Engineering Confessions

Spending most of my time around engineers, I forget that certain things aren’t common knowledge.  For example, I recently had to explain that buildings are not designed to survive earthquakes.  Rather, they are designed to not kill people during earthquakes, then afterwards we’ll knock em down and rebuild.

Engineers make this sound noble: “We’re in the business of providing life safety.”  They even get a bit of a chip on their shoulder about it: “How many thousands of lives do we save every year?  Yet they pay us less than doctors.  Totally Unfair.”

The reality is that it wouldn’t be economical to design structures to stay elastic (read: not break) during seismic events; the steel and concrete involved would be daunting.  Instead, buildings are designed for 15-25% of the expected major earthquake force, and above that they bend, crack, yield, etc.  All that deformation dissipates energy…and tends to destroy the structure.  Occupants are (usually) fine, but fixing the damaged building is more expensive than it’s worth.

Thus, all our time is spent designing things that are meant to fall down, either through tectonics or dynamite.  Nothing we do is permanent; the skyscraper cannot hold; every tower inherently is of Babel.

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