be able to show people.
I don't do seismic design, so I don't have a good feeling for it.  Hence my question.
Admittedly, the situation posed is hypothetical, but most people are faced with dozens of hypotethical, what-if situations each day.  And manage to deal with them.
Say it was an "open" parking garage in DC.  Low seismic.  20 psf wind.  Gravity load would control.  How would the same parking garage in San Francisco look different?
Gail Kelley

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